A method for improving ceramic substrate warpage based on symmetrical copper layer arrangement and centroid control
By symmetrically arranging the copper layers and controlling the center of mass, the warping and twisting problems caused by the mismatch of thermal expansion coefficients in AMB ceramic substrates were solved, thereby improving the flatness of the substrate and the product yield, and meeting the needs of automated production.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- JIANGSU FERROTEC SEMICON TECH CO LTD
- Filing Date
- 2026-03-13
- Publication Date
- 2026-06-02
AI Technical Summary
In the prior art, the AMB ceramic substrate warps and twists due to the mismatch of the thermal expansion coefficients between the copper layer and the ceramic layer, which affects product yield and heat dissipation efficiency. Furthermore, the traditional residual copper ratio balancing method cannot effectively control the micro torque effect, resulting in complex twisted shapes.
By symmetrically arranging copper layers and adjusting the centroid, residual copper ratio balancing, centroid alignment, and auxiliary balancing copper block design are carried out to ensure the symmetry and stress balance of the copper layer pattern on the AMB ceramic substrate. The substrate is then fabricated using the standard AMB process.
It effectively suppresses the warping and twisting of AMB ceramic substrates, improves substrate flatness, reduces product void rate and warping, and meets the requirements of automated production.
Smart Images
Figure CN122138719A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of semiconductor manufacturing technology, specifically a method for improving the warpage of ceramic substrates based on symmetrical copper layer arrangement and centroid control. Background Technology
[0002] AMB ceramic substrates (such as AMB-AlN and AMB-Si3N4) have become key packaging materials for high-power semiconductor devices due to their excellent thermal conductivity, insulation, and reliability. The AMB process uses solder containing active elements at high temperatures to firmly bond the copper layer to the ceramic layer.
[0003] However, copper has a coefficient of thermal expansion (CTE) of approximately 17 ppm / ℃, while AlN ceramic has a CTE of approximately 4.5 ppm / ℃. This significant CTE mismatch leads to inconsistent shrinkage during cooling after soldering, generating substantial thermal stress within the substrate and ultimately causing the AMB ceramic substrate to warp. Excessive warpage not only increases the difficulty of subsequent chip mounting and wire bonding processes, affecting product yield, but also results in poor contact with the heat dissipation substrate during module packaging, creating thermal resistance and impacting heat dissipation efficiency. Furthermore, excessive warpage generates additional stress during mechanical fixing, increasing the risk of ceramic layer cracking and affecting product reliability.
[0004] Currently, the industry generally uses the "residual copper ratio balance method" as the theoretical basis for controlling warpage. The core idea of this theoretical method is to design the same or similar copper area ratio (i.e., residual copper ratio) on both sides of the substrate (i.e., the patterned side and the non-patterned side) to offset the thermal stress caused by CTE mismatch on both sides, thereby reducing the overall warpage.
[0005] However, in actual large-scale industrial production, this method has serious limitations, often resulting in unacceptable "twisted" shapes in the products, rather than simple "warping." This "twisting" means that the substrate surface lacks a uniform reference plane and is more difficult to predict and compensate for than simple "warping," thus having a greater negative impact on subsequent automated production processes. Therefore, this method only considers the macroscopic proportion of the copper area, completely ignoring the torque effect generated by the microscopic spatial distribution of the copper layer pattern on the substrate.
[0006] Therefore, it is of great significance to develop a layout design method that can effectively suppress the twisting and warping of AMB ceramic substrates. Summary of the Invention
[0007] The purpose of this invention is to provide a method for improving the warpage of ceramic substrates based on symmetrical copper layer arrangement and centroid control, so as to solve the problems mentioned in the prior art.
[0008] To achieve the above objectives, the present invention provides the following technical solution: A method for improving the warpage of ceramic substrates based on symmetrical copper layer arrangement and centroid control includes the following steps: S1: Balancing the residual copper content of the AMB ceramic substrate. S2: Calculate the centroid coordinates G0 of the AMB ceramic substrate, G1 of the patterned copper pattern in the AMB ceramic substrate structure, and G2 of the non-patterned copper pattern in the AMB ceramic substrate structure, respectively. S3: Perform a symmetrical design on the AMB ceramic substrate from step S2; S4: Align the centroid of the AMB ceramic substrate from step S3. S5: The AMB ceramic substrate from step S4 is prepared using the standard AMB process.
