Warping improvement method of copper-clad ceramic substrate

Abstract

The invention relates to the technical field of copper-clad ceramic substrates, in particular to a warping improvement method of a copper-clad ceramic substrate. Comprising the following steps: step 1, optimization design of a film graph: (1) calculating a residual copper rate difference value delta R according to a graph surface residual copper rate and a non-graph surface residual copper rate of a copper-clad ceramic substrate; (2) dynamically adjusting the process edge width of the long edge of the copper-clad ceramic substrate according to the delta R to enable the delta R to reach a target value, and then performing Dimple hole arrangement to obtain a pre-optimized copper-clad ceramic substrate; and 2, stress release: carrying out heat treatment on the pre-optimized copper-clad ceramic substrate obtained in the step 1 to obtain a finished product.

Description

Technical Field

[0001] The invention relates to the technical field of copper-clad ceramic substrates, and in particular to a method for improving warpage of copper-clad ceramic substrates. Background Art

[0002] With the rapid development of automotive power modules, copper-clad ceramic substrates (hereinafter referred to as "substrates") are becoming increasingly common in power modules. Substrates must be soldered to various components during the packaging process, and their surface flatness directly impacts soldering reliability and module life.

[0003] The existing technology mainly improves warpage through the following methods: First, thinning the copper layer by grinding the non-graphic surface is a commonly used means to balance thermal expansion stress, thereby adjusting the residual copper rate difference to improve warpage, but 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 rate by reducing the process edge, and improves warpage by adjusting the process edge, but it is not combined with structural optimization and the effect is limited; third, patent CN221885105U positions or balances welding stress, thereby improving warpage through Dimple hole arrangement, but the hole arrangement and process parameters are not systematically designed, and the warpage cannot be accurately controlled.

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

[0005] In summary, it is of great significance to solve the above problems and study a method for improving the warpage of copper-clad ceramic substrates. Summary of the Invention

[0006] The object of the present invention is to provide a method for improving the warpage of a copper-clad ceramic substrate to solve the problems raised in the prior art.

[0007] To achieve the above object, the present invention provides the following technical solutions:

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

[0009] Step 1: Film pattern optimization design:

[0010] (1) Calculate the residual copper rate difference ΔR based on the residual copper rate on the patterned surface and the residual copper rate on the non-patterned surface of the copper-clad ceramic substrate;

[0011] (2) According to the above ΔR, the long side process edge width of the copper-clad ceramic substrate is dynamically adjusted so that ΔR reaches the target value, and then the Dimple hole arrangement is performed to obtain a pre-optimized copper-clad ceramic substrate;

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

[0013] In a further scheme, according to the above ΔR, the width of the long side process edge of the copper-clad ceramic substrate is dynamically adjusted according to the formula of the residual copper rate difference ΔR = non-graphic surface residual copper rate - graphic surface residual copper rate; non-graphic surface residual copper rate = copper area ratio of the non-graphic surface of the copper-clad ceramic substrate × copper thickness; graphic surface residual copper rate = copper area ratio of the graphic surface of the copper-clad ceramic substrate × copper thickness.

[0014] More optimally, in step 1, the residual copper rate difference ΔR=the residual copper rate of the non-graphic surface-the residual copper rate of the graphic surface.

[0015] More optimally, the non-patterned surface residual copper rate = copper area ratio of the non-patterned surface of the copper-clad ceramic substrate × copper thickness; the patterned surface residual copper rate = copper area ratio of the patterned surface of the copper-clad ceramic substrate × copper thickness.

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

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

[0018] More optimally, in step 2, the specific parameters of the heat treatment are: temperature range of 250°C to 300°C; holding time of 3 to 10 minutes; nitrogen concentration ≥ 99.99% and oxygen content ≤ 50 ppm in the gas atmosphere.

[0019] In a further solution, the heat treatment uses a zoned temperature-controlled nitrogen heating furnace (temperature difference ≤±2°C) to ensure that the copper-clad ceramic substrate is heated evenly, thereby causing the warping to become gentle.

