A method for designing the margin of a DCB substrate

Abstract

The invention relates to the technical field of DCB substrate manufacturing. A method for designing the margin of a DCB substrate comprises the steps of first determining the margin of the back copper foil, determining the margin of the back copper foil, controlling the margin of the front copper foil to be greater than the margin of the back copper foil, and making the difference between the margin of the front copper foil and the margin of the back copper foil less than or equal to a set value; the margin of the back copper foil is the distance between the back copper foil and the edge of an adjacent ceramic sheet; and the margin of the front copper foil is the distance between the front copper foil and the edge of an adjacent ceramic sheet. By establishing a design method for the margin of the front copper foil, the product margin difference is controlled within a certain range, so that the residual copper rate on the front and back sides is reduced, thereby reducing the generation of cracks in the corner area of ​​the product and improving the reliability of product use.

Description

Technical Field

[0001] The invention relates to the technical field of DCB substrate manufacturing, and in particular to a method for designing a margin. Background Art

[0002] The DCB substrate is a double-sided copper-clad ceramic substrate. The front side is the working side. Its graphic surface is used to weld components such as chips, and the back copper foil is the heat dissipation surface. In the margin design of the DCB substrate film drawing, the margin of the back graphic is designed based on the maximum design of the heat dissipation area and the withstand voltage, and is generally designed to be around 0.5mm. After ensuring the position of the welding chips and other components, the design of the margin of the front graphic is relatively arbitrary. In actual use, it is found that when the difference in the margins between the front and back sides of the product is large, that is, the difference in the residual copper rate between the front and back sides is too large, cracks are prone to occur in the corner area, resulting in product scrapping. Although stress release holes are opened on the back copper foil to reduce thermal stress and prevent cracks, the effect is not obvious. The main reason is that due to the heating and cooling process and the different thermal expansion coefficients of copper and ceramics, the ceramics are pulled by copper on the front and back sides, causing cracks.

[0003] Currently, there is a lack of a design method for adjusting the margin of the DCB substrate under different circumstances. Summary of the invention

[0004] In view of the problems existing in the prior art, the present invention provides a method for designing a DCB substrate margin, which solves at least one of the above technical problems.

[0005] The present invention provides a method for designing a DCB substrate margin, which is characterized in that the back copper foil margin is first determined, the back copper foil margin is determined, the front copper foil margin is controlled to be greater than the back copper foil margin, and the difference between the front copper foil margin and the back copper foil margin is less than or equal to a set value;

[0006] The back copper foil margin is the distance between the back copper foil and the edge of the adjacent tile;

[0007] The front copper foil margin is the distance between the front copper foil and the edge of the adjacent ceramic tile.

[0008] By establishing a design method for the front copper foil margin, the product margin difference is controlled within a certain range, the residual copper rate on the front and back sides is reduced, thereby reducing the occurrence of cracks in the corner area of ​​the product and improving the reliability of product use.

[0009] More preferably, the set value is 0.2 mm.

[0010] Further preferably, the back copper foil margin is 0.5 mm.

[0011] Further preferably, at least one row of stress release holes is provided near the edge of the back copper foil, the distance from the side of the stress release hole closest to the edge away from the edge to the edge of the back copper foil is 0.8 mm, and the spacing between adjacent rows of stress release holes is 0.8 mm;

[0012] The difference between the front copper foil margin and the back copper foil margin is less than or equal to 0.2mm.

[0013] Further preferably, the back copper foil is not provided with stress release holes, and the difference between the margin of the front copper foil and the margin of the back copper foil is less than or equal to 0.2 mm.

[0014] Further preferably, the method for determining the set value is as follows:

[0015] Test pieces with different back copper foil margins and different front copper foil margins are selected for furnace endurance test. The size of the test piece that achieves the best result is selected as the optimal size, and the difference between the back copper foil margin and the front copper foil margin of the optimal size is used as the set value.

[0016] Further preferably, experimental pieces having the difference between the front copper foil margin and the back copper foil margin of 0.8 mm, 0.6 mm, 0.4 mm, 0.2 mm, 0 mm, -0.2 mm, and -0.4 mm, respectively, are selected for the experiment.

