HDI plate manufacturing process for pen electronic camera module

Abstract

The invention discloses an HDI plate manufacturing process for a pen electronic camera module, and the process comprises the steps: carrying out the multi-frequency acoustic wave penetration and temperature gradient processing of a substrate, and obtaining the pre-detection data of the substrate; in the laser drilling process, short-pulse multi-frequency acoustic waves and local heat regulation are applied to a target hole area, and micropore acoustic reflection data are obtained; the method comprises the following steps: independently regulating and controlling the temperature of a plurality of areas of a board surface before chemical copper deposition treatment, and recording acoustic scanning data to form a regional acoustic characteristic spectrum; performing acoustic wave excitation according to a preset time interval in the chemical copper deposition process to obtain monitoring data of the copper deposition process; periodic thermal excitation and fluid disturbance are applied in the electroplating process, and electroplating dynamic monitoring data are obtained; after electroplating is completed, temperature circulation and stress excitation treatment are carried out, and the evaluation result of the internal structure of the micro-through hole is obtained. According to the technical scheme, the micro-through-hole structure with the bubble micro-migration tendency can be accurately identified and screened in the manufacturing process, and the long-term reliability and the use stability of the HDI plate are effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of detection in the manufacturing process of high - density interconnect printed circuit boards, and particularly to a manufacturing process for HDI boards used in laptop camera modules. Background Art

[0002] The HDI (High Density Interconnection) board for laptop camera modules is a high - density interconnect printed circuit board, specifically designed to support the electrical connection and signal transmission of camera modules. This HDI board usually adopts a multi - layer structure design, including 4 - 8 circuit layers, and the layers are interconnected through microvias. The overall thickness is usually in the range of 0.6 - 0.8 mm. Due to the pursuit of thinness and lightness in laptops, the space for camera modules is extremely limited. The HDI board needs to achieve a high - density component layout and complex signal line arrangement within a very small area, and at the same time meet the electrical performance requirements for high - definition video transmission.

[0003] The existing HDI board manufacturing process mainly includes steps such as substrate selection, laser drilling, microvia electroplating, circuit formation, and surface treatment. Among them, in the microvia electroplating process, a combination of chemical deposition and electroplating is used. First, a thin copper seed layer is deposited on the insulating resin hole wall, and then the copper layer is thickened through an electrochemical reaction until a reliable conductive path is formed. However, due to the extremely small diameter of the microvias in the HDI board for camera modules (usually 30 - 50 microns) and the high aspect ratio, the current distribution is uneven during electroplating. Coupled with limited solution flow, it is easy to form tiny bubbles inside the microvias. These bubbles may be completely covered by the subsequently deposited copper layer during electroplating, forming a structure with a complete appearance but voids inside. Traditional X - ray and AOI (Automated Optical Inspection) detections mainly focus on static defects and are difficult to detect such internal bubbles covered by the copper layer. In addition, such defects do not immediately affect the product function in the initial state, but in application scenarios such as long - time video conferencing of cameras, the heat generated during continuous operation will cause these bubbles to expand and migrate, eventually leading to intermittent connection failures and seriously affecting the user experience. Summary of the Invention

[0004] The main purpose of the present invention is to solve the technical problem that internal bubbles in the manufacturing process of microvias of existing HDI boards are difficult to detect because they are covered by the copper layer.

[0005] The first aspect of the present invention provides an HDI board manufacturing process for a laptop camera module, and the HDI board manufacturing process for the laptop camera module includes: Perform multi-frequency acoustic wave penetration and temperature gradient processing on the substrate to obtain substrate acoustic response data and thermal response data, and use the acoustic response data and thermal response data as substrate pre-inspection data; According to the substrate pre-inspection data, apply short-pulse multi-frequency acoustic waves to the target hole area during laser drilling, record the acoustic reflection signal at the moment of drilling, and perform local heat control on the hole wall area to obtain micro-hole acoustic reflection data; Before chemical copper plating treatment, according to the micro-hole acoustic reflection data, independently control the temperature of multiple areas on the board surface, record the multi-frequency acoustic scanning data of the hole walls in each area under thermal pulse excitation, and form a regional acoustic characteristic map; During chemical copper plating, according to the regional acoustic characteristic map, apply multi-band acoustic wave excitation to the hole area at preset time intervals, record the acoustic reflection signal attenuation curve during the formation of the metal seed layer, and obtain copper plating process monitoring data; During electroplating, according to the copper plating process monitoring data, apply periodic thermal excitation and fluid disturbance to the board surface, record the propagation characteristics of multi-frequency acoustic waves in the electroplating solution, and obtain electroplating dynamic monitoring data through adaptive signal processing; After electroplating is completed, according to the electroplating dynamic monitoring data, perform temperature cycling and stress excitation treatment on the finished product, record the acoustic wave reflection data inside the holes, and obtain the evaluation result of the internal structure of the micro-vias through multi-dimensional data analysis.

[0006] Preferably, the performing multi-frequency acoustic wave penetration and temperature gradient processing on the substrate to obtain substrate acoustic response data and thermal response data, and using the acoustic response data and thermal response data as substrate pre-inspection data includes: Apply acoustic waves of a first frequency band to the acoustic coupling medium layer provided between adjacent resin layers of the substrate, and record the acoustic wave buffer stress data and interlayer bonding strength data of the acoustic coupling medium layer; According to the acoustic wave buffer stress data and the interlayer bonding strength data, apply acoustic waves of a second frequency band to the interface between the resin layer and the copper foil layer of the substrate, and record the acoustic wave amplitude data and acoustic wave phase difference data of the interface bonding part; Determine the first temperature range according to the acoustic wave amplitude data, apply a first temperature gradient to the substrate within the first temperature range, and record the first thermal stress distribution data; determine the second temperature range according to the acoustic wave phase difference data, apply a second temperature gradient to the substrate within the second temperature range, and record the second thermal stress distribution data; perform an acoustic scan on the thermal stress concentration region through the acoustic coupling medium layer according to the first thermal stress distribution data and the second thermal stress distribution data, and record the acoustic characteristic data of the microvoids and abnormal interlayer bonding regions inside the substrate. Perform stress compensation processing on the acoustic wave buffer stress data and the interlayer bonding strength data according to the thermal stress distribution data, perform abnormal correction processing on the acoustic wave amplitude data and the acoustic wave phase difference data according to the acoustic characteristic data, and combine the data after the compensation processing and the correction processing to form the pre-inspection data of the substrate.

[0007] Preferably, according to the acoustic wave buffer stress data and the interlayer bonding strength data, applying an acoustic wave in a second frequency band to the interface between the resin layer and the copper foil layer of the substrate, and recording the acoustic wave amplitude data and the acoustic wave phase difference data of the interface bonding part, including: Determine the acoustic wave action parameters according to the acoustic wave buffer stress data, apply a first sub-band acoustic wave corresponding to the acoustic wave action parameters to the interface bonding part between the rough surface area of the outer copper foil of the substrate and the adjacent resin layer, and record the acoustic wave scattering intensity data of the rough surface area of the outer copper foil. Determine the acoustic wave penetration depth parameters according to the interlayer bonding strength data, apply a second sub-band acoustic wave corresponding to the acoustic wave penetration depth parameters to the interface bonding part between the inner copper foil and the resin layer of the substrate in the high scattering region indicated by the acoustic wave scattering intensity data, and record the acoustic wave attenuation data of the interface between the inner copper foil and the resin layer. Perform amplitude superposition processing on the acoustic wave scattering intensity data and the acoustic wave attenuation data to form acoustic wave amplitude data, and perform phase superposition processing on the acoustic wave scattering intensity data and the acoustic wave attenuation data to form acoustic wave phase difference data.

[0008] Preferably, according to the pre-inspection data of the substrate, applying a short-pulse multi-frequency acoustic wave to the target hole area during laser drilling, recording the acoustic reflection signal at the moment of drilling, and performing local heat regulation on the hole wall area to obtain the micro-hole acoustic reflection data, including: Determine the acoustic wave action range and acoustic wave action timing of the hole area according to the pre-inspection data of the substrate, apply a first-band short-pulse acoustic wave corresponding to the acoustic wave action range and the acoustic wave action timing to the target hole area, and record the substrate acoustic reflection reference data before drilling. According to the acoustic reflection reference data, during the laser drilling ablation process, short-pulse acoustic waves in a second frequency band are applied layer by layer to the hole wall, and the sudden change data of the acoustic wave amplitude and the phase shift data during the ablation process of each layer are recorded; According to the sudden change data of the acoustic wave amplitude, a first temperature control parameter is determined, and a first local temperature gradient corresponding to the first temperature control parameter is applied to the hole wall area, and the first hole wall temperature response data is recorded; according to the phase shift data, a second temperature control parameter is determined, and a second local temperature gradient corresponding to the second temperature control parameter is applied to the hole wall area, and the second hole wall temperature response data is recorded; According to the first hole wall temperature response data and the second hole wall temperature response data, short-pulse acoustic waves in a third frequency band are applied to the hole wall, and the acoustic scattering data of the hole wall microcracks and the acoustic attenuation data of the resin residue are recorded, and the sudden change data of the acoustic wave amplitude, the phase shift data, the first hole wall temperature response data, the second hole wall temperature response data, the acoustic scattering data of the hole wall microcracks and the acoustic attenuation data of the resin residue are combined to form microhole acoustic reflection data.

[0009] Preferably, the step of applying short-pulse acoustic waves in a second frequency band layer by layer to the hole wall during the laser drilling ablation process according to the acoustic reflection reference data and recording the sudden change data of the acoustic wave amplitude and the phase shift data during the ablation process of each layer includes: According to the acoustic reflection reference data, first sub-band short-pulse acoustic waves are applied to the ablation area of the outer copper foil, and the acoustic wave reflection data of the metal layer and the copper foil residue distribution data during the ablation process of the outer copper foil are recorded; According to the acoustic wave reflection data of the metal layer, second sub-band short-pulse acoustic waves are applied to the alternating ablation area of the resin layer and the inner copper foil, and the acoustic characteristics data of material peeling at the resin-metal interface and the acoustic characteristics data of resin decomposition are recorded; The acoustic wave reflection data of the metal layer, the copper foil residue distribution data, the acoustic characteristics data of material peeling and the acoustic characteristics data of resin decomposition are combined and analyzed to form the sudden change data of the acoustic wave amplitude and the phase shift data.

[0010] Preferably, before the electroless copper plating process, according to the microhole acoustic reflection data, temperature independent regulation is performed on multiple areas of the board surface, and the multi-frequency acoustic scanning data of the hole walls of each area under thermal pulse excitation is recorded to form a regional acoustic characteristic map, including: Before the electroless copper plating process, according to the sudden change area of the acoustic wave amplitude and the phase shift area in the microhole acoustic reflection data, the board surface is divided into multiple temperature independent regulation units, and independent temperature control parameters are set for each temperature independent regulation unit; According to the temperature control parameters of each temperature independent control unit, apply a first thermal pulse wave to the hole walls of each area, apply a first frequency band acoustic scanning wave to the hole walls at the peak moment of the first thermal pulse wave, and record the acoustic wave scattering data caused by the transient expansion of the hole walls; According to the acoustic wave scattering data, determine the stress response parameters of the hole walls of each area, apply a second thermal pulse wave to each temperature independent control unit, apply a second frequency band acoustic scanning wave to the hole walls at the valley moment of the second thermal pulse wave, and record the acoustic wave attenuation data caused by the transient contraction of the hole walls; According to the acoustic wave attenuation data, determine the strain distribution parameters of the hole walls of each area, apply a third thermal pulse wave to each temperature independent control unit, apply a third frequency band acoustic scanning wave to the hole walls during the duration of the third thermal pulse wave, and record the acoustic characteristics data of microcracks in the hole walls and the data on the migration trend of voids; Partition and combine the acoustic wave scattering data, the acoustic wave attenuation data, the acoustic characteristics data of microcracks in the hole walls, and the data on the migration trend of voids according to the temperature independent control unit to form a regional acoustic characteristic map.

