Method for improving glue shortage of thick copper circuit board

Abstract

The invention relates to the technical field of circuit board processing, in particular to a method for improving glue shortage of a thick copper circuit board. A method for improving glue shortage of a thick copper circuit board comprises the steps that a copper plate laminated body is obtained, the copper plate laminated body comprises at least one core plate and at least one semi-solid composite layer, the semi-solid composite layer comprises a plurality of prepregs, each prepreg comprises a resin layer and glass cloth, the core plate comprises two copper plates and an insulating layer, and the two copper plates are arranged on the insulating layer; the copper plate of the core plate close to the semi-solid composite layer is provided with an etching area; pressing the copper plate laminated body; the number of the prepreg layers satisfies the following formula: Z > = [H + h1 * (1-x1) + h2 * (1-x2)] / (m-n-H) or Z > = [H + h1 * (1-x1)] / (m-n-H). The number of layers of the prepregs is dynamically adjusted, it is ensured that the etching area of the core plate can be fully filled with resin in the pressing process, the defect of glue shortage caused by insufficient resin is avoided, and balance of structural strength and reliability is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of circuit board processing, and more particularly, to a method for improving the lack of glue in thick copper circuit boards. Background Art

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

[0003] However, the industrial application of ultra-thick copper structures faces significant process challenges. When the copper layer thickness exceeds a certain thickness, the groove depth formed after line etching increases sharply, which poses higher requirements for the filling ability of the interlayer dielectric resin. The existing lamination design is prone to two major technical defects when dealing with ultra-thick copper structures: 1) The vacuum area formed by the obstruction of the resin flow front leads to incomplete glue filling and the generation of microvoids in the dielectric layer during the thermal pressing process; 2) The insufficient thickness of the resin layer after curing causes stress concentration at the copper layer-dielectric interface. These problems manifest as obvious delamination phenomena after thermal stress testing, resulting in the problem of board explosion and ultimately the failure of the circuit board.

[0004] Therefore, there is an urgent need to develop a method for improving the lack of glue in thick copper circuit boards to avoid the lack of glue in ultra-thick copper plates.

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

[0006] An object of the present invention is to provide a method for improving the lack of glue in thick copper circuit boards to solve the technical problems in the prior art that thick copper plates are prone to lack of glue, resulting in board explosion and circuit board failure.

[0007] To achieve the above object of the present invention, the following technical solutions are specifically adopted:

[0008] A method for improving the lack of glue in thick copper circuit boards includes the following steps:

[0009] Obtain a copper plate laminate, the copper plate laminate includes at least one core board and at least one semi-solid composite layer, the semi-solid composite layer includes a plurality of prepregs, each prepreg includes a resin layer and a glass cloth located inside it, the core board includes two copper plates and an insulating layer in the middle, and an etching area is provided on the copper plate surface of the core board close to the semi-solid composite layer; perform a pressing process on the copper plate laminate.

[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)] / (m - n - H). When both surfaces of the semi-solid composite layer are respectively in contact with the etched areas of the two core boards, the copper plate laminate satisfies formula (II): Z≥[H + h1×(1 - x1)+h2×(1 - x2)] / (m - n - H). Wherein, Z is the number of prepreg sheets, and in formula (I), Z takes the integer closest to [H + h1×(1 - x1)] / (m - n - H); in formula (II), Z takes the integer closest to [H + h1×(1 - x1)+h2×(1 - x2)] / (m - n - H); H is the distance between the glass cloth after pressing and the adjacent copper plate or the adjacent prepreg; h1 and h2 respectively represent the thicknesses of the copper plates adjacent to the semi-solid composite layer, x1 is the residual copper rate of the chip with the copper plate thickness of h1, and x2 is the residual copper rate of the chip with the copper plate thickness of h2; m is the theoretical pressing thickness of a single prepreg sheet; n is the thickness of the glass cloth.

[0011] In some embodiments, H≥5μm.

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

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

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

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

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

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

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

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

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

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

[0022] In some embodiments, when only one side surface of the semi-solid composite layer is in contact with the etched area of the core board, the other side 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 laminate.

