A test method for PTH controlled-depth stepped copper foil

Abstract

This invention belongs to the field of PCB board testing technology, specifically relating to a testing method for PTH (Polymerization Thermoplastic Hole) controlled-depth stepped copper foil. The method includes multiple PCB boards to be tested, all of which undergo drilling, controlled-depth step drilling, and stepped hole drilling. A baking board is used to support and heat the PCB boards. The heated PCB boards undergo copper plating, thickening, and full-board electroplating. The electroplated PCB boards are then rolled into SET boards and reflow soldered. This invention tests different types of substrates using different copper plating processes to identify the causes of PCB delamination after reflow soldering and wave soldering. Based on this, the copper plating solution is improved by adding polyethylene glycol and a mixture of polyethylene glycol and ethylenediaminetetraacetic acid (EDTA) to the solution in stages and adjusting the pH value to find a pH environment suitable for tensile testing. This ensures that the copper layer adhesion strength is maintained after copper plating and addition, reducing the generation of defective boards.

Description

Technical Field

[0001] This invention belongs to the field of PCB board testing technology, specifically relating to a testing method for PTH controlled-depth stepped copper foil. Background Technology

[0002] In the field of printed circuit board (PCB) manufacturing, PTH (Plating Through Hole) technology is a key process step. It involves drilling holes in the PCB and then forming a conductive metal layer, usually a copper layer, on the hole wall through chemical deposition or electrolytic deposition to achieve electrical connection between the inner and outer layers of the multilayer board. In this process, controlling the deposition depth of the copper layer in the hole, i.e., the precision of the depth step copper layer, is crucial to ensuring the performance and reliability of the PCB.

[0003] In existing PTH (Polymerization and Thoroughfare) processes, the control of copper layer thickness is particularly critical, as it directly affects the electrical performance and reliability of the PTH. This is especially true at high steps (such as transition areas between different board thicknesses), where controlling the copper layer thickness is even more difficult. If the copper layer at the step is too thin, it may lead to poor electrical connectivity or reduced reliability. If it is too thick, it may affect signal integrity and reduce copper layer adhesion. During reflow soldering and wave soldering, the PCB board is prone to blistering or delamination. Therefore, when thickening the copper layer in the plating process, it is essential to test the impact of copper layer adhesion on the PCB board. Summary of the Invention

[0004] The purpose of this invention is to provide a testing method for PTH controlled-depth stepped copper foil, which can effectively test the process of PTH controlled-depth stepped copper foil to improve the electrical performance and reliability of PCB boards.

[0005] The specific technical solution adopted by this invention is as follows: A testing process for PTH controlled-depth stepped copper foil includes: Multiple PCBs under test, all of which have undergone drilling, controlled-depth router steps, and router step holes; A baking plate, used to hold and heat the PCB board to be tested; The heated PCB board to be tested is subjected to copper plating, thickening and full-board electroplating. The copper plating step includes adding polyethylene glycol and a mixture of polyethylene glycol and ethylenediaminetetraacetic acid to the copper plating solution in batches, and adjusting the pH value of the copper plating solution until the PCB board can still pass the adhesion strength test after copper plating and copper addition. The electroplated PCB board to be tested is rolled into a SET board and then reflow soldered. The steps for testing the PCB board under test include: S1. The PCB board to be tested is classified into multiple groups, and drilling, depth control of the step drilling, and step drilling of each group are performed one by one. S2. Place the PCB board to be tested into the baking plate and heat it at a constant temperature of 180℃ for 2 hours. S3. After heating, the PCB board to be tested is subjected to copper plating, then copper is added to thicken it, and the thickened PCB board to be tested is subjected to full-board electroplating. S4. The electroplated PCB board to be tested is rolled into a SET board and reflow soldered through a reflow soldering machine. The PCB board to be tested is observed to see if there is any bubbling. If yes, it indicates that the PCB board under test has failed the test; otherwise, it indicates that the PCB board under test has passed the test. S5. Perform tensile tests on qualified PCB boards and compile the test results into a test report; The electroplated PCB board to be tested is rolled into a SET board and then reflow soldered.

[0006] In a preferred embodiment, the PCB board under test includes a bare board and a laminated multilayer board.