[0011] Preferably, during the electroless copper plating process, according to the regional acoustic characteristic map, apply multi-frequency band acoustic wave excitation to the hole areas at preset time intervals, record the acoustic reflection signal attenuation curve during the formation of the metal seed layer, and obtain the monitoring data during the electroless copper plating process, including: During the electroless copper plating process, determine the electroless copper plating monitoring time sequence of each hole area according to the regional acoustic characteristic map and the preset time interval, pause the flow of the electroless copper plating solution at the pause point of each electroless copper plating monitoring time sequence, apply an electroless copper plating start detection wave to the hole area, and record the acoustic reflection characteristic data during the nucleation stage of the metal seed layer; Apply an electroless copper plating growth detection wave to different hole areas according to the acoustic reflection characteristic data, and record the metal grain growth distribution data and the interface bonding state data; Apply an electroless copper plating process detection wave to the hole area according to the metal grain growth distribution data and the interface bonding state data, and record the change curve of the seed layer continuity and the change curve of the hole wall coverage; Conduct dynamic characteristic analysis on the change curve of the seed layer continuity and the change curve of the hole wall coverage according to the preset time interval, and combine the acoustic reflection characteristic data, the metal grain growth distribution data, the interface bonding state data, and the dynamic characteristic analysis results to form the monitoring data during the electroless copper plating process.

[0012] Preferably, during the electroplating process, according to the monitoring data during the electroless copper plating process, apply periodic thermal excitation and fluid disturbance to the board surface, record the propagation characteristics of multi-frequency acoustic waves in the electroplating solution, and obtain the electroplating dynamic monitoring data through adaptive signal processing, including: During the electroplating process, according to the seed layer continuity change curve in the copper deposition process monitoring data, a first electroplating thermal pulse is applied to the high-density micro-hole clustering area, and a second electroplating thermal pulse is applied to the surrounding trace area, and the temperature gradient distribution data of the micro-hole area and the trace area is recorded; According to the temperature gradient distribution data, a first fluid perturbation is applied to the high-density micro-hole clustering area, and a second fluid perturbation is applied to the surrounding trace area. Under the action of the double-fluid perturbation, an electroplating acoustic detection wave is applied to the deep and shallow micro-hole areas, and the acoustic propagation attenuation data of micro-holes with different depth-to-diameter ratios is recorded; According to the acoustic propagation attenuation data, a low-frequency electroplating monitoring wave is applied to the high-density micro-hole clustering area, and a high-frequency electroplating monitoring wave is applied to the surrounding trace area, and the bottom current density distribution data of the micro-holes and the hole wall coating stress distribution data are recorded; Perform a sub-region compensation operation on the current density distribution data, record the coating thickness distribution curve of the deep and shallow micro-holes, perform a hierarchical processing on the hole wall coating stress distribution data, and record the bubble migration characteristic curve of micro-holes with different depth-to-diameter ratios; Perform an adaptive signal filtering process on the coating thickness distribution curve and the bubble migration characteristic curve, and combine the temperature gradient distribution data, the acoustic propagation attenuation data, the current density distribution data, the hole wall coating stress distribution data, the coating thickness distribution curve after the adaptive signal filtering process, and the bubble migration characteristic curve after the adaptive signal filtering process to form electroplating dynamic monitoring data.

[0013] Preferably, after the electroplating is completed, according to the electroplating dynamic monitoring data, the finished product is subjected to temperature cycling and stress excitation treatment, the in-hole acoustic wave reflection data is recorded, and the internal structure evaluation result of the micro-vias is obtained through multi-dimensional data analysis, including: After the electroplating is completed, according to the electroplating dynamic monitoring data, the coating on the inner wall of the micro-holes is evaluated in sub-regions, the temperature cycling parameters and stress excitation parameters are determined, a first temperature cycle is applied to the finished product, and the thermal cycle gradient data and cyclic stress accumulation data of each micro-hole area are recorded; According to the thermal cycle gradient data and the cyclic stress accumulation data, a second temperature cycle is applied to the finished product, and at the same time, a finished product evaluation acoustic wave is applied to the inner wall of the micro-holes, and the acoustic attenuation trend data and acoustic phase shift characteristic data inside the micro-holes are recorded; According to the acoustic attenuation trend data and the acoustic phase shift characteristic data, mechanical stress excitation is applied to the micro-holes, and the structural deformation parameters and void evolution data of the coating on the inner wall of the micro-holes are recorded; Comprehensively process the thermal cycle gradient data, the cyclic stress accumulation data, the acoustic attenuation trend data, the acoustic phase shift characteristic data, the structural deformation parameters and the void evolution data to form the internal structure evaluation result of the micro-vias.

[0014] Throughout the manufacturing process, detection and monitoring means that combine multi-frequency acoustic waves with temperature gradients are set at each stage described in the solution. This enables continuous tracking of any risk factors that may cause bubbles or voids inside the pores before the micro-pores are fully formed and before the metal layer is deposited and covered. At the beginning of the manufacturing process, the substrate is subjected to multi-frequency acoustic wave penetration combined with temperature gradient treatment. In this way, acoustic response and thermal stress distribution information can be collected at the interface between the resin layer and the copper foil layer, as well as at deep positions in the laminated dielectric. This information can distinguish areas with weak interlayer bonding or containing fine voids, provide early warnings for subsequent micro-pore processing, and record it in the pre-inspection data of the substrate. Subsequently, during the laser drilling stage, short-pulse multi-frequency acoustic waves are applied to the target hole area, and local heat regulation is carried out during the ablation process. The possible cracks or resin residues on the hole wall are identified by the changes in the amplitude and phase of the acoustic waves under different temperature conditions. With this real-time monitoring, potential defect areas can be detected in a timely manner, preventing the subsequent metallization process from blindly depositing a copper layer on the defective hole wall.

[0015] Before the electroless copper plating treatment, the solution stipulates independent temperature regulation for multiple regions and records the multi-frequency acoustic scanning results of the hole wall under thermal pulse excitation. By doing so, the distribution of micro-cracks or voids in the substrate can be revealed region by region, and the corresponding regional acoustic characteristic maps can be obtained. When formally entering the electroless copper plating process, the solution flow is paused at preset time nodes, and multi-band acoustic waves are applied to the hole area again. The attenuation trend of the acoustic reflection signal during the formation of the metal seed layer is continuously observed. If the seed layer shows problems such as poor adhesion or uneven coverage during growth, the acoustic wave will exhibit abnormal amplitude and attenuation curves on the hole wall surface, which can help determine whether internal voids or micro-bubbles are being generated. These dynamic monitoring data can also be combined with the previously collected regional maps to specifically correct the copper plating conditions and prevent the further development of defects.

[0016] When entering the electroplating stage, the solution proposes using the state of the seed layer monitored during the electroless copper plating process to apply different thermal pulses and fluid disturbances to the clustered areas of high-density micro-pores and the surrounding trace areas respectively, and apply multi-frequency acoustic waves with adaptive signal processing to hole positions with different depth-to-diameter ratios. This can more precisely capture the current non-uniformity caused by the high aspect ratio at the bottom of the micro-pores and the possible locations where bubbles may accumulate. By observing the acoustic propagation attenuation, hole wall stress distribution, and bubble migration curves at any time, the current density can be locally reduced or the solution flow can be enhanced in a timely manner, so that the bubbles are excluded or exposed at an early stage of formation. Once a void wrapped by a copper layer is generated inside the hole, obvious signal anomalies will also appear under the combined action of the thermal pulse and the acoustic wave, which can be further located and remedied.

[0017] After the electroplating is completely finished, temperature cycling and stress excitation means are used in conjunction with acoustic wave reflection detection at this time, so that those bubbles or pore wall voids that did not cause functional abnormalities initially but are prone to expansion under subsequent thermal expansion and mechanical vibration exhibit characteristic responses in the detection data. The combined performance of acoustic attenuation and phase shift, combined with the recording of the deformation of the inner wall plating structure and the evolution of voids, can screen out the micro-pores that still pose potential risks, and subsequent treatments can be taken according to the different degrees of void evolution. This continuous multi-stage acoustic and temperature coupling detection cycle controls the defect risks of the entire microvia from the base material to the finished product within the range visible at an early stage, avoiding the deficiency of the traditional method that only performs single detection and cannot find the bubbles covered by the copper layer.

[0018] Through the above method, it is possible to monitor and dispose of the micro-bubbles that are expected to be generated or already exist on the pore wall in the whole process. The multi-frequency acoustic waves and temperature regulation complement each other, so that any small voids or poor bonding cannot be easily covered up. After identifying the substrate defects in the early stage, the drilling process is adjusted in time. During the electroless copper deposition stage, the growth state of the seed layer is observed multiple times and the electroplating parameters are corrected in cooperation. In the later stage, multi-dimensional investigations of temperature and stress will also be carried out in the finished product state. These steps are connected in series to form a systematic screening and correction means for internal bubble defects, significantly reducing the risk of intermittent failure of micro-pores due to thermal stress expansion in a high-speed signal transmission environment. Thus, it can be seen that this process of integrating detection and manufacturing can transform the potential hidden dangers proposed in the background into specific objects that can be monitored and prevented, solving the problems that it is difficult to detect the bubbles covered by the copper layer in time and unstable failures will occur in the later stage. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on the structures shown in these drawings.

[0020] Figure 1 It is a schematic diagram of an embodiment of the manufacturing process of an HDI board for a laptop camera module in an embodiment of the present invention.

[0021] The realization, functional characteristics and advantages of the object of the present invention will be further described in conjunction with the embodiments with reference to the drawings. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0022] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0023] It should be noted that if there are directional indications (such as up, down, left, right, front, back...) involved in the embodiments of the present invention, the directional indications are only used to explain the relative position relationship and movement conditions between components in a specific posture. If the specific posture changes, the directional indications will also change accordingly.

[0024] In addition, the descriptions involving "first", "second", etc. in the present invention are only for descriptive purposes, and cannot be understood as indicating or implying their relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of the features. In addition, "and / or" throughout the text includes three scenarios. Taking A and / or B as an example, it includes the technical solution of A, the technical solution of B, and the technical solution that A and B are satisfied simultaneously. In addition, the technical solutions between the various embodiments can be combined with each other, which must be based on the ability of those of ordinary skill in the art to implement. When the combination of technical solutions conflicts with each other or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the protection scope required by the present invention.

[0025] An embodiment of the present application provides a manufacturing process for an HDI board for a laptop camera module. Figure 1 It is a flowchart of a manufacturing process for an HDI board for a laptop camera module provided by an embodiment of the present application. In this embodiment, the method includes: Please refer to Figure 1 , perform multi-frequency acoustic wave penetration and temperature gradient processing on the substrate to obtain substrate acoustic response data and thermal response data, and use the acoustic response data and thermal response data as substrate pre-inspection data; In an embodiment of the present invention, the performing multi-frequency acoustic wave penetration and temperature gradient processing on the substrate to obtain substrate acoustic response data and thermal response data, and using the acoustic response data and thermal response data as substrate pre-inspection data includes: Apply acoustic waves of the first frequency band to the acoustic coupling medium layer disposed between adjacent resin layers of the substrate, and record the acoustic wave buffer stress data and interlayer bonding strength data of the acoustic coupling medium layer; According to the acoustic wave buffer stress data and the interlayer bonding strength data, apply an acoustic wave in a second frequency band to the interface between the resin layer and the copper foil layer of the substrate, and record the acoustic wave amplitude data and the acoustic wave phase difference data at the interface bonding part; Determine a first temperature range according to the acoustic wave amplitude data, apply a first temperature gradient to the substrate within the first temperature range, and record first thermal stress distribution data; determine a second temperature range according to the acoustic wave phase difference data, apply a second temperature gradient to the substrate within the second temperature range, and record second thermal stress distribution data; perform an acoustic scan on the thermal stress concentration area through the acoustic coupling medium layer according to the first thermal stress distribution data and the second thermal stress distribution data, and record the acoustic characteristic data of the microvoids and the abnormal interlayer bonding areas inside the substrate; Perform stress compensation processing on the acoustic wave buffer stress data and the interlayer bonding strength data according to the thermal stress distribution data, perform abnormal correction processing on the acoustic wave amplitude data and the acoustic wave phase difference data according to the acoustic characteristic data, and combine the data after the compensation processing and the correction processing to form pre-inspection data of the substrate.