[0017] Further preferably, experimental pieces with one row, two rows and three rows of stress release holes formed on the back copper foil and experimental pieces without stress release holes are selected for the experiment.

[0018] Further preferably, the test environment of the furnace endurance test is H2:N2=1:9, the test temperature is 325°C±10°C, and the test time is more than 150 seconds.

[0019] Further preferably, after the test pieces with different back copper foil margins and different front copper foil margins are subjected to the furnace endurance test, the crack defects in the corner area are related to the difference in the front and back margins;

[0020] When the edge difference is ≤0.2mm, the number of furnace passes is the largest, that is, the possibility of cracks is the smallest.

[0021] The present invention establishes a design method for the margin of a DCB substrate pattern based on data from a product furnace endurance test, so that the margin difference between the front and back sides of the product is within a certain range, the residual copper rate on the front and back sides is reduced, thereby reducing the generation of cracks in the corner area of ​​the product and improving the reliability of the product.

[0022] The present invention provides a method for designing a DCB substrate margin, which has the following beneficial effects:

[0023] After the margin of the back pattern is determined, the margin of the front pattern can be directly calculated, which is convenient for design and can ensure that the difference in the margins between the front and back sides is minimized, and the residual copper rate on the front and back sides is also minimized, reducing the defect of cracks in the corner area.

[0024] The maximum number of furnace passes, which reflects the reliability of the product, can be increased to more than 15 times, thus extending the service life of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of a specific embodiment 1 of the present invention without a stress release hole;

[0026] Figure 2 It is a schematic diagram of a row of stress release holes in specific embodiment 1 of the present invention;

[0027] Figure 3 This is a schematic diagram of a case where two rows of stress release holes are provided in a specific embodiment 1 of the present invention;

[0028] Figure 4 This is a schematic diagram of a specific embodiment 1 of the present invention with three rows of stress release holes. DETAILED DESCRIPTION

[0029] See also Figures 1 to 4 Embodiment 1, a method for designing the margin of a DCB substrate, first determining the margin of the back copper foil, determining the margin of the back copper foil, controlling the margin of the front copper foil to be greater than the margin of the back copper foil, and the difference between the margin of the front copper foil and the margin of the back copper foil is less than or equal to a set value; the margin of the back copper foil is the distance between the back copper foil and the edge of the adjacent ceramic tile; the margin of the front copper foil is the distance between the front copper foil and the edge of the adjacent ceramic tile. By establishing a design method for the margin of the front copper foil to control the product margin difference within a certain range, the residual copper rate on the front and back sides is reduced, thereby reducing the generation of cracks in the corner area of ​​the product and improving the reliability of product use.

[0030] The method for determining the set value is as follows: select test pieces with different back copper foil margins and different front copper foil margins for furnace endurance test, select the size of the test piece that achieves the best result as the optimal size, and use the difference between the back copper foil margin and the front copper foil margin of the optimal size as the set value.

[0031] The experiment was conducted by selecting test pieces with the difference between the front copper foil margin and the back copper foil margin being 0.8mm, 0.6mm, 0.4mm, 0.2mm, 0mm, -0.2mm, and -0.4mm respectively.

[0032] Experimental pieces with one row of stress release holes, two rows of stress release holes, and three rows of stress release holes, as well as experimental pieces without stress release holes, were selected for the experiment.

[0033] The test environment of the furnace endurance test is H2:N2=1:9, the test temperature is 325°C±10°C, and the test time is more than 150 seconds.

[0034] The furnace resistance test data is as follows:

[0035]

[0036] In the above table, the margins of the back copper foil are all 0.5mm. The distance from the side of the stress relief hole closest to the edge away from the edge to the edge of the back copper foil is 0.8mm, and the spacing between adjacent rows of stress relief holes is 0.8mm.

[0037] After the furnace endurance test was carried out on the test pieces with different back copper foil margins and different front copper foil margins, the occurrence of cracks in the corner area was related to the difference in the front and back margins; when the margin difference was ≤0.2mm, the number of furnace endurance tests was the largest, that is, the possibility of cracks was the smallest.