[0007] In a preferred embodiment, the baking plate is heated by plasma heating for 2 hours at a temperature of 180°C.

[0008] In a preferred embodiment, the copper plating includes horizontal copper plating and black hole process copper plating.

[0009] In a preferred embodiment, the testing items for the PTH controlled-depth stepped copper foil include copper foil separation test and tensile test.

[0010] In a preferred embodiment, the copper separation test includes two reflow soldering cycles and one wave soldering cycle.

[0011] In a preferred embodiment, the HOZ tensile force in the tensile test is ≥1.1 kg / cm.

[0012] In a preferred embodiment, in step S2, the baking plate is preheated until the temperature of the baking plate reaches 180°C and then stopped, and the baking plate is kept at a constant temperature.

[0013] In a preferred embodiment, in step S3, before performing full-board electroplating on the PCB board to be tested, burrs and adhesive residue from drilling are removed from the PCB board.

[0014] The technical effects achieved by this invention are as follows: This invention tests different types of substrates using various copper plating processes to identify the causes of PCB delamination after reflow soldering and wave soldering. Based on this, corresponding improvements are made to the copper plating solution. By adding polyethylene glycol and a mixture of polyethylene glycol and ethylenediaminetetraacetic acid to the copper plating solution in stages and adjusting the pH value of the solution, a pH environment suitable for tensile testing is found. This ensures that the copper layer on the PCB can still maintain its adhesion strength after copper plating, reducing the occurrence of defective boards and enhancing customer trust and satisfaction. Attached Figure Description

[0015] Figure 1 This is a HOZ tensile test diagram from an embodiment of the present invention. Detailed Implementation

[0016] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0017] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0018] Secondly, the term "an embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in a preferred embodiment" appearing in different places throughout this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that mutually excludes other embodiments.

[0019] Please see Figure 1 As shown, this invention provides a test method for PTH controlled-depth stepped copper foil, comprising: Multiple PCBs under test, all of which underwent drilling, controlled-depth router drilling, and router-stepped holes. A baking plate, used to hold and heat the PCB board to be tested; The heated PCB board to be tested is subjected to copper plating, thickening and full-board electroplating. The copper plating step includes adding polyethylene glycol and a mixture of polyethylene glycol and ethylenediaminetetraacetic acid to the copper plating solution in batches, and adjusting the pH value of the copper plating solution until the PCB board can still pass the adhesion strength test after copper plating and copper addition. The electroplated PCB board to be tested is rolled into a SET board and then reflow soldered.

[0020] In this invention, the PTH controlled-depth step copper foil testing process mainly includes the following steps: drilling holes, controlling-depth step routing, and routing step holes in the PCB board to be tested; using a baking plate to support the PCB board to be tested and heating it; performing copper plating, thickening, and full-board electroplating on the heated PCB board to be tested; and finally, routing the electroplated PCB board to be tested into a SET board and reflow soldering it.

[0021] In the drilling, controlled-depth step-mounting, and step-mounting hole stages, the PCB board under test is first precisely drilled to ensure that the diameter and depth of the holes meet the design requirements. Next, the inner walls of the holes are finely machined using a controlled-depth step-mounting process to form a stepped structure. Finally, step-mounting hole treatment is performed to further optimize the hole structure. The baking plate, as the tool supporting the PCB board under test, has a significant impact on the heating effect due to its material and structural design. Reasonable temperature and time control allows the PCB board under test to be fully preheated, providing favorable conditions for the subsequent electroplating process. On the heated PCB board, copper plating is first performed to form a uniform copper layer. Then, a thickening process is used to increase the thickness of the copper layer and improve conductivity. Finally, full-board electroplating is performed to make the copper layer more uniform and smooth, meeting the conductivity and heat dissipation requirements of the PCB board. After electroplating, the PCB board under test is machined into a SET board, giving it a specific shape and size. Finally, reflow soldering ensures that the components on the SET board form a good electrical connection with the PCB board, ensuring the stability and reliability of the product.

[0022] The PCBs under test include bare boards and laminated multilayer boards. The heating method for the boards is plasma heating, with a heating time of 2 hours and a heating temperature of 180℃. The copper plating includes horizontal copper plating and black hole copper plating. The test items for PTH controlled depth stepped copper plating include copper plating separation test and tensile test. The copper plating separation test includes two reflow soldering and one wave soldering. The HOZ tensile force in the tensile test is ≥1.1Kg / cm, which is achieved through the improvement of the copper plating solution.