[0023] In some embodiments, the copper laminate satisfies the relational expression: L2 = L1×β, L1 = (D - K), 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 pressing of the copper laminate, L1 is the theoretical thickness of the semi-solid composite layer after pressing of the copper laminate, D is the theoretical thickness of the semi-solid composite layer, β is the correction coefficient, and β is 85% - 95%.

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

[0025] In some embodiments, the pressing process uses a pressure increasing process before the maximum pressure process and a pressure decreasing 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 decreasing 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] By constructing the relational expression, the present invention can dynamically adjust the number of prepreg layers Z to ensure that the resin can fully fill the etched area of the core board during the pressing process, avoid the "resin shortage" defect caused by insufficient resin, avoid the decrease of the interlayer bonding force caused by excessive resin, and achieve the balance between structural strength and reliability. Brief Description of the Drawings

[0028] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0029] Figure 1 Schematic diagram of the copper plate laminate of the 4-layer copper plate of the present invention;

[0030] Figure 2 Schematic diagram of the structure of the copper plate laminate of Embodiment 1 of the present invention;

[0031] Figure 3 Schematic diagram of the prepreg of the present invention;

[0032] Figure 4 Laminating section view of the copper plate laminate of Embodiment 3 of the present invention;

[0033] Figure 5 Laminating section view of the copper plate laminate of Comparative Example 1 of the present invention;

[0034] Figure 6 Interlacing diagram of warp and weft yarns of 106 and 1080 specification glass cloths.

[0035] Reference numerals:

[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 - Etching area. Specific embodiments

[0037] The following will describe the implementation schemes of the present invention in detail in combination with the embodiments. However, those skilled in the art will understand that the following embodiments are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention. For those conditions not specified in the embodiments, they are carried out according to the conventional conditions or the conditions recommended by the manufacturer. For the reagents or instruments not specified for the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0038] According to one aspect of the present invention, the present invention relates to a method for improving the lack of glue in a thick copper circuit board, including the following steps:

[0039] Obtain a copper plate laminate, which includes at least one core board and at least one semi-solid composite layer. The semi-solid composite layer includes a number of prepregs, and each prepreg includes a resin layer and a glass cloth inside it. The core board includes two copper plates and an insulating layer in the middle. An etching area is provided on the copper plate surface of the core board close to the semi-solid composite layer; perform lamination processing on the copper plate laminate.

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

[0041] By constructing a relational expression, the present invention can dynamically adjust the number of prepreg layers Z to ensure that the resin can fully fill the core board etching area during the lamination process, avoid the "resin shortage" defect caused by insufficient resin, avoid the decrease in interlayer bonding force caused by excessive resin, and achieve the balance of structural strength and reliability.

[0042] The materials in the laminate involved in the present invention are all conventional existing materials. The resin layer includes epoxy resin, modified epoxy resin, polyphenylene ether resin, etc. The core board is obtained by conventional methods.

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

[0044] In some embodiments, h1 satisfies: 105μm≤h1≤420μm. In some embodiments, h2 satisfies: 105μm≤h2≤420μm. For example, 105μm, 120μm, 150μm, 200μm, 250μm, 300μm, 350μm, 400μm, 420μm, etc., or the range values between any two of them.

[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 the range values between any two of them. The residual copper rate refers to that after the copper layer of the core board is etched, there will be a circuit area and a substrate area without circuits. The percentage of the area of the circuit area in the area of the entire copper layer is the residual copper rate.

[0046] In some embodiments, n satisfies: 10 μm ≤ n ≤ 100 μm, such as 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, etc., or the range values between any two of them. Glass cloth, also called fiberglass, is a reinforcing material for the circuit board substrate. It is woven by fiberglass bundles in the warp and weft directions and provides excellent mechanical properties in the circuit board. The glass cloth has several through holes, and the area of any of the through holes is 1.5 mm 2 ~5 mm 2 ; It is necessary to use prepregs with a larger opening size of the glass cloth, such as the glass cloth of 106 and 1080. The interweaving method of the warp and weft yarns of the 106 and 1080 specifications has a large opening. These glass cloths with large openings facilitate the flow of colloid components such as resin between the prepregs under high temperature and high pressure to fully flow and fill the voids. In some embodiments, the resin layer content in the prepreg is greater than or equal to 65%, such as 65%, 70%, 80% or 90%, etc. An appropriate resin layer content can better fill the thick copper circuit layer during the lamination process.