[0009] Furthermore, the centroid coordinates are the coordinates of the geometric center point of the two-dimensional planar figure; The centroid coordinates G0 are (0, 0), G1 are (Xc, Yc), and G2 are (Xs, Ys).
[0010] Furthermore, during the process of balancing the residual copper rate, the residual copper rate Rc of the patterned surface in the AMB ceramic substrate structure and the residual copper rate Rs of the non-patterned surface in the AMB ceramic substrate structure should meet the following requirements: |Rc-Rs|÷Rmax<10%; where Rmax is the highest residual copper rate among Rc and Rs.
[0011] Furthermore, during the symmetry design process, the copper patterns on the patterned and non-patterned surfaces of the AMB ceramic substrate structure are mirror-symmetric or rotationally symmetric about the central axes X and Y of the substrate.
[0012] Furthermore, during the symmetry design process, the symmetry deviation of a single copper layer is ≤ ±0.5% of the corresponding dimension of the AMB ceramic substrate; the symmetry deviation is the maximum distance from the midpoint of the line connecting any feature point on the patterned surface and non-patterned surface of the copper pattern to its symmetry point in the AMB ceramic substrate structure to the theoretical symmetry axis.
[0013] Furthermore, during the centroid alignment process, the centroid coordinates G1 of the patterned copper pattern in the AMB ceramic substrate structure and G2 of the non-patterned copper pattern in the AMB ceramic substrate structure are controlled so that their projection points on the projection plane perpendicular to the AMB ceramic substrate plane are aligned with the centroid coordinates G0 of the AMB ceramic substrate, thus obtaining centroid projection G1.1 and centroid projection G2.1 respectively.
[0014] Furthermore, the alignment deviation between the centroid projection G1.1 and the centroid projection G2.1 is ≤ ±2% of the maximum external dimensions of the AMB ceramic substrate; The alignment deviation of the centroid projection G1.1 is |G1-G0|=√(Xc2 +Yc 2 ); The alignment deviation of the centroid projection G2.1 is |G2-G0|=√(Xs) 2 +Ys 2 ).
[0015] Furthermore, when the functional copper pattern in the AMB ceramic substrate structure cannot meet the centroid alignment requirements, a symmetrical auxiliary balancing copper block is added to the non-functional area on the smaller side. The balancing copper block is located at the edge of the AMB ceramic substrate, and then steps S1-S5 are performed.
[0016] Furthermore, the minimum spacing between the balancing copper block and the nearest functional circuit is >0.3mm, the maximum side length of a single balancing copper block is <10% of the corresponding side length of the AMB ceramic substrate, and the total area of the balancing copper blocks is ≤3% of the total copper area of the non-patterned surface of the AMB ceramic substrate; the total copper area of the non-patterned surface is the sum of the functional copper area of the non-patterned surface and the copper area of the balancing copper block.
[0017] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention introduces and quantifies geometric symmetry and centroid projection alignment. On one hand, this method ensures symmetrical copper pattern layout on both sides of the substrate. During cooling, it effectively reduces uneven tensile stress caused by copper shrinkage in local areas, preventing torque generated by uneven tensile stress and thus preventing warping or complex torsional deformation of the substrate. On the other hand, this invention effectively solves the problem of symmetrical pattern layout, which cannot be characterized and controlled by the single macroscopic parameter of "residual copper ratio balance method". It effectively ensures the symmetry of the stress center, prevents the generation of internal torque, improves the overall flatness of the substrate, reduces the product void rate, and lowers the product void rate caused by warping and torsion to below 0.5%.
[0018] 2. This invention, by independently optimizing the non-graphical surface pattern and flexibly utilizing the auxiliary balancing copper block, ensures that even under the harsh conditions of inherent asymmetry caused by the functional design of the graphic surface, the overall stress can still be efficiently balanced by aligning the centroid of the non-graphical surface with the geometric center. Simultaneously, this invention effectively eliminates distortion, ensuring that the ratio of the height difference at the four corners of the substrate to the center warpage is <1.5, guaranteeing that the substrate shape is a uniform arc shape rather than a saddle shape. Attached Figure Description
[0019] Figure 1 This is a schematic diagram of the AMB ceramic substrate structure of the present invention. Detailed Implementation
[0020] 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.
