A method for improving the lack of glue of thick copper circuit board

Abstract

The application relates to the technical field of circuit board processing, in particular to a method for improving glue deficiency of thick copper circuit boards. The method for improving glue deficiency of thick copper circuit boards comprises the following steps: obtaining a copper plate laminated body, the copper plate laminated body comprising at least one core plate and at least one semi-solid composite layer, the semi-solid composite layer comprising a plurality of semi-cured sheets, the semi-cured sheet comprising a resin layer and glass cloth, the core plate comprising two copper plates and an insulating layer, and the copper plate of the core plate close to the semi-solid composite layer being provided with an etching area; pressing the copper plate laminated body; and the number of the semi-cured sheet layers satisfying the formula: Z >= [H+h1*(1-x1)+h2*(1-x2)] / (m-n-H) or Z >= [H+h1*(1-x1)] / (m-n-H). The application dynamically adjusts the number of the semi-cured sheets, ensures that the resin can fully fill the etching area of the core plate in the pressing process, avoids the glue deficiency defect caused by insufficient resin, and realizes the balance between the structural strength and reliability.

Description

Technical Field

[0001] This invention relates to the field of circuit board processing technology, and more specifically, to a method for improving the lack of adhesive in thick copper circuit boards. Background Technology

[0002] With the rapid development of power electronic equipment towards high power density, integration and lightweight, ultra-thick copper circuit boards, with their excellent current carrying capacity and heat dissipation characteristics, have gradually replaced the copper wire winding technology of traditional flux motors and become the preferred solution for high-power circuit design.

[0003] However, the industrial application of ultra-thick copper structures faces significant technological challenges. When the copper layer thickness exceeds a certain limit, the depth of the trenches formed after circuit etching increases dramatically, placing higher demands on the filling capacity of the interlayer dielectric resin. Existing stack-up designs are prone to two major technical defects when dealing with ultra-thick copper structures: 1) Vacuum areas formed by obstructed resin flow fronts lead to incomplete filling, resulting in micropores in the dielectric layer during thermosetting; 2) Insufficient resin layer thickness after curing causes stress concentration at the copper-dielectric interface. These problems manifest as obvious delamination after thermal stress testing, leading to board explosion and ultimately circuit board failure.

[0004] Therefore, there is an urgent need to develop a method to improve the glue shortage in thick copper circuit boards in order to avoid glue shortage in ultra-thick copper boards.

[0005] In view of this, the present invention is hereby proposed. Summary of the Invention

[0006] One objective of this invention is to provide a method for improving the glue shortage of thick copper circuit boards, so as to solve the technical problem in the prior art that thick copper boards are prone to glue shortage, leading to board explosion and circuit board failure.

[0007] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted:

[0008] A method for improving insufficient adhesive on thick copper circuit boards includes the following steps:

[0009] A copper plate laminate is obtained, the copper plate laminate comprising at least one core plate and at least one semi-solid composite layer, the semi-solid composite layer comprising a plurality of semi-cured sheets, each semi-cured sheet comprising a resin layer and a glass cloth located inside therein, the core plate comprising two copper plates and an insulating layer therebetween, and an etched area is provided on the surface of the copper plate of the core plate near the semi-solid composite layer; the copper plate laminate is subjected to a pressing process.

[0010] When only one surface of the semi-solid composite layer is in contact with the etched area of ​​the core board, the copper plate laminate satisfies formula (I): Z≥[H+h1×(1-x1)] / (mnH). When both surfaces of the semi-solid composite layer are in contact with the etched areas of the two core boards respectively, the copper plate laminate satisfies formula (II): Z≥[H+h1×(1-x1)+h2×(1-x2)] / (mnH). Where Z is the number of prepreg layers, and Z in formula (Ⅰ) is the integer closest to [H+h1×(1-x1) / ] / (mnH); Z in formula (Ⅱ) is the integer closest to [H+h1×(1-x1)+h2×(1-x2)] / (mnH); H is the distance between the laminated glass cloth and the adjacent copper plate or the adjacent prepreg; h1 and h2 represent the thickness of the copper plate adjacent to the prepreg composite layer, x1 is the residual copper rate of the chip with copper plate thickness h1, and x2 is the residual copper rate of the chip with copper plate thickness h2; m is the theoretical thickness of a single prepreg; and n is the thickness of the glass cloth.

