A method for processing a double-sided panel metalized slot hole

Abstract

The application discloses a kind of processing methods of metallization slot hole of double-sided panel, comprising the following steps: S1. substrate cutting: select the substrate of adaptation double-sided panel production, complete cutting processing according to preset size, the processing method of the metallization slot hole of this double-sided panel, through the double structure optimization of outer layer pad widening and guard hole design, widen pad covers stress concentration area, enhance the bonding force of metallization layer and substrate, reduce interface peeling risk;Guard hole effectively disperses electroplating, hot stress and chemical stress generated by pressing, avoids stress concentration, fundamentally solves the core pain point of the stratification of metallization slot hole, blister in the prior art, compared with the way of improving defects in prior art only by single process adjustment, the structure optimization scheme of the application is more targeted and effective, the method for improving blister by filling resin in similar technology has higher process complexity, and the application does not need additional hole filling process.

Description

Technical Field

[0001] This invention relates to the field of printed circuit board processing related products, specifically a method for processing metallized slots on double-sided boards. Background Technology

[0002] Double-sided boards, as an important type of printed circuit board, have been widely used in communications, consumer electronics, and industrial control due to their compact structure and moderate cost. Metallized vias, as the core structure for interlayer conductivity and component soldering in double-sided boards, directly determine the electrical performance, mechanical reliability, and lifespan of the double-sided board, making them one of the key processes in double-sided board production.

[0003] The conventional manufacturing process for metallized slots on double-sided boards is as follows: substrate slotting → slot pretreatment → copper plating → outer layer circuit fabrication → solder mask → post-processing. In this process, the outer layer pads at the metallized slot location are designed with the minimum conventional width, and no additional protective structure is set around the slot, resulting in many technical defects during processing.

[0004] Specifically, during the copper plating and electroplating processes, stress concentration easily occurs at the junction of the metallized slot wall and the substrate. Furthermore, the thermal and chemical stresses generated during lamination and electroplating continue to act on the substrate surrounding the slot. In addition, the conventionally designed outer pads are relatively narrow, providing insufficient reinforcement and protection for the substrate around the slot and lacking an effective stress dispersion structure. This leads to a series of problems in actual production: delamination and blistering occur at the interface between the metallized slot and the substrate, damaging the conductivity and adhesion of the metallized layer; delamination and blistering further cause copper layer detachment from the slot wall and open circuits, severely affecting the overall electrical performance of the double-sided board; defective products require rework and replating or even scrap, significantly reducing production yield and increasing manufacturing costs; simultaneously, the delamination and blistering problem is further exacerbated by changes in ambient temperature and humidity during subsequent use, severely reducing the lifespan and reliability of the double-sided board, failing to meet the high stability requirements of industrial control and other fields.

[0005] Currently, the delamination and bubbling problem in metallized slots has become a core pain point in the quality control of double-sided panel manufacturing processes. Existing processing methods cannot fundamentally solve this problem. Therefore, developing a processing method for metallized slots in double-sided panels that can effectively avoid the above defects and improve processing quality and efficiency has become an urgent technical problem that needs to be solved by those skilled in the art. Summary of the Invention

[0006] The purpose of this invention is to provide a method for machining metallized slots in double-sided panels to solve the problems mentioned in the background art.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a method for processing metallized slots in a double-sided panel, comprising the following steps:

[0008] S1. Substrate cutting: Select a substrate suitable for double-sided panel production and cut it to the preset size;

[0009] S2. Metallization Slot Hole Cutting: Using integrated slotting and drilling equipment, metallization slot holes are processed at preset positions on the substrate. During processing, the two ends of the slot hole are first drilled to form the beginning and end holes, and then the middle material is removed to form a complete slot hole, ensuring that the slot length is not less than twice the slot width.

[0010] S3. Slot baking: Place the substrate with metallized slots into an oven and bake at 150°C for 2 hours to remove mechanical stress and moisture in the slots and improve the curing degree of the substrate resin.

[0011] S4. Copper plating metallization: The baked substrate is subjected to pretreatment of the slots, followed by copper plating and electroplating. The thickness of the copper plating layer is controlled to be 0.5-0.8μm, and the average thickness of the electroplated copper layer is ≥20μm to achieve slot metallization.