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

[0021] More optimally, the reduction range of the width of the long side process edge is 0% to 80%, and the minimum width after adjustment is ≥2mm.

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

[0023] More optimally, the Dimple holes are circular in shape; the diameter of the Dimple holes is 0.4-0.8 mm, and the hole spacing is 1.5-3.5 times the hole diameter; the depth of the Dimple holes is 50%-70% of the copper thickness of the copper-clad ceramic substrate.

[0024] More optimally, the rule for arranging the Dimple holes is: one row of Dimple holes is set for every 1 mm of the process edge width along the long side.

[0025] In a further solution, the residual copper rate is further balanced by reducing the local copper area ratio through dimple hole arrangement. Since there is a production and processing positioning mark point on the short side process edge width, dimple hole arrangement is not performed on the long side process edge width to avoid misjudgment of the equipment during production.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] (1) The present invention replaces grinding by film pattern design and Dimple hole arrangement to maintain the integrity of the substrate surface without destructive process;

[0028] (2) The process edge adjustment of this solution is dynamically matched with the Dimple hole arrangement, and the two are optimized synergistically, and the accuracy of residual copper rate difference control is improved.

[0029] (3) This solution suppresses oxidation reaction by releasing thermal stress in a nitrogen environment, reducing residual thermal stress and lowering the warpage value to below 0.4mm (conventional process>0.8mm);

[0030] (4) This solution is universal and compatible, and can be applied to substrates of different sizes (4mm×4mm to 150mm×150mm) and is compatible with AMB / DBC processes. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0032] Figure 1 Optimize the design of the structure diagram before the film diagram;

[0033] Figure 2 Optimize the design of the structure diagram for the film diagram;

[0034] Figure 3 is the warpage box plot of Example 1;

[0035] Figure 4 is the warpage box plot of Example 2;

[0036] Figure 5 is the warpage box plot of Example 3;

[0037] Figure 6 is the warpage box plot of Example 4;

[0038] Figure 7is the warpage box plot of Comparative Example 1;

[0039] Figure 8 is the warpage box plot of comparative example 2;

[0040] Figure 9 is the warpage box plot of comparative example 3;

[0041] Figure 10 This is the warpage box plot of Comparative Example 4. DETAILED DESCRIPTION

[0042] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

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

[0044] (1) Before film pattern optimization design Figure 1 As shown in the figure, the shaded part is ceramic, the rest is copper foil, and the lines are circuit grooves; after the film pattern is optimized, Figure 2 As shown, the shaded part is ceramic, the rest is copper foil, the lines are circuit grooves, and the circles are Dimple holes;

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

[0046] Example 1: A method for improving 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 15 mm, such as Figure 1 As shown in FIG, according to the residual copper rate of the graphic surface and the residual copper rate of the non-graphic surface of the copper-clad ceramic substrate, the residual copper rate difference ΔR is calculated according to the formula: residual copper rate difference ΔR = non-graphic surface residual copper rate - graphic surface residual copper rate; (2) the copper-clad ceramic substrate is dynamically adjusted according to ΔR, the width of the long side process edge is reduced by 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 width of the long side process edge, the hole spacing is 1.2mm, and the depth of the dimple holes is 60% of the copper thickness of the copper-clad ceramic substrate, as shown in FIG. Figure 2 As shown, a pre-optimized copper-clad ceramic substrate is obtained;

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

[0049] Example 2: A method for improving 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 10 mm. According to the residual copper rate of the graphic surface and the residual copper rate of the non-graphic surface of the copper-clad ceramic substrate, the residual copper rate difference ΔR is calculated according to the formula: residual copper rate difference ΔR = non-graphic surface residual copper rate - graphic surface residual copper rate; (2) The copper-clad ceramic substrate is dynamically adjusted according to ΔR, and the reduction range of the long side process edge width is 80%. The minimum width after adjustment is 2 mm. Then, two rows of circular dimple holes with a diameter of 0.8 mm are added to the long side process edge width. The hole spacing is 1.2 mm, and the depth of the dimple holes is 60% of the copper thickness of the copper-clad ceramic substrate, thereby obtaining a pre-optimized copper-clad ceramic substrate;