[0026] The following specifically describes the steps involved in the above embodiments: The acoustic coupling medium layer provided between adjacent resin layers of the substrate usually uses a modified epoxy resin or an elastomer-modified resin material, and inorganic fillers (such as silica particles or alumina particles) can be added thereto to improve the acoustic wave conduction performance. This coupling medium layer not only meets the requirements of electrical insulation but also can maintain a stable structure under the action of external stress and acoustic waves. It is realized by introducing a thin layer of material between the resin layers during the lamination stage, and after curing, it can be closely attached to the adjacent resin layers and has appropriate elasticity. If a modified epoxy resin is used, the material has high adhesiveness and mechanical properties after thermal curing; if an elastomer-modified composite resin is used, the internal elastic components can buffer the interlayer stress and allow the acoustic wave to propagate in the medium layer with a small attenuation rate. When applying an acoustic wave in a first frequency band to this medium layer, a multi-frequency ultrasonic detection system can be used as the instrument, and the detection probe is ultrasonically coupled with a water-based or oil-based coupling agent outside the plate. The first frequency band can be selected within the range of about 5 MHz to 15 MHz, which is beneficial to penetrate the medium layer and detect its absorption or transmission characteristics of vibration. The acoustic wave buffer stress data recorded in this process reflects the numerical value of the stress absorption ability of the medium material, and the interlayer bonding strength data quantifies the firmness of the bonding between the medium layer and the resin by analyzing the interface reflection coefficient and the phase drift. The reason for using this frequency band is to balance the penetration depth and resolution, which is convenient for identifying minor bonding abnormalities or over-hardened areas in the medium layer with a lower thickness. After completing the above detection, the acoustic response of the internal coupling medium layer without significant temperature load can be understood, providing a reference for identifying deep defects in the substrate.

[0027] Based on the first frequency band detection results (acoustic wave buffer stress data and interlayer bond strength data), the weak bonding parts or stress abnormal areas of the coupling medium layer can be located. When performing advanced detection on the interface between the resin layer and the copper foil layer at these parts, a second frequency band acoustic wave can be applied. To meet the requirements of fine imaging and defect recognition of the metal-resin interface, the second frequency band can be selected in the range of about 15 MHz to 30 MHz, and the acoustic impedance difference is more likely to capture local voids or rough contact surfaces in this frequency band. During detection, the ultrasonic probe is aligned with the target interface area and combined with a water-based couplant or a thin film coupling method, so that the ultrasonic pulse passes through the upper resin layer to reach the copper foil interface. If there are cracks or non-tight fits at the interface, the receiving end will observe abnormal amplitude peaks or significant increases in phase shift amounts in the echo signal. The acoustic wave amplitude data usually represents the reflection ratio intensity of the interface in this frequency band and is used to judge whether there are large voids; the phase difference data is related to the micro-perturbation of the local interface thickness or the refraction path between material layers and can be used to identify more subtle peeling signs. Through this step, the detection results between the coupling medium layer and the resin layer can be cross-verified, further locking in the potential problem areas at the resin-copper foil junction and providing a detection target area for subsequent temperature gradient loading.

[0028] Based on the obtained acoustic wave amplitude data, the section where large voids or local material non-uniformity is located can be inferred, thereby setting the first temperature range; based on the phase difference data, the more subtle interface perturbation parts can be inferred, thereby setting the second temperature range. During specific implementation, a local infrared radiation source or a temperature control table can be used to apply different temperature gradients to these target sections, and continuously scan the target area in the previous frequency band (or an adjusted small-step frequency band) during the heating or cooling process, and record the first thermal stress distribution data and the second thermal stress distribution data. The first temperature range can be selected, for example, between 40°C and 80°C to simulate the stress distribution under a lower temperature load; the second temperature range can be selected between 80°C and 120°C to observe the material mismatch behavior in a higher temperature working environment. If there is a sudden change in the strong acoustic reflection amplitude in a specific temperature section, it can indicate thermal stress concentration here. After completing the recording of these two temperature ranges, a more refined acoustic scan can be performed on these thermal stress concentration areas again through the previously set acoustic coupling medium layer. When the coupling medium layer conducts acoustic waves to micro-voids or bonding anomalies, the reflection signal will show peaks or waveform distortions that are completely different from the normal area in terms of amplitude and phase. Through this process, more accurate position and size information of micro-voids and interlayer anomalies inside the substrate can be obtained. Combining these data, the thermal stress accumulation that may occur in the material at different temperature ranges can be distinguished, assisting in judging the severity of the defect.

[0029] According to the above thermal stress distribution data, stress compensation can be performed on the acoustic wave buffer stress data and interlayer bonding strength data, that is, the parts with high stress concentration and low bonding strength are marked as key hidden danger areas under the same spatial coordinates. At this time, it is necessary to make abnormal corrections to the acoustic wave amplitude data and phase difference data based on the acoustic characteristic data, especially for parts where obvious peak shifts repeatedly appear in multiple detections or different temperature gradients. It is necessary to give higher weights in the signal processing algorithm to confirm their authenticity. If some areas have high values ​​due to local bubbles or transient noise in a single detection, they can be removed or downgraded at this stage. After completing these corrections, all information after compensation and correction can be integrated into the same data set to form substrate pre-inspection data. The data includes the mechanical and acoustic matching between the interfaces and the stress sensitivity under different temperature gradients, which can provide guidance for subsequent laser drilling and metallization process adjustments. For example, if the interlayer adhesion is low and the thermal stress concentration is high in a certain place during the inspection, the ablation power can be reduced and the heat dissipation time can be extended in the laser processing to avoid further tearing of the hole wall; if a large number of interface abnormalities are found, a higher solution fluidity or more uniform temperature control strategy can be adopted during chemical copper deposition to make the metal adhesion more complete. Relying on these substrate pre-inspection data, the probability of serious invisible bubbles or hole wall delamination defects in high-density interconnect boards in the later stage can be reduced.

[0030] In one embodiment of the present invention, applying a second frequency band acoustic wave to the interface between the resin layer and the copper foil layer of the substrate according to the acoustic wave buffering stress data and the interlayer bonding strength data, and recording the acoustic wave amplitude data and the acoustic wave phase difference data of the interface bonding part, comprises: Determine the acoustic wave action parameter according to the acoustic wave buffer stress data, apply a first sub-band acoustic wave corresponding to the acoustic wave action parameter to the interface between the rough surface area of ​​the outer copper foil of the substrate and the adjacent resin layer, and record the acoustic wave scattering intensity data of the rough surface area of ​​the outer copper foil; Determine the acoustic wave penetration depth parameter according to the interlayer bonding strength data, apply a second sub-band acoustic wave corresponding to the acoustic wave penetration depth parameter to the interface bonding portion between the inner copper foil and the resin layer of the substrate in the high scattering region indicated by the acoustic wave scattering intensity data, and record the acoustic wave attenuation data of the interface between the inner copper foil and the resin layer; The sound wave scattering intensity data and the sound wave attenuation data are subjected to amplitude superposition processing to form sound wave amplitude data, and the sound wave scattering intensity data and the sound wave attenuation data are subjected to phase superposition processing to form sound wave phase difference data.

[0031] The following is a detailed description of the steps involved in the above embodiment: When determining the acoustic wave action parameters based on the acoustic wave buffer stress data, it is necessary to combine the previously obtained acoustic wave buffer stress curve with the material properties to deduce the waveform frequency and pulse energy most suitable for the rough area on the surface of the outer copper foil. The acoustic wave action parameters include emission frequency, pulse width, output power, etc., and are used to ensure that there are sufficiently obvious scattering and reflection differences of the acoustic wave on the rough metal surface. During implementation, an ultrasonic scanning system with multi-band output function can be used. The probe is coupled with the surface of the outer copper foil through a water-based or oil-based coupling agent, and the first sub-band acoustic wave is emitted point by point or line by line according to the said parameters. The rough area on the surface of the outer copper foil refers to the part with a large surface height difference caused by mechanical pressing or chemical etching during the manufacturing process. Under the irradiation of the acoustic wave, a high scattering amount will appear in this area. The acoustic wave scattering intensity data is integrated by the receiving end for the amplitude, time delay and spatial distribution of the echo signal. If the scattering intensity increases significantly at certain positions, it indicates that the surface roughness is higher or there is particle accumulation at that place. Through this process, the true acoustic reflection performance of the interface between the outer copper foil and the adjacent resin layer under different roughness conditions can be identified, and it provides a basis for adjusting the emission frequency and penetration mode when detecting the inner layer part subsequently. When adopting this step, if the emission frequency is too low, the scattering contrast of the fine surface defects will be weakened; if it is too high, it is easily submerged by the instantaneous surface reflection. Therefore, this sub-band is usually designed within the range that meets the scattering sensitivity of the outer copper foil surface and can maintain sufficient penetration ability, such as in the range of about 10 MHz to 15 MHz. By recording and processing the acoustic wave scattering intensity data, a more effective quantitative evaluation of the voids or local unevenness caused by the surface roughness can be carried out.

[0032] When determining the acoustic wave penetration depth parameter based on the interlayer bonding strength data, it is necessary to comprehensively consider the evaluation results of the resin-metal adhesion condition in the early stage. For example, if the bonding degree between the copper foil and the resin in a certain area is not firm, higher acoustic energy is more likely to be used to ensure sufficient penetration. During this process, the high-scattering area can be regarded as the part where significant scattering reflection has occurred on the surface. If the probe continues to detect at different angles or higher frequencies, part of the energy can penetrate to the interface between the inner copper foil and the resin layer. Therefore, in the high-scattering area, the second sub-band acoustic wave corresponding to the acoustic wave penetration depth parameter is applied. A common setting method is to adjust the frequency to slightly higher than the first sub-band (such as 15 MHz to 25 MHz), and adjust the pulse duration and transmission power to make it have better discrimination for the inner layer position. If there are thickness unevenness, voids or delamination at the interface between the inner copper foil and the resin layer in this sub-band, the echo energy will gradually attenuate and generate a recordable signal curve at the receiving end, which is called the acoustic wave attenuation data. If the attenuation amplitude is too large, it indicates that the interface bonding strength is poor, or there are multiple interface scattering surfaces. For example, in a laminated structure, if the inner copper foil is the third layer, the resin and the copper foil may be in a semi-peeled state due to hot pressing or uneven local filler distribution. After applying a higher frequency band, continuous and obvious energy jump points can be detected, and the attenuation degree can be judged accordingly. Through this process, the bonding differences between the inner layer and the outer layer can be detected separately, and the penetration depth and scattering intensity can be combined to distinguish whether there are only surface roughness problems or deep void problems. The design of the parameter range should, on the one hand, ensure that there is no excessive reflection on the high-scattering surface of the outer layer resulting in signal saturation, and on the other hand, ensure that sufficient energy enters the inner layer so that the attenuation waveform can be accurately collected.