[0012] S5. Widening of outer pads and fabrication of guard holes: Widened outer pads are fabricated around the metallized slot holes, and guard holes are fabricated around the slot holes; the outer pads are widened by 8-12 mils compared to the original conventional pads, and the widened area of ​​the pads completely covers the stress concentration area at the edge of the slot hole. The overlap width between the pads and the edge of the slot hole is not less than 10 mils, and the pad material is the same as that of the outer layer circuit; the guard holes are non-metallized through holes with a diameter of 15-20 mils, distributed in a uniform ring array. The distance between the guard holes and the edge of the slot hole is 20-25 mils, and the center-to-center distance of the guard holes on the same side is 30-35 mils. The guard holes are processed simultaneously with the metallized slot holes, and the hole wall roughness Ra≤1.0μm;

[0013] S6. Outer layer circuit etching: Using conventional etching process, the outer layer circuit of the substrate is etched, retaining the widened pads, guard holes and the preset outer layer circuit;

[0014] S7. Solder resist: A solder resist layer is applied to the surface of the etched substrate to protect the non-soldering areas;

[0015] S8. Tin spraying treatment: Tin spraying treatment is performed on the soldering area of ​​the substrate to improve soldering reliability;

[0016] S9. Finished Product Inspection: Conduct comprehensive inspection of the finished substrate, and add a special inspection for metallized slots. Use X-ray to check whether there is delamination at the interface between the slot and the substrate, and use metallographic sections to observe whether there is blistering. At the same time, check whether the position accuracy of the guard holes and the width of the pads meet the design requirements. If they pass, they are considered finished products.

[0017] In a preferred embodiment of the present invention, in step S5, the pad widening size and the number of guard hole arrays are adjusted according to the size of the metallization slot: when the slot size is ≥5mm, the pad widening size is 12mil, and the guard hole array is increased by 1-2 rows; when the slot size is <5mm, the pad widening size is 8mil, and the guard holes are distributed according to the basic array.

[0018] As a preferred embodiment of the present invention, in step S4, the pretreatment of the slot before copper plating includes degreasing, micro-etching, and activation treatment to ensure the cleanliness of the inner wall of the slot and improve the adhesion between the copper plating layer and the slot wall.

[0019] As a preferred embodiment of the present invention, in step S5, the number of protective holes in the array is flexibly adjusted according to the specific size of the metallized slot, so as to ensure that the stress around the slot can be effectively dispersed through the protective holes.

[0020] As a preferred embodiment of the present invention, in step S9, the finished product inspection also includes appearance inspection and electrical performance inspection. The appearance inspection uses a combination of visual inspection and a 10x magnifying glass to check for defects on the substrate surface, and the electrical performance inspection checks for open circuits and short circuits in the circuit.

[0021] Compared with the prior art, the beneficial effects of the present invention are:

[0022] This method for processing metallized slots on double-sided boards employs a dual structural optimization approach: widening the outer pads and designing guard holes. The widened pads cover the stress concentration area of ​​the slot, enhancing the adhesion between the metallized layer and the substrate and reducing the risk of interface peeling. The guard holes effectively disperse the thermal and chemical stresses generated during electroplating and lamination, preventing stress concentration. This fundamentally solves the core problems of delamination and blistering in existing metallized slots. Compared to existing methods that only adjust a single process to improve defects, the structural optimization scheme of this invention is more targeted and effective. Similar techniques that improve blistering by filling with resin have higher process complexity, while this invention eliminates the need for an additional filling process. Attached Figure Description

[0023] Figure 1 This is a schematic flowchart of a method for machining metallized slots on a double-sided panel according to the present invention. Detailed Implementation

[0024] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0025] In the description of this invention, it should be noted that the terms "upper," "lower," "inner," "outer," "front end," "rear end," "both ends," "one end," and "the other end," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0026] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installed," "equipped with," "connected," etc., should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0027] Please see Figure 1 One embodiment provided by the present invention:

[0028] Example 1: Machining of metallized slots in double-sided panels with slot size < 5mm

[0029] A method for machining metallized slots on a double-sided panel includes the following steps:

[0030] S1. Substrate cutting: Select FR-4 substrate and cut it to a size of 100mm×80mm, ensuring that the substrate surface is free of damage and stains.

[0031] S2. Metallization Slot Hole Cutting: Using an integrated slotting and drilling equipment, metallization slot holes are processed at preset positions on the substrate. The slot hole size is 4mm×1mm (slot length 4mm, slot width 1mm, slot length is 4 times slot width, meeting the requirement that the slot length is not less than twice the slot width). During processing, the first and last holes at both ends of the slot hole are drilled first, and then the middle material is removed to ensure that the slot hole edges are smooth and the dimensions are accurate.

