A method for improving the warpage of copper-clad ceramic substrates

Abstract

This invention relates to the field of copper-clad ceramic substrate technology, specifically a method for improving the warpage of copper-clad ceramic substrates. It includes the following steps: Step 1: Film pattern optimization design: (1) Calculate the difference in residual copper rate ΔR based on the residual copper rate of the patterned surface and the residual copper rate of the non-patterned surface of the copper-clad ceramic substrate; (2) Based on the above ΔR, dynamically adjust the width of the long side process edge of the copper-clad ceramic substrate so that ΔR reaches the target value, and then perform dimple hole arrangement to obtain a pre-optimized copper-clad ceramic substrate; Step 2: Stress relief: Perform heat treatment on the pre-optimized copper-clad ceramic substrate obtained in Step 1 to obtain the finished product.

Description

Technical Field

[0001] This invention relates to the field of copper-clad ceramic substrate technology, specifically a method for improving the warpage of copper-clad ceramic substrates. Background Technology

[0002] With the rapid development of automotive power modules, copper-clad ceramic substrates (hereinafter referred to as "substrates") are increasingly widely used in power modules. During the packaging process, the substrate needs to be soldered to various components, and its surface flatness directly affects the soldering reliability and module lifespan.

[0003] Existing technologies mainly improve warpage through the following methods: First, thinning the copper layer by grinding the non-patterned surface is a common method to balance thermal expansion stress, thereby adjusting the residual copper ratio difference to improve warpage. However, grinding will damage the surface morphology of the substrate, causing customers to refuse to use it due to appearance requirements. Second, patent CN113993285A reduces the residual copper ratio by shrinking the process edge, thereby adjusting the process edge to improve warpage, but without combining structural optimization, the effect is limited. Third, patent CN221885105U improves warpage by positioning or balancing welding stress, thereby using dimple hole arrangement, but without systematically designing the hole arrangement and process parameters, it is impossible to accurately control warpage.

[0004] Existing technologies cannot achieve dynamic control of residual copper ratio without changing the surface morphology; in addition, there is a lack of synergistic optimization of process parameters and structural design, resulting in insufficient warpage improvement (typical value >0.8mm).

[0005] In conclusion, addressing the aforementioned issues and developing a method to improve the warpage of copper-clad ceramic substrates is of great significance. Summary of the Invention

[0006] The purpose of this invention is to provide a method for improving the warpage of copper-clad ceramic substrates, so as to solve the problems mentioned in the prior art.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A method for improving the warpage of a copper-clad ceramic substrate includes the following steps:

[0009] Step 1: Film chart optimization design:

[0010] (1) The difference in residual copper rate ΔR is calculated based on the residual copper rate of the patterned surface and the residual copper rate of the non-patterned surface of the copper-clad ceramic substrate.

[0011] (2) Based on the above ΔR, dynamically adjust the width of the long side process edge of the copper-clad ceramic substrate so that ΔR reaches the target value, and then perform Dimple hole arrangement to obtain the pre-optimized copper-clad ceramic substrate.

[0012] Step 2: Stress relief: The pre-optimized copper-clad ceramic substrate obtained in Step 1 is subjected to heat treatment to obtain the finished product.

[0013] In a further proposed solution, based on the aforementioned ΔR, the width of the long side of the copper-clad ceramic substrate is dynamically adjusted according to the formula: ΔR = residual copper rate of non-patterned surface - residual copper rate of patterned surface; residual copper rate of non-patterned surface = copper area ratio of non-patterned surface of copper-clad ceramic substrate × copper thickness; residual copper rate of patterned surface = copper area ratio of patterned surface of copper-clad ceramic substrate × copper thickness.

[0014] In a more optimized manner, in step 1, the residual copper rate difference ΔR = residual copper rate of non-patterned surface - residual copper rate of patterned surface.

[0015] More optimally, the residual copper ratio of the non-patterned surface is equal to the copper area ratio of the non-patterned surface of the copper-clad ceramic substrate multiplied by the copper thickness; the residual copper ratio of the patterned surface is equal to the copper area ratio of the patterned surface of the copper-clad ceramic substrate multiplied by the copper thickness.

[0016] Ideally, in step 1, the target value is the absolute value of ΔR ≤ 1.5%.

[0017] In a further proposed solution, the reason for using the non-patterned surface residual copper rate minus the patterned surface residual copper rate is that the side with the higher residual copper rate is usually the non-patterned surface.