[0011] In some implementations, H ≥ 5 μm.

[0012] In some implementations, h1 satisfies: 105μm≤h1≤420μm.

[0013] In some implementations, h2 satisfies: 105μm≤h2≤420μm.

[0014] In some implementations, x1 satisfies: 10% ≤ x1 < 100%.

[0015] In some implementations, x2 satisfies: 10% ≤ x2 < 100%.

[0016] In some implementations, n satisfies: 10μm≤n≤100μm.

[0017] In some implementations, m satisfies: 25μm≤m≤200μm.

[0018] In some embodiments, the glass cloth has a plurality of through holes, wherein the area of ​​any one of the through holes is 1.5 mm². 2 ~5mm 2 .

[0019] In some embodiments, the resin layer content in the prepreg is greater than or equal to 65%.

[0020] In some implementations, when multiple glass cloths have different through-hole specifications, the glass cloth with larger through-holes is closer to the core board.

[0021] In some implementations, when the resin content of the prepreg is different, the prepreg with a higher resin content is closer to the core board.

[0022] In some embodiments, the semi-solid composite layer has only one surface in contact with the etched area of ​​the core board, while the other surface of the semi-solid composite layer is in contact with the outer copper layer. The outer copper layer is located on the outermost side of the copper plate laminate.

[0023] In some embodiments, the copper plate laminate satisfies the following relationship: L2=L1×β, L1=(DK), K=h1×(1-x1)+h2×(1-x2), or K=h1×(1-x1); where L2 is the actual thickness of the semi-solid composite layer after the copper plate laminate is pressed, L1 is the theoretical thickness of the semi-solid composite layer after the copper plate laminate is pressed, D is the theoretical thickness of the semi-solid composite layer, and β is a correction coefficient, which is 85%~95%.

[0024] In some embodiments, the maximum pressure of the pressing process is 430–450 psi, and the pressing time at the maximum pressure is 130–150 min.

[0025] In some embodiments, the pressing process involves a pressure-increasing process before the maximum pressure process and a pressure-reducing process after the maximum pressure process; the pressure-increasing process includes a first pressure increase, a second pressure increase, and a third pressure increase; the pressure-reducing process includes a first pressure decrease, a second pressure decrease, and a third pressure decrease; the pressure of the first pressure increase is 90–110 psi, and the holding time of the first pressure increase is 3–6 min; the pressure of the second pressure increase is 240–260 psi, and the holding time of the second pressure increase is 5–7 min; the pressure of the third pressure increase is 370–390 psi, and the holding time of the third pressure increase is 9–11 min; the pressure of the first pressure decrease is 290–310 psi, the pressure of the second pressure decrease is 190–210 psi, the pressure of the third pressure decrease is 90–110 psi, and the holding times of the first pressure decrease, the second pressure decrease, and the third pressure decrease are 8–12 min, respectively.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0027] This invention, by constructing a relational formula, can dynamically adjust the number of layers Z of the prepreg to ensure that the resin can fully fill the etched area of ​​the core board during the pressing process, avoiding the "insufficient glue" defect caused by insufficient resin, and avoiding the decrease in interlayer bonding force caused by excessive resin, thus achieving a balance between structural strength and reliability. Attached Figure Description

[0028] 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.

[0029] Figure 1 This is a schematic diagram of the copper plate stack of the four-layer copper plate of the present invention;

[0030] Figure 2 This is a schematic diagram of the structure of the copper plate laminate of Embodiment 1 of the present invention;

[0031] Figure 3 This is a schematic diagram of the prepreg of the present invention;

[0032] Figure 4 This is a cross-sectional view of the copper plate laminate of Embodiment 3 of the present invention.

[0033] Figure 5 This is a cross-sectional view of the pressing process in Comparative Example 1 of the present invention;

[0034] Figure 6 This is a diagram showing the warp and weft yarn interlacing of 106 and 1080 specification glass cloth.