[0038] The present invention establishes a design method for the margin of a DCB substrate pattern based on data from a product furnace endurance test, so that the margin difference between the front and back sides of the product is within a certain range, the residual copper rate on the front and back sides is reduced, thereby reducing the generation of cracks in the corner area of ​​the product and improving the reliability of the product.

[0039] The set value is 0.2mm. The margin of the back copper foil is 0.5mm. At least one row of stress release holes is opened near the edge of the back copper foil. The distance from the side of the stress release hole closest to the edge away from the edge to the edge of the back copper foil is 0.8mm, and the spacing between adjacent rows of stress release holes is 0.8mm; the difference between the margin of the front copper foil and the margin of the back copper foil is less than or equal to 0.2mm.

[0040] Specific:

[0041] 1) When there is no dimple on the back pattern (the back copper foil is not provided with stress release holes), the front copper foil margin a (the distance from the copper foil edge to the porcelain edge) is designed to be ab≤0.2;

[0042] a≤0.2+b;

[0043] Where b is the back copper foil margin (the distance from the copper foil edge to the porcelain edge), b = 0.5mm (fixed value); 0.2 is the maximum difference between the front and back margins. Figure 1 .

[0044] 2) When there is a dimple (stress release hole) on the back pattern, the front copper foil margin a and the back hole margin c (the distance from the hole edge to the porcelain edge) are designed as follows:

[0045] 2.1) When a row of stress release holes is

[0046] ab≤0.2;

[0047] a≤0.2+b;

[0048] c=b+0.8, where 0.8 is the distance from the dimple hole to the edge of the back copper foil, a fixed value. Figure 2 .

[0049] 2.2) When there are two rows of stress release holes,

[0050] ab≤0.2;

[0051] a≤b+0.2;

[0052] c=b+2*0.8, where 0.8 is the distance from the stress release hole to the edge of the back copper foil, a fixed value. Figure 3 .

[0053] 2.3) When there are three rows of stress release holes,

[0054] ab≤0.2;

[0055] a≤0.2+b;

[0056] c=b+3*0.8, where 0.8 is the distance from the stress release hole to the edge of the back copper foil, a fixed value. Figure 4 .

[0057] The above are only preferred embodiments of the present invention. It should be pointed out that, for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for designing a DCB substrate margin, characterized in that: First determine the back copper foil margin, determine the back copper foil margin, control the front copper foil margin to be larger than the back copper foil margin, and the difference between the front copper foil margin and the back copper foil margin is less than or equal to the set value; The back copper foil margin is the distance between the back copper foil and the edge of the adjacent tile; The front copper foil margin is the distance between the front copper foil and the edge of the adjacent tile; At least one row of stress release holes is provided near the edge of the back copper foil, the distance from the side of the stress release hole closest to the edge away from the edge to the edge of the back copper foil is 0.8 mm, and the spacing between adjacent rows of stress release holes is 0.8 mm; the difference between the margin of the front copper foil and the margin of the back copper foil is less than or equal to 0.2 mm; Alternatively, the back copper foil is not provided with stress release holes, and the difference between the margin of the front copper foil and the margin of the back copper foil is less than or equal to 0.2 mm; The setting value is determined as follows: Select test pieces with different back copper foil margins and different front copper foil margins to conduct furnace endurance test, select the size of the test piece that achieves the best result as the optimal size, and use the difference between the back copper foil margin and the front copper foil margin of the optimal size as the set value; The experimental pieces with the difference between the front copper foil margin and the back copper foil margin of 0.8mm, 0.6mm, 0.4mm, 0.2mm, 0mm, -0.2mm, and -0.4mm were selected for the experiment; The experiment was conducted by selecting test pieces with one row of stress release holes, two rows of stress release holes, and three rows of stress release holes on the back copper foil and a test piece without stress release holes. The test environment of the furnace resistance test is H2:N2=1:9, the test temperature is 325℃±10℃, and the test time is more than 150 seconds; After the furnace endurance test was conducted on the test pieces with different back copper foil margins and different front copper foil margins, the crack defects in the corner area were related to the difference in front and back margins; When the edge difference is ≤0.2mm, the number of furnace passes is the largest, that is, the possibility of cracks is the smallest.

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