[0033] After two scans of the first sub-band and the second sub-band are completed, acoustic wave scattering intensity data and acoustic wave attenuation data are obtained respectively. Amplitude superposition processing refers to performing point-by-point operations on the scattering intensity curve and the attenuation intensity curve in the amplitude direction in the same coordinate system, so as to synthesize a waveform that can better reflect the overall reflection energy distribution, and record it as acoustic wave amplitude data. If the outer scattering peak and the inner attenuation peak overlap in a certain area, an obvious amplitude anomaly peak will appear after superposition, which can be used to preliminarily locate the area with both surface roughness and interface peeling risk. Phase superposition processing uses a similar principle. After correcting the phase of the received signal, the scattering phase curve and the attenuation phase curve are superimposed point by point to obtain acoustic wave phase difference data. If the phase jump directions of the two interfaces are the same or the cumulative phase difference increases significantly, it indicates that the signal undergoes multiple interface reflections and refractions in this area, and there is a high probability of the existence of interlayer cavities or delamination phenomena. By separating and then combining the amplitude and phase, the roughness changes that only affect energy attenuation can be distinguished from the structural voids that have a more significant impact on the phase. If only the amplitude is observed, some delamination defects may be misled by high scattering; if only the phase is observed, it is difficult to quantify the fine surface roughness. Therefore, this two-way superposition processing can clearly present the comprehensive characteristics of outer layer roughness and inner layer peeling, and form a more targeted set of acoustic wave amplitude data and acoustic wave phase difference data, providing a reliable discrimination basis for further detections such as subsequent temperature loads or drilling processes.

[0034] Please continue to refer to Figure 1 , according to the pre-inspection data of the substrate, apply short-pulse multi-frequency acoustic waves to the target hole area during the laser drilling process, record the acoustic reflection signal at the moment of drilling, and perform local heat control on the hole wall area to obtain micro-hole acoustic reflection data; In an embodiment of the present invention, the step of applying short-pulse multi-frequency acoustic waves to the target hole area during the laser drilling process according to the pre-inspection data of the substrate, recording the acoustic reflection signal at the moment of drilling, and performing local heat control on the hole wall area to obtain micro-hole acoustic reflection data includes: Determine the acoustic wave action range and acoustic wave action time sequence of the hole area according to the pre-inspection data of the substrate, apply short-pulse acoustic waves of the first frequency band corresponding to the acoustic wave action range and the acoustic wave action time sequence to the target hole area, and record the substrate acoustic reflection reference data before drilling; According to the acoustic reflection reference data, apply short-pulse acoustic waves of the second frequency band layer by layer to the hole wall during the laser drilling ablation process, and record the acoustic wave amplitude mutation data and phase shift data during the ablation process of each layer; Determine a first temperature control parameter based on the sudden change data of the acoustic wave amplitude, apply a first local temperature gradient corresponding to the first temperature control parameter to the hole wall area, and record first hole wall temperature response data; determine a second temperature control parameter based on the phase shift data, apply a second local temperature gradient corresponding to the second temperature control parameter to the hole wall area, and record second hole wall temperature response data; Apply a third - frequency - band short - pulse acoustic wave to the hole wall according to the first hole wall temperature response data and the second hole wall temperature response data, record hole wall micro - crack acoustic scattering data and resin residue acoustic attenuation data, and combine the acoustic wave amplitude sudden change data, the phase shift data, the first hole wall temperature response data, the second hole wall temperature response data, the hole wall micro - crack acoustic scattering data, and the resin residue acoustic attenuation data to form micro - hole acoustic reflection data.

[0035] The following specifically describes the steps involved in the above - mentioned embodiments: Determine the acoustic wave action range and acoustic wave action timing in the hole area according to the substrate pre - inspection data. It is necessary to identify the coordinate positions corresponding to the target hole area, the possible defect distribution, and the acoustic characteristics of the material in this area from the existing substrate acoustic scanning results. During implementation, a series of emission pulse parameters can be set in the control software of the ultrasonic detection device, including pulse frequency, pulse width, and repetition timing, to ensure that the emitted acoustic wave only covers the hole area to be processed. The first - frequency - band short - pulse acoustic wave can be selected between 5 MHz and 15 MHz, and combined with the best incident angle and pulse energy determined in the early stage to avoid interfering with adjacent areas at the emission moment. When applying the first - frequency - band short - pulse acoustic wave to the target hole area, the acoustic detection device collects the echo signal before the laser ablation starts and forms the substrate acoustic reflection reference data before drilling based on parameters such as amplitude, phase, and attenuation. If the amplitude of the reference data at a certain position is abnormally high or the phase shows a jump, it can be inferred that there are local interface defects or non - uniformity of the inner - layer material at that place. The first frequency band used in this step is usually not too high to achieve stable penetration and collect uniform reflection information in a relatively large area. The consideration for this is to balance the resolution and penetration depth. When the material thickness and acoustic impedance difference are large, a clear overall reflection distribution can be obtained through a lower - frequency band, while avoiding missing possible superficial defects. Through this process, the initial acoustic state of the hole area can be obtained, which is convenient for dynamic comparison and determination during the subsequent laser drilling process.

[0036] According to the above acoustic reflection reference data, during the laser drilling and ablation process, short-pulse acoustic waves in the second frequency band are applied layer by layer to the hole wall. The method is to fix the ultrasonic probe on an adjustable bracket, maintaining an appropriate angle or arranging it adjacent to the laser processing head, so that laser ablation and acoustic detection can be carried out synchronously in the same hole area. The second frequency band is selected to be higher than the first frequency band, generally in the range of 15 MHz to 30 MHz, in order to more sensitively capture the material boundary between layers during hole wall ablation. As the laser gradually ablates the resin or metal layer by layer, the height of the hole wall surface will change and material detachment will occur, which will cause transient mutations in the amplitude and phase of the echo signal. The acoustic detection device records the collected echo signal in real time. Through the amplitude mutation data, the ablation degree or edge roughness of each layer of material can be judged, while the phase shift data can identify the situation where the adhesion between layers is not firm or microcracks are expanding. For example, after drilling off the outer copper foil, if there is local peeling between the resin layer and the copper foil, the phase jump will increase significantly. The sub-pulse timing in this step can be triggered synchronously or asynchronously according to the operating frequency of the laser, ensuring that the acoustic wave is applied in time for detection after each ablation is completed. The reason for choosing a higher frequency band is to improve the detection sensitivity to subtle structural changes in the hole wall and make a more refined resolution of the acoustic impedance difference between material layers.

[0037] When determining the first temperature control parameter based on the acoustic wave amplitude mutation data, it is necessary to focus on marking the positions where significant amplitude jumps occurred in the previous step, considering that the material at these positions is more likely to suffer local damage when heated or stressed. The operator can arrange a micro heat source (such as a small-area infrared heating plate) near the laser head or in the hole wall area, heat the corresponding position to the temperature gradient range corresponding to the first temperature control parameter within the set time, and then record the hole wall temperature response data through a thermal imager or temperature sensor. If new cracks or significant material expansion deformation occur on the hole wall during heating, the acoustic wave echo amplitude curve will change again. When determining the second temperature control parameter based on the phase shift data, the idea is similar to that of amplitude mutation, but more attention is paid to the possible inclined gaps or abnormal adhesion deep inside the material. If a large continuous shift is found during the phase detection stage, it indicates that shear cracks are likely to appear on the hole wall under high and low temperature cycles. At this time, the temperature gradient can be higher or lower, and the specific range can be selected in the range of 50°C to 100°C or a larger interval. By recording the first hole wall temperature response data and the second hole wall temperature response data, the stress release and deformation laws of the hole wall under different thermal gradients can be understood, so as to determine which parts are more likely to produce hole wall defects.

[0038] Based on the first hole wall temperature response data and the second hole wall temperature response data, a third-band short-pulse acoustic wave is applied to the hole wall. This step is mainly used to verify whether microcracks have been formed and whether there is resin residue after heating or cooling. The third band can be located between 30 MHz and 50 MHz to capture a higher-resolution microstructure of the hole wall. In actual operation, the ultrasonic probe can be aligned with the target position of the hole wall, and high-frequency short pulses are synchronously emitted and the scattering and attenuation conditions in the echo signal are recorded. If there are obvious microcracks, the scattering peaks will be relatively concentrated and have a higher amplitude; if the resin residue on the hole wall has not been completely removed in this section, the echo will show a characteristic viscous tail in the attenuation mode. After aggregating the acoustic wave amplitude mutation data, phase shift data, first hole wall temperature response data, second hole wall temperature response data, hole wall microcrack acoustic scattering data, and resin residue acoustic attenuation data, normalization or hierarchical mapping can be performed through data processing software to form an overall micro-hole acoustic reflection data. This comprehensive data can show the evolution process of the hole wall during the laser processing and thermal excitation processes, providing an intuitive evaluation basis for the fine hole wall quality of high-density interconnect boards. If both significant scattering and attenuation appear in the data analysis results, special optimization is required in subsequent processes or repeated drilling to avoid potential bubble generation or hole wall peeling. In this way, the probability of forming blind holes or voids in the subsequent chemical deposition and electroplating processes can be reduced, and the hole wall quality can better meet the high-reliability requirements of compact electronic products.

[0039] In an embodiment of the present invention, according to the acoustic reflection reference data, a second-band short-pulse acoustic wave is applied layer by layer to the hole wall during the laser drilling ablation process, and the acoustic wave amplitude mutation data and phase shift data during the ablation process of each layer are recorded, including: Apply a first sub-band short-pulse acoustic wave to the ablation area of the outer copper foil according to the acoustic reflection reference data, and record the metal layer acoustic wave reflection data and copper foil residue distribution data during the ablation process of the outer copper foil; According to the metal layer acoustic wave reflection data, apply a second sub-band short-pulse acoustic wave to the alternating ablation area of the resin layer and the inner copper foil, and record the material peeling acoustic characteristic data and resin decomposition acoustic characteristic data at the resin-metal interface; Combine and analyze the metal layer acoustic wave reflection data, the copper foil residue distribution data, the material peeling acoustic characteristic data, and the resin decomposition acoustic characteristic data to form acoustic wave amplitude mutation data and phase shift data.

[0040] The following specifically describes the steps involved in the above embodiment: When applying the first sub-band short-pulse acoustic wave to the ablation area of the outer copper foil based on the acoustic reflection reference data, it is necessary to first obtain the acoustic distribution information on the surface of the outer copper foil before laser processing and calibrate the ablation range in the control software. During implementation, a multi-band ultrasonic emission device can be used to send short-pulse acoustic signals with a pulse frequency between 10 MHz and 15 MHz to the area of the outer copper foil that may be affected by the laser, and the echo characteristics are recorded in real time at the receiving end. The acoustic wave reflection data of the metal layer reflects the echo intensity and phase of the copper foil at different depths and etching processes; the copper foil residue distribution data is calculated by the scanning system and is used to mark the metal debris or oxide layer that still exists after local ablation. If the acoustic wave reflection value of a certain area suddenly drops and the residue distribution value increases significantly, it indicates that loose copper foil fragments are generated by laser etching here, which may affect the hole-forming quality of the subsequent resin layer. The range of 10 MHz to 15 MHz is selected in this step to simultaneously have high sensitivity to the metal surface and the ability to identify local micro-defects, which helps to timely distinguish the metal integrity near the hole opening during the outer layer etching.

