Method for acquiring actual lamination thickness reference value of prepreg

Abstract

The invention discloses a method for acquiring an actual lamination thickness reference value of a prepreg in the technical field of PCB (Printed Circuit Board) process optimization, and aims to solve the problem that the method for acquiring the actual lamination thickness reference value of the prepreg in the prior art consumes manpower, materials and time. The method comprises the following steps: obtaining a press coefficient according to the actual lamination thickness and the theoretical calculation thickness; the basis weight of the first prepreg is combined with the press coefficient, the resin density and the cloth basis weight and density to obtain an actual lamination thickness reference value of the first prepreg; the method comprises the following steps of: pressing a test sample prepreg to obtain a pressing machine coefficient with universality under the same pressing machine equipment and pressing parameter setting; therefore, the actual lamination thickness reference value of the first prepreg can be obtained according to the physical parameters of the cloth base and the physical parameters of the first prepreg which is made of the same resin material as the test sample prepreg, so that the actual lamination thickness reference value of the first prepreg is prevented from being obtained through multiple tests; and the problem that testing consumes manpower, materials and time is avoided.

Description

TECHNICAL FIELD

[0001] The application relates to a method for obtaining a reference value of a press-bonded actual thickness of a prepreg, and belongs to the technical field of PCB process optimization. BACKGROUND

[0002] The prepreg is an important raw material for manufacturing a PCB, and the press-bonding is one of main steps for manufacturing the PCB, and the thickness of the prepreg changes during the press-bonding.

[0003] The prepreg of a PCB changes into a solidified state after the press-bonding, but the resin density of different types of prepregs is different, so the thickness of the prepregs made of different resin materials is different after the press-bonding by different types of press-bonding machines and parameters under the same conditions. In order to ensure that the medium thickness of the PCB after the press-bonding meets the design value, the manufacturer needs to obtain the theoretical thickness of the prepreg after the press-bonding corresponding to each combination of resin material, press-bonding machine and parameter as a reference, but obtaining these reference values needs a large amount of practical tests, and the human resources, materials and time consumed are large.

[0004] Therefore, the existing method for obtaining the reference value of the press-bonded actual thickness of the prepreg has the problems of consuming human resources, materials and time. SUMMARY

[0005] The application aims to overcome the deficiencies in the prior art and provide a method for obtaining the reference value of the actual thickness of the prepreg after the press-bonding under the premise that the press-bonding machine and parameters are fixed.

[0006] To achieve the above object, the application adopts the following technical scheme: The application provides a method for obtaining the reference value of the press-bonded actual thickness of a prepreg, comprising: obtaining the basis weight of a cloth base and the density of the cloth base; obtaining the press-bonded actual thickness of a test sample prepreg, and obtaining a press machine coefficient according to the press-bonded actual thickness and the theoretically calculated thickness of the prepreg; obtaining the basis weight of a first prepreg and the density of a prepreg resin, and obtaining the reference value of the press-bonded actual thickness of the first prepreg according to the basis weight of the first prepreg, the press machine coefficient, the density of the prepreg resin, the basis weight of the cloth base and the density of the cloth base.

[0007] In some embodiments of the application, the obtaining of the basis weight of the first prepreg and the density of the prepreg resin comprises, preparing a square mold with a standard size; heating the prepreg resin to an actual process temperature, and pouring the prepreg resin into the square mold; obtaining a standard size resin cube after the prepreg resin is cured; obtaining the density of the resin cube using a densimeter method or a specific gravity method, and taking the density of the resin cube as the density of the prepreg resin.

[0008] In some embodiments of the present application, the method for obtaining the basis weight and the density of the cloth substrate comprises, obtaining a cloth substrate raw material; cutting a standard size cloth substrate from the cloth substrate raw material; obtaining the weight of the standard size cloth substrate using an electronic scale, and obtaining the basis weight of the cloth substrate according to the weight of the standard size cloth substrate; obtaining the density of the cloth substrate based on the weight of the standard size cloth substrate using a liquid pycnometer method or a gas pycnometer method.

[0009] In some embodiments of the present application, the method for obtaining the actual thickness of the test prepreg comprises: obtaining the design stacking mode of copper foil and PCB; stacking the test prepreg and the copper foil in a press equipment according to the design stacking mode of the PCB; pressing the test prepreg and the copper foil using the press equipment to obtain a PCB sample; measuring the actual thickness of the PCB sample, and obtaining the actual thickness of the test prepreg according to the actual thickness of the PCB sample and the number of pressing layers.