[0047] In some embodiments, when multiple glass cloths have different through hole specifications, the glass cloth with a larger through hole is closer to the core board. In some embodiments, when the resin layer content of the prepreg is different, the prepreg with a larger resin layer content is closer to the core board. So that the prepreg close to the position where glue needs to be filled has sufficient resin to flow and fill the voids during the lamination process.

[0048] In some embodiments, m satisfies: 25 μm ≤ m ≤ 200 μm, such as 25 μm, 50 μm, 75 μm, 100 μm, 125 μm, 150 μm, 175 μm, 200 μm, etc., or the range values between any two of them. The lamination theoretical thickness of a single prepreg includes the thickness of the glass cloth and the thickness of the resin layer.

[0049] In some embodiments, when only one side surface of the semi-solid composite layer is in contact with the etched area of the core board, the other side 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, and a plurality of core boards and a plurality of semi-solid composite sheets are alternately laminated and disposed between the two outer copper layers; etching regions are provided on both side surfaces of the core boards.

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

[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 board is 3 to 6.

[0053] In some embodiments, the copper plate laminate satisfies the relationship: L2 = L1×β, L1 = (D - K), 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 pressing of the copper plate laminate, L1 is the theoretical thickness of the semi-solid composite layer after pressing of the copper plate laminate, D is the theoretical thickness of the semi-solid composite layer, which is the sum of the products of the thicknesses of different types and specifications of glass cloth and their corresponding numbers; β is a correction coefficient, and β is 85% - 95%.

[0054] Since ultra-thick copper plates usually require a larger amount of flowing glue, both the pressure and the high-pressure time in the pressing parameters used during pressing are relatively large. In the special pressing parameters of thick copper plates, both the pressure and the high-pressure time are relatively large. When the resin is in a molten state and under high pressure during pressing, part of the glue will be extruded to the edge of the plate, which will result in relatively more glue remaining at the edge of the plate and cause a decrease in the glue content in the product area. Therefore, the thickness of the dielectric layer after pressing is relatively smaller than the theoretical value. By collecting and analyzing data on the thickness of the dielectric layer under the same pressing conditions for thick copper plates, it is found that the actual dielectric thickness is 5% - 15% smaller than the theoretical dielectric thickness. Therefore, a correction coefficient β of 85% - 95% can be multiplied when calculating the theoretical dielectric thickness.

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

[0056] In some embodiments, the pressing process employs a pressure boosting process before the maximum pressure treatment and a pressure reducing process after the maximum pressure treatment; the pressure boosting process includes a first pressure boost, a second pressure boost, and a third pressure boost; the pressure reducing process includes a first pressure reduction, a second pressure reduction, and a third pressure reduction. The pressure of the first pressure boost is 90 - 110 psi (such as 90 psi, 100 psi, 110 psi, etc.), and the holding time of the first pressure boost is 3 - 6 min (such as 4 min, 5 min, or 6 min, etc.); the pressure of the second pressure boost is 240 - 260 psi (such as 240 psi, 250 psi, 260 psi, etc.), and the holding time of the second pressure boost is 5 - 7 min (such as 5 min, 6 min, or 7 min); the pressure of the third pressure boost is 370 - 390 psi (such as 370 psi, 380 psi, 390 psi, etc.), and the holding time of the third pressure boost is 9 - 11 min (such as 9 min, 10 min, 11 min, etc.); the pressure of the first pressure reduction is 290 - 310 psi (such as 290 min, 295 min, 300 min, 305 min, etc.), the pressure of the second pressure reduction is 190 - 210 psi (such as 190 psi, 195 psi, 200 psi, 210 psi, etc.), the pressure of the third pressure reduction is 90 - 110 psi (90 psi, 95 psi, 100 psi, 105 psi, etc.), and the holding times of the first pressure reduction, the second pressure reduction, and the third pressure reduction are 8 - 12 min (such as 8 min, 9 min, 10 min, or 11 min, etc.) respectively.