[0041] When applying the second sub-band short-pulse acoustic wave to the alternating ablation area of the resin layer and the inner copper foil based on the obtained acoustic wave reflection data of the metal layer, it is necessary to focus on monitoring the delamination or decomposition of the inner interface and the resin material. During implementation, the emission frequency can be adjusted to the range of 15 MHz to 25 MHz, and the pulse width and power are maintained within the peak range allowed by the system. The acoustic characteristic data of material peeling at the resin-metal interface is identified by observing the high-amplitude multiple reflection peaks or phase anomalies in the echo. If the degree of peeling increases, the echo pattern will show discontinuity; the acoustic characteristic data of resin decomposition can be judged by the characteristic peak shape when the resin generates gasification or carbonization after the ablation temperature rises. For example, when the laser gradually removes the contact surface between the resin and the inner copper foil layer by layer, if a significant embrittlement waveform appears in the resin is monitored at the receiving end, it indicates that the material has undergone coking or large-area shrinkage under the thermal shock. The range higher than the first sub-band is selected in this step for the consideration of more delicate detection of the deep resin-metal interface, enabling the system to distinguish the material peeling states caused by outer layer etching and inner layer heating.

[0042] When combining the acoustic reflection data of the metal layer, the residual distribution data of the copper foil, the acoustic characteristics data of material peeling, and the acoustic characteristics data of resin decomposition for analysis, the integrated software can perform multiple matching of amplitude and phase for each item of information in the same coordinate system. If the residual of the outer copper foil and the peeling of the inner layer material occur simultaneously in a certain area and the resin decomposition sign is obvious, an abrupt change in acoustic wave amplitude will be formed in the analysis result, manifested as a large fluctuation in the echo intensity at local points; if the phase comparison indicates multiple jumps in the refraction path between the copper foil and the resin, an obvious abnormality in the phase shift data will occur. By synthesizing these characteristics, it is possible to accurately identify whether irreversible resin coking or interface voids are generated during the ablation process, avoiding potential hazards in subsequent through-hole electroplating. This process incorporates the outer metal residue and the inner interface change into the same framework for evaluation, which can not only clarify the true process of each ablation layer but also better monitor the evolution of potential defects at different depths. This idea of cross-layer data combination improves the control of the microvia forming quality of high-density interconnect boards and provides an accurate reference position for potential hazards such as bubbles or voids in subsequent electroless copper plating and electroplating processes.

[0043] Please continue to refer to Figure 1 , before the electroless copper plating treatment, according to the microvia acoustic reflection data, independently regulate the temperature of multiple areas on the board surface, record the multi-frequency acoustic scanning data of the hole walls in each area under the excitation of a thermal pulse, and form a regional acoustic characteristic map; In an embodiment of the present invention, the step of, before the electroless copper plating treatment, independently regulating the temperature of multiple areas on the board surface according to the microvia acoustic reflection data, recording the multi-frequency acoustic scanning data of the hole walls in each area under the excitation of a thermal pulse, and forming a regional acoustic characteristic map includes: Before the electroless copper plating treatment, according to the acoustic wave amplitude mutation area and the phase shift area in the microvia acoustic reflection data, divide the board surface into multiple temperature-independent regulation units, and set independent temperature control parameters for each of the temperature-independent regulation units; According to the temperature control parameters of each temperature-independent regulation unit, apply a first thermal pulse wave to the hole walls of each area, and apply a first-frequency acoustic scanning wave to the hole walls at the peak moment of the first thermal pulse wave, and record the acoustic wave scattering data caused by the transient expansion of the hole walls; According to the acoustic wave scattering data, determine the stress response parameters of the hole walls in each area, apply a second thermal pulse wave to each temperature-independent regulation unit, and apply a second-frequency acoustic scanning wave to the hole walls at the valley moment of the second thermal pulse wave, and record the acoustic wave attenuation data caused by the transient contraction of the hole walls; According to the acoustic wave attenuation data, determine the strain distribution parameters of the hole walls in each area, apply a third thermal pulse wave to each temperature-independent regulation unit, and apply a third-frequency acoustic scanning wave to the hole walls during the duration of the third thermal pulse wave, and record the acoustic characteristics data of microcracks and the data of the void migration trend of the hole walls; Partition and combine the acoustic wave scattering data, the acoustic wave attenuation data, the acoustic characteristics data of the hole wall microcracks, and the cavity migration trend data according to the temperature independent control units to form a regional acoustic characteristics map.

[0044] The following specifically describes the steps involved in the above embodiments: Before the electroless copper plating treatment, divide the plate surface into multiple temperature independent control units according to the acoustic wave amplitude mutation region and the phase shift region in the micro-hole acoustic reflection data. The specific method is to first draw a distribution map of the micro-hole positions and acoustic signals on the data processing platform, and mark the regions with significant amplitude changes or obvious phase drifts as high-risk sections. Subsequently, according to the material thickness and the plate surface layout, integrate these high-risk sections and the relatively stable sections around them into several independent temperature control units. Each temperature independent control unit is set with independent temperature control parameters. A common method is to arrange local heating modules or infrared radiation sources below or on the side of the unit. If the acoustic wave amplitude mutation regions are relatively scattered, they can be separately divided into a group to accurately adjust their heating amplitude; if the phase shift regions are continuous and concentrated, set a higher or lower temperature range and cooperate with a time pulse scheme for heating or cooling. The reason for dividing into multiple temperature units is to retain the room for targeted adjustment for different defect types: amplitude mutation often indicates non-uniformity on the surface or near the surface of the hole wall, and may require a relatively gentle temperature gradient; phase shift is generally related to deep peeling or cavity formation, and requires a larger range or more intense temperature perturbation to reveal internal problems. This can execute appropriate temperature curves for different control units respectively during the next thermal pulse application and obtain more distinguishable acoustic feedback.

[0045] According to the temperature control parameters of each temperature independent control unit, apply a first thermal pulse wave to the regional hole wall first, and apply a first frequency band acoustic scanning wave at the peak moment. The first thermal pulse wave usually simulates the transient response of the hole wall in the medium temperature range through short-time heating. The common parameter range is a temperature rise of 60°C to 80°C and the time is maintained for several seconds. The first frequency band acoustic scanning wave can be selected in the range of about 10 MHz to 15 MHz. Align the acoustic probe to the target hole area and scan under the thermal pulse peak to record the acoustic wave scattering data caused by the transient expansion of the hole wall. This scattering data is manifested as the change in echo intensity and waveform. If the hole wall material has a small amount of deformation or a small range of protrusions under the thermal shock, the scattering peak will mutate. The reason for choosing the medium temperature range is to facilitate observing the early stress distribution when the material has inconsistent thermal expansion, and using acoustic waves in the range of 10 MHz to 15 MHz can achieve a balance between better penetration and sensitivity. Through this process, it is possible to identify which control units have obvious material displacement or edge deformation after local heating, and thus infer the preliminary stress bearing capacity of the hole wall.

[0046] After determining the stress response parameters of the pore wall based on the acoustic wave scattering data, a second thermal pulse wave is applied to the same temperature independent control unit, and a second frequency band acoustic scanning wave is applied at the valley moment. This step mainly observes the instantaneous contraction state of the pore wall during a certain degree of cooling or temperature reduction process to capture whether the reverse stress release will cause new cracks or delamination. The parameter range of the second thermal pulse wave can be set between 40 °C and 60 °C or lower to form a sufficient temperature difference with the peak temperature of the previous step, thereby amplifying the thermal contraction effect of the pore wall material. The second frequency band acoustic scanning wave is usually higher than the first frequency band, about 15 MHz to 25 MHz. Through this high-frequency band scanning, finer cracks or interface delamination can be captured at the moment when the pore wall cools down, and the recorded acoustic wave attenuation data is caused by the transient contraction of the pore wall. If there is local embrittlement or microcracks in the pore wall, obvious wave valleys or irregular delays will appear in the attenuation curve in a short time. The reason for choosing to detect expansion first and then contraction is that some defects will only close or further tear during the cooling stage, resulting in different performances from when the temperature rises. By comparing the acoustic curves before and after, it can be confirmed which control units are more likely to fluctuate under thermal cycling, so as to further screen in the next stage.

[0047] After determining the strain distribution parameters of the pore wall in each region based on the acoustic wave attenuation data, a third thermal pulse wave is applied to each temperature independent control unit, and a third frequency band acoustic scanning wave is applied to the pore wall during the duration of this pulse to record the acoustic characteristic data of the pore wall microcracks and the data on the migration trend of the voids. The third thermal pulse wave is usually carried out under high temperature or rapid temperature rise conditions around 100 °C, which can make the relative displacement of potential cracks or pores appear faster. The third frequency band acoustic scanning wave can be selected in the range of 25 MHz to 35 MHz, focusing on detecting the acoustic anomalies of the microcrack propagation under high temperature stress and the gas transfer from the voids to the pore wall. If the scattering peak continues to increase or the echo phase has multiple misalignments in a certain section after rising to high temperature, it indicates that there has been obvious expansion or migration of microcracks or voids in the pore wall. The purpose of the high temperature stage is to further amplify the thermal expansion difference of the defects inside the material, ensuring that even the cracks that were not detected at medium and low temperatures in the initial stage will be amplified under high temperature conditions and clearly captured in the acoustic scanning. Through this process, the final behavior of each temperature independent control unit under high temperature stress can be qualitatively and quantitatively recorded.

[0048] Finally, the acoustic wave scattering data, acoustic wave attenuation data, acoustic characteristics data of microcracks on the hole wall, and data on the migration trend of voids are partitioned and combined according to the temperature independent control units to form a regional acoustic characteristics map. This map can be presented in the data analysis software in the form of multi-layer superposition or color contrast, with different colors or markings representing the acoustic anomalies or defect distributions at different temperature segments. For example, if an abnormal scattering occurs in a certain unit during the first thermal pulse and continues to expand during the second and third thermal pulses, it can be regarded as a high-risk section, and measures such as extending the deposition time or local reinforcement need to be taken during electroless copper plating. For units that are relatively stable both at medium temperature and high temperature, they can be classified as low-risk areas, and the conventional process can be maintained during subsequent copper plating. By partitioning and combining data such as scattering and attenuation, the dynamic evolution process of hole wall defects in each temperature range can be analyzed, and the gradual diffusion path of voids from small to large can be further evaluated. It can be seen that by adopting the strategy of independent temperature control and supplemented by acoustic scanning waves of different frequency bands, a comprehensive inspection of the micro-hole walls of HDI boards before electroless copper plating can be achieved, reducing the risk of bubble encapsulation caused by micro-voids or material delamination in the holes during subsequent metallization, and providing a basis for customized process parameters for subsequent electroplating.

[0049] Please continue to refer to Figure 1 , during the electroless copper plating process, according to the regional acoustic characteristics map, multi-frequency acoustic wave excitation is applied to the hole area at a preset time interval, and the attenuation curve of the acoustic reflection signal during the formation of the metal seed layer is recorded to obtain the monitoring data of the copper plating process; In an embodiment of the present invention, the step of, during the electroless copper plating process, according to the regional acoustic characteristics map, applying multi-frequency acoustic wave excitation to the hole area at a preset time interval, recording the attenuation curve of the acoustic reflection signal during the formation of the metal seed layer, and obtaining the monitoring data of the copper plating process includes: During the electroless copper plating process, determine the copper plating monitoring time sequence of each hole area according to the regional acoustic characteristics map and the preset time interval, pause the flow of the electroless copper plating solution at the pause point of each copper plating monitoring time sequence, apply a copper plating start detection wave to the hole area, and record the acoustic reflection characteristic data during the nucleation stage of the metal seed layer; Apply a copper plating growth detection wave to different hole areas according to the acoustic reflection characteristic data, and record the metal grain growth distribution data and the interface bonding state data; According to the metal grain growth distribution data and the interface bonding state data, apply a copper plating process detection wave to the hole area, and record the continuity change curve of the seed layer and the change curve of the hole wall coverage; Perform dynamic feature analysis on the continuous change curve of the seed layer and the change curve of the hole wall coverage according to the preset time interval, and combine the acoustic reflection feature data, the metal grain growth distribution data, the interface bonding state data, and the dynamic feature analysis results to form the monitoring data of the electroless copper deposition process.