[0018] In a more optimized manner, the specific parameters of the heat treatment in step 2 are as follows: temperature range of 250℃~300℃; holding time of 3~10 minutes; and in the gas atmosphere, nitrogen concentration ≥99.99% and oxygen content ≤50ppm.

[0019] In a further embodiment, the heat treatment employs a zoned temperature-controlled nitrogen heating furnace (temperature difference ≤ ±2℃) to ensure uniform heating of the copper-clad ceramic substrate, thereby promoting a smoother warping.

[0020] Ideally, the warpage value of the finished product is ≤0.4mm.

[0021] In a more optimized manner, the reduction range of the width of the long side process edge is 0%~80%, and the adjusted minimum width is ≥2mm.

[0022] In a further proposed solution, since adjusting the width of the short side process edge of the copper-clad ceramic substrate requires space for the placement of the mark point, the width of the short side process edge is not adjusted; only the width of the long side process edge is adjusted, and the reduction range is dynamically adjusted based on the difference in the target residual copper rate.

[0023] In a more optimized manner, the Dimple hole is circular; the diameter of the Dimple hole is 0.4~0.8mm, the hole spacing is 1.5~3.5 times the hole diameter; and the depth of the Dimple hole is 50%~70% of the copper thickness of the copper-clad ceramic substrate.

[0024] A more optimized rule for the arrangement of Dimple holes is: one row of Dimple holes is set for every 1mm of the process edge width along the long side.

[0025] In a further proposed solution, dimple holes are arranged to reduce the proportion of local copper area and further balance the residual copper rate. Since there are positioning marks for production processing on the short side process edge width, dimple holes are not arranged on the short side process edge width to avoid equipment misjudgment during production.

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

[0027] (1) The present invention replaces grinding with film pattern design and dimple hole arrangement to maintain the integrity of the substrate surface, rather than a destructive process;

[0028] (2) The process edge adjustment and Dimple hole arrangement of this scheme are dynamically matched and optimized together, thereby improving the control accuracy of residual copper rate difference.

[0029] (3) This solution reduces residual thermal stress by inhibiting oxidation reaction through thermal stress release in a nitrogen environment, and reduces warpage value to below 0.4 mm (traditional process >0.8 mm).

[0030] (4) This solution is universal and compatible, applicable to substrates of different sizes (4mm×4mm to 150mm×150mm), and compatible with AMB / DBC processes. Attached Figure Description

[0031] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0032] Figure 1 Before optimizing the design of the film diagram;

[0033] Figure 2 The structural diagram after optimization of the film diagram;

[0034] Figure 3 The warped box plot of Example 1;

[0035] Figure 4 The warped box plot of Example 2;

[0036] Figure 5 The warped box plot of Example 3;

[0037] Figure 6 The warped box plot of Example 4;

[0038] Figure 7This is a box plot of warped curves for Comparative Example 1;

[0039] Figure 8 The box plot is for Comparative Example 2;

[0040] Figure 9 The box plot is for Comparative Example 3;

[0041] Figure 10 This is a box plot of warped curves for Comparative Example 4. Detailed Implementation

[0042] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0043] In the following embodiments, it is specifically noted that:

[0044] (1) Before the optimization design of the film diagram, as shown Figure 1 As shown in the image, the shaded area represents ceramic, the remaining area represents copper foil, and the lines represent circuit grooves; the optimized film image is as follows. Figure 2 As shown in the figure, the shaded area is ceramic, the rest is copper foil, the lines are circuit grooves, and the circles are dimple holes;

[0045] (2) Non-patterned surface residual copper ratio = copper area ratio of non-patterned surface of copper-clad ceramic substrate × copper thickness; patterned surface residual copper ratio = copper area ratio of patterned surface of copper-clad ceramic substrate × copper thickness.