[0035] Figure label:

[0036] 1-First core board, 2-Second core board, 3-Second semi-solid composite layer, 4-Outer copper layer, 5-First semi-solid composite layer, 6-Glass cloth, 7-Resin layer, 101-Copper plate, 102-Insulating layer, 1011-Etched area. Detailed Implementation

[0037] The embodiments of the present invention will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer are followed. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0038] According to one aspect of the present invention, the present invention relates to a method for improving insufficient adhesive on thick copper circuit boards, comprising the following steps:

[0039] A copper plate laminate is obtained, the copper plate laminate comprising at least one core plate and at least one semi-solid composite layer, the semi-solid composite layer comprising a plurality of semi-cured sheets, each semi-cured sheet comprising a resin layer and a glass cloth located inside therein, the core plate comprising two copper plates and an insulating layer therebetween, and an etched area is provided on the surface of the copper plate of the core plate near the semi-solid composite layer; the copper plate laminate is subjected to a pressing process.

[0040] When only one surface of the semi-solid composite layer is in contact with the etched area of ​​the core board, the copper plate laminate satisfies formula (I): Z≥[H+h1×(1-x1)] / (mnH). When both surfaces of the semi-solid composite layer are in contact with the etched areas of the two core boards respectively, the copper plate laminate satisfies formula (II): Z≥[H+h1×(1-x1)+h2×(1-x2)] / (mnH). Where Z is the number of prepreg layers, and Z in formula (Ⅰ) is the integer closest to [H+h1×(1-x1) / ] / (mnH); Z in formula (Ⅱ) is the integer closest to [H+h1×(1-x1)+h2×(1-x2)] / (mnH); H is the distance between the laminated glass cloth and the adjacent copper plate or the adjacent prepreg; h1 and h2 represent the thickness of the copper plate adjacent to the prepreg composite layer, x1 is the residual copper rate of the chip with copper plate thickness h1, and x2 is the residual copper rate of the chip with copper plate thickness h2; m is the theoretical thickness of a single prepreg; and n is the thickness of the glass cloth.

[0041] This invention, by constructing a relational formula, can dynamically adjust the number of layers Z of the prepreg to ensure that the resin can fully fill the etched area of ​​the core board during the pressing process, avoiding the "insufficient glue" defect caused by insufficient resin, and avoiding the decrease in interlayer bonding force caused by excessive resin, thus achieving a balance between structural strength and reliability.

[0042] The materials used in the laminates involved in this invention are all conventional materials. The resin layers include epoxy resin, modified epoxy resin, polyphenylene ether resin, etc. The core board is obtained using conventional methods.

[0043] In some implementations, H is ≥ 5μm, such as 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, etc. A larger H ensures the reliability and electrical performance of the circuit board.

[0044] In some implementations, h1 satisfies: 105μm ≤ h1 ≤ 420μm. In some implementations, h2 satisfies: 105μm ≤ h2 ≤ 420μm. For example, 105μm, 120μm, 150μm, 200μm, 250μm, 300μm, 350μm, 400μm, 420μm, etc., or any value within a range of two.

[0045] In some embodiments, x1 satisfies: 10% ≤ x1 < 100%. In some embodiments, x2 satisfies: 10% ≤ x2 < 100%. The values ​​of x2 and x1 are, for example, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, etc., or any range between the two. Residual copper rate refers to the percentage of the area of ​​the trace area to the total area of ​​the copper layer after etching, where there are trace areas and non-trace substrate areas.

[0046] In some implementations, n satisfies: 10μm ≤ n ≤ 100μm, for example, 10μm, 20μm, 30μm, 40μm, 50μm, 60μm, 70μm, 80μm, 90μm, 100μm, etc., or any value within a range of two. Glass cloth, also called fiberglass, is a reinforcing material for circuit board substrates, woven from warp and weft fiberglass bundles, providing excellent mechanical properties in circuit boards. The glass cloth has several through holes, each with an area of ​​1.5mm². 2 ~5mm 2 Prepregs with larger openings in the glass cloth are required, such as 106 or 1080 glass cloth. The large openings in the warp and weft interlacing of 106 and 1080 glass cloth facilitate the flow of resin and other colloidal components between the prepregs under high temperature and pressure, ensuring sufficient filling of gaps. In some embodiments, the resin content in the prepreg is greater than or equal to 65%, for example, 65%, 70%, 80%, or 90%. A suitable resin content allows for better filling of thick copper circuit layers during the lamination process.