[0050] The following specifically describes the steps involved in the above embodiments: When setting the electroless copper deposition monitoring time sequence for each hole area according to the regional acoustic feature map and the preset time interval, it is necessary to first read the hole wall information of high risk, low risk, and medium risk in the acoustic feature map in the data processing software. The preset time interval refers to the time point when the solution flow is paused at regular intervals in the electroless copper deposition tank, so that the detection device emits an acoustic signal and collects the echo in a stable environment. During implementation, an electric valve control device can be installed on the electroless copper deposition tank, and through a control signal synchronized with the scanning system, the solution circulation is closed during the corresponding period to keep the plating solution in the hole relatively static. At this time, an electroless copper deposition start detection wave is emitted for the hole area. Generally, the pulse frequency is selected between 10 MHz and 15 MHz, and the acoustic reflection feature data in the nucleation stage of the metal seed layer is recorded at the receiving end. If a reflection peak shape different from the normal range is detected in a certain hole area, it indicates that the adhesion situation or nucleation rate in this area is relatively uneven, and local stirring needs to be strengthened or the electroless copper deposition time needs to be extended during subsequent operations. The consideration of this step is to ensure the monitoring accuracy in the initial stage of electroless copper deposition, so as to identify whether there are problems such as incomplete seed layer coverage or poor interface bonding in the hole area.

[0051] According to the acoustic reflection feature data obtained in the previous step, an electroless copper deposition growth detection wave can be applied to different hole areas to track the growth distribution of metal grains on the resin hole wall and the interface bonding state. During implementation, after the electroless copper deposition solution resumes flowing, it will provide continuous copper ion deposition opportunities for the hole wall, and the acoustic probe intermittently emits detection waves to the target hole area at a pulse frequency of 15 MHz to 25 MHz, and the receiving end will obtain the echo changes during the metal growth process. If the copper grains on the hole wall are evenly distributed, the amplitude of the echo waveform will gradually increase over time and remain relatively smooth; if there are local agglomerations or voids, the echo curve may show abnormal amplitude jumps at certain moments. At the same time, the interface bonding state data is obtained based on the acquisition of the attenuation coefficient and phase information. If there is peeling between the deposited grains and the resin, the attenuation coefficient will increase sharply. This can identify unstable growth areas in real time and adjust the corresponding process parameters in a timely manner, such as adjusting the local solution flow rate or adding auxiliary complexing agents, to make the deposition process more balanced. The consideration of doing this is to prevent stress concentration on the hole wall or microbubble hazards in the later stage caused by insufficient coverage in the early stage.

[0052] Based on the metal grain growth distribution data and the interface bonding state data, a detection wave can be applied to the target hole area during the copper deposition process, and the change curves of the seed layer continuity and the hole wall coverage are recorded. The detection wave during the copper deposition process can be selected in the range of 25 MHz to 35 MHz to accurately capture the transition characteristics of the grain growth from dispersion to connection. The change curve of the seed layer continuity mainly judges the coverage degree of the metal film on the hole wall by monitoring the echo amplitude and time delay. Once it shows a stable rise and reaches the threshold value during a certain period, it indicates that the hole wall already has a sufficiently complete metal layer. The change curve of the hole wall coverage is analyzed by a zoning algorithm. If it is detected that a large area of the hole wall still shows non-metal reflection locally, the coverage remains in the low-value area, and it is necessary to extend the copper deposition time additionally or strengthen the stirring locally to ensure that there is no risk of hole wall exposure in the subsequent electroplating stage. The consideration of the above steps is reflected in the phased monitoring strategy, avoiding ending the copper deposition too early or too late, and ensuring that the metal adhesion of the micro-holes and the hole walls meets the established requirements.

[0053] The dynamic characteristic analysis is carried out on the change curves of the seed layer continuity and the hole wall coverage according to the preset time interval, and the acoustic reflection characteristic data, the metal grain growth distribution data, the interface bonding state data and the dynamic characteristic analysis results are combined to form the monitoring data of the copper deposition process. The implementation method is to input the acoustic waveforms and derived parameters collected in the previous stages into the comprehensive analysis module, and by means of time series comparison and curve fitting methods, the adhesion degree and growth uniformity of the same hole area at different times are extracted. If a certain hole area shows a stable rise in the waveform and a low grain distribution dispersion under multiple pause detections, the copper deposition process can be determined to be stable and safe; if a certain hole area shows waveform fluctuations or phase mutations multiple times, the monitoring data of the copper deposition process will automatically generate a warning prompt to remind to take adjustment measures. The integrated data can be packaged and output for further reference during the formal electroplating, realizing a segmented adaptive process. Through this process, defects or uneven growth trends can be detected in time before the seed layer reaches full maturity, thus avoiding the formation of covered micro-holes or poorly adhered areas in the hole wall later, and providing guarantee for the long-term stable operation of the high-density board of the notebook computer camera module.

[0054] Please continue to refer to Figure 1 , during the electroplating process, according to the monitoring data of the copper deposition process, a periodic thermal excitation and fluid disturbance are applied to the board surface, the propagation characteristics of multi-frequency acoustic waves in the electroplating solution are recorded, and the electroplating dynamic monitoring data are obtained through adaptive signal processing; In an embodiment of the present invention, the step of applying a periodic thermal excitation and fluid disturbance to the board surface according to the monitoring data of the copper deposition process during the electroplating process, recording the propagation characteristics of multi-frequency acoustic waves in the electroplating solution, and obtaining the electroplating dynamic monitoring data through adaptive signal processing includes: During the electroplating process, according to the seed layer continuity change curve in the copper deposition process monitoring data, a first electroplating thermal pulse is applied to the high-density micro-hole clustering area, and a second electroplating thermal pulse is applied to the surrounding trace area, and the temperature gradient distribution data of the micro-hole area and the trace area is recorded; According to the temperature gradient distribution data, a first fluid perturbation is applied to the high-density micro-hole clustering area, and a second fluid perturbation is applied to the surrounding trace area. Under the action of the dual-fluid perturbation, an electroplating acoustic detection wave is applied to the deep and shallow micro-hole areas, and the acoustic propagation attenuation data of micro-holes with different depth-to-diameter ratios is recorded; According to the acoustic propagation attenuation data, a low-frequency electroplating monitoring wave is applied to the high-density micro-hole clustering area, and a high-frequency electroplating monitoring wave is applied to the surrounding trace area, and the current density distribution data at the bottom of the micro-hole and the plating stress distribution data on the hole wall are recorded; Perform sub-region compensation operations on the current density distribution data, record the plating thickness distribution curves of the deep and shallow micro-holes, perform hierarchical processing on the plating stress distribution data on the hole wall, and record the bubble migration characteristic curves of micro-holes with different depth-to-diameter ratios; Perform adaptive signal filtering processing on the plating thickness distribution curve and the bubble migration characteristic curve, and combine the temperature gradient distribution data, the acoustic propagation attenuation data, the current density distribution data, the plating stress distribution data on the hole wall, the plating thickness distribution curve after adaptive signal filtering processing, and the bubble migration characteristic curve after adaptive signal filtering processing to form electroplating dynamic monitoring data.

[0055] The following specifically describes the steps involved in the above embodiments: Based on the seed layer continuity change curve in the monitoring data during the electroless copper plating process, it is necessary to identify which areas belong to high-density microvia clusters and which areas are mainly covered by traces. The specific method is to read the seed layer integrity information obtained in the previous stage, aggregate the closely distributed microvia areas together in the data visualization software, mark them as high-density microvia cluster areas, and then mark the areas mainly with traces or large-area copper surfaces around as peripheral trace areas. Based on this division, a first electroplating thermal pulse is applied to the high-density microvia cluster areas, and a second electroplating thermal pulse is applied to the peripheral trace areas. The first electroplating thermal pulse is generally set in the range of 50°C to 70°C, so that the temperature of the plating solution in the clustered holes can rise rapidly, thereby improving the solution fluidity and accelerating the chemical reaction in the holes; the second electroplating thermal pulse can be slightly lower, such as between 40°C and 60°C, to ensure that the temperature of the plating solution in the trace area maintains an upward trend without causing local overheating. When performing this operation, the common method is to control the temperature of different zones in the electroplating tank, so that the heaters in the corresponding areas work independently. By using a temperature sensor or an infrared thermometer to detect the plate surface in these two different temperature ranges at the end of the thermal pulse, the temperature gradient distribution data of the microvia area and the trace area can be obtained. If a steep rise in the gradient is detected in the high-density microvia cluster area, it indicates that the thermal load in this area has increased significantly, which is suitable for subsequent enhancement of local disturbance or adjustment of the current density to avoid bubble accumulation at the bottom of the holes. The reason for setting different thermal pulse ranges is that the temperature response requirements of microvias and large-area traces are different, and they need to be treated separately to improve the uniformity and quality stability of the finished product.

[0056] According to the obtained temperature gradient distribution data, a first fluid disturbance can be applied to the high-density microvia cluster areas in sequence, a second fluid disturbance can be applied to the peripheral trace areas, and an electroplating acoustic detection wave can be emitted under the action of the dual-fluid disturbance. During implementation, the electroplating tank is often equipped with a programmable stirring paddle or a bubble injection device, which can apply different intensities of fluid disturbance to specific zones. The first fluid disturbance can be set with a higher flow rate or a more significant stirring frequency to make the plating solution in the microvia area flow rapidly; the second fluid disturbance is relatively gentle to prevent excessive solution turbulence near the traces from affecting the coating uniformity. In this state, an electroplating acoustic detection wave (adjustable from 10 MHz to 20 MHz) is emitted to the deep and shallow microvia areas, and the probe can be set above the plate surface and scanned in real time through water-based coupling or electroplating solution coupling. The acoustic propagation attenuation data is obtained by monitoring the echo energy and time delay. If there are large bubbles or accumulated precipitates in the hole, the acoustic attenuation will increase significantly, and the waveform will also show irregular oscillations. After recording these attenuation data, the flow guiding effects of holes with different depth-to-diameter ratios under the dual-fluid disturbance can be compared, and abnormal deposition points caused by insufficient liquid injection at the bottom of local holes can be identified. The reason for setting different fluid disturbance intensities is that deep holes rely more on a high flow rate of the solution to carry away bubbles or residues than shallow holes, and using too high a flow rate in the large trace area may cause the metal surface to be uneven.

[0057] According to the acoustic propagation attenuation data, a low-frequency electroplating monitoring wave can be applied to the high-density micro-hole clustering area, a high-frequency electroplating monitoring wave can be applied to the surrounding wiring area, and the current density distribution data at the bottom of the micro-holes and the stress distribution data of the plating layer on the hole wall can be recorded. The low-frequency electroplating monitoring wave (such as 5 MHz to 10 MHz) has stronger penetration in deep holes and better recognition of large-scale defects, which is conducive to detecting whether the current density at the bottom of the hole is too high or too low. If there are electroplating dead corners or bumps at the bottom of the deep hole, the echo intensity and phase of this waveband will quickly deviate from the normal values. The high-frequency electroplating monitoring wave (such as 15 MHz to 25 MHz) is suitable for fine detection of the wiring area. If the stress of the plating layer at the edge of the wiring is too high or cracks occur, the high-frequency signal attenuation and phase jump will increase significantly. During implementation, a multi-band ultrasonic detection device can be used to scan the entire board surface in the order of low frequency first and then high frequency within the same measurement cycle, and the echoes can be recorded in different time periods. If the current density in the deep hole is significantly too high, a spike will appear in the echo energy diagram; if there are cracks in the wiring, local phase distortion will appear in the high-frequency data. The reason for designing this parallel idea of low frequency and high frequency is that different regions require different detection focuses. In order to quickly locate potential over-electroplating or edge stress concentration in deep holes, different wavebands need to be used respectively to provide a more reliable judgment basis.