[0010] In some embodiments of the present application, the method for measuring the actual thickness of the PCB sample comprises, removing the outer copper foil of the PCB sample using an etchant; measuring the actual thickness of the PCB sample from which the outer copper foil is removed.

[0011] In some embodiments of the present application, the method for measuring the actual thickness of the PCB sample comprises, measuring the actual thickness values of 25 points on the PCB sample; eliminating the maximum value and the minimum value from the actual thickness values of the 25 points, and obtaining the actual thickness values of the remaining 23 points; taking the average value of the actual thickness values of the 23 points as the actual thickness of the PCB sample.

[0012] In some embodiments of the present application, the actual thickness reference value of the first prepreg is obtained by the following formula: , In the formula, F is the actual thickness reference value of the first prepreg after pressing, E is the theoretically calculated thickness of the first prepreg, a is the press coefficient, A is the basis weight of the first prepreg, B is the basis weight of the cloth base, C is the density of the prepreg resin, D is the density of the cloth base, β is the unit conversion coefficient between the basis weight of the first prepreg and the basis weight of the cloth base, F1 is the actual thickness of the test sample prepreg after pressing, and E1 is the theoretically calculated thickness of the test sample prepreg.

[0013] In some embodiments of the present application, the basis weight of the first prepreg is in units of g / 64in2, the basis weight of the cloth base is in units of g / m2, and the unit conversion coefficient β = 412.9.

[0014] Compared with the prior art, the present application has the following beneficial effects: The method for obtaining the actual thickness reference value of the prepreg after pressing provided by the present application can obtain the press coefficient with universality under the same press equipment and pressing parameter settings after obtaining the actual thickness of the test sample prepreg after pressing, and then the actual thickness reference value of the first prepreg after pressing can be obtained according to the physical parameters of the cloth base and the physical parameters of the first prepreg which are the same as the resin material of the test sample prepreg, thereby avoiding the problem of testing the actual thickness reference value of the first prepreg after pressing for multiple times and avoiding the problem of consuming manpower, materials and time in testing. BRIEF DESCRIPTION OF DRAWINGS

[0015] In order to more clearly illustrate the technical solutions in the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0016] Figure 1 is the step flow chart of the method for obtaining the actual thickness reference value of the prepreg after pressing provided by the present application; Figure 2 is a schematic diagram of the layer position when the test sample prepreg and the copper foil are pressed according to the designed stacking mode; Figure 3 is a schematic diagram of uniform arrangement of points on one surface of the PCB sample when the 25-point method is used to test the thickness of the PCB sample; In the figure: 1, test sample prepreg; 2, copper foil; 3, point. DETAILED DESCRIPTION

[0017] The technical solutions of this application / the embodiments thereof will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application / the embodiments thereof, and not all embodiments thereof. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit this application / the application thereof or its application or use. Example 1

[0018] This embodiment provides a method for obtaining a reference value of the actual thickness of a prepreg during lamination, in order to solve the problems of high manpower, material, and time consumption in existing methods for obtaining the reference value of the actual thickness of a prepreg during lamination.

[0019] Figure 1 This is a flowchart illustrating a method for obtaining a reference value for the actual thickness of a prepreg during lamination, as described in Embodiment 1 of the present invention. This flowchart merely illustrates the logical sequence of the method described in this embodiment. Without conflict, different methods may be used in other possible embodiments of the present invention. Figure 1 Complete the steps shown or described in the order indicated.

[0020] refer to Figure 1 The method for obtaining the reference value of the actual thickness of the prepreg lamination provided in this embodiment includes, Obtain the basis weight and density of the fabric substrate; the fabric substrate is the skeleton material of the PCB, so the physical parameters of the fabric substrate need to be considered when obtaining the reference value of the actual thickness of the prepreg lamination. Obtain the actual thickness of the prepreg 1 under lamination, and obtain the press coefficient based on the actual thickness and the theoretical thickness of the prepreg. The press coefficient represents the degree of deviation between the actual thickness and the theoretical thickness under the current press equipment and pressing parameter settings. This degree of deviation has a certain universality under the same press equipment and pressing parameter settings. The basis weight and resin density of the first prepreg are obtained. Based on the basis weight of the first prepreg, combined with the press coefficient, resin density, fabric basis weight, and fabric density, a reference value for the actual pressed thickness of the first prepreg is obtained. By pressing the test sample prepreg 1 to obtain a universally applicable press coefficient under the same press equipment and pressing parameter settings, the reference value for the actual pressed thickness of the first prepreg can be obtained based on the physical parameters of the fabric and the physical parameters of the first prepreg, which uses the same resin material as the test sample prepreg 1. This avoids the process of obtaining the reference value for the actual pressed thickness of the first prepreg through multiple tests, thus avoiding the problems of wasted manpower, materials, and time. Example 2