[0047] In some embodiments, when multiple glass cloths have different through-hole specifications, the glass cloth with larger through-holes is closer to the core board. In some embodiments, when the resin content of the prepreg is different, the prepreg with a higher resin content is closer to the core board. This ensures that the prepreg near the location requiring adhesive filling has sufficient resin flow to fill the gaps during the pressing process.

[0048] In some implementations, m satisfies: 25μm ≤ m ≤ 200μm, for example, 25μm, 50μm, 75μm, 100μm, 125μm, 150μm, 175μm, 200μm, etc., or any value within a range of two. The theoretical thickness of a single prepreg sheet includes the thickness of the glass cloth and the thickness of the resin layer.

[0049] In some embodiments, the semi-solid composite layer has only one surface in contact with the etched area of ​​the core board, while the other surface of the semi-solid composite layer is in contact with the outer copper layer. The outer copper layer is located on the outermost side of the copper plate laminate.

[0050] In some embodiments, the copper plate laminate further includes two outer copper layers, multiple core plates and multiple semi-solid composite sheets are alternately stacked and located between the two outer copper layers; the two sides of the core plates are provided with etched areas.

[0051] In some embodiments, the copper plate laminate includes an outer copper layer, a first semi-solid composite layer, a first core plate, a second semi-solid composite layer, a second core plate, the first semi-solid composite layer, and the outer copper layer, which are stacked sequentially.

[0052] In some embodiments, the number of prepreg sheets between the copper plates is 5 to 10; the number of prepreg sheets between the outer copper layer and the adjacent core plate is 3 to 6.

[0053] In some embodiments, the copper plate laminate satisfies the following relationship: L2=L1×β, L1=(DK), K=h1×(1-x1)+h2×(1-x2), or K=h1×(1-x1); where L2 is the actual thickness of the semi-solid composite layer after the copper plate laminate is pressed, L1 is the theoretical thickness of the semi-solid composite layer after the copper plate laminate is pressed, D is the theoretical thickness of the semi-solid composite layer, which is the sum of the product of the thickness of different types and specifications of glass cloth and their corresponding number of sheets; β is a correction coefficient, β is 85%~95%.

[0054] Because ultra-thick copper plates typically require a larger amount of adhesive, the pressure and high-pressure time used in the lamination process are both higher. Due to the specific lamination parameters for thick copper plates, the resin is in a molten state and under high pressure during lamination. Some adhesive is squeezed to the edge of the plate, resulting in relatively more residual adhesive at the edge and a reduced adhesive content in the product area. Therefore, the thickness of the laminated dielectric layer is relatively smaller than the theoretical value. Data collection and analysis of the dielectric layer thickness under the same lamination conditions for thick copper plates show that the actual dielectric thickness is 5%-15% smaller than the theoretical dielectric thickness. Therefore, when calculating the theoretical dielectric thickness, a correction factor β of 85%-95% can be applied.

[0055] In some embodiments, the maximum pressure of the pressing process is 430 to 450 psi, such as 430 psi, 440 psi, 450 psi, etc., and the pressing process time at the maximum pressure is 130 to 150 min, such as 130 min, 140 min, or 150 min, etc.

[0056] In some embodiments, the pressing process involves a pressure increase before the maximum pressure treatment and a pressure decrease after the maximum pressure treatment; the pressure increase includes a first pressure increase, a second pressure increase, and a third pressure increase; the pressure decrease includes a first pressure decrease, a second pressure decrease, and a third pressure decrease. The pressure of the first pressure increase is 90–110 psi (e.g., 90 psi, 100 psi, 110 psi), and the holding time of the first pressure increase is 3–6 min (e.g., 4 min, 5 min, or 6 min, etc.); the pressure of the second pressure increase is 240–260 psi (e.g., 240 psi, 250 psi, 260 psi, etc.), and the holding time of the second pressure increase is 5–7 min (e.g., 5 min, 6 min, or 7 min); the pressure of the third pressure increase is 370–390 psi (e.g., 370 psi, 380 psi, 390 psi, etc.), and the holding time of the third pressure increase is 9–11 min (e.g., 9 min, 11 min, etc.). The pressure of the first pressure drop is 290–310 psi (e.g., 290 min, 295 min, 300 min, 305 min, etc.), the pressure of the second pressure drop is 190–210 psi (e.g., 190 psi, 195 psi, 200 psi, 210 psi, etc.), and the pressure of the third pressure drop is 90–110 psi (e.g., 90 psi, 95 psi, 100 psi, 105 psi, etc.). The holding time of the first, second, and third pressure drops is 8–12 min (e.g., 8 min, 9 min, 10 min, or 11 min, etc.).