[0032] S3. Slot baking: Place the substrate with metallized slots into the oven, set the temperature to 150℃, and bake for 2 hours to remove mechanical stress and moisture from the slots.

[0033] S4. Copper plating metallization: The substrate is degreased, micro-etched, and activated, followed by copper plating, with the copper plating layer thickness controlled at 0.5μm; then electroplating is performed, with the average thickness of the electroplated copper layer controlled at 20μm, to complete the slot metallization.

[0034] S5. Widening of outer layer pads and fabrication of guard holes: The outer layer pads are widened by 8 mils based on the standard width, and the overlap width between the pads and the edge of the slot is 10 mils. The pad material is the same as that of the outer layer circuitry. The guard holes are non-metallic through holes with a diameter of 15 mils. They are distributed in a ring array around the slot, with a spacing of 20 mils between the guard holes and the edge of the slot. The center spacing of the guard holes on the same side is 30 mils. They are processed simultaneously with the slot using an integrated slotting and drilling machine, and the hole wall roughness Ra=0.8μm.

[0035] S6. Outer layer etching: Use conventional acid etching process, etching temperature 35℃, etching time 60s, retain widened pads, guard holes and preset outer layer circuits.

[0036] S7. Solder resist: Solder resist ink is coated on the surface of the substrate, and after exposure and development, a solder resist layer is formed, covering the non-soldering area.

[0037] S8. Tin spraying: The soldering area is tin-sprayed using a hot air leveling process, with the tin layer thickness controlled at 2-3μm.

[0038] S9. Finished Product Inspection: X-ray inspection shows no delamination at the interface between the slot and the substrate; metallographic sectioning shows no blistering; the positional accuracy deviation of the guard hole is ≤0.1mm; the pad widening dimension meets the 8mil requirement; visual inspection shows no damage or oxidation; electrical performance inspection shows no open circuit or short circuit; thus, the product is deemed a qualified finished product.

[0039] Example 2: Machining of metallized slots in double-sided panels with slot size ≥ 5mm

[0040] A method for machining metallized slots on a double-sided panel includes the following steps:

[0041] S1. Substrate cutting: Select FR-4 substrate and cut it to a size of 120mm×100mm, ensuring that the substrate surface is free of damage and stains.

[0042] S2. Metallization Slot Hole Cutting: Using an integrated slotting and drilling equipment, metallization slot holes are processed at preset positions on the substrate. The slot hole size is 6mm×2mm (slot length 6mm, slot width 2mm, slot length is 3 times slot width, meeting the requirement that the slot length is not less than twice the slot width). During processing, the beginning and end holes at both ends of the slot hole are drilled first, and then the middle material is removed to ensure that the slot hole edges are smooth and the dimensions are accurate.

[0043] S3. Slot baking: Place the substrate with metallized slots into the oven, set the temperature to 150℃, and bake for 2 hours to remove mechanical stress and moisture from the slots.

[0044] S4. Immersion Copper Plating Metallization: Degrease, micro-etch, and activate the substrate, then perform immersion copper plating, controlling the thickness of the immersion copper layer to be 0.8 μm; then perform electroplating, controlling the average thickness of the electroplated copper layer to be 22 μm to complete the metallization of the via holes.

[0045] S5. Outer Layer Pad Widening and Guard Hole Fabrication: The outer layer pads are widened by 12 mil based on the conventional width, and the overlapping width between the pad and the edge of the via hole is 12 mil. The material of the pad is the same as that of the outer layer circuit; the guard holes are non-metallized through holes with a diameter of 20 mil, distributed in a circular array around the via holes (one row is added compared to the basic array). The distance between the guard hole and the edge of the via hole is 25 mil, and the center-to-center distance of the guard holes on the same side is 35 mil. A slotted drilling integrated device is used to process synchronously with the via holes, and the surface roughness Ra of the hole wall is 0.9 μm.

[0046] S6. Outer Layer Circuit Etching: Use the conventional acidic etching process, with an etching temperature of 38 °C and an etching time of 70 s, retaining the widened pads, guard holes, and the preset outer layer circuits.

[0047] S7. Solder Mask: Apply solder mask ink on the surface of the substrate, and form a solder mask layer after exposure and development to cover the non-welding areas.