[0023] In this embodiment, the PCBs under test mainly include two types: bare boards and laminated multilayer boards. To ensure the quality of the PCBs during the manufacturing process, plasma heating is usually used for baking. This heating method has the advantages of uniformity, speed, and environmental friendliness, and can effectively improve the temperature resistance and electrical performance of the PCBs. During the baking process, the heating time and temperature are crucial. According to industry standards and practical experience, the heating time is usually set to 2 hours, and the heating temperature is controlled at 180℃. This ensures that the PCBs are fully heated to achieve the expected heating effect, while avoiding deformation or damage to the PCBs due to excessive temperature or time. In addition to baking, copper plating is also a key step in the PCB manufacturing process. Copper plating mainly includes two methods: horizontal copper plating and black hole copper plating. Horizontal copper plating forms a uniform copper layer on the surface of the PCB to improve its conductivity, while black hole copper plating fills blind and buried vias in multilayer boards to ensure smooth transmission of electronic signals. After the copper plating process is completed, the main... To achieve the optimal pH environment for tensile testing, polyethylene glycol and a mixture of polyethylene glycol and ethylenediaminetetraacetic acid (EDTA) are added to the copper plating solution in stages, and the pH is adjusted to 12.5. This significantly improves copper layer adhesion (HOZ tensile strength ≥ 1.1 kg / cm), effectively resolving delamination issues after reflow and wave soldering. To ensure PCB quality and reliability, a PTH (Polymerization Tolerance) test is conducted. This test includes copper separation and tensile testing. The copper separation test verifies the strength of the bond between the copper and the substrate to prevent detachment or peeling during use. This test involves two reflow soldering cycles and one wave soldering cycle to simulate the high temperature and stress environment of actual use. The tensile test measures the tensile strength of the copper itself. According to industry standards, the HOZ tensile strength in the tensile test should be above 1.1 kg / cm. This requirement ensures that the copper will not break or deteriorate under external force, thus guaranteeing product stability and reliability.

[0024] The steps for testing the PCB board under test include: S1. Classify the PCB board to be tested into multiple groups, and drill holes, control the depth of the router steps, and router the router step holes one by one. S2. Place the PCB board to be tested into the baking plate and heat it at a constant temperature of 180℃ for 2 hours. S3. After heating, the PCB board to be tested is subjected to copper plating, then copper is added to thicken it, and the thickened PCB board to be tested is subjected to full-board electroplating. S4. The electroplated PCB board to be tested is rolled into a SET board and reflow soldered through a reflow soldering machine. The PCB board to be tested is observed to see if there is any bubbling. If yes, it indicates that the board has failed the test; otherwise, it indicates that the board has passed the test. S5. Perform tensile tests on qualified PCB boards and summarize the test results into a test report.

[0025] As described in steps S1-S5 above, after obtaining the PCB board to be tested, the PCB boards are first classified according to different specifications and batches to ensure that each group of boards has similar process and material characteristics. Then, these boards undergo pre-processing steps such as drilling, controlled-depth router drilling, and router-stepped holes. The purpose of these steps is to make sufficient preparations for subsequent testing and ensure the accuracy and reliability of the test results. Next, the processed PCB boards are placed in a baking tray and heated at a constant temperature of 180℃ for 2 hours. The purpose of this step is to stabilize the materials on the PCB board through high-temperature treatment, providing a good foundation for subsequent copper plating. After heating, the PCB board undergoes copper plating treatment to make the copper layer more uniform and dense. Then, by thickening the copper layer, the PC... The conductivity and mechanical strength of board B are assessed. Subsequently, the thickened PCB board undergoes full-board electroplating to enhance its corrosion resistance and aesthetics. After electroplating, the PCB board is rolled into a SET board and reflow soldered. The PCB board is then observed for blistering. Blistering indicates a problem in the previous processing and the board fails the test. Conversely, the absence of blistering indicates good quality and a passing test. For PCB boards that pass the test, a tensile test is performed to evaluate their mechanical strength and toughness, ensuring they can withstand various stresses and vibrations in practical applications. Finally, all test results are compiled into a test report for a comprehensive evaluation and improvement of the PCB board quality, providing a strong basis for subsequent production and improvement.