[0046] Example 1: A method for improving the warpage of a copper-clad ceramic substrate, comprising the following steps:

[0047] Step 1: Film pattern optimization design: (1) The long side process edge width of the copper-clad ceramic substrate is 15mm, such as Figure 1 As shown, based on the residual copper rate of the patterned surface and the residual copper rate of the non-patterned surface of the copper-clad ceramic substrate, and the formula residual copper rate difference ΔR = non-patterned surface residual copper rate - patterned surface residual copper rate, the residual copper rate difference ΔR is calculated; (2) The copper-clad ceramic substrate is dynamically adjusted according to ΔR, the reduction of the long side process edge width is 80%, and the minimum width after adjustment is 3mm. Then, 3 rows of circular dimple holes with a diameter of 0.8mm are added to the long side process edge width, the hole spacing is 1.2mm, and the depth of the dimple hole is 60% of the copper thickness of the copper-clad ceramic substrate, such as Figure 2 As shown, a pre-optimized copper-clad ceramic substrate was obtained;

[0048] Step 2: Under a nitrogen atmosphere, with a nitrogen concentration of 99.99% and an oxygen content of 50ppm, the pre-optimized copper-clad ceramic substrate obtained in Step 1 is heat-treated in a zone-controlled temperature nitrogen heating furnace at 300℃ for 10 minutes to obtain the finished product.

[0049] Example 2: A method for improving the warpage of a copper-clad ceramic substrate, comprising the following steps:

[0050] Step 1: Film pattern optimization design: (1) The long side process edge width of the copper-clad ceramic substrate is 10mm. According to the residual copper rate of the patterned surface and the residual copper rate of the non-patterned surface of the copper-clad ceramic substrate, the residual copper rate difference ΔR = residual copper rate of non-patterned surface - residual copper rate of patterned surface is calculated to obtain the residual copper rate difference ΔR; (2) The copper-clad ceramic substrate is dynamically adjusted according to ΔR. The reduction of the long side process edge width is 80%, and the minimum width after adjustment is 2mm. Then, two rows of circular dimple holes with a diameter of 0.8mm are added to the long side process edge width. The hole spacing is 1.2mm, and the depth of the dimple hole is 60% of the copper thickness of the copper-clad ceramic substrate to obtain the pre-optimized copper-clad ceramic substrate.

[0051] Step 2: Under a nitrogen atmosphere, with a nitrogen concentration of 99.99% and an oxygen content of 50ppm, the pre-optimized copper-clad ceramic substrate obtained in Step 1 is heat-treated in a zone-controlled temperature nitrogen heating furnace at 300℃ for 10 minutes to obtain the finished product.

[0052] Example 3: A method for improving the warpage of a copper-clad ceramic substrate, comprising the following steps:

[0053] Step 1: Film pattern optimization design: (1) The long side process edge width of the copper-clad ceramic substrate is 4mm. According to the residual copper rate of the patterned surface and the residual copper rate of the non-patterned surface of the copper-clad ceramic substrate, the residual copper rate difference ΔR = residual copper rate of non-patterned surface - residual copper rate of patterned surface is calculated. (2) The copper-clad ceramic substrate is dynamically adjusted according to ΔR. The reduction of the long side process edge width is 50%. The minimum width after adjustment is 2mm. Then, two rows of circular dimple holes with a diameter of 0.8mm are added to the long side process edge width. The hole spacing is 1.2mm. The depth of the dimple hole is 60% of the copper thickness of the copper-clad ceramic substrate. The pre-optimized copper-clad ceramic substrate is obtained.

[0054] Step 2: Under a nitrogen atmosphere, with a nitrogen concentration of 99.99% and an oxygen content of 50ppm, the pre-optimized copper-clad ceramic substrate obtained in Step 1 is heat-treated in a zone-controlled temperature nitrogen heating furnace at 300℃ for 10 minutes to obtain the finished product.

[0055] Example 4: A method for improving the warpage of a copper-clad ceramic substrate, comprising the following steps:

[0056] Step 1: Film pattern optimization design: (1) The long side process edge width of the copper-clad ceramic substrate is 2.5mm. According to the residual copper rate of the patterned surface and the residual copper rate of the non-patterned surface of the copper-clad ceramic substrate, the residual copper rate difference ΔR = residual copper rate of non-patterned surface - residual copper rate of patterned surface is calculated to obtain the residual copper rate difference ΔR; (2) According to ΔR, the copper-clad ceramic substrate is dynamically adjusted. Two rows of circular dimple holes with a diameter of 0.8mm are added to the long side process edge width. The hole spacing is 1.2mm. The depth of the dimple hole is 60% of the copper thickness of the copper-clad ceramic substrate to obtain the pre-optimized copper-clad ceramic substrate;

[0057] Step 2: Under a nitrogen atmosphere, with a nitrogen concentration of 99.99% and an oxygen content of 50ppm, the pre-optimized copper-clad ceramic substrate obtained in Step 1 is heat-treated in a zone-controlled temperature nitrogen heating furnace at 300℃ for 10 minutes to obtain the finished product.