[0021] This embodiment provides a method for obtaining the reference value of the actual thickness of the prepreg during lamination. This embodiment is an optimization based on Embodiment 1 to improve the technical effect and refine the technical solution. For details not described in this embodiment, please refer to Embodiment 1.

[0022] As one embodiment, Embodiment 1 mentions obtaining the basis weight of the first prepreg and the density of the prepreg resin. Regarding the density of the prepreg resin, the reference values ​​provided by the manufacturer are often based on the manufacturer's testing environment. Due to differences in ambient temperature and air pressure, PCB manufacturers should conduct secondary testing locally to correct the data, as detailed below: Prepare a standard-sized square mold; the material of the square mold should ideally be similar to that of the press equipment to achieve a similar thermal conductivity, simulating the PCB manufacturing environment; Heat the prepreg resin to the actual process temperature, then pour the prepreg resin into a square mold; After the prepreg resin cures, a resin cube of standard size is obtained; The density of the resin cubes is obtained using a hydrometer method or a specific gravity method, and the density of the resin cubes is used as the density of the prepreg resin.

[0023] The density of the prepreg resin obtained by the above method is more valuable for reference.

[0024] Example 1 also mentions obtaining the basis weight and density of the fabric. As one example, it includes... Obtaining fabric-based raw materials; Cut standard-sized fabric sheets from the fabric raw material; Use an electronic scale to obtain the weight of a standard-sized fabric substrate, and then obtain the basis weight of the fabric substrate based on the weight of the standard-sized fabric substrate; using an electronic scale to obtain the weight of a standard-sized fabric substrate provides more accurate data. The density of the fabric substrate is obtained by testing standard-sized fabric substrates using either the liquid specific gravity bottle method or the gas specific gravity bottle method, based on the weight of the fabric substrate.

[0025] To better bond with resin materials, the fabric substrate used as the PCB skeleton is often a porous material. Traditional volume measurement methods cannot accurately obtain its density. Therefore, the liquid specific gravity bottle method or gas specific gravity bottle method is used. By allowing fluid to penetrate into the gaps in the fabric substrate, the volume of a standard-sized fabric substrate sheet is accurately collected. Combined with the weight of the standard-sized fabric substrate sheet obtained by an electronic scale, the density of the fabric substrate is accurately obtained.

[0026] As one embodiment, the actual thickness of the prepreg 1 was obtained by pressing as follows: Obtain the design stacking method of copper foil 2 and PCB; refer to Figure 2According to the PCB design stacking method, test sample prepreg 1 and copper foil 2 are stacked in the press equipment; actual pressing simulation is carried out; A PCB sample was obtained by pressing the prepreg 1 and copper foil 2 together using a press. Under normal circumstances, the thickness of copper foil 2 can be ignored. The actual thickness of the PCB sample is measured, and the actual thickness of the prepreg 1 is obtained based on the actual thickness of the PCB sample and the number of lamination layers.

[0027] For example, Figure 2 The PCB sample used two test sample prepreg sheets 1 stacked together. Therefore, the actual thickness of the PCB sample can be obtained by dividing the actual thickness of the test sample prepreg sheet 1 by 2.

[0028] As one embodiment, some PCBs have thicker copper foil 2 (e.g., copper plates). To achieve higher simulation accuracy for the reference value, the aforementioned measurement of the actual thickness of the PCB sample includes... Use an etchant to remove the outer copper foil 2 of the PCB sample; The actual thickness of the PCB sample after the outer copper foil 2 was removed was measured.

