Method for pre-bending copper foil after pre-oxidation

Abstract

The invention discloses a method for pre-bending a copper foil after pre-oxidation. The invention discloses a method for pre-bending a copper foil after pre-oxidation. The method comprises the following steps: step 1, pre-oxidation of the copper foil; step 2, reverse pre-bending of the copper foil; the pre-oxidized copper foil is placed on a lower die of a pre-bending die, and the oxidized surface faces upwards; the lower die of the pre-bending die descends, the upper and lower surfaces of the copper foil are attached to the upper forming surface of the upper die and the lower forming surface of the lower die respectively, and the oxidation surface of the copper foil is a concave surface; the pre-bent copper foil is placed on the ceramic plate in an arch mode, and the oxidation face faces the ceramic plate; and step 3, sintering. The peeling strength and the yield of the sintered product can be improved.

Description

Technical Field

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

[0002] The copper foil used for sintering the DCB substrate needs to be pre-bent after the pre-oxidation process, and then placed on the ceramic plate for high-temperature sintering.

[0003] At present, DCB manufacturers generally adopt the pre-bending process of pre-bending the copper foil with both sides tilted up (positive pre-bending) after pre-bending, and the convex surface (oxidized surface) of the copper foil faces the ceramic board when placed (see Figure 3 This pre-bending process uses the copper foil's own gravity to gradually collapse from the middle to the edge at high sintering temperature, and discharges the gas generated during sintering. However, the products sintered by this copper foil pre-bending process will have a large number of white spots distributed in a trumpet shape near the middle area (see Figure 4 ), which has a great impact on the product peeling strength and yield. Summary of the invention

[0004] In view of the problems existing in the prior art, the present invention provides a method for pre-oxidation and pre-bending of copper foil, which solves at least one of the above technical problems.

[0005] The technical solution of the present invention is: a method for pre-oxidizing and pre-bending copper foil, characterized in that it comprises the following steps:

[0006] Step 1: pre-oxidation of copper foil;

[0007] Step 2: reverse pre-bending of the copper foil;

[0008] Place the pre-oxidized copper foil on the lower mold of the pre-bending mold with the oxidized surface facing upwards;

[0009] The lower mold of the pre-bending mold descends, and the upper and lower surfaces of the copper foil are respectively attached to the upper molding surface of the upper mold and the lower molding surface of the lower mold, so that the oxidized surface of the copper foil is concave;

[0010] Place the pre-bent copper foil on the ceramic plate in an arched manner, with the oxidized surface facing the ceramic plate;

[0011] Step three: sintering.

[0012] The present invention can improve the peeling strength and yield of sintered products.

[0013] Further preferably, in the step 1, when the copper foil is pre-oxidized, the oxidation temperature is 700° C. to 900° C.;

[0014] The oxygen flow rate is 25l / min~45l / min;

[0015] Oxygen concentration is 300-500PPM;

[0016] The oxidation time is 8 to 12 minutes;

[0017] The oxidation rate is 150-170 mm / min.

[0018] Further preferably, the upper molding surface of the upper mold and the lower molding surface of the lower mold are both arc-shaped cylindrical surfaces;

[0019] The radius of the upper molding surface of the upper mold is 150 mm to 350 mm;

[0020] The radius of the lower molding surface of the lower mold is 150 mm to 350 mm.

[0021] Further preferably, the radius of the upper molding surface of the upper mold is smaller than the radius of the lower molding surface of the lower mold, and the difference is the thickness of the copper foil.

[0022] Further preferably, in the step three, during sintering, the temperature of the sintering constant temperature zone is 1070°C to 1085°C; the sintering time is 25min to 40min; the sintering speed is 30 to 50mm / min; and the nitrogen flow rate is 130l / min to 150l / min.

[0023] Further preferably, the thickness of the copper foil is 0.20 mm to 0.40 mm;

[0024] The thickness of the ceramic plate is 0.25 mm to 1.0 mm.

[0025] Further preferably, the length of the copper foil is 182 mm to 186 mm, and the width is 130 mm to 135 mm;

[0026] The length of the ceramic plate is 186 mm to 192 mm, and the width is 135 mm to 140 mm.

[0027] Further preferably, the lower mold comprises an arc-shaped bottom plate with lower sides on the left and right sides and a higher center, the rear side of the arc-shaped bottom plate is connected to a limiting guide plate, and one side of the copper foil is used to abut against the limiting guide plate;

[0028] The upper mold is longitudinally slidably connected to the limiting guide plate.