[0026] Secondly, in step S2, the baking plate is preheated until the temperature of the baking plate reaches 180°C and then kept at a constant temperature. In step S3, before the PCB board to be tested is fully electroplated, the burrs and glue residue after drilling on the PCB board are removed.

[0027] Example 1

[0028] A testing process for PTH controlled-depth stepped copper foil, including lamination of multilayer boards, is described below: Drilling of 2.0mm H / H substrates for laminating multilayer boards, controlling the depth of step drilling, and drilling step holes; Baking plate at 180℃, constant temperature for 2 hours, plasma heating; Polyethylene glycol is added, copper plating is performed using a black hole process, the plate is then thickened, and the entire board is electroplated. The SET board is formed by reflow soldering twice and wave soldering once. Observe whether delamination occurs and perform a tensile test.

[0029] In this embodiment, polyethylene glycol is added to the copper plating solution before the copper plating process. This reduces the surface tension between the liquid and the solid, making it easier for the copper plating solution to be evenly distributed on the substrate surface. Before copper plating, it can help thoroughly clean the PCB board surface to remove grease, dirt and oxides. During the copper plating process, adding polyethylene glycol to the copper plating solution can improve the stability of the solution and the adhesion of the copper layer, effectively improving the quality of the PCB board.

[0030] Example 2

[0031] A testing process for PTH controlled-depth stepped copper foil, including lamination of multilayer boards, is described below: Drilling of 2.0mm H / H substrates for laminating multilayer boards, controlling the depth of step drilling, and drilling step holes; Baking plate at 180℃, constant temperature for 2 hours, plasma heating; Add ethylenediaminetetraacetic acid (EDTA) to perform black hole copper plating, then thicken the plating and electroplat the entire board. The SET board is formed by reflow soldering twice and wave soldering once. Observe whether delamination occurs.

[0032] In this embodiment, during the copper plating process, ethylenediaminetetraacetic acid (EDTA) is added to the copper plating solution. In an alkaline environment, copper ions readily react with hydroxide ions to form insoluble copper hydroxide precipitate. EDTA prevents this precipitation by forming a stable complex with copper ions, ensuring that copper ions can exist stably in the solution. This helps control the distribution and deposition rate of metal ions, thereby improving the uniformity and adhesion of the copper layer and effectively improving the quality of the PCB board.

[0033] Example 3

[0034] A testing process for PTH controlled-depth stepped copper foil, including lamination of multilayer boards, is described below: Drilling of 2.0mm H / H substrates for laminating multilayer boards, controlling the depth of step drilling, and drilling step holes; Baking plate at 180℃, constant temperature for 2 hours, plasma heating; Add polyethylene glycol and ethylenediaminetetraacetic acid, control the pH value to 12.5, perform horizontal copper plating, then thicken the plating, and finally perform full-board electroplating. The circuit board is formed using a router, reflowed twice, and wave soldered once. Observe for delamination. In this embodiment, polyethylene glycol is added to the copper plating solution before the copper plating process. At the start of the copper plating process, polyethylene glycol and ethylenediaminetetraacetic acid (EDTA) are added, and the pH of the copper plating solution is controlled at 12.5. In this alkaline environment, copper ions readily react with hydroxide ions to form insoluble copper hydroxide precipitate. EDTA prevents this precipitation by forming a stable complex with copper ions, ensuring that copper ions can exist stably in the solution. This helps control the distribution and deposition rate of metal ions, thereby improving the uniformity and adhesion of the copper layer.

[0035] Pull tests were performed on the PCB boards after copper plating as described in Examples 1 to 3, and the test results are as follows:

[0036] As described above, when a mixture of polyethylene glycol and ethylenediaminetetraacetic acid (EDTA) is added, the polyethylene glycol and EDTA do not react chemically with each other. Furthermore, in an environment with a pH of 12.5, the PCB board can pass the tensile test, with a HOZ tensile strength reaching 1.28 kg / cm, which exceeds the IPC standard. Therefore, it has strong tensile strength. This ensures that the PTH copper foil with controlled depth steps does not delaminate after customer reflow soldering and wave soldering, effectively solving the problem of PCB board delamination.