[0057] Appropriate pressing process conditions are more conducive to ensuring the pressing effect, ensuring the glue filling effect, improving the structural stability and electrochemical performance of the circuit board, and having higher reliability.

[0058] In some embodiments, if the pressing process conditions do not meet the above conditions, a phenomenon of lack of glue will occur, and the performance of the circuit board will be reduced.

[0059] In some embodiments, riveting and fusing are performed before the pressing process, and the fusing temperature is 190°C - 315°C (such as 190°C, 200°C, 250°C, 300°C, 315°C, etc.), and the time is 20 s - 90 s (such as 20 s, 30 s, 40 s, 50 s, 60 s, 70 s, 80 s, or 90 s, etc.).

[0060] After the circuit board finished product undergoes thermal stress treatments such as reflow soldering and tin floating, there are no defects such as delamination and explosion of the board, and when the product is taken for slicing and section processing, no lack of glue problem is observed under a microscope.

[0061] In some embodiments, a schematic diagram of a copper clad laminate with 4 thick copper layers is as 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 etching area is provided on the surface of the copper layer close to the second semi-solid composite layer 3. The semi-solid composite layer includes a plurality of prepregs, and each prepreg includes a resin layer 7 and a glass cloth 6 located inside it.

[0062] The following will be further explained and illustrated in combination with specific embodiments and comparative examples.

[0063] Example 1

[0064] A method for improving the lack of glue in a thick copper circuit board 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 board 1, the second semi-solid composite layer 3, the second core board 2, the first semi-solid composite layer, and the second outer copper layer 4 arranged in layers. The first core board 1 and the second core board 2 each independently include two copper plates 101 and the insulating layer 102 in the middle thereof. Etching areas 1011 are provided on both side surfaces of the first core board 1 and the second core board 2. The first semi-solid composite layer 5 and the second semi-solid composite layer 3 each independently include a plurality of prepregs. Each prepreg includes a resin layer and a glass cloth located inside it. The number of prepregs in the second semi-solid composite layer 3 is calculated according to the formula Z≥[H + h1×(1 - x1) + h2×(1 - x2)] / (m - n - H), where Z is the number of prepreg layers, and Z takes the integer closest to [H + h1×(1 - x1) + h2×(1 - x2)] / (m - n - H); H is the distance between the glass cloth after lamination and the adjacent copper plate or the adjacent prepreg, H is taken as 10μm, h1 and h2 respectively represent the thicknesses of the copper plates adjacent to the semi-solid composite layer, h1 = h2 = 210μm, x1 is the residual copper rate of the chip with a copper plate thickness of h1, x2 is the residual copper rate of the chip with a copper plate thickness of h2, x1 = x2 = 72%, m is the theoretical lamination thickness of a single prepreg, m = 86μm, n is the glass cloth thickness, n = 53μm, and the 1080 specification is adopted, as Figure 6 shown. The number of prepregs in the first semi-solid composite layer 5 is calculated according to the formula Z≥[H + h1×(1 - x1)] / (m - n - H) or Z≥[h2×(1 - x2)] / (m - n - H), and Z takes the integer closest to [H + h1×(1 - x1)] / (m - n - H) or [h2×(1 - x2)] / (m - n - H). The number of prepregs and the value of H in the first semi-solid composite layer 5 and the second semi-solid composite layer 3 are shown in Table 1 below.

[0066] (b) Stack 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 in sequence to obtain a 101-layer copper board laminate. As Figure 2 shown, after being fixed by riveting and fusing methods (temperature is 300 °C, time is 60 s), press-fit treatment is carried out to obtain an intermediate product of the circuit board. The process parameters of the press-fit treatment include:

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

[0068] 2) Pressure: 250 psi, holding time: 6 min; pressure rise 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) Then, after drilling, circuiting, and outer layer etching to form internal and external layer interconnection, finally, solder mask ink covering and surface treatment steps are carried out to obtain a finished circuit board.