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

[0052] Example 3: A method for improving 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 4 mm. According to the residual copper rate of the graphic surface and the residual copper rate of the non-graphic surface of the copper-clad ceramic substrate, the residual copper rate difference ΔR is calculated according to the formula of residual copper rate difference ΔR = non-graphic surface residual copper rate - graphic surface residual copper rate; (2) The copper-clad ceramic substrate is dynamically adjusted according to ΔR, and the reduction range of the long side process edge width is 50%. The minimum width after adjustment is 2 mm. Then, two rows of circular dimple holes with a diameter of 0.8 mm are added to the long side process edge width. The hole spacing is 1.2 mm, and the depth of the dimple holes is 60% of the copper thickness of the copper-clad ceramic substrate to obtain a pre-optimized copper-clad ceramic substrate;

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

[0055] Example 4: A method for improving 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 2.5 mm. According to the residual copper rate of the graphic surface and the residual copper rate of the non-graphic surface of the copper-clad ceramic substrate, the residual copper rate difference ΔR is calculated according to the formula: residual copper rate difference ΔR = non-graphic surface residual copper rate - graphic surface residual copper rate; (2) According to ΔR, the copper-clad ceramic substrate is dynamically adjusted, and two rows of circular dimple holes with a diameter of 0.8 mm are added to the long side process edge width. The hole spacing is 1.2 mm, and the depth of the dimple holes is 60% of the copper thickness of the copper-clad ceramic substrate to obtain a pre-optimized copper-clad ceramic substrate;

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

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

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

[0060] Comparative Example 3, based on Example 3, without performing film pattern optimization design and heat treatment, and only performing calculation of the residual copper rate difference ΔR, a copper-clad ceramic substrate was obtained.

[0061] Comparative Example 4, based on Example 4, without performing film pattern optimization design and heat treatment, and only performing calculation of the residual copper rate difference ΔR, a copper-clad ceramic substrate was obtained.

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

[0063]

[0064]

[0065] Table 1

[0066] Result analysis: According to the data analysis in Table 1, it can be seen that according to the data of Examples 1 to 4, the film pattern optimization design and heat treatment of this scheme are carried out to release thermal stress, reduce the warpage value and ΔR, and obtain a copper-clad ceramic substrate with improved warpage; However, according to the data of Comparative Examples 1 to 4, the warpage of the copper-clad ceramic substrate obtained without implementing the film pattern optimization design and thermal stress release of this scheme is not improved.

[0067] 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 embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims, not the foregoing description, and all variations within the meaning and range of equivalents of the claims are intended to be included therein. Any reference sign in a claim should not be construed as limiting the claim to which it relates.

Claims

1. A method for improving warpage of a copper-clad ceramic substrate, characterized in that: The following steps are involved: Step 1: Film pattern optimization design: (1) Calculate the residual copper rate difference ΔR based on the residual copper rate on the patterned surface and the residual copper rate on the non-patterned surface of the copper-clad ceramic substrate; (2) According to the above ΔR, the long side process edge width of the copper-clad ceramic substrate is dynamically adjusted so that ΔR reaches the target value, and then the Dimple hole arrangement is performed to obtain a pre-optimized copper-clad ceramic substrate; Step 2: Stress release: The pre-optimized copper-clad ceramic substrate obtained in step 1 is subjected to heat treatment to obtain a finished product.

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

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

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

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

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

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

8. The method for improving warpage of a copper-clad ceramic substrate according to claim 1, wherein: The Dimple holes are circular in shape; the diameter of the Dimple holes is 0.4-0.8 mm, and the hole spacing is 1.5-3.5 times the hole diameter; the depth of the Dimple holes is 50%-70% of the copper thickness of the copper-clad ceramic substrate.

9. The method for improving warpage of a copper-clad ceramic substrate according to claim 1, wherein: The rule for dimple hole arrangement is: one row of dimple holes is set for every 1mm of process edge width on the long side.

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