[0029] It is convenient to realize the arc bending of copper foil.

[0030] A method for pre-oxidizing and pre-bending copper foil, characterized in that it comprises the following steps:

[0031] Step 1: pre-oxidation of copper foil;

[0032] The oxidation temperature is 700℃~900℃;

[0033] The oxygen flow rate is 25l / min~45l / min;

[0034] Oxygen concentration is 300-500PPM;

[0035] The oxidation time is 8 to 12 minutes;

[0036] The oxidation speed is 150-170 mm / min;

[0037] Step 2: reverse pre-bending of the copper foil;

[0038] Place the pre-oxidized copper foil on the lower mold of the pre-bending mold with the oxidized surface facing upwards;

[0039] The lower mold of the pre-bending mold descends, and the upper and lower surfaces of the copper foil are respectively attached to the upper molding surface of the upper mold and the lower molding surface of the lower mold, so that the oxidized surface of the copper foil is concave;

[0040] The upper molding surface of the upper mold and the lower molding surface of the lower mold are both arc-shaped cylindrical surfaces;

[0041] The radius of the upper molding surface of the upper mold is 150 mm to 350 mm;

[0042] The radius of the lower molding surface of the lower mold is 150 mm to 350 mm;

[0043] The radius of the upper molding surface of the upper mold is smaller than the radius of the lower molding surface of the lower mold, and the difference is the thickness of the copper foil;

[0044] Place the pre-bent copper foil on the ceramic plate in an arched manner, with the oxidized surface facing the ceramic plate;

[0045] The copper foil has a length of 182 mm to 186 mm and a width of 130 mm to 135 mm;

[0046] The length of the ceramic plate is 186 mm to 192 mm, and the width is 135 mm to 140 mm;

[0047] Step three, sintering;

[0048] The temperature of the sintering constant temperature zone is 1070°C to 1085°C; the sintering time is 25min to 40min; the sintering speed is 30 to 50mm / min; and the nitrogen flow rate is 130l / min to 150l / min.

[0049] Compared with the prior art, the present invention has the following beneficial effects:

[0050] During the sintering process of copper foil and ceramic, copper and ceramic plate will move relative to each other. If the copper foil is pre-bent in a positive direction, the oxidized surface of the copper foil will rub against the ceramic plate during the whole process before cooling. The friction will destroy the fragile oxide layer or the generated liquid phase, resulting in white spots. And this relative movement will be more obvious at the edge of the copper foil, so the white spots will appear in a bell-mouth shape.

[0051] After the copper foil is subjected to a reverse pre-bending process, due to the arching of the copper foil, the oxide layer of the copper foil contacts the ceramic plate only at high temperature, which reduces the contact time, that is, reduces the friction time between the copper and the ceramic plate, and can effectively slow down the destruction of the oxide film under high temperature conditions, thereby eliminating the trumpet-shaped white spots and improving the peeling strength and the yield rate of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 This is a schematic diagram of the structure during sintering of the specific embodiment 1 of the present invention;

[0053] Figure 2 This is a microscope image of the sintered specific embodiment 1 of the present invention;

[0054] Figure 3 This is a schematic diagram of the structure during traditional sintering;

[0055] Figure 4 This is a microscope image after traditional sintering.

[0056] In the figure, 1 is a copper foil, 2 is a ceramic sheet, 11 is an oxidized surface, and 12 is a non-oxidized surface. DETAILED DESCRIPTION

[0057] See also Figure 1 to Figure 2 , Specific embodiment 1, a method for pre-bending copper foil after pre-oxidation, comprising the following steps: step 1, pre-oxidation of copper foil; step 2, reverse pre-bending of copper foil; placing the pre-oxidized copper foil on the lower mold of the pre-bending mold, with the oxidized surface facing upward; the lower mold of the pre-bending mold descends, and the upper and lower surfaces of the copper foil are respectively attached to the upper molding surface of the upper mold and the lower molding surface of the lower mold, so that the oxidized surface of the copper foil is concave; placing the pre-bent copper foil in an arched manner on a ceramic plate, with the oxidized surface facing the ceramic plate; step 3, sintering. The present invention can improve the peel strength and yield of the sintered product.

[0058] In the step 1, when the copper foil is pre-oxidized, the oxidation temperature is 700°C to 900°C; the oxygen flow rate is 25l / min to 45l / min; the oxygen concentration is 300 to 500PPM; the oxidation time is 8min to 12min; and the oxidation speed is 150 to 170mm / min.