[0058] Perform regional compensation operations on the current density distribution data, record the plating thickness distribution curves of deep and shallow micro-holes, and perform hierarchical processing on the stress distribution data of the plating layer on the hole wall to obtain the bubble migration characteristic curves of micro-holes with different depth-to-diameter ratios. Regional compensation operation means that after distinguishing the high-density micro-hole clustering area from the general hole area or the wiring area in the detection software, different reference current density models are set, and difference correction is performed according to the actually measured time-sequence curve. For example, if the measured current at the deep hole is high and accompanied by large fluctuations, the corresponding error amount is subtracted in the subsequent calculation to obtain a thickness distribution closer to the actual plating growth rate. The stress distribution data of the plating layer on the hole wall can be obtained based on stress measurement sensors or stress calculation methods based on ultrasonic echo attenuation and phase characteristics. If there is a sudden change in the pressure gradient in the hole or there are bubbles rising along the hole wall, it will show a unique curve impact form in the time-sequence diagram. The bubble migration characteristic curve is thus formed, which can help determine whether there are invisible voids caused by bubbles being covered by metal or whether they are likely to spread in the subsequent high-temperature environment. Splitting deep holes and shallow holes in this way is to more accurately evaluate the actual situation of each depth-to-diameter ratio during the electroplating process, rather than generally treating all holes as the same situation, which improves the capture rate of potential bubble problems.

[0059] Perform adaptive signal filtering on the aforementioned coating thickness distribution curve and bubble migration characteristic curve, and then combine the temperature gradient distribution data, acoustic propagation attenuation data, current density distribution data, stress distribution data of the coating on the hole wall, the filtered coating thickness distribution curve, and the filtered bubble migration characteristic curve to form electroplating dynamic monitoring data. Adaptive signal filtering can adopt common algorithms such as wavelet transform or adaptive harmonic decomposition to remove the random noise and interference parts and retain the stable signals generated by the actual metal growth or bubble evolution. For example, the instantaneous spikes that appear due to stirring impact in the high-frequency monitoring wave time series can be filtered out. If bubbles persist in the holes, repeatable peaks or valleys will be formed in the curve. By combining the filtered curve with the previously recorded temperature and acoustic propagation attenuation information, a comprehensive judgment on the growth status and stress distribution of each hole in different electroplating stages can be established and presented in the form of data charts or three-dimensional visualizations. In this way, the real-time monitoring and dynamic adjustment of the entire electroplating process can be effectively coordinated, avoiding the hidden danger of good appearance but internal voids, and can also remain stable in subsequent high-temperature applications (such as the long-term operation of laptop cameras). In summary, the design of these steps starts from the differentiated requirements of high-density micro-holes and wiring areas, realizes process control through thermal pulses, fluid disturbances, and multi-frequency acoustic detection, and uses programmable sub-region compensation and signal filtering algorithms for data integration, greatly improving the detection rate and processing efficiency of bubbles and internal stress.

[0060] Please continue to refer to Figure 1 , after electroplating is completed, according to the electroplating dynamic monitoring data, perform temperature cycling and stress excitation on the finished product, record the acoustic wave reflection data inside the holes, and obtain the evaluation result of the internal structure of the micro-vias through multi-dimensional data analysis.

[0061] In an embodiment of the present invention, the step of, after electroplating is completed, according to the electroplating dynamic monitoring data, perform temperature cycling and stress excitation on the finished product, record the acoustic wave reflection data inside the holes, and obtain the evaluation result of the internal structure of the micro-vias through multi-dimensional data analysis includes: After electroplating is completed, perform sub-region evaluation on the coating on the inner wall of the micro-holes according to the electroplating dynamic monitoring data, determine the temperature cycling parameters and stress excitation parameters, apply the first temperature cycle to the finished product, and record the thermal cycle gradient data and cyclic stress accumulation data of each micro-hole region; According to the thermal cycle gradient data and the cyclic stress accumulation data, apply the second temperature cycle to the finished product, and at the same time apply the finished product evaluation acoustic wave to the inner wall of the micro-holes, and record the acoustic attenuation trend data and acoustic phase shift characteristic data inside the micro-holes; According to the acoustic attenuation trend data and the acoustic phase shift characteristic data, apply mechanical stress excitation to the micro-holes, and record the structural deformation parameters and void evolution data of the coating on the inner wall of the micro-holes; Comprehensively process the thermal cycle gradient data, the cyclic stress accumulation data, the acoustic attenuation trend data, the acoustic phase shift characteristic data, the structural deformation parameters, and the void evolution data to form an evaluation result of the internal structure of the microvia.

[0062] The following specifically describes the steps involved in the above embodiments: After electroplating is completed, the plating layer on the inner wall of the micro-holes is evaluated in zones based on the electroplating dynamic monitoring data. The main method is to map the current density distribution, bubble migration trajectory, and stress information of the plating layer on the hole wall in the previous stage into the coordinate system of the entire board, and then separately process the holes with different depth-to-diameter ratios and the adjacent trace areas. By analyzing these parameters, it is possible to identify the parts prone to cracks or blind areas at the bottom of the holes, so as to determine the subsequent temperature cycle parameters and stress excitation parameters. The first temperature cycle can be set as a temperature rising and falling process within the range of 50°C to 70°C, and multi-point thermoelectric coupling monitoring is carried out on each micro-hole area of the finished product during the temperature rising or falling period. The thermal cycle gradient data is obtained by recording the instantaneous temperature difference between the surface and the inner layer of the hole wall through a temperature sensor or an infrared detection device, and the cyclic stress accumulation data is calculated by a stress detection module or an acoustic algorithm relying on micro-deformation perception. If a significant increase in the thermal gradient and continuous superposition of stress values occur in a certain group of holes within this temperature range, more stringent high-temperature inspections are required subsequently to avoid cracks or voids in the holes in these areas under large temperature changes.

[0063] According to the thermal cycle gradient data and the cyclic stress accumulation data, apply a second temperature cycle to the finished product, and at the same time apply an evaluation acoustic wave for the finished product to the inner wall of the micro-holes to collect the acoustic attenuation trend data and phase shift characteristic data inside the micro-holes. The second temperature cycle is generally wider than the temperature range in the previous step, such as 60°C to 100°C or higher, aiming to simulate the extreme thermal environment that may occur during the long-term operation of a laptop camera. The evaluation acoustic wave for the finished product can be emitted by a multi-band ultrasonic emission device, and the probe cooperates with the coupling agent to send high-frequency or medium-frequency pulsed waves into the inner wall of the hole. The echo signal will be attenuated and phase-shifted due to micro-voids or defects at the junction of the metal and the resin. The attenuation trend data can reflect the bonding firmness of the metal layer during the thermal expansion and contraction process. If the air inside the micro-voids becomes free during heat diffusion, the echo energy will be significantly reduced; the phase shift characteristic data is related to the depth of the defect or the degree of delamination. If a slight tear occurs locally on the hole wall, the echo phase will jump at this point. Adjusting the second temperature cycle parameters in this way helps to truly evaluate the stability of the plating layer under a larger thermal stress range.

[0064] According to the acoustic attenuation trend data and phase shift characteristic data, mechanical stress excitation can be applied to the micropores to record the structural deformation parameters and void evolution data of the inner wall coating of the micropores. The mechanical stress excitation method includes configuring a vibration source on the back or side of the finished board to make the hole wall produce controlled deformation within a limited range, so as to observe the response of the acoustic signal to the external force impact. The structural deformation parameters can be obtained by detecting the micro-displacement of the inner wall of the hole during the synchronization period of the probe and the vibration source; the void evolution data is combined with the phase shift and attenuation changes mentioned above to evaluate whether the encapsulated bubbles in the hole will continue to spread along the micro-cracks of the coating. For example, if the metal layer of the hole wall is not sufficiently bonded to the substrate, there will be instantaneous reflection enhancement or abnormal scattering distribution under stress excitation, and the process of the cavity moving or expanding in the aperture direction can be tracked in the detection software. This step focuses on the mechanical and acoustic coupling of the hole wall to ensure that a strong electrical connection can be maintained in harsh use environments.

[0065] The thermal cycle gradient data, cyclic stress accumulation data, acoustic attenuation trend data, acoustic phase shift characteristic data, structural deformation parameters and void evolution data are processed comprehensively, and finally the internal structure evaluation results of the micro-through hole are formed. The comprehensive processing can adopt a multi-dimensional data fusion algorithm to superimpose the acoustic test curves under different temperature ranges and stress ranges in the same coordinate system, and determine the distribution and failure mechanism of high-risk holes through trend comparison and abnormal clustering. If a hole area remains stable in multiple rounds of temperature cycles and mechanical excitations, it means that the electroplating layer and the substrate are well combined; if multiple parameters are detected to jump violently at the same time, it indicates that the internal voids or cracks have entered the irreversible stage, and corrective measures need to be taken in terminal screening or thickening treatment. This dynamic evaluation in the finished product state allows the HDI board of the laptop camera module to be fully verified in a large temperature difference and mechanical vibration environment to reduce the probability of intermittent connection failures during use. Combined with the segmented analysis of each data, the goal of balancing high-precision detection and large-scale production capacity requirements can be achieved.

[0066] The above description is only a preferred embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification and drawings under the inventive concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. An HDI board manufacturing process for a laptop camera module, characterized in that, Including: Performing multi - frequency acoustic wave penetration and temperature gradient processing on a substrate to obtain substrate acoustic response data and thermal response data, and using the acoustic response data and thermal response data as substrate pre - inspection data; According to the substrate pre - inspection data, applying short - pulse multi - frequency acoustic waves to the target hole area during laser drilling, recording the acoustic reflection signal at the moment of drilling, and performing local heat regulation on the hole wall area to obtain micro - hole acoustic reflection data; Before chemical copper plating treatment, according to the micro - hole acoustic reflection data, independently regulating the temperature of multiple areas on the board surface, recording the multi - frequency acoustic scanning data of the hole walls in each area under thermal pulse excitation, and forming a regional acoustic characteristic map; During chemical copper plating, according to the regional acoustic characteristic map, applying multi - band acoustic waves to the hole area at preset time intervals, recording the attenuation curve of the acoustic reflection signal during the formation of the metal seed layer, and obtaining copper plating process monitoring data; During electroplating, according to the copper plating process monitoring data, applying periodic thermal excitation and fluid disturbance to the board surface, recording the propagation characteristics of multi - frequency acoustic waves in the electroplating solution, and obtaining electroplating dynamic monitoring data through adaptive signal processing; After electroplating, according to the electroplating dynamic monitoring data, performing temperature cycling and stress excitation treatment on the finished product, recording the acoustic wave reflection data inside the holes, and obtaining the evaluation result of the internal structure of the micro - via through multi - dimensional data analysis.