[0057] Suitable lamination conditions are more conducive to ensuring lamination effect, ensuring glue filling effect, improving the structural stability and electrochemical performance of the circuit board, and making it more reliable.

[0058] In some implementations, if the lamination process does not meet the above conditions, insufficient adhesive may occur, resulting in reduced circuit board performance.

[0059] In some embodiments, riveting and fusion are performed before pressing, with a fusion temperature of 190°C to 315°C (e.g., 190°C, 200°C, 250°C, 300°C, 315°C, etc.) and a time of 20s to 90s (e.g., 20s, 30s, 40s, 50s, 60s, 70s, 80s, or 90s, etc.).

[0060] After undergoing thermal stress treatments such as reflow soldering and tin bleaching, the finished circuit board is free from defects such as delamination and board bursting. Furthermore, after cutting the product into sections and examining the cross-sections under a microscope, no missing adhesive issues are found.

[0061] In some embodiments, a schematic diagram of a copper plate laminate with four thick copper plates is shown below. Figure 1As shown, it includes a first core board 1, a second core board 2, and a second semi-solid composite layer 3 located between the two core boards. The first core board 1 and the second core board 2 each independently include two copper plates and an insulating layer. An etched area is provided on the surface of the copper layer near the second semi-solid composite layer 3. The semi-solid composite layer includes a plurality of semi-cured sheets, each semi-cured sheet including a resin layer 7 and a glass cloth 6 located inside it.

[0062] The following explanation, combined with specific embodiments and comparative examples, further illustrates the point.

[0063] Example 1

[0064] A method for improving insufficient adhesive on thick copper circuit boards includes the following steps:

[0065] (a) Obtain the materials of each layer of the copper plate 101 laminate, including the first outer copper layer 4, the first semi-solid composite layer 5, the first core plate 1, the second semi-solid composite layer 3, the second core plate 2, and the second outer copper layer 4 of the first semi-solid composite layer. The first core plate 1 and the second core plate 2 each independently include two copper plates 101 and an insulating layer 102 between them. Etched areas 1011 are provided on both sides of the first core plate 1 and the second core plate 2. The first semi-solid composite layer 5 and the second semi-solid composite layer 3 each independently include a number of semi-cured sheets. Each semi-cured sheet includes a resin layer and a glass cloth located inside it. The number of semi-cured sheets in the second semi-solid composite layer 3 is determined according to the formula Z≥[H+h1×(1-x1)+h2×(1 The formula [H+h1×(1-x1)+h2×(1-x2)] / (mnH) is calculated, where Z is the number of prepreg layers, and Z is the integer closest to [H+h1×(1-x1)+h2×(1-x2)] / (mnH); H is the distance between the laminated glass cloth and the adjacent copper plate or adjacent prepreg, H is 10μm; h1 and h2 represent the thickness of the copper plate adjacent to the prepreg composite layer, h1=h2=210μm; x1 is the residual copper rate of the chip with copper plate thickness h1; x2 is the residual copper rate of the chip with copper plate thickness h2, x1=x2=72%; m is the theoretical thickness of a single prepreg, m=86μm; n is the thickness of the glass cloth, n=53μm; using 1080 specification, such as... Figure 6 As shown. The number of prepreg sheets in the first semi-solid composite layer 5 is calculated using the formula Z≥[H+h1×(1-x1)] / (mnH) or Z≥[h2×(1-x2)] / (mnH), where Z is the integer closest to [H+h1×(1-x1)] / (mnH) or [h2×(1-x2)] / (mnH). The number of prepreg sheets and the H value of the first semi-solid composite layer 5 and the second semi-solid composite layer 3 are shown in Table 1 below.