[0077] Example 2

[0078] A method for improving the lack of glue in a thick copper circuit board, the difference from the example is that:

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

[0080] The number of sheets and H value of the prepreg 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 the lack of glue in a thick copper circuit board, the difference from the example is that:

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

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

[0085] Example 4

[0086] A method for improving the lack of glue in a thick copper circuit board, which is different from the example in that:

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

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

[0089] Example 5

[0090] A method for improving the lack of glue in a thick copper circuit board, which is different from the example in that:

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

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

[0093] Example 6

[0094] A method for improving the lack of glue in a thick copper circuit board, which is different from Example 1 in that:

[0095] The copper layer thickness is 6 oz.

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

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

[0098] Example 7

[0099] A method for improving the lack of glue in a thick copper circuit board, which is different from Example 1 in that:

[0100] The copper layer thickness is 7 oz.

[0101] According to the formula L1 = (D - K), 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 lamination of the copper plate 101 laminate, D is the theoretical thickness of the semi-solid composite layer, h1 and x1 respectively represent the thickness and residual copper rate of the core board on one side surface of the copper plate 101 laminate, and h2 and x2 respectively represent the thickness and residual copper rate of the core board on the other side surface of the copper plate 101 laminate.

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

[0103] Example 8

[0104] A method for improving the lack of glue in a thick copper circuit board, different from Example 1 in that:

[0105] The copper layer thickness is 8 oz.

[0106] According to the formula L1 = (D - K), 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 lamination of the copper plate 101 laminate, D is the theoretical thickness of the semi-solid composite layer, h1 and x1 respectively represent the thickness and residual copper rate of the core board on one side surface of the copper plate 101 laminate, and h2 and x2 respectively represent the thickness and residual copper rate of the core board on the other side surface of the copper plate 101 laminate.

[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, comprising 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 board 1, the second semi-solid composite layer 3, the second core board 2, the second outer copper layer 4 of the first semi-solid composite layer. The first core board 1 and the second core board 2 each independently include two copper plates 101 and the insulating layer 102 in the middle thereof; etching regions 1011 are provided on both side surfaces of the first core board 1 and the second core board 2. The first semi-solid composite layer 5 and the second semi-solid composite layer 3 each independently include a plurality of prepregs. Each prepreg includes a resin layer and a glass cloth located inside it. The distance between the pressed glass cloth and the adjacent copper plate or the adjacent prepreg 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 lamination thickness of a single prepreg is 86 μm, the glass cloth thickness is 53 μm, and the 1080 specification is adopted. The number of prepregs in the first semi-solid composite layer 5 is 3, and the number of prepregs in the second semi-solid composite layer 3 is 6.

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

[0112] Experimental Example

[0113] I. Number of prepreg sheets, H value, and glue filling effect of Examples 1 - 5.

[0114] Table 1 Glue filling effect

[0115]

[0116] As can be seen from Table 1, there is no obvious lack of glue in the circuit board obtained by the method of the present invention. The lamination section of the thick copper layer stack obtained by the method of Example 3 is as Figure 4 shown. The lamination section of Comparative Example 1 is as Figure 5 shown, with obvious lack of glue.

[0117] II. Thickness of the laminated semi-solid composite layer of Examples 6 - 8

[0118] The measurement method of the thickness of the laminated semi-solid composite layer is to take a cross-sectional picture by slicing and then measure it with a microscope. The measurement sites of the slices taken include the board edge and the board center to obtain the dielectric thickness distribution of the overall board surface.

[0119] Table 2 Thickness of the laminated semi-solid composite layer

[0120]

[0121] As can be seen from Table 2, the actual dielectric layer thickness of the present invention is 5% - 15% smaller than the theoretical dielectric layer thickness, that is, L2 = L1×β, where L2 is the actual thickness of the semi-solid composite layer after lamination of the copper plate stack, L1 is the theoretical thickness of the semi-solid composite layer after lamination of the copper plate stack, and β is the correction coefficient, and β is 85% - 95%.