[0059] The upper molding surface of the upper mold and the lower molding surface of the lower mold are both arc-shaped cylindrical surfaces; the radius of the upper molding surface of the upper mold is 150mm-350mm; the radius of the lower molding surface of the lower mold is 150mm-350mm. The radius of the upper molding surface of the upper mold is smaller than the radius of the lower molding surface of the lower mold, and the difference is the thickness of the copper foil.

[0060] In step three, during sintering, the temperature of the sintering constant temperature zone is 1070°C to 1085°C; the sintering time is 25min to 40min; the sintering speed is 30 to 50mm / min; and the nitrogen flow rate is 130l / min to 150l / min.

[0061] The thickness of the copper foil is 0.20 mm to 0.40 mm; the thickness of the ceramic plate is 0.25 mm to 1.0 mm.

[0062] The length of the copper foil is 182mm to 186mm, and the width is 130mm to 135mm; the length of the ceramic plate is 186mm to 192mm, and the width is 135mm to 140mm.

[0063] The lower mold includes an arc-shaped bottom plate with lower sides and a higher center. The rear side of the arc-shaped bottom plate is connected to a limit guide plate. One side of the copper foil is used to resist the limit guide plate. The upper mold is longitudinally slidably connected to the limit guide plate. This facilitates the arc bending of the copper foil.

[0064] A method for pre-oxidizing and pre-bending copper foil comprises the following steps:

[0065] Step 1, pre-oxidation of copper foil; oxidation temperature is 700℃~900℃; oxygen flow rate is 25l / min~45l / min; oxygen concentration is 300~500PPM; oxidation time is 8min~12min; oxidation speed is 150~170mm / min;

[0066] Step 2, reverse pre-bending of copper foil; placing the pre-oxidized copper foil on the lower mold of the pre-bending mold with the oxidized surface facing upward; the lower mold of the pre-bending mold descends, and the upper and lower surfaces of the copper foil are respectively attached to the upper molding surface of the upper mold and the lower molding surface of the lower mold, so that the oxidized surface of the copper foil is concave; the upper molding surface of the upper mold and the lower molding surface of the lower mold are both arc-shaped cylindrical surfaces; the radius of the upper molding surface of the upper mold is 150mm~350mm; the radius of the lower molding surface of the lower mold is 150mm~350mm; the radius of the upper molding surface of the upper mold is smaller than the radius of the lower molding surface of the lower mold, and the difference is the thickness of the copper foil; the pre-bent copper foil is placed on the ceramic plate in an arched manner with the oxidized surface facing the ceramic plate; the length of the copper foil is 182mm~186mm, and the width is 130mm~135mm; the length of the ceramic plate is 186mm~192mm, and the width is 135mm~140mm;

[0067] Step three, sintering; the temperature of the sintering constant temperature zone is 1070°C to 1085°C; the sintering time is 25min to 40min; the sintering speed is 30 to 50mm / min; the nitrogen flow rate is 130l / min to 150l / min.

[0068] Comparative Example 1:

[0069] Step 1: pre-oxidation of copper foil; Step 2: positive pre-bending of copper foil; placing the pre-oxidized copper foil on the lower mold of the pre-bending mold, with the oxidized surface facing upward; lowering the lower mold of the pre-bending mold, and attaching the upper and lower surfaces of the copper foil to the upper molding surface of the upper mold and the lower molding surface of the lower mold, respectively, so that the oxidized surface of the copper foil is convex; placing the pre-bent copper foil on the ceramic plate, with the oxidized surface facing the ceramic plate (see Figure 3 ); Step three, sintering.

[0070] Comparison of reverse pre-bending of copper foil (Specific Example 1) and forward pre-bending (Comparative Example 1):

[0071] project Reverse pre-bending (Specific embodiment 1) Positive pre-bending (Comparative Example 1) Sintering yield 95.5％ 89％ Peel strength 415~425Mpa 385~395Mpa

[0072] Microscope diagram of the copper foil surface after sintering, see Figure 2 .from Figure 1 It can be observed that when thick copper foil is sintered, a large number of sintering bubbles are avoided and there are no bubbles on the surface.

[0073] Comparative Example 1: After the pre-oxidation method is used, the surface of the copper foil after sintering is shown in the microscope diagram. Figure 4 .from Figure 4 It can be observed that after the thick copper foil is sintered, a large number of sintering bubbles and white spots appear.