[0066] (b) The outer copper layer 4, the first semi-solid composite layer 5, the first core board 1, the second semi-solid composite layer 3, the second core board 2, the first semi-solid composite layer 5, and the outer copper layer 4 are stacked sequentially to obtain a copper plate 101 laminate, as shown below. Figure 2 As shown, after being fixed by riveting and fusion (temperature 300℃, time 60s), the circuit board intermediate product is obtained through pressing. The process parameters for pressing include:

[0067] 1) Pressure: 100 psi, holding time: 5 min.

[0068] 2) Pressure: 250 psi, holding time: 6 min; pressurization time: 4 min.

[0069] 3) Pressure: 380 psi, holding time: 10 min.

[0070] 4) Pressure: 440 psi, holding time: 10 min.

[0071] 5) Pressure: 440 psi, holding time: 10 min.

[0072] 6) Pressure: 440 psi, holding time: 125 min.

[0073] 7) Pressure: 300 psi, holding time: 10 min.

[0074] 8) Pressure: 200 psi, holding time: 10 min.

[0075] 9) Pressure: 100 psi, holding time: 10 min.

[0076] (c) After drilling, circuitry, and outer layer etching, the inner and outer layers are interconnected. Finally, the circuit board is finished by applying solder resist ink and surface treatment.

[0077] Example 2

[0078] A method for improving insufficient adhesive on thick copper circuit boards differs from the embodiments in that:

[0079] The thickness of copper plate 101 is 245μm.

[0080] The number of semi-cured sheets and H-values ​​of the first semi-solid composite layer 5 and the second semi-solid composite layer 3 are shown in Table 1 below.

[0081] Example 3

[0082] A method for improving insufficient adhesive on thick copper circuit boards differs from the embodiments in that:

[0083] The thickness of copper plate 101 is 280μm.

[0084] The number of semi-cured sheets and H-values ​​of the first semi-solid composite layer 5 and the second semi-solid composite layer 3 are shown in Table 1 below.

[0085] Example 4

[0086] A method for improving insufficient adhesive on thick copper circuit boards differs from the embodiments in that:

[0087] The thickness of copper plate 101 is 315μm.

[0088] The number of semi-cured sheets and H-values ​​of the first semi-solid composite layer 5 and the second semi-solid composite layer 3 are shown in Table 1 below.

[0089] Example 5

[0090] A method for improving insufficient adhesive on thick copper circuit boards differs from the embodiments in that:

[0091] The thickness of copper plate 101 is 350μm.

[0092] The number of semi-cured sheets and H-values ​​of the first semi-solid composite layer 5 and the second semi-solid composite layer 3 are shown in Table 1 below.

[0093] Example 6

[0094] A method for improving insufficient adhesive on thick copper circuit boards differs from Example 1 in that:

[0095] The copper layer is 6 oz thick.

[0096] According to the formula L1=(DK), K=h1×(1-x1)+h2×(1-x2), or K=h1×(1-x1); where L1 is the theoretical thickness of the semi-solid composite layer after the copper plate 101 laminate is pressed, D is the theoretical thickness of the semi-solid composite layer, h1 and x1 represent the thickness of the core plate and the residual copper ratio on one side of the copper plate 101 laminate, respectively, and h2 and x2 represent the thickness of the core plate and the residual copper ratio on the other side of the copper plate 101 laminate, respectively.

[0097] Test the actual thickness of the semi-solid composite layer.

[0098] Example 7

[0099] A method for improving insufficient adhesive on thick copper circuit boards differs from Example 1 in that:

[0100] The copper layer is 7 oz thick.

[0101] According to the formula L1=(DK), K=h1×(1-x1)+h2×(1-x2), or K=h1×(1-x1); where L1 is the theoretical thickness of the semi-solid composite layer after the copper plate 101 laminate is pressed, D is the theoretical thickness of the semi-solid composite layer, h1 and x1 represent the thickness of the core plate and the residual copper ratio on one side of the copper plate 101 laminate, respectively, and h2 and x2 represent the thickness of the core plate and the residual copper ratio on the other side of the copper plate 101 laminate, respectively.