[0122] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for improving the lack of glue in thick copper circuit boards, characterized in that, It includes the following steps: Obtain a copper plate laminate, which includes at least one core board and at least one semi-solid composite layer. The semi-solid composite layer includes a plurality of prepregs, each prepreg includes a resin layer and a glass cloth inside it. The core board includes two copper plates and an insulating layer in the middle. An etching area is provided on the copper plate surface of the core board close to the semi-solid composite layer; Perform a lamination process on the copper plate laminate; When only one side surface of the semi-solid composite layer is in contact with the etching area of the core board, the copper plate laminate satisfies formula (Ⅰ): Z≥[H+h1×(1 - x1)] / (m - n - H); When both side surfaces of the semi-solid composite layer are respectively in contact with the etching areas of two core boards, the copper plate laminate satisfies formula (Ⅱ): Z≥[H+h1×(1 - x1)+h2×(1 - x2)] / (m - n - H); Wherein, Z is the number of prepreg layers, and Z in formula (Ⅰ) takes the integer closest to [H+h1×(1 - x1)] / (m - n - H); Z in formula (Ⅱ) takes the integer closest to [H+h1×(1 - x1)+h2×(1 - x2)] / (m - n - H); H is the distance between the glass cloth after lamination and the adjacent copper plate or adjacent prepreg; h1 and h2 respectively represent the thicknesses of the copper plates adjacent to the semi-solid composite layer, x1 is the residual copper rate of the chip with a copper plate thickness of h1, and x2 is the residual copper rate of the chip with a copper plate thickness of h2; m is the theoretical lamination thickness of a single prepreg, and n is the thickness of the glass cloth.

2. The method for improving the lack of glue in a thick copper circuit board according to claim 1, wherein It includes at least one of the following features (1) to (7): (1) The H≥5μm; (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 the lack of glue in a thick copper circuit board according to claim 1, characterized in that, It includes at least one of the following features (1) to (2): (1) The glass cloth has a number of through holes, and the area of any of the through holes is 1.5 mm 2 to 5 mm 2 ; (2) The resin layer content in the prepreg is greater than or equal to 65%.

4. The method for improving the lack of glue in a thick copper circuit board according to claim 3, wherein When multiple glass cloths have different via hole specifications, the glass cloth with a larger via hole is closer to the core board.

5. The method for improving the lack of glue in a thick copper circuit board according to claim 3, characterized in that, When the resin layer contents of the prepregs are different, the prepreg with a larger resin layer content is closer to the core board.

6. The method for improving the lack of glue in a thick copper circuit board according to claim 1, wherein When only one side surface of the semi-solid composite layer is in contact with the etching area of the core board, the other side surface of the semi-solid composite layer is in contact with an outer copper layer.

7. The method for improving the lack of glue in a thick copper circuit board according to claim 1, characterized in that, The copper plate laminate satisfies the relational expression: L2 = L1×β, L1=(D - K), K = h1×(1 - x1)+h2×(1 - x2), or K = h1×(1 - x1); wherein, L2 is the actual thickness of the semi-solid composite layer of the copper plate laminate after lamination, L1 is the theoretical thickness of the semi-solid composite layer of the copper plate laminate after lamination, D is the theoretical thickness of the semi-solid composite layer, β is a correction coefficient, and β is 85%~95%.

8. The method for improving the lack of glue in a thick copper circuit board according to claim 1, wherein The maximum pressure of the lamination treatment is 430 - 450 psi, and the treatment time of the lamination treatment at the maximum pressure is 130 - 150 min.

9. The method for improving the lack of glue in a thick copper circuit board according to claim 8, wherein, The lamination treatment adopts a pressure boosting treatment before the maximum pressure treatment and a pressure reducing treatment after the maximum pressure treatment; the pressure boosting treatment includes a first pressure boost, a second pressure boost, and a third pressure boost; the pressure reducing treatment includes a first pressure reduction, a second pressure reduction, and a third pressure reduction.

10. The method for improving the lack of glue in a thick copper circuit board according to claim 9, wherein, The pressure of the first pressure boost is 90 - 110 psi, and the holding time of the first pressure boost is 3 - 6 min; the pressure of the second pressure boost is 240 - 260 psi, and the holding time of the second pressure boost is 5 - 7 min; the pressure of the third pressure boost is 370 - 390 psi, and the holding time of the third pressure boost is 9 - 11 min; The pressure of the first pressure reduction is 290 - 310 psi, the pressure of the second pressure reduction is 190 - 210 psi, the pressure of the third pressure reduction is 90 - 110 psi, and the holding times of the first pressure reduction, the second pressure reduction, and the third pressure reduction are 8 - 12 min respectively.

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