[0037] Comparative Example 1

[0038] A testing process for PTH (Polymerization Thermoplastic Hollow) controlled-depth stepped copper foil, including a bare board, and the testing steps are as follows: Drill 2.0mm H / H substrate holes in the bare board, and control the depth of the step holes and the step holes. Baking plate at 180℃, constant temperature for 2 hours, plasma heating; After copper plating in the factory, the board is baked at 150℃ for 2 hours, then thickened and electroplated throughout. The SET board is formed by reflow soldering twice and wave soldering once. Observe whether delamination occurs.

[0039] In this comparative example, a bare board was prepared as the test object. During the testing process, equipment such as a drilling machine, a milling machine, and an oven were used, along with processes such as plasma heating and electroplating. First, the bare board was drilled with a hole diameter of 2.0 mmH / H. During drilling, the drill bit speed and feed rate needed to be carefully controlled to ensure drilling quality and accuracy. Next, the milling machine was used to create controlled-depth steps and stepped holes, forming steps of a certain depth within the holes to facilitate subsequent processes. During the step-cutting process, the milling cutter speed and feed rate were controlled to ensure the accuracy and flatness of the steps. After the step-cutting was completed, the bare board was placed in an oven for baking. The oven temperature was set to 180℃ and maintained for 2 hours to remove moisture and organic matter from the surface of the bare board, improving the adhesion of subsequent processes. Simultaneously, plasma heating further improved the activity and cleanliness of the bare board surface. After baking... After processing, the board undergoes an in-plant copper plating process. Copper plating is the process of forming a thin copper layer on the surface of the bare board, which can improve the conductivity and adhesion of the bare board. After copper plating, the board is baked again. The oven temperature is set to 150℃ and held for 2 hours to further solidify the copper layer and improve its stability and durability. Then, the copper layer is thickened to increase its thickness and conductivity. Finally, a full-board electroplating process is performed to make the copper layer surface smoother and flatter. After the electroplating process is completed, the bare board is rolled into a SET board. Then, reflow soldering and wave soldering are performed. Reflow soldering involves placing the SET board in a reflow oven for heating to melt the solder and connect it to the pads. Wave soldering involves placing the SET board in a wave soldering machine and soldering the joints through the molten solder wave. The blistering and delamination phenomena of the solder joints in these two soldering methods are recorded, and the number of delamination or blistering is counted and treated as defective products. The defect rate is then calculated based on these.

[0040] Comparative Example 2

[0041] A testing process for PTH (Polymerization Thermoplastic Hollow) controlled-depth stepped copper foil, including a bare board, and the testing steps are as follows: Drill 2.0mm H / H substrate holes in the bare board, and control the depth of the step holes and the step holes. Baking plate at 180℃, constant temperature for 2 hours, plasma heating; External horizontal copper plating, then thickening, and full-board electroplating; The SET board is formed by reflow soldering twice and wave soldering once. Observe whether delamination occurs.

[0042] In this comparative example, a bare board was prepared as the test object. During the testing process, equipment such as a drilling machine, a milling machine, and an oven were used, along with processes such as plasma heating and electroplating. First, the bare board was drilled with a hole diameter of 2.0 mmH / H. During drilling, the drill bit speed and feed rate needed to be carefully controlled to ensure drilling quality and accuracy. Next, the milling machine was used to create controlled-depth steps and stepped holes, forming steps of a certain depth within the holes to facilitate subsequent processes. During the step-cutting process, the milling cutter speed and feed rate were controlled to ensure the accuracy and flatness of the steps. After the step-cutting was completed, the bare board was placed in an oven for baking. The oven temperature was set to 180℃ and maintained for 2 hours to remove moisture and organic matter from the surface of the bare board, improving the adhesion of subsequent processes. Simultaneously, plasma heating was used. This process can further improve the activity and cleanliness of the bare board surface. After baking, an external horizontal copper plating process is performed. Copper plating is the process of forming a thin copper layer on the surface of the bare board, which can improve the conductivity and adhesion of the bare board. Then, the copper layer is thickened to increase its thickness and conductivity. Finally, a full-board electroplating process is performed to make the copper layer surface smoother and flatter. After the electroplating process is completed, the bare board is rolled into a SET board. Then, reflow soldering and wave soldering are performed. Reflow soldering involves placing the SET board in a reflow oven for heating to melt the solder and connect it to the pads. Wave soldering involves placing the SET board in a wave soldering machine and soldering the joints through the molten solder wave. The blistering and delamination phenomena of the solder joints in these two soldering methods are recorded, and the number of delamination or blistering is counted and treated as defective products. The defect rate is then calculated based on these.