[0029] As one embodiment, reference Figure 3 Measure the actual thickness of the PCB sample, including The actual thickness values ​​at 25 points 3 on the PCB sample are measured; the 25 points 3 can be randomly or uniformly distributed on the surface of the PCB sample. The maximum and minimum values ​​were removed from the actual thickness values ​​at 25 points 3 to eliminate potential measurement errors, leaving 23 actual thickness values ​​at 23 points 3. The average value of the actual thickness at 23 points 3 is taken as the actual thickness of the PCB sample.

[0030] The actual thickness of the PCB sample obtained by the above method was obtained by taking 25 points to get the thickness that is closest to the actual situation.

[0031] As one embodiment, the reference value for the actual thickness of the first prepreg during lamination is obtained by calculating the following formula: , In the formula, F is the reference value of the actual thickness of the first semi-cured sheet, E is the theoretical calculated thickness of the first semi-cured sheet, α is the press coefficient, A is the basis weight of the first semi-cured sheet, B is the basis weight of the cloth base, C is the density of the resin in the semi-cured sheet, D is the density of the cloth base, β is the unit conversion coefficient between the basis weight of the first semi-cured sheet and the basis weight of the cloth base, F1 is the actual thickness of the test sample semi-cured sheet 1, and E1 is the theoretical calculated thickness of the test sample semi-cured sheet 1.

[0032] Since the pressing coefficient α is obtained by comparing the actual thickness of the test sample prepreg 1 with the theoretically calculated thickness, test sample prepregs of varying thicknesses can be selected to obtain multiple pressing coefficients α. The average value is then taken as the final pressing coefficient α. Because the first prepreg and the test sample prepreg 1 are made of the same material, the density C of the prepreg resin is a fixed value, and the same fabric base is used. Therefore, the basis weight B and density D of the fabric base can also be fixed values. The unit conversion factor β varies depending on the numerical units of the basis weight A of the first prepreg and the basis weight B of the fabric base. For first prepregs of different thicknesses, their basis weight A is measured. A is the only independent variable, and the only dependent variable is the reference value F of the actual thickness of the first prepreg during pressing.

[0033] As one embodiment, the basis weight of the first prepreg is expressed in g / 64in², which is commonly used in the industry, and the basis weight of the cloth is expressed in g / m², which is commonly used in the industry. According to the conversion between imperial and metric units, the area conversion factor from 64 in² to cm² is β=64 × 6.4516 ≈ 412.9.

[0034] Below is a more specific example. Refer to Table 1 for the physical data of the first semi-cured sheet of different thicknesses. The meanings of A, B, C, D, E, F and α are the same as above, only the wording is different. The unit conversion factor β is 412.9.

[0035] Prepreg with R / C=71, i.e., the first serial number 1, was used as test sample prepreg 1. Prepreg is abbreviated as PP, and the cloth base is made of fiberglass cloth. It was used to obtain the reference value of the actual thickness of the other three types of prepregs.

[0036] Table 1. Physical data of first prepregs of different thicknesses

[0037] The measured basis weight (B) of the fabric substrate of test sample semi-cured sheet 1 was 26 g / m², the density (D) of the fabric substrate was 2.3 g / cm³, and the density (C) of the prepreg resin was 1.35 g / cm³. Using traditional theory, the theoretically calculated thickness (E1) of test sample semi-cured sheet 1 was 0.00604 cm. Test sample semi-cured sheet 1 was then... Figure 2 The actual thickness F1 of the prepreg 1 tested by the pressing test was 0.00601 cm, and the pressing coefficient α was calculated to be 99.51%. Using the 99.51% calculation coefficient α and other known data in Table 1, the basis weight A of the first prepregs corresponding to serial numbers 2, 3 and 4 (4.1 g / 64 in², 4.4 g / 64 in² and 4.75 g / 64 in², respectively) can be used to obtain reference values ​​F for the actual pressing thickness of 0.00653 cm, 0.00706 cm and 0.00769 cm, respectively.

[0038] Different press equipment and pressing parameter combinations correspond to different press coefficients α. However, under the same press coefficient α, only a small number of types of prepregs can be measured. Then, by using the press coefficient α and other physical parameters, the actual pressing thickness reference value of prepregs of almost all types and thicknesses of this resin can be obtained, which greatly reduces the consumption of manpower, resources and time.

[0039] As one embodiment, the test sample prepreg 1 can be 8 inches * 8 inches in size, the square mold size is 1 cm * 1 cm * 1 cm, and the standard size cloth substrate size is 1 m * 1 m.