[0058] Comparative Example 1: Based on Example 1, without performing film plot optimization design and heat treatment, only the residual copper rate difference ΔR was calculated to obtain a copper-clad ceramic substrate.

[0059] Comparative Example 2: Based on Example 2, without performing film plot optimization design and heat treatment, only the residual copper rate difference ΔR was calculated to obtain a copper-clad ceramic substrate.

[0060] Comparative Example 3, based on Example 3, does not perform film plot optimization design or heat treatment, but only calculates the residual copper rate difference ΔR to obtain a copper-clad ceramic substrate.

[0061] Comparative Example 4, based on Example 4, does not perform film plot optimization design or heat treatment, but only calculates the difference in residual copper rate ΔR to obtain a copper-clad ceramic substrate.

[0062] Testing experiments: The residual copper rate on the front side, the residual copper rate on the back side before adjustment, the residual copper rate on the back side after adjustment, the ΔR before adjustment, the ΔR after adjustment, and the warpage value of Examples 1-4 and Comparative Examples 1-4 were tested and calculated. The results are shown in Table 1. Based on the results, warpage box plots of Examples 1-4 and Comparative Examples 1-4 were plotted. Figures 3-10 As shown;

[0063]

[0064] Results Analysis: According to the data analysis in Table 1, based on the data from Examples 1-4, the film pattern optimization design and heat treatment implemented in this scheme result in thermal stress release, reduced warpage value and ΔR, and improved warpage of the copper-clad ceramic substrate. However, based on the data from Comparative Examples 1-4, the warpage of the copper-clad ceramic substrate obtained without implementing the film pattern optimization design and thermal stress release scheme was not improved.

[0065] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A method for improving the warpage of a copper-clad ceramic substrate, characterized in that: Includes the following steps: Step 1: Film chart optimization design: (1) The difference in residual copper rate ΔR is calculated based on the residual copper rate of the patterned surface and the residual copper rate of the non-patterned surface of the copper-clad ceramic substrate. (2) Based on the above ΔR, dynamically adjust the width of the long side process edge of the copper-clad ceramic substrate so that ΔR reaches the target value, and then perform Dimple hole arrangement to obtain the pre-optimized copper-clad ceramic substrate. Step 2: Stress relief: The pre-optimized copper-clad ceramic substrate obtained in Step 1 is subjected to heat treatment to obtain the finished product; The dimple hole is circular; its diameter is 0.4~0.8mm, and the spacing between holes is 1.5~3.5 times the hole diameter; the depth of the dimple hole is 50%~70% of the copper thickness of the copper-clad ceramic substrate. The rule for arranging Dimple holes is: one row of Dimple holes is set for every 1mm of the process edge width along the long side.

2. The method for improving warpage of a copper-clad ceramic substrate according to claim 1, characterized in that: In step 1, the residual copper rate difference ΔR = residual copper rate of non-patterned surface - residual copper rate of patterned surface.

3. The method for improving warpage of a copper-clad ceramic substrate according to claim 2, characterized in that: The residual copper ratio of the non-patterned surface = the proportion of copper area on the non-patterned surface of the copper-clad ceramic substrate × copper thickness; the residual copper ratio of the patterned surface = the proportion of copper area on the patterned surface of the copper-clad ceramic substrate × copper thickness.

4. The method for improving warpage of a copper-clad ceramic substrate according to claim 1, characterized in that: In step 1, the target value is the absolute value of ΔR ≤ 1.5%.

5. The method for improving warpage of a copper-clad ceramic substrate according to claim 1, characterized in that: In step 2, the specific parameters of the heat treatment are: temperature range of 250℃~300℃; holding time of 3~10 minutes; and in the gas atmosphere, nitrogen concentration ≥99.99% and oxygen content ≤50ppm.

6. The method for improving warpage of a copper-clad ceramic substrate according to claim 1, characterized in that: The warpage value of the finished product is ≤0.4mm.

7. The method for improving warpage of a copper-clad ceramic substrate according to claim 1, characterized in that: The reduction range of the width of the long side process edge is 0%~80%, and the minimum width after adjustment is ≥2mm.

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