[0043] Comparative Example 3

[0044] A testing process for PTH (Polymerization Thermoplastic Hollow) controlled-depth stepped copper foil, including a bare board, and the testing steps are as follows: Drill 2.0mm H / H substrate holes in the bare board, and control the depth of the step holes and the step holes. Baking plate at 180℃, constant temperature for 2 hours, plasma heating; External black hole process for copper plating, then thickening, and full board electroplating; The SET board is formed by reflow soldering twice and wave soldering once. Observe whether delamination occurs.

[0045] In this comparative example, a bare board was prepared as the test object. During the testing process, equipment such as a drilling machine, a milling machine, and an oven were used, along with processes such as plasma heating and electroplating. First, the bare board was drilled with a hole diameter of 2.0 mmH / H. During drilling, the drill bit speed and feed rate needed to be carefully controlled to ensure drilling quality and accuracy. Next, the milling machine was used to create controlled-depth steps and stepped holes, forming steps of a certain depth within the holes to facilitate subsequent processes. During the step-cutting process, the milling cutter speed and feed rate were controlled to ensure the accuracy and flatness of the steps. After the step-cutting was completed, the bare board was placed in an oven for baking. The oven temperature was set to 180℃ and maintained for 2 hours to remove moisture and organic matter from the surface of the bare board, improving the adhesion of subsequent processes. Simultaneously, plasma heating was used. This process can further improve the activity and cleanliness of the bare board surface. After baking, an external black hole copper plating process is performed. Copper plating is the process of forming a thin copper layer on the surface of the bare board, which can improve the conductivity and adhesion of the bare board. Then, the copper layer is thickened to increase its thickness and conductivity. Finally, a full-board electroplating process is performed to make the copper layer surface smoother and flatter. After the electroplating process is completed, the bare board is rolled into a SET board. Then, reflow soldering and wave soldering are performed. Reflow soldering involves placing the SET board in a reflow oven for heating to melt the solder and connect it to the pads. Wave soldering involves placing the SET board in a wave soldering machine and soldering the joints through the molten solder wave. The blistering and delamination phenomena of the solder joints in these two soldering methods are recorded, and the number of delamination or blistering is counted and treated as defective products. The defect rate is then calculated based on these results.

[0046] Comparative Example 4

[0047] A testing process for PTH controlled-depth stepped copper foil, including lamination of multilayer boards, is described below: Drilling of 2.0mm H / H substrates for laminating multilayer boards, controlling the depth of step drilling, and drilling step holes; Baking plate at 180℃, constant temperature for 2 hours, plasma heating; After copper plating in the factory, the board is baked at 150℃ for 2 hours, then thickened and electroplated throughout. The SET board is formed by reflow soldering twice and wave soldering once. Observe whether delamination occurs.

[0048] In this comparative example, a 2.0mm H / H substrate is first laminated to ensure a tight bond between the layers. Next, drilling is performed on the laminated multilayer board, with precise control over the depth of the drilled steps and the drilled holes being crucial. Accurate control of the drilling depth ensures the quality of each through-hole. After drilling, the multilayer board undergoes a series of heat treatment processes. First, it is baked at 180℃ for 2 hours to release internal stress and enhance its heat and corrosion resistance. Next, plasma heating technology further improves the surface activity and weldability of the board. After heat treatment, the multilayer board undergoes copper plating. After completing the copper plating process in the factory, the multilayer board is baked again at 150℃. The circuit is kept at a constant temperature for 2 hours to ensure a tight bond between the copper plating layer and the substrate, improving the overall strength of the multilayer board. Subsequently, a thickening process is performed to enhance the conductivity of the multilayer board. Finally, a full-board electroplating process is used to coat the surface of the multilayer board with a uniform copper layer, improving its conductivity and corrosion resistance. After electroplating, the multilayer board is spun into a SET board and then subjected to reflow soldering and wave soldering. The reflow soldering process is performed twice, and the wave soldering process is performed once. These soldering processes aim to ensure a strong connection between the components within the multilayer board. Finally, the effectiveness of the PTH (Positioning-Thickness) controlled-depth copper plating test process is evaluated by observing and detecting whether delamination occurs in the multilayer board. PCBs exhibiting delamination or blistering are considered defective, providing data support for calculating the board defect rate.

