Press-fit PCB PP thickness measuring method

Abstract

The invention relates to the technical field of PCBs (Printed Circuit Board), in particular to a method for measuring the PP thickness of a laminated PCB, which comprises the following steps of: preparing a copper foil and an auxiliary substrate; dividing the PP layers with different numbers of PP into three groups and overlapping the PP layers in the same PCB, wherein the different numbers comprise one piece of PP, two pieces of PP and three pieces of PP; overlapping an auxiliary substrate between each group of PP layers, and overlapping a copper foil on the surface of the outer PP layer; the laminated PCB boards are subjected to press fit; slicing and sampling are carried out on the laminated PCB; measuring thickness data of different PP layers in each slice under a metallographic microscope; and calculating the theoretical thickness of the PP according to the measured data. A plurality of groups of PP samples are simultaneously laminated in the same PCB for lamination, so that each sample is formed in the same heated and pressed environment, thickness data with consistency and representativeness are obtained, thickness deviation and deformation errors caused by traditional independent lamination of the samples are avoided, and the precision and efficiency of PP thickness measurement are remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of PCB technology, and more specifically to a method for measuring the thickness of laminated PCBs (PP). Background Technology

[0002] With the development of multilayer PCB manufacturing processes, the thickness control of prepreg (PP) during lamination has become a key factor affecting the thickness and dielectric stability of the finished board. Substrate manufacturers typically calculate the theoretical thickness of PP using theoretical formulas, but actual lamination results are affected by processing parameters such as equipment performance, temperature, pressure, and time, leading to deviations between theoretical and actual thicknesses. Therefore, in PCB manufacturing, actual lamination verification is necessary to determine the optimal design thickness of PP.

[0003] In existing technologies, copper foil is typically laminated with one, two, or three sheets of polypropylene (PP) and then the thickness is measured using a slicing tool or micrometer to estimate the theoretical thickness of the PP. However, this method is prone to deformation of individually laminated PP samples, leading to measurement errors. Furthermore, the large number of samples, cumbersome preparation and measurement processes, and low efficiency make it unsuitable for large-scale process verification. Summary of the Invention

[0004] The technical objective of this invention is to provide a method for measuring the thickness of PP in laminated PCB boards, so as to improve the accuracy and efficiency of PP thickness measurement and reduce measurement errors caused by sample deformation.

[0005] To achieve the above-mentioned technical objectives, the present invention provides the following technical solution: The present invention provides a method for measuring the thickness of laminated PCB board PP, comprising the following steps: Prepare copper foil and auxiliary substrate; The PP layers of different quantities are divided into three groups and stacked on the same PCB board. The different quantities include 1 PP, 2 PP and 3 PP. The auxiliary substrate is stacked between each group of PP layers; the copper foil is stacked on the surface of the outer PP layer; The stacked PCB boards are then laminated. The laminated PCB board is sliced ​​and sampled. Thickness data of different PP layers in each slice were measured under a metallographic microscope; The theoretical thickness of PP is calculated based on the measured thickness data.

[0006] Preferably, the copper foil is STD copper foil with a thickness of 1 / 2 OZ, and the smooth side of the copper foil faces the PP.

[0007] Preferably, the auxiliary substrate is a core board with a thickness greater than 10 mil.

[0008] The process of laminating the stacked PCB boards includes ensuring that the temperature, pressure, and time of the lamination parameters meet the material guideline requirements, and that the pressure and temperature rise are kept at the midpoint of the material guideline requirement range.

[0009] Furthermore, the PCB board after lamination is sliced ​​and sampled, including: using a fixed scooping and forming program to automatically cut and sample, with 9 sampling positions; preferably, the 9 sampling positions are arranged diagonally on the PCB board.

[0010] Furthermore, the thickness data of different PP layers in each slice were measured under a metallographic microscope, including: after the cut slices were coated with glue and ground, they were observed and measured under a metallographic microscope at 200x magnification.

[0011] Furthermore, the theoretical thickness of PP is calculated based on the measured thickness data, including: For each slice, 10 sets of data were measured on the PP layer of 1 PP slice, the PP layer of 2 PP slices, and the PP layer of 3 PP slices. After removing the maximum and minimum values, the average values ​​were calculated and recorded as avg1, avg2, and avg3 respectively. The theoretical thickness of one sheet of PP = (avg1 + avg2 + avg3) / 3; The theoretical thickness of 2 sheets of PP = (avg1 + avg2 + avg3) / 3 × 2; The theoretical thickness of 3 PP sheets = avg1 + avg2 + avg3.

[0012] Specifically, the PCB board's stacked structure from top to bottom consists of: outer copper foil, 1 sheet of PP PP layer, 2 sheets of PP PP layer, 3 sheets of PP PP layer, and outer copper foil.