[0074] 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 pre-oxidizing and pre-bending copper foil, characterized in that: The steps include: Step 1: pre-oxidation of copper foil; Step 2: reverse pre-bending of the copper foil; Place the pre-oxidized copper foil on the lower mold of the pre-bending mold with the oxidized surface facing upwards; The lower mold of the pre-bending mold descends, and the upper and lower surfaces of the copper foil are respectively attached to the upper molding surface of the upper mold and the lower molding surface of the lower mold, so that the oxidized surface of the copper foil is concave; Place the pre-bent copper foil on the ceramic plate in an arched manner, with the oxidized surface facing the ceramic plate; Step three: sintering.

2. A method for pre-bending copper foil after pre-oxidation according to claim 1, characterized in that: In the step 1, when the copper foil is pre-oxidized, the oxidation temperature is 700° C. to 900° C.; The oxygen flow rate is 25l / min~45l / min; Oxygen concentration is 300-500PPM; The oxidation time is 8 to 12 minutes; The oxidation rate is 150-170 mm / min.

3. The method for pre-oxidizing and pre-bending copper foil according to claim 1, characterized in that: The upper molding surface of the upper mold and the lower molding surface of the lower mold are both arc-shaped cylindrical surfaces; The radius of the upper molding surface of the upper mold is 150 mm to 350 mm; The radius of the lower molding surface of the lower mold is 150 mm to 350 mm.

4. The method for pre-oxidizing and pre-bending copper foil according to claim 1, characterized in that: The radius of the upper molding surface of the upper mold is smaller than the radius of the lower molding surface of the lower mold, and the difference is the thickness of the copper foil.

5. The method for pre-oxidizing and pre-bending copper foil according to claim 1, characterized in that: In the step three, during sintering, the temperature of the sintering constant temperature zone is 1070° C. to 1085° C.; the sintering time is 25 min to 40 min; the sintering speed is 30 to 50 mm / min; and the nitrogen flow rate is 130 l / min to 150 l / min.

6. The method for pre-oxidizing and pre-bending copper foil according to claim 1, characterized in that: The thickness of the copper foil is 0.20 mm to 0.40 mm; The thickness of the ceramic plate is 0.25 mm to 1.0 mm.

7. The method for pre-bending copper foil after pre-oxidation according to claim 1, characterized in that: The length of the copper foil is 182 mm to 186 mm, and the width is 130 mm to 135 mm; The length of the ceramic plate is 186 mm to 192 mm, and the width is 135 mm to 140 mm.

8. The method for pre-bending copper foil after pre-oxidation according to claim 1, characterized in that: The lower mold comprises an arc-shaped bottom plate with lower sides on the left and right sides and a higher center, the rear side of the arc-shaped bottom plate is connected to a limiting guide plate, and one side of the copper foil is used to abut against the limiting guide plate; The upper mold is longitudinally slidably connected to the limiting guide plate.

9. A method for pre-oxidizing and pre-bending copper foil, characterized in that: The steps include: Step 1: pre-oxidation of copper foil; The oxidation temperature is 700℃~900℃; The oxygen flow rate is 25l / min~45l / min; Oxygen concentration is 300-500PPM; The oxidation time is 8 to 12 minutes; The oxidation speed is 150-170 mm / min; Step 2: reverse pre-bending of the copper foil; Place the pre-oxidized copper foil on the lower mold of the pre-bending mold with the oxidized surface facing upwards; The lower mold of the pre-bending mold descends, and the upper and lower surfaces of the copper foil are respectively attached to the upper molding surface of the upper mold and the lower molding surface of the lower mold, so that the oxidized surface of the copper foil is concave; The upper molding surface of the upper mold and the lower molding surface of the lower mold are both arc-shaped cylindrical surfaces; The radius of the upper molding surface of the upper mold is 150 mm to 350 mm; The radius of the lower molding surface of the lower mold is 150 mm to 350 mm; The radius of the upper molding surface of the upper mold is smaller than the radius of the lower molding surface of the lower mold, and the difference is the thickness of the copper foil; Place the pre-bent copper foil on the ceramic plate in an arched manner, with the oxidized surface facing the ceramic plate; The copper foil has a length of 182 mm to 186 mm and a width of 130 mm to 135 mm; The length of the ceramic plate is 186 mm to 192 mm, and the width is 135 mm to 140 mm; Step three, sintering; The temperature of the sintering constant temperature zone is 1070°C to 1085°C; the sintering time is 25min to 40min; the sintering speed is 30 to 50mm / min; and the nitrogen flow rate is 130l / min to 150l / min.

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