2. The manufacturing process of the HDI board for the laptop camera module according to claim 1, characterized in that, The performing multi - frequency acoustic wave penetration and temperature gradient processing on a substrate to obtain substrate acoustic response data and thermal response data, and using the acoustic response data and thermal response data as substrate pre - inspection data includes: Applying acoustic waves of a first frequency band to an acoustic coupling medium layer disposed between adjacent resin layers of the substrate, and recording the acoustic wave buffer stress data and inter - layer bonding strength data of the acoustic coupling medium layer; According to the acoustic wave buffer stress data and the inter - layer bonding strength data, applying acoustic waves of a second frequency band to the interface between the resin layer and the copper foil layer of the substrate, and recording the acoustic wave amplitude data and acoustic wave phase difference data at the interface bonding part; Determining a first temperature range according to the acoustic wave amplitude data, applying a first temperature gradient to the substrate in the first temperature range, and recording the first thermal stress distribution data; determining a second temperature range according to the acoustic wave phase difference data, applying a second temperature gradient to the substrate in the second temperature range, and recording the second thermal stress distribution data; performing acoustic scanning on the thermal stress concentration area through the acoustic coupling medium layer according to the first thermal stress distribution data and the second thermal stress distribution data, and recording the acoustic characteristic data of the internal micro - voids and abnormal inter - layer bonding areas of the substrate; Performing stress compensation processing on the acoustic wave buffer stress data and the inter - layer bonding strength data according to the thermal stress distribution data, performing abnormal correction processing on the acoustic wave amplitude data and the acoustic wave phase difference data according to the acoustic characteristic data, and combining the data after compensation processing and correction processing to form substrate pre - inspection data.

3. The manufacturing process of the HDI board for the laptop camera module according to claim 2, characterized in that, Applying an acoustic wave of a second frequency band to the interface between the resin layer and the copper foil layer of the substrate according to the acoustic wave buffer stress data and the interlayer bonding strength data, and recording the acoustic wave amplitude data and the acoustic wave phase difference data at the interface bonding part, including: Determining the acoustic wave action parameters according to the acoustic wave buffer stress data, applying an acoustic wave of a first sub-frequency band corresponding to the acoustic wave action parameters to the interface bonding part between the rough area of the outer copper foil surface of the substrate and the adjacent resin layer, and recording the acoustic wave scattering intensity data of the rough area of the outer copper foil surface; Determining the acoustic wave penetration depth parameters according to the interlayer bonding strength data, applying an acoustic wave of a second sub-frequency band corresponding to the acoustic wave penetration depth parameters to the interface bonding part between the inner copper foil and the resin layer of the substrate in the high scattering area indicated by the acoustic wave scattering intensity data, and recording the acoustic wave attenuation data of the interface between the inner copper foil and the resin layer; Performing amplitude superposition processing on the acoustic wave scattering intensity data and the acoustic wave attenuation data to form acoustic wave amplitude data, and performing phase superposition processing on the acoustic wave scattering intensity data and the acoustic wave attenuation data to form acoustic wave phase difference data.

4. The manufacturing process of the HDI board for the laptop camera module according to claim 1, characterized in that, Applying a short-pulse multi-frequency acoustic wave to the target hole area during the laser drilling process according to the pre-inspection data of the substrate, recording the acoustic reflection signal at the moment of drilling, and performing local heat control on the hole wall area to obtain micro-hole acoustic reflection data, including: Determining the acoustic wave action range and the acoustic wave action time sequence of the hole area according to the pre-inspection data of the substrate, applying a short-pulse acoustic wave of a first frequency band corresponding to the acoustic wave action range and the acoustic wave action time sequence to the target hole area, and recording the substrate acoustic reflection reference data before drilling; Applying a short-pulse acoustic wave of a second frequency band to each layer of the hole wall during the laser drilling ablation process according to the acoustic reflection reference data, and recording the acoustic wave amplitude mutation data and the phase shift data during the ablation process of each layer; Determining a first temperature control parameter according to the acoustic wave amplitude mutation data, applying a first local temperature gradient corresponding to the first temperature control parameter to the hole wall area, and recording the first hole wall temperature response data; determining a second temperature control parameter according to the phase shift data, applying a second local temperature gradient corresponding to the second temperature control parameter to the hole wall area, and recording the second hole wall temperature response data; Applying a short-pulse acoustic wave of a third frequency band to the hole wall according to the first hole wall temperature response data and the second hole wall temperature response data, recording the acoustic wave scattering data of micro-cracks on the hole wall and the acoustic wave attenuation data of resin residue, and combining the acoustic wave amplitude mutation data, the phase shift data, the first hole wall temperature response data, the second hole wall temperature response data, the acoustic wave scattering data of micro-cracks on the hole wall and the acoustic wave attenuation data of resin residue to form micro-hole acoustic reflection data.

5. The manufacturing process of the HDI board for the laptop camera module according to claim 4, characterized in that, Applying a short-pulse acoustic wave of a second frequency band to each layer of the hole wall during the laser drilling ablation process according to the acoustic reflection reference data, and recording the acoustic wave amplitude mutation data and the phase shift data during the ablation process of each layer, including: Apply a first sub-band short-pulse acoustic wave to the ablation area of the outer copper foil according to the acoustic reflection reference data, and record the acoustic wave reflection data of the metal layer and the copper foil residue distribution data during the ablation process of the outer copper foil; Apply a second sub-band short-pulse acoustic wave to the alternating ablation area of the resin layer and the inner copper foil according to the acoustic wave reflection data of the metal layer, and record the material peeling acoustic characteristic data and the resin decomposition acoustic characteristic data of the resin-metal interface; Combine and analyze the acoustic wave reflection data of the metal layer, the copper foil residue distribution data, the material peeling acoustic characteristic data, and the resin decomposition acoustic characteristic data to form acoustic wave amplitude mutation data and phase shift data.

6. The manufacturing process of the HDI board for the laptop camera module according to claim 1, wherein Before the electroless copper plating treatment, independently regulate the temperature of multiple areas on the board surface according to the micro-hole acoustic reflection data, record the multi-frequency acoustic scanning data of the hole walls in each area under the thermal pulse excitation, and form a regional acoustic characteristic map, including: Before the electroless copper plating treatment, divide the board surface into multiple temperature-independent regulation units according to the acoustic wave amplitude mutation area and the phase shift area in the micro-hole acoustic reflection data, and set independent temperature control parameters for each temperature-independent regulation unit; Apply a first thermal pulse wave to the hole walls in each area according to the temperature control parameters of each temperature-independent regulation unit, and apply a first-band acoustic scanning wave to the hole walls at the peak moment of the first thermal pulse wave, and record the acoustic wave scattering data caused by the transient expansion of the hole walls; Determine the stress response parameters of the hole walls in each area according to the acoustic wave scattering data, apply a second thermal pulse wave to each temperature-independent regulation unit, and apply a second-band acoustic scanning wave to the hole walls at the valley moment of the second thermal pulse wave, and record the acoustic wave attenuation data caused by the transient contraction of the hole walls; Determine the strain distribution parameters of the hole walls in each area according to the acoustic wave attenuation data, apply a third thermal pulse wave to each temperature-independent regulation unit, and apply a third-band acoustic scanning wave to the hole walls during the duration of the third thermal pulse wave, and record the micro-crack acoustic characteristic data and the void migration trend data of the hole walls; Partition and combine the acoustic wave scattering data, the acoustic wave attenuation data, the micro-crack acoustic characteristic data of the hole walls, and the void migration trend data according to the temperature-independent regulation units to form a regional acoustic characteristic map.

7. The manufacturing process of the HDI board for the laptop camera module according to claim 1, characterized in that, During the electroless copper plating process, apply multi-band acoustic wave excitation to the hole areas at preset time intervals according to the regional acoustic characteristic map, and record the acoustic reflection signal attenuation curve during the formation of the metal seed layer to obtain the electroless copper plating process monitoring data, including: During the electroless copper plating process, determine the electroless copper plating monitoring time sequence of each hole area according to the regional acoustic characteristic map and the preset time interval, pause the flow of the electroless copper plating solution at the pause point of each electroless copper plating monitoring time sequence, apply an electroless copper plating start detection wave to the hole area, and record the acoustic reflection characteristic data of the metal seed layer nucleation stage; Apply an electroless copper plating growth detection wave to different hole areas according to the acoustic reflection characteristic data, and record the metal grain growth distribution data and the interface bonding state data; According to the metal grain growth distribution data and the interface bonding state data, a copper deposition process detection wave is applied to the hole area, and the seed layer continuity change curve and the hole wall coverage change curve are recorded; According to the preset time interval, dynamic feature analysis is performed on the seed layer continuity change curve and the hole wall coverage change curve, and the acoustic reflection feature data, the metal grain growth distribution data, the interface bonding state data, and the dynamic feature analysis results are combined to form copper deposition process monitoring data.

8. The manufacturing process of the HDI board for the laptop camera module according to claim 1, wherein, During the electroplating process, according to the copper deposition process monitoring data, periodic thermal excitation and fluid disturbance are applied to the board surface, the propagation characteristics of multi-frequency acoustic waves in the electroplating solution are recorded, and electroplating dynamic monitoring data is obtained through adaptive signal processing, including: During the electroplating process, according to the seed layer continuity change curve in the copper deposition process monitoring data, a first electroplating thermal pulse is applied to the high-density micro-hole clustering area, and a second electroplating thermal pulse is applied to the surrounding trace area, and the temperature gradient distribution data of the micro-hole area and the trace area is recorded; According to the temperature gradient distribution data, a first fluid disturbance is applied to the high-density micro-hole clustering area, a second fluid disturbance is applied to the surrounding trace area, and an electroplating acoustic detection wave is applied to the deep and shallow micro-hole areas under the action of the double fluid disturbance, and the acoustic propagation attenuation data of micro-holes with different depth-to-diameter ratios is recorded; According to the acoustic propagation attenuation data, a low-frequency electroplating monitoring wave is applied to the high-density micro-hole clustering area, and a high-frequency electroplating monitoring wave is applied to the surrounding trace area, and the current density distribution data at the bottom of the micro-hole and the stress distribution data of the hole wall coating are recorded; Regional compensation operations are performed on the current density distribution data, the coating thickness distribution curves of the deep and shallow micro-holes are recorded, hierarchical processing is performed on the stress distribution data of the hole wall coating, and the bubble migration characteristic curves of micro-holes with different depth-to-diameter ratios are recorded; Adaptive signal filtering processing is performed on the coating thickness distribution curve and the bubble migration characteristic curve, and the temperature gradient distribution data, the acoustic propagation attenuation data, the current density distribution data, the stress distribution data of the hole wall coating, the coating thickness distribution curve after adaptive signal filtering processing, and the bubble migration characteristic curve after adaptive signal filtering processing are combined to form electroplating dynamic monitoring data.

9. The manufacturing process of the HDI board for the laptop camera module according to claim 1, characterized in that, After the electroplating is completed, according to the electroplating dynamic monitoring data, the finished product is subjected to temperature cycling and stress excitation treatment, the acoustic wave reflection data in the hole is recorded, and the internal structure evaluation result of the microvia is obtained through multi-dimensional data analysis, including: After the electroplating is completed, according to the electroplating dynamic monitoring data, the coating on the inner wall of the micro-hole is evaluated by region, the temperature cycling parameters and stress excitation parameters are determined, a first temperature cycle is applied to the finished product, and the thermal cycle gradient data and cyclic stress accumulation data of each micro-hole area are recorded; According to the thermal cycle gradient data and the cyclic stress accumulation data, a second temperature cycle is applied to the finished product, and at the same time, an evaluation acoustic wave of the finished product is applied to the inner wall of the micro-hole, and the acoustic attenuation trend data and acoustic phase shift characteristic data inside the micro-hole are recorded; Apply mechanical stress excitation to the micro-holes according to the acoustic attenuation trend data and the acoustic phase shift characteristic data, and record the structural deformation parameters and void evolution data of the coating on the inner wall of the micro-holes; Comprehensively process the thermal cycle gradient data, the cyclic stress accumulation data, the acoustic attenuation trend data, the acoustic phase shift characteristic data, the structural deformation parameters and the void evolution data to form an evaluation result of the internal structure of the micro-vias.

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