[0049] Comparative Example 5

[0050] A testing process for PTH controlled-depth stepped copper foil, including lamination of multilayer boards, is described below: Drilling of 2.0mm H / H substrates for laminating multilayer boards, controlling the depth of step drilling, and drilling step holes; Baking plate at 180℃, constant temperature for 2 hours, plasma heating; External horizontal copper plating, then thickening, and full-board electroplating; The SET board is formed by reflow soldering twice and wave soldering once. Observe whether delamination occurs.

[0051] In this comparative example, a 2.0mm H / H substrate is first laminated to ensure a tight bond between the layers. Next, drilling is performed on the laminated multilayer board, with precise control over the depth of the stepped holes and the quality of each through-hole ensured. After drilling, the multilayer board undergoes a series of heat treatment processes. First, it is baked at 180℃ for 2 hours to release internal stress and enhance its heat and corrosion resistance. Next, plasma heating technology is used to further improve the surface activity and weldability of the board. After heat treatment, the multilayer board undergoes external horizontal copper plating to ensure a tight bond between the copper layer and the substrate. The tight bonding of components enhances the overall strength of the multilayer board. Subsequently, a thickening process is applied to improve its conductivity. Finally, a uniform copper layer is applied to the surface of the multilayer board through a full-board electroplating process, improving its conductivity and corrosion resistance. After electroplating, the multilayer board is spun into a SET board and undergoes reflow soldering and wave soldering. The reflow soldering process is performed twice, and the wave soldering process is performed once. These soldering processes aim to ensure a strong connection between the components within the multilayer board. Finally, the effectiveness of the PTH (Package-Thickness) controlled-depth step copper foil testing process is evaluated by observing and detecting whether delamination occurs in the multilayer board. PCBs exhibiting delamination or blistering are considered defective, providing data support for calculating the board defect rate.

[0052] Comparative Example 6

[0053] A testing process for PTH controlled-depth stepped copper foil, including lamination of multilayer boards, is described below: Drilling of 2.0mm H / H substrates for laminating multilayer boards, controlling the depth of step drilling, and drilling step holes; Baking plate at 180℃, constant temperature for 2 hours, plasma heating; External black hole process for copper plating, then thickening, and full board electroplating; The SET board is formed by reflow soldering twice and wave soldering once. Observe whether delamination occurs.

[0054] In this comparative example, a 2.0mm H / H substrate is first laminated to ensure a tight bond between the layers. Next, drilling is performed on the laminated multilayer board, with precise control over the depth of the stepped holes and the quality of each through-hole ensured. After drilling, the multilayer board undergoes a series of heat treatment processes. First, the board is baked at 180℃ for 2 hours to release internal stress and enhance its heat and corrosion resistance. Next, plasma heating technology is used to further improve the surface activity and weldability of the board. After heat treatment, the multilayer board undergoes an external black hole process. The process involves copper plating followed by thickening to enhance the conductivity of the multilayer board. Finally, a full-board electroplating process covers the surface of the multilayer board with a uniform copper layer, improving its conductivity and corrosion resistance. After electroplating, the multilayer board is spun into a SET board and then undergoes reflow soldering and wave soldering. The reflow soldering process is performed twice, and the wave soldering process is performed once. These soldering processes aim to ensure a strong connection between the components within the multilayer board. Finally, the effectiveness of the PTH (Positioning-Thickness) controlled-depth copper plating test process is evaluated by observing and inspecting the multilayer board for delamination. PCBs exhibiting delamination or blistering are considered defective, providing data support for calculating the board defect rate.

