Manufacturing method of aluminum nitride-copper composite substrate for power device based on DPC technology

Abstract

The invention discloses a manufacturing method of an aluminum nitride-copper composite substrate for a power device based on a DPC technology, and belongs to the field of electronic packaging. The manufacturing method comprises the following steps of (1) laser drilling, (2) seed layer sputtering, (3) photoetching development, (4) electrocoppering thickening, (5) film stripping etching, (6) nickel-palladium-gold plating and (7) cutting. According to the aluminum nitride-copper substrate prepared based on the manufacturing method, the heat conductivity of the aluminum nitride-copper substrate can be improved from 170-250 W / (m.K) to 220-330 W / (m.K) by adjusting the hole distribution density, the hole diameter and the surface copper layer thickness of a welding area of a power chip, the heat conductivity and the expansion coefficient of the material can be adjusted, high-precision machining is conducted on surface patterns, and electrical interconnection is achieved. In conclusion, compared with mainstream metal composite materials such as copper-molybdenum copper-copper, molybdenum copper, tungsten copper and the like, the composite material disclosed by the invention is lower in cost, has an obvious price advantage, and is particularly suitable for packaging application of high-power devices.

Description

Technical Field

[0001] The present invention belongs to the field of electronic packaging, and in particular relates to a method for manufacturing an aluminum nitride-copper composite substrate for power devices based on a DPC process. Background Art

[0002] With the rapid development of electronic devices and components toward miniaturization, high integration, low cost, and high power output, the heat generated per unit volume of various devices has increased dramatically, placing higher demands on the heat dissipation of packaging materials. If this heat cannot be dissipated promptly, the component will not function properly and, in severe cases, may even burn out. Solid-state high-power devices, also known as power tubes, are widely used in aviation, aerospace, wireless communications, broadcasting and television, geological exploration, nuclear energy testing, weather forecasting, and other fields. Based on semiconductor material, they primarily include silicon LDMOS devices, GaAs devices, and the latest GaN and SiC devices. The accompanying packaging carrier is an integral component of the device, providing mechanical support, electrical interconnection, environmental protection, and heat dissipation paths for the chip. Previously, copper-based metal composites were often used as heat dissipation carriers for power devices. However, their thermal conductivity generally did not exceed 200 W / (m·K), making electrical interconnection impossible. Furthermore, the corresponding material cost did not meet the low-cost requirements of the components. Consequently, existing copper-based metal carriers suffer from insufficient heat dissipation capacity, high cost, mismatch with the chip's expansion coefficient, and inability to electrically interconnect. Summary of the Invention

[0003] Purpose of the invention: The purpose of the present invention is to provide a method for manufacturing an aluminum nitride-copper composite substrate for power devices based on the DPC process, which has low cost, excellent conductivity, adjustable expansion coefficient, and can achieve high-precision surface processing, and is particularly suitable for high-power device packaging applications.

[0004] Technical solution: The method for manufacturing an aluminum nitride-copper composite substrate for power devices based on the DPC process of the present invention comprises the following steps:

[0005] (1) Laser drilling: drilling holes on aluminum nitride substrates using a laser process;

[0006] (2) Sputtering seed layer: magnetron sputtering a metal seed layer on the surface of the punched aluminum nitride substrate;

[0007] (3) Photolithography and development: A dry film is applied to the metal seed layer, which is then exposed through a photolithography mask and developed to form the desired circuit pattern.

[0008] (4) Electroplating copper thickening: Immerse the developed aluminum nitride substrate in an electroplating solution to thicken the copper layer in the exposed metal seed layer area and fill the vias to form a conductor circuit;

[0009] (5) Stripping etching: Remove the residual dry film by chemical solution, and use etching solution to remove the seed layer not covered by the copper layer;

[0010] (6) Nickel-palladium-gold plating: The copper layer on the surface of the aluminum nitride substrate after copper plating is chemically treated and plated with a nickel-palladium-gold layer to meet the requirements of power chip bonding and welding processes;

[0011] (7) Cutting: Cut into individual aluminum nitride-copper substrates that meet size requirements through scribing or laser processing.

[0012] Furthermore, in step (1), the thickness of the aluminum nitride substrate is 0.1-1.5 mm; in the laser drilling, infrared laser processing is selected, the average laser power is 10-50 W, the spot diameter is 10-50 μm, and the number of repetitions is ≥2 times.

[0013] Furthermore, in step (1), in the laser drilling, the drilling density is such that the center distance between adjacent holes is ≥ 3 times the hole diameter, and the hole diameter size is ≥ 50 μm. The drilling density is adjusted according to the thermal conductivity requirements of the composite substrate. The higher the drilling density, the higher the thermal conductivity of the substrate.

[0014] Furthermore, in step (2), the metal seed layer is a Ti layer and a Cu layer, the thickness of the Ti layer is 200-600 nm, and the thickness of the Cu layer is 1-7 μm.

[0015] Furthermore, in step (3), the thickness of the dry film is 10-100 μm.

[0016] Furthermore, in step (4), an accelerator, an inhibitor, and a leveler are additionally added to the electroplating solution, wherein the accelerator is a sulfur-containing compound, such as sodium polydisulfide dipropylene glycol sulfonate, the inhibitor is a high molecular weight polymer surfactant, such as polyethylene glycol, and the leveler is a nitrogen-containing heterocyclic compound and its derivatives, such as tetrahydrothiazolidinethione, etc., which can achieve fast and defect-free filling of electroplated copper; the use