[0021] Example 1: A method for improving ceramic substrate warpage based on symmetrical copper layer arrangement and centroid control: Taking an AMB-Si3N4 substrate of 190mm×138mm×0.92mm as an example, S1: Perform residual copper ratio balancing: The residual copper content on the pattern surface, Rc, is 82.74%. The residual copper content on the non-patterned surface, Rs, is 88.52%. The relative difference is |82.74% - 88.52%| / 88.52% ≈ 6.53% (<10%, which meets the requirements); S2: According to the EDA software calculation, the coordinates of the geometric center G0 of the substrate are (0, 0), the coordinates of the centroid G1 of the patterned copper pattern are (0.3mm, 0.2mm), and the coordinates of the centroid G2 of the non-patterned copper pattern are (-0.2mm, -0.1mm). S3: Symmetrical design: The maximum deviation of the symmetry of the graphic surface is 0.28mm (<64mm*0.5%=0.32mm); The maximum symmetry deviation of non-graphic surfaces is 0.22mm (<45mm*0.5%=0.225mm); which meets the specifications. S4: Centroid Alignment: The maximum external dimension of the AMB ceramic substrate is L = √(64² + 45²) ≈ 78.40 mm; The alignment deviation of the centroid projection G1.1 of the copper graphic on the graphic surface is |G1-G0|≈0.36mm (<L*2%=1.57mm). The alignment deviation of the centroid projection G2.1 of the non-graphic copper pattern is |G2-G0|≈0.22mm (<L*2%=1.57mm). S5: AMB-Si3N4 ceramic substrate is prepared using the standard AMB process.
[0022] Example 2: A method for improving ceramic substrate warpage based on symmetrical copper layer arrangement and centroid control: Taking an AMB-AlN substrate of 190mm×138mm×1.235mm as an example, with copper foil specifications of 184mm×132mm, the following layout design is performed while keeping the functional layout of the graphic surface unchanged: S1: Add auxiliary balancing copper blocks: Add multiple regular balancing copper blocks to the non-graphical surface, with a total area of 110 mm². 2 Furthermore, the distance between the balancing copper block and the nearest functional circuit is 0.5mm (>0.3mm). Total copper area of non-graphic surfaces = 190 * 138 * 89.6% + 110 = 23603.12 mm² 2 ; 110mm 2 ≤23603.12*3%=708.09mm 2 ; S2: Perform residual copper ratio balancing: The residual copper content on the pattern surface, Rc, is 79.32%. The residual copper content on the non-patterned surface, Rs = 90.02%, The relative difference is |79.32% - 90.02%| / 90.02% ≈ 11.89% (slightly higher than the auxiliary specification of 10%, but under the centroid alignment principle, the residual copper balance requirement can be appropriately relaxed). S3: According to the EDA software calculation, the coordinates of the geometric center G0 of the substrate are (0, 0), the coordinates of the centroid G1 of the patterned copper pattern are (3.4mm, 1.8mm), and the coordinates of the centroid G2 of the non-patterned copper pattern are (0.2mm, 0.1mm). S4: Centroid Alignment: The maximum external dimension of the AMB ceramic substrate is L = √(64² + 45²) ≈ 78.40 mm; The alignment deviation of the centroid projection G1.1 of the copper graphic on the graphic surface is |G1-G0|≈3.85mm (>L*2%=1.57mm). The alignment deviation of the centroid projection G2.1 of the non-graphic copper pattern is |G2-G0|≈0.22mm (<L*2%=1.57mm). S6: AMB-AlN ceramic substrates are prepared using the standard AMB process.
[0023] Comparative Example 1: A method for improving ceramic substrate warpage based on symmetrical copper layer arrangement and centroid control: Taking an AMB-Si3N4 substrate of 190mm×138mm×0.92mm as an example, the following layout design was carried out: S1: Perform residual copper ratio balancing: The residual copper content on the pattern surface, Rc, is 78.56%. The residual copper content on the non-patterned surface, Rs, is 80.36%. The relative difference is |78.56% - 80.36%| / 80.36% = 2.24% (<10%, which meets the requirements).