[0013] The beneficial effects of this invention are as follows: 1. This invention involves simultaneously stacking different numbers (1, 2, or 3 sheets) of PP layers on the same PCB board, with an auxiliary substrate and outer copper foil interposed between them for overall lamination. This allows the PP layers of different stacks to cure and form under the same lamination environment. This structural arrangement ensures that the heating and pressure conditions of each group of samples are consistent, allowing multiple sets of thickness data to be obtained in a single lamination. This effectively avoids measurement errors caused by uneven sample stress and resin flow differences in traditional group lamination methods, achieving high-precision determination of the theoretical thickness of PP and significantly improving the consistency and reliability of the measurement.

[0014] 2. This invention uses a core plate with a thickness greater than 10 mil as an auxiliary substrate, which provides stable support for each PP layer during the lamination process, restricting the deformation and flow of the PP layers under high temperature and high pressure conditions, and maintaining the flatness and thickness uniformity between the layers. This design further improves the structural stability of the measurement slices, making the microscopic measurement data more representative and repeatable, thereby improving the measurement accuracy.

[0015] 3. This invention also employs a fixed-program automatic cutting method to take nine samples at diagonal intersections on the laminated PCB board. Standardized cutting and positional distribution achieve multi-point measurement averaging. Combined with precise observation under a metallographic microscope and extreme value removal and averaging of the data, the impact of human error and local thickness deviations can be effectively reduced. This method significantly improves measurement efficiency and the scientific rigor of data statistics, providing a more reliable basis for PP thickness design and lamination process optimization. Attached Figure Description

[0016] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0017] The above and other aspects of the invention will now be described by way of example only, with reference to the accompanying drawings, in which: Figure 1 This is a schematic diagram of the PCB board structure according to an embodiment of the present invention; Figure 2 This is a schematic diagram of a PCB board slice according to an embodiment of the present invention. Detailed Implementation

[0018] To better understand the above technical solutions, the following will provide a detailed explanation of the technical solutions in conjunction with the accompanying drawings and specific implementation methods.

[0019] Example 1: like Figure 1As shown, this embodiment provides a method for measuring the thickness of polypropylene (PP) in a laminated PCB board, including the following steps: preparing copper foil and an auxiliary substrate; stacking PP layers of different quantities (1 PP, 2 PP, and 3 PP) in three groups on the same PCB board. The PP is a conventional glass fiber reinforced epoxy resin prepreg, with a model consistent with the board under test to ensure representative measurement results. The auxiliary substrate is stacked between each group of PP layers to form independent pressure spaces, avoiding interference from resin flow. The copper foil is stacked on the surface of the outer PP layer, using standard STD copper foil with a thickness of 1 / 2 oz, with the smooth side of the copper foil facing the PP to ensure consistency with actual PCB lamination conditions.

[0020] The stacked PCB boards are then laminated. The lamination process parameters are set according to the material guideline requirements. The temperature is controlled in the range of 180℃ to 190℃, the pressure is controlled in the range of 180 to 200 psi, the heating rate is maintained in the range of 2.0℃ / min to 2.5℃ / min, and the holding time is 30 to 45 minutes to ensure that the resin is fully cured and flows evenly.

[0021] like Figure 2 As shown, after the PCB board is cooled and the sample is removed, a fixed scooping and forming program is used to automatically cut and sample. There are 9 sampling positions, and the 9 sampling points are distributed diagonally along the PCB board to ensure that the thickness measurement is representative and comprehensive.

[0022] After being filled with resin and ground, the cut samples were observed and their thickness measured under a metallographic microscope at 200x magnification. Thickness data for 1 PP layer, 2 PP layers, and 3 PP layers were recorded during the measurement. Ten sets of thickness data were measured for each set. The maximum and minimum values ​​were removed, and the average values ​​were calculated and recorded as avg1, avg2, and avg3, respectively.

[0023] The theoretical thickness of each PP layer is calculated using the following formulas: Theoretical thickness of 1 PP layer = (avg1 + avg2 + avg3) / 3; Theoretical thickness of 2 PP layers = (avg1 + avg2 + avg3) / 3 × 2; Theoretical thickness of 3 PP layers = avg1 + avg2 + avg3. By simultaneously laminating different combinations of PP layer numbers on the same PCB board, each sample is formed under the same hot-pressing conditions, ensuring consistency and comparability of measurement data. This avoids thickness deviations and deformation errors caused by traditional individual lamination methods, thereby achieving high-precision measurement of the theoretical thickness of PP.

[0024] Example 2: This embodiment further optimizes some structural and process parameters based on Embodiment 1. The auxiliary substrate uses a 12mil thick core board made of epoxy glass cloth copper-clad laminate. By setting a core board of this thickness between the PP layers, it can play a role in uniform pressure transmission and shaping during the lamination process, further restricting the flow and thickness deformation of PP under high temperature and high pressure conditions, and improving the flatness and measurement stability of the slice structure.