[0055] If we count the total number of times 'a' and the number of times 'b' are used in comparative examples 1 to 6, then the formula for calculating the defect rate is: DR = (a / b) × 100%, where DR represents the defect rate. Obtain the standard defect rate (SDR) and compare it with the defect rate (DR); If SDR > DR, it indicates that the produced board is qualified; If SDR≤DR, it indicates that the produced board is unqualified.

[0056] Tensile test Tensile tests were performed on the plates in Comparative Examples 1 to 6. According to the IPC-TM-650 2.4.8.1 test manual, the HOZ tensile force should be ≥1.1Kg / cm. The test results of Comparative Examples 1 to 6 were all between 0.02 and 0.04 kg / mm ​​(0.2 to 0.4 kg / cm), while those of Comparative Examples 2 and 5, which underwent horizontal copper plating, were between 0.35 and 0.4 kg / cm, all of which were unqualified. As mentioned above, the bonding strength of the PTH with controlled depth steps, made using the copper plating and copper addition method, is insufficient and cannot meet the tensile test requirements of IPC-TM-6502.4.8.1. The potential failure probability is high, and it cannot effectively guarantee that the copper foil of the PTH with controlled depth steps will not delaminate after the customer's reflow soldering and wave soldering.

[0057] The tensile test results are shown in the table below:

[0058] The above description is merely a preferred embodiment of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention. Structures, devices, and operating methods not specifically described or explained in this invention are implemented according to conventional methods in the art unless otherwise specified or limited.

Claims

1. A test method for PTH controlled-depth stepped copper foil, characterized in that: include: Multiple PCBs under test, all of which have undergone drilling, controlled-depth router steps, and router step holes; A baking plate, used to hold and heat the PCB board to be tested; The heated PCB board to be tested is subjected to copper plating, thickening and full-board electroplating. The copper plating step includes adding polyethylene glycol and a mixture of polyethylene glycol and ethylenediaminetetraacetic acid to the copper plating solution in batches, and adjusting the pH value of the copper plating solution until the PCB board can still pass the adhesion strength test after copper plating and copper addition. The electroplated PCB board to be tested is rolled into a SET board and then reflow soldered. The steps for testing the PCB board under test include: S1. The PCB board to be tested is classified into multiple groups, and drilling, depth control of the step drilling, and step drilling of each group are performed one by one. S2. Place the PCB board to be tested into the baking plate and heat it at a constant temperature of 180℃ for 2 hours. S3. After heating, the PCB board to be tested is subjected to copper plating, then copper is added to thicken it, and the thickened PCB board to be tested is subjected to full-board electroplating. S4. The electroplated PCB board to be tested is rolled into a SET board and reflow soldered through a reflow soldering machine. The PCB board to be tested is observed to see if there is any bubbling. If yes, it indicates that the PCB board under test has failed the test; otherwise, it indicates that the PCB board under test has passed the test. S5. Perform tensile tests on qualified PCB boards and summarize the test results into a test report.

2. The test method for PTH controlled-depth stepped copper foil according to claim 1, characterized in that: The PCB board under test includes a bare board and a laminated multilayer board.

3. The test method for PTH controlled-depth stepped copper foil according to claim 1, characterized in that: The baking plate is heated by plasma heating for 2 hours at a temperature of 180°C.

4. The test method for PTH controlled-depth stepped copper foil according to claim 1, characterized in that: The copper plating includes horizontal copper plating and black hole copper plating.

5. The test method for PTH controlled-depth stepped copper foil according to claim 1, characterized in that: The testing items for the PTH controlled-depth stepped copper foil include copper foil separation test and tensile test.

6. The test method for PTH controlled-depth stepped copper foil according to claim 5, characterized in that: The copper foil separation test includes two reflow soldering cycles and one wave soldering cycle.

7. The test method for PTH controlled-depth stepped copper foil according to claim 5, characterized in that: The HOZ tensile force in the tensile test is ≥1.1Kg / cm.

8. The test method for PTH controlled-depth stepped copper foil according to claim 1, characterized in that: In step S2, the baking plate is preheated until the temperature of the baking plate reaches 180°C and then kept at a constant temperature.

9. The test method for PTH controlled-depth stepped copper foil according to claim 1, characterized in that: In step S3, before performing full-board electroplating on the PCB board to be tested, burrs and adhesive residue from drilling holes on the PCB board are removed first.

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