[0102] Test the actual thickness of the semi-solid composite layer.

[0103] Example 8

[0104] A method for improving insufficient adhesive on thick copper circuit boards differs from Example 1 in that:

[0105] The copper layer is 8 oz thick.

[0106] According to the formula L1=(DK), K=h1×(1-x1)+h2×(1-x2), or K=h1×(1-x1); where L1 is the theoretical thickness of the semi-solid composite layer after the copper plate 101 laminate is pressed, D is the theoretical thickness of the semi-solid composite layer, h1 and x1 represent the thickness of the core plate and the residual copper ratio on one side of the copper plate 101 laminate, respectively, and h2 and x2 represent the thickness of the core plate and the residual copper ratio on the other side of the copper plate 101 laminate, respectively.

[0107] Test the actual thickness of the semi-solid composite layer.

[0108] Comparative Example 1

[0109] A method for preparing a thick copper circuit board includes the following steps:

[0110] (a) Obtain the materials of each layer of the copper plate 101 laminate, including the first outer copper layer 4, the first semi-solid composite layer 5, the first core plate 1, the second semi-solid composite layer 3, the second core plate 2, and the second outer copper layer 4 of the first semi-solid composite layer. The first core plate 1 and the second core plate 2 each independently include two copper plates 101 and an insulating layer 102 between them. The two sides of the first core plate 1 and the second core plate 2 are provided with etching areas 1011. The first semi-solid composite layer 5 and the second semi-solid composite layer 3 each independently include a number of semi-cured sheets. Each semi-cured sheet includes a resin layer and a glass cloth located inside it. The distance between the glass cloth after lamination and the adjacent copper plate or the adjacent semi-cured sheet is 10 μm. The thickness of the copper plate adjacent to the semi-solid composite layer is 280 μm. The residual copper rate of the chip is 72%. The theoretical thickness of a single semi-cured sheet is 86 μm. The thickness of the glass cloth is 53 μm. The 1080 specification is adopted. The first semi-solid composite layer 5 has 3 semi-cured sheets, and the second semi-solid composite layer 3 has 6 sheets.

[0111] Steps (b) and (c) are the same as in Example 3.

[0112] Experimental Example

[0113] I. Number of semi-cured sheets, H value and filling effect in Examples 1-5.

[0114] Table 1. Filling effect

[0115]

[0116] As shown in Table 1, the circuit board obtained by the method of the present invention has no obvious missing adhesive. The laminated cross-section of the thick copper laminate obtained by the method of Example 3 is as follows: Figure 4 As shown. The pressed slice of Comparative Example 1 is shown. Figure 5 As shown, there is a clear lack of glue.

[0117] II. Thickness of the Pressed Semi-solid Composite Layer in Examples 6-8

[0118] The thickness of the laminated semi-solid composite layer is measured by taking a cross-sectional image of the slice and then measuring it with a microscope. The measurement points of the slice include the edge and center of the plate to obtain the overall thickness distribution of the plate surface.

[0119] Table 2 Thickness of Pressed Semi-solid Composite Layer

[0120]

[0121] As shown in Table 2, the actual dielectric layer thickness of the present invention is 5%-15% smaller than the theoretical dielectric layer thickness, i.e., L2 = L1 × β, where L2 is the actual thickness of the semi-solid composite layer after the copper plate laminate is pressed, L1 is the theoretical thickness of the semi-solid composite layer after the copper plate laminate is pressed, and β is a correction coefficient, which is 85% to 95%.