[0024] S2: According to the EDA software calculation, the coordinates of the geometric center G0 of the substrate are (0, 0), the coordinates of the centroid G1 of the copper pattern on the patterned surface are (3.2mm, 2.1mm), and the coordinates of the centroid G2 of the copper pattern on the non-patterned surface are (-2.5mm, -1.8mm). S3: Symmetrical design: The maximum deviation of the symmetry of the graphic surface is 1.80mm (<64mm*0.5%=0.32mm). The maximum symmetry deviation of the non-graphic surface is 0.25mm (<45mm*0.5%=0.225mm); S4: Centroid Alignment: The maximum external dimension of the AMB ceramic substrate is L = √(64² + 45²) ≈ 78.40 mm; The alignment deviation of the centroid projection G1.1 of the copper graphic on the graphic surface is |G1-G0|≈3.82mm (>L*2%≈1.57mm). The alignment deviation of the centroid projection G2.1 of the non-graphic copper pattern is |G2-G0|≈3.08mm (>L*2%≈1.57mm). S5: AMB-Si3N4 ceramic substrate is prepared using the standard AMB process.
[0025] Comparative Example 2: A method for improving ceramic substrate warpage based on symmetrical copper layer arrangement and centroid control: Taking an AMB-AlN substrate of 190mm×138mm×1.235mm as an example, with copper foil specifications of 184mm×132mm, the following layout design is carried out while keeping the functional layout of the graphic surface unchanged: S1: Perform residual copper ratio balancing: The residual copper content on the pattern surface, Rc, is 79.45%. The residual copper content on the non-patterned surface, Rs, is 85.35%. The relative difference is |79.45% - 85.35%| / 85.35% = 6.91% (<10%, which meets the requirements).
[0026] S2: According to the EDA software calculation, the coordinates of the geometric center G0 of the substrate are (0, 0), the coordinates of the centroid G1 of the patterned copper pattern are (3.4mm, 1.8mm), and the coordinates of the centroid G2 of the non-patterned copper pattern are (3.3mm, 1.7mm). S3: Symmetrical design: The maximum deviation of the symmetry of the graphic surface is 2.70 mm; The maximum symmetry deviation of the non-graphical surface is 0.29 mm; S4: Centroid Alignment: The maximum external dimension of the AMB ceramic substrate is L = √(64² + 45²) ≈ 78.40 mm; The alignment deviation of the centroid projection G1.1 of the copper graphic on the graphic surface is |G1-G0|≈3.85mm (>L*2%≈1.57mm). The alignment deviation of the centroid projection G2.1 of the non-graphic copper pattern is |G2-G0|≈3.71mm (>L*2%≈1.57mm). S5: AMB-AlN ceramic substrates are prepared using the standard AMB process.
[0027] The AMB ceramic substrates prepared in the above examples and comparative examples were cooled to room temperature, and the warpage of the substrates was tested. The specific testing method is as follows: Warpage detection: Using a non-contact optical scanner conforming to JESD22-B112A standard, the substrate is placed freely on the platform, and the height difference between its highest and lowest points is measured. Twist determination: Extract the Z values of the four corner points of the substrate (2mm from the edge), calculate the ratio of the differences between the two sets of diagonals, and if the ratio is greater than 2, it is determined that there is significant twist. Void rate detection: This involves detecting the area ratio of voids in the solder layer and automatically calculating the void rate of the substrate using 2D X-Ray image analysis software.
[0028] The test results are shown in Table 1 below.
[0029] Table 1. Test data of substrate warpage performance
[0030] Conclusion: Starting with layout design, this invention introduces and quantifies "geometric symmetry" and "centroid projection alignment" to balance the stress distribution of the substrate during cooling, thereby obtaining a flat substrate with low warpage and no twist.
[0031] In Comparative Example 1, only the residual copper ratio balancing method was used to prepare the AMB-Si3N4 ceramic substrate. In order to consider the symmetrical arrangement of the copper layer and the control of the centroid, the copper pattern layout was severely asymmetrical, and both the symmetry and the centroid were deviated. As a result, the prepared AMB ceramic substrate was prone to warping or twisting, which affected the product yield of the subsequent chip mounting process.
[0032] In Comparative Example 2, the AMB-AlN ceramic substrate used did not have auxiliary balancing copper blocks added to the non-patterned surface of the AMB-AlN substrate. The patterns on the patterned and non-patterned surfaces were simple and consistent, causing the centroids G1 and G2 to deviate from the geometric center of the substrate. The difference in lever arms of the shrinkage forces on both sides of the substrate was large, and the torque of the twisting force could not be effectively canceled. This resulted in the centroid of the copper layer being severely biased to one side, causing the manufactured substrate to have a large warpage and obvious twisting, which could not meet the requirements of automated mounting.