[0048] S8. Hot Air Solder Leveling Treatment: Use the hot air solder leveling process to perform hot air solder leveling treatment on the welding areas, and control the thickness of the solder layer to be 2 - 3 μm.

[0049] S9. Final Product Inspection: It is detected by X-ray that there is no delamination at the bonding interface between the via holes and the substrate, and it is observed by metallographic sectioning that there is no blistering; the position accuracy deviation of the guard holes is ≤ 0.1 mm, and the widened size of the pads meets the requirement of 12 mil; there is no damage or oxidation in the appearance inspection, and there is no open circuit or short circuit in the electrical performance inspection, and it is determined as a qualified final product.

[0050] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be encompassed within the present invention. Any reference signs in the claims should not be regarded as limiting the claims involved.

Claims

1. A method for machining metallized slots on a double-sided panel, characterized in that: Includes the following steps: S1. Substrate cutting: Select a substrate suitable for double-sided panel production and cut it to the preset size; S2. Metallization Slot Hole Cutting: Using integrated slotting and drilling equipment, metallization slot holes are processed at preset positions on the substrate. During processing, the two ends of the slot hole are first drilled to form the beginning and end holes, and then the middle material is removed to form a complete slot hole, ensuring that the slot length is not less than twice the slot width. S3. Slot baking: Place the substrate with metallized slots into an oven and bake at 150°C for 2 hours to remove mechanical stress and moisture in the slots and improve the curing degree of the substrate resin. S4. Copper plating metallization: The baked substrate is subjected to pretreatment of the slots, followed by copper plating and electroplating. The thickness of the copper plating layer is controlled to be 0.5-0.8μm, and the average thickness of the electroplated copper layer is ≥20μm to achieve slot metallization. S5. Widening of outer pads and fabrication of guard holes: Widened outer pads are fabricated around the metallized slot holes, and guard holes are fabricated around the slot holes; the outer pads are widened by 8-12 mils compared to the original conventional pads, and the widened area of ​​the pads completely covers the stress concentration area at the edge of the slot hole. The overlap width between the pads and the edge of the slot hole is not less than 10 mils, and the pad material is the same as that of the outer layer circuit; the guard holes are non-metallized through holes with a diameter of 15-20 mils, distributed in a uniform ring array. The distance between the guard holes and the edge of the slot hole is 20-25 mils, and the center-to-center distance of the guard holes on the same side is 30-35 mils. The guard holes are processed simultaneously with the metallized slot holes, and the hole wall roughness Ra≤1.0μm; S6. Outer layer circuit etching: Using conventional etching process, the outer layer circuit of the substrate is etched, retaining the widened pads, guard holes and the preset outer layer circuit; S7. Solder resist: A solder resist layer is applied to the surface of the etched substrate to protect the non-soldering areas; S8. Tin spraying treatment: Tin spraying treatment is performed on the soldering area of ​​the substrate to improve soldering reliability; S9. Finished Product Inspection: Conduct comprehensive inspection of the finished substrate, and add a special inspection for metallized slots. Use X-ray to check whether there is delamination at the interface between the slot and the substrate, and use metallographic sections to observe whether there is blistering. At the same time, check whether the position accuracy of the guard holes and the width of the pads meet the design requirements. If they pass, they are considered finished products.

2. The method for machining metallized slots on a double-sided panel according to claim 1, characterized in that: In step S5, the pad widening size and the number of guard hole arrays are adjusted according to the size of the metallization slot: when the slot size is ≥5mm, the pad widening size is 12mil, and the guard hole array is increased by 1-2 rows; when the slot size is <5mm, the pad widening size is 8mil, and the guard holes are distributed according to the basic array.

3. The method for machining metallized slots on a double-sided panel according to claim 1, characterized in that: In step S4, the pretreatment of the slots before copper plating includes degreasing, micro-etching, and activation treatment to ensure the cleanliness of the inner wall of the slots and improve the adhesion between the copper plating layer and the slot wall.

4. The method for machining metallized slots on a double-sided panel according to claim 1, characterized in that: In step S5, the number of protective holes in the array is flexibly adjusted according to the specific size of the metallized slot, ensuring that the stress around the slot can be effectively dispersed through the protective holes.

5. The method for machining metallized slots on a double-sided panel according to claim 1, characterized in that: In step S9, the finished product inspection also includes appearance inspection and electrical performance inspection. Appearance inspection uses visual inspection combined with a 10x magnifying glass to check for defects on the substrate surface. Electrical performance inspection checks for open circuits and short circuits in the circuit.

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