[0122] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for improving insufficient adhesive on thick copper circuit boards, characterized in that, Includes the following steps: A copper plate laminate is obtained, the copper plate laminate comprising at least one core plate and at least one semi-solid composite layer, the semi-solid composite layer comprising a plurality of semi-cured sheets, each semi-cured sheet comprising a resin layer and a glass cloth located inside therein, the core plate comprising two copper plates and an insulating layer therebetween, and an etched area is provided on the surface of the copper plate of the core plate near the semi-solid composite layer. The copper plate laminate is subjected to a pressing process; When only one side of the semi-solid composite layer is in contact with the etched area of ​​the core board, the copper plate laminate satisfies formula (Ⅰ): Z≥[H+h1×(1-x1)] / (mnH); When the two sides of the semi-solid composite layer are in contact with the etched areas of the two core plates respectively, the copper plate laminate satisfies formula (II): Z≥[H+h1×(1-x1)+h2×(1-x2)] / (mnH); Where Z is the number of prepreg layers, and Z in formula (Ⅰ) is the integer closest to [H+h1×(1-x1)] / (mnH); Z in formula (Ⅱ) is the integer closest to [H+h1×(1-x1)+h2×(1-x2)] / (mnH); H is the distance between the laminated glass cloth and the adjacent copper plate or the adjacent prepreg; h1 and h2 represent the thickness of the copper plate adjacent to the prepreg composite layer, x1 is the residual copper rate of the chip with copper plate thickness h1, and x2 is the residual copper rate of the chip with copper plate thickness h2; m is the theoretical thickness of a single prepreg; and n is the thickness of the glass cloth.

2. The method for improving insufficient adhesive on thick copper circuit boards according to claim 1, characterized in that, It includes at least one of the following features (1) to (7): (1) The H ≥ 5 μm; (2) The h1 satisfies: 105μm≤h1≤420μm; (3) The h2 satisfies: 105μm≤h2≤420μm; (4) The x1 satisfies: 10% ≤ x1 < 100%; (5) The x2 satisfies: 10% ≤ x2 < 100%; (6) The n satisfies: 10μm≤n≤100μm; (7) The m satisfies: 25μm≤m≤200μm.

3. The method for improving insufficient adhesive on thick copper circuit boards according to claim 1, characterized in that, It includes at least one of the following features (1) to (2): (1) The glass cloth has several through holes, and the area of ​​any one of the through holes is 1.5 mm². 2 ~5mm 2 ; (2) The resin layer content in the semi-cured sheet is greater than or equal to 65%.

4. The method for improving insufficient adhesive on thick copper circuit boards according to claim 3, characterized in that, When multiple glass cloths have different through-hole specifications, the glass cloth with larger through-holes is closer to the core board.

5. The method for improving insufficient adhesive on thick copper circuit boards according to claim 3, characterized in that, When the resin content of the prepreg is different, the prepreg with a higher resin content is closer to the core board.

6. The method for improving insufficient adhesive on thick copper circuit boards according to claim 1, characterized in that, When only one side of the semi-solid composite layer is in contact with the etched area of ​​the core board, the other side of the semi-solid composite layer is in contact with the outer copper layer.

7. The method for improving insufficient adhesive on thick copper circuit boards according to claim 1, characterized in that, The copper plate laminate satisfies the following relationship: L2=L1×β, L1=(DK), K=h1×(1-x1)+h2×(1-x2), or K=h1×(1-x1); where L2 is the actual thickness of the semi-solid composite layer after the copper plate laminate is pressed, L1 is the theoretical thickness of the semi-solid composite layer after the copper plate laminate is pressed, D is the theoretical thickness of the semi-solid composite layer, and β is a correction coefficient, which is 85%~95%.

8. The method for improving insufficient adhesive on thick copper circuit boards according to claim 1, characterized in that, The maximum pressure of the pressing process is 430–450 psi, and the pressing time at the maximum pressure is 130–150 min.

9. The method for improving insufficient adhesive on thick copper circuit boards according to claim 8, characterized in that, The pressing process employs a pressure-increasing process before the maximum pressure process and a pressure-reducing process after the maximum pressure process; the pressure-increasing process includes a first pressure increase, a second pressure increase, and a third pressure increase; the pressure-reducing process includes a first pressure reduction, a second pressure reduction, and a third pressure reduction.

10. The method for improving insufficient adhesive on thick copper circuit boards according to claim 9, characterized in that, The first pressurization pressure is 90–110 psi, and the holding time is 3–6 min; the second pressurization pressure is 240–260 psi, and the holding time is 5–7 min; the third pressurization pressure is 370–390 psi, and the holding time is 9–11 min. The pressure of the first pressure drop is 290–310 psi, the pressure of the second pressure drop is 190–210 psi, and the pressure of the third pressure drop is 90–110 psi. The holding times of the first, second, and third pressure drops are 8–12 min, respectively.

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