[0040] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are used only for the convenience of describing the invention and 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, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0041] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installed," "connected," "linked," "located in," "equipped with," "located in," "installed," "set," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances. "Hinged connection" includes "rotational connection."

[0042] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for obtaining a reference value for the actual thickness of a prepreg during lamination, characterized in that, include: Obtain the basis weight and density of the fabric. Obtain the actual thickness of the test sample prepreg (1) during pressing, and obtain the press coefficient based on the actual thickness of the pressing and the theoretical thickness of the prepreg. Obtain the basis weight of the first prepreg and the density of the prepreg resin. Based on the basis weight of the first prepreg, combined with the press coefficient, the density of the prepreg resin, the basis weight of the cloth base, and the density of the cloth base, obtain a reference value for the actual pressing thickness of the first prepreg.

2. The method for obtaining the reference value of the actual thickness of the prepreg during lamination according to claim 1, characterized in that, The process of obtaining the basis weight of the first prepreg and the density of the prepreg resin includes, Prepare a square mold of standard size; Heat the prepreg resin to the actual process temperature and pour the prepreg resin into the square mold; After the semi-cured sheet resin cures, a resin cube of standard size is obtained; The density of the resin cube is obtained using a hydrometer method or a specific gravity method, and the density of the resin cube is used as the density of the prepreg resin.

3. The method for obtaining the reference value of the actual thickness of the prepreg during lamination according to claim 1, characterized in that, The process of obtaining the basis weight and density of the fabric includes, Obtaining fabric-based raw materials; Standard-sized fabric sheets are cut from the fabric raw material; The weight of the standard-sized fabric substrate is obtained using an electronic scale, and the basis weight of the fabric substrate is obtained based on the weight of the standard-sized fabric substrate. The density of the fabric substrate is obtained by testing the standard-sized fabric substrate using either the liquid specific gravity bottle method or the gas specific gravity bottle method, based on the weight of the fabric substrate.

4. The method for obtaining the reference value of the actual thickness of the prepreg during lamination according to claim 1, characterized in that, The actual thickness of the prepreg (1) test sample was obtained by: Obtain the design stacking method of copper foil (2) and PCB; According to the PCB design stacking method, the test sample prepreg (1) and the copper foil (2) are stacked in the press equipment. The test sample prepreg (1) and the copper foil (2) are pressed together using the press equipment to obtain a PCB sample; The actual thickness of the PCB sample is measured, and the actual thickness of the prepreg (1) of the test sample is obtained based on the actual thickness of the PCB sample and the number of lamination layers.

5. The method for obtaining the reference value of the actual thickness of the prepreg during lamination according to claim 4, characterized in that, The measurement of the actual thickness of the PCB sample includes, The outer copper foil of the PCB sample was removed using an etchant (2); The actual thickness of the PCB sample after the outer copper foil (2) was removed was measured.

6. The method for obtaining the reference value of the actual thickness of the prepreg lamination according to claim 4, characterized in that, The measurement of the actual thickness of the PCB sample includes, The actual thickness values ​​were measured at 25 points (3) on the PCB sample; The maximum and minimum values ​​are removed from the actual thickness values ​​of the 25 points (3), leaving the actual thickness values ​​of 23 points (3); The average value of the actual thickness of the 23 points (3) is taken as the actual thickness of the PCB sample.

7. The method for obtaining the reference value of the actual thickness of the prepreg during lamination according to claim 1, characterized in that, The reference value for the actual thickness of the first prepreg after lamination is obtained by the following formula: ， In the formula, F is the reference value of the actual thickness of the first semi-cured sheet, E is the theoretical calculated thickness of the first semi-cured sheet, α is the press coefficient, A is the basis weight of the first semi-cured sheet, B is the basis weight of the cloth base, C is the density of the resin in the semi-cured sheet, D is the density of the cloth base, β is the unit conversion coefficient between the basis weight of the first semi-cured sheet and the basis weight of the cloth base, F1 is the actual thickness of the test sample semi-cured sheet (1) and E1 is the theoretical calculated thickness of the test sample semi-cured sheet (1).

8. The method for obtaining the reference value of the actual thickness of the prepreg lamination according to claim 7, characterized in that, The basis weight of the first semi-cured sheet is expressed in g / 64in², the basis weight of the cloth base is expressed in g / m², and the unit conversion factor β = 412.9.

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