[0025] In this embodiment, as Figure 1 As shown, the PCB board's stacked structure from top to bottom consists of: an outer copper foil, one PP layer, two PP layers, three PP layers, and an outer copper foil. During the lamination process, the temperature, pressure, and time are all maintained within the midpoint of the material guideline requirements to ensure consistent heating and pressure conditions for different PP layers, resulting in a more stable sample thickness after lamination.

[0026] After slicing, the material was observed under a metallographic microscope at 200x magnification. The thickness data obtained was statistically analyzed, and after extreme value removal and averaging, a more accurate theoretical thickness of PP was obtained.

[0027] The optimized scheme in this embodiment improves the repeatability and representativeness of thickness data while ensuring overall measurement efficiency, and further reduces measurement errors caused by local deformation or uneven resin distribution, thereby providing more reliable data support for thickness design and parameter calibration of PCB lamination process.

[0028] The description herein is provided to enable those skilled in the art to implement or use the present disclosure. Various modifications to the present disclosure will be readily apparent to those skilled in the art, and the general principles defined herein can be applied to other variations without departing from the scope of the disclosure. Therefore, this disclosure is not limited to the examples and designs described herein, but should be given the broadest scope consistent with the principles and novel features disclosed herein.

[0029] Although one or more exemplary embodiments of this disclosure have been described with reference to the accompanying drawings, those skilled in the art will understand that various changes in form and detail may be made therein without departing from the spirit and scope of this disclosure as defined by the appended claims.

[0030] The foregoing description is merely illustrative of this disclosure, and modifications may be made to the invention in light of the above detailed description. The terminology used in the appended claims should not be construed as limiting the invention to the specific embodiments disclosed in the specification. Rather, the scope of the invention will be fully defined by the appended claims, which will be interpreted according to established principles of claim interpretation.

Claims

1. A method for measuring the thickness of a laminated PCB board (PP), characterized in that, Includes the following steps: Prepare copper foil and auxiliary substrate; The PP layers of different quantities are divided into three groups and stacked on the same PCB board. The different quantities include 1 PP, 2 PP and 3 PP. The auxiliary substrate is stacked between each group of PP layers; the copper foil is stacked on the surface of the outer PP layer; The stacked PCB boards are then laminated. The laminated PCB board is sliced ​​and sampled. Thickness data of different PP layers in each slice were measured under a metallographic microscope; The theoretical thickness of PP is calculated based on the measured thickness data.

2. The method for measuring the thickness of laminated PCB board PP according to claim 1, characterized in that: The copper foil is STD copper foil with a thickness of 1 / 2 OZ, and the smooth side of the copper foil faces PP.

3. The method for measuring the thickness of laminated PCB board PP according to claim 1, characterized in that: The auxiliary substrate is a core board with a thickness greater than 10 mil.

4. The method for measuring the thickness of laminated PCB board PP according to claim 1, characterized in that, The laminated PCB boards are pressed together, including ensuring that the temperature, pressure, and time of the pressing parameters meet the material guideline requirements, and that the pressure and temperature rise are kept at the midpoint of the material guideline requirement range.

5. The method for measuring the thickness of laminated PCB board PP according to claim 1, characterized in that, The PCB board after lamination is sliced ​​and sampled, including: using a fixed scooping and forming program to automatically cut and sample, with 9 sampling positions; the 9 sampling positions are arranged diagonally on the PCB board.

6. The method for measuring the thickness of laminated PCB board PP according to claim 1, characterized in that, The thickness data of different PP layers in each slice were measured under a metallographic microscope, including: the slices were cut, coated with glue and ground, and then observed and measured under a metallographic microscope at 200x magnification.

7. The method for measuring the thickness of laminated PCB board PP according to claim 1, characterized in that, The theoretical thickness of PP is calculated based on the measured thickness data, including: For each slice, 10 sets of data were measured on the PP layer of 1 PP slice, the PP layer of 2 PP slices, and the PP layer of 3 PP slices. After removing the maximum and minimum values, the average values ​​were calculated and recorded as avg1, avg2, and avg3 respectively. The theoretical thickness of one sheet of PP = (avg1 + avg2 + avg3) / 3; The theoretical thickness of 2 sheets of PP = (avg1 + avg2 + avg3) / 3 × 2; The theoretical thickness of 3 PP sheets = avg1 + avg2 + avg3.

8. The method for measuring the thickness of laminated PCB board PP according to claim 1, characterized in that: The PCB board's stacked structure, from top to bottom, consists of: outer copper foil, one PP layer, two PP layers, three PP layers, and outer copper foil.

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