[0033] 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 the spirit or essential characteristics of the invention. 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, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.
Claims
1. A method for improving the warpage of ceramic substrates based on symmetrical copper layer arrangement and centroid control, characterized in that: Includes the following steps: S1: Balance the residual copper content of the AMB ceramic substrate; S2: Calculate the centroid coordinates G0 of the AMB ceramic substrate, G1 of the patterned copper pattern in the AMB ceramic substrate structure, and G2 of the non-patterned copper pattern in the AMB ceramic substrate structure, respectively. S3: Perform a symmetrical design on the AMB ceramic substrate from step S2; S4: Align the centroid of the AMB ceramic substrate from step S3. S5: The AMB ceramic substrate from step S4 is prepared using the standard AMB process.
2. The method for improving ceramic substrate warpage based on symmetrical copper layer arrangement and centroid control according to claim 1, characterized in that: The centroid coordinates are the coordinates of the geometric center point of the two-dimensional planar figure; The centroid coordinates G0 are (0, 0), G1 are (Xc, Yc), and G2 are (Xs, Ys).
3. The method for improving ceramic substrate warpage based on symmetrical copper layer arrangement and centroid control according to claim 1, characterized in that: During the process of balancing the residual copper rate, the residual copper rate Rc of the patterned surface in the AMB ceramic substrate structure and the residual copper rate Rs of the non-patterned surface in the AMB ceramic substrate structure should meet the following requirements: |Rc-Rs|÷Rmax<10%; where Rmax is the highest residual copper rate among Rc and Rs.
4. The method for improving ceramic substrate warpage based on symmetrical copper layer arrangement and centroid control according to claim 1, characterized in that: In the process of the symmetry design, the copper patterns on the patterned and non-patterned surfaces of the AMB ceramic substrate structure are mirror-symmetric or rotationally symmetric about the central axes X and Y of the substrate.
5. The method for improving ceramic substrate warpage based on symmetrical copper layer arrangement and centroid control according to claim 1, characterized in that: During the symmetry design process, the symmetry deviation of a single copper layer is ≤ ±0.5% of the corresponding dimension of the AMB ceramic substrate; the symmetry deviation is the maximum distance from the midpoint of the line connecting any feature point on the patterned surface and non-patterned surface of the copper pattern to its symmetry point in the AMB ceramic substrate structure to the theoretical symmetry axis.
6. The method for improving ceramic substrate warpage based on symmetrical copper layer arrangement and centroid control according to claim 1, characterized in that: During the centroid alignment process, the centroid coordinates G1 of the patterned copper pattern in the AMB ceramic substrate structure and G2 of the non-patterned copper pattern in the AMB ceramic substrate structure are controlled so that the projection points on the projection plane perpendicular to the AMB ceramic substrate plane are aligned with the centroid coordinates G0 of the AMB ceramic substrate, resulting in centroid projections G1.1 and G2.1 respectively.
7. The method for improving ceramic substrate warpage based on symmetrical copper layer arrangement and centroid control according to claim 6, characterized in that: The alignment deviation of the centroid projections G1.1 and G2.1 is ≤ ±2% of the maximum external dimensions of the AMB ceramic substrate; The alignment deviation of the centroid projection G1.1 is |G1-G0|=√(Xc 2 +Yc 2 ); The alignment deviation of the centroid projection G2.1 is |G2-G0|=√(Xs) 2 +Ys 2 ).
8. The method for improving ceramic substrate warpage based on symmetrical copper layer arrangement and centroid control according to claim 1, characterized in that: When the functional copper pattern in the AMB ceramic substrate structure cannot meet the centroid alignment requirements, symmetrical auxiliary balancing copper blocks are added to the non-functional area on the smaller side, and then steps S1-S5 are performed.
9. The method for improving ceramic substrate warpage based on symmetrical copper layer arrangement and centroid control according to claim 8, characterized in that: The minimum spacing between the balancing copper block and the nearest functional circuit is >0.3mm, the maximum side length of a single balancing copper block is <10% of the corresponding side length of the AMB ceramic substrate, and the total area of the balancing copper blocks is ≤3% of the total copper area of the non-patterned surface of the AMB ceramic substrate; the total copper area of the non-patterned surface is the sum of the copper area of the functional copper on the non-patterned surface and the copper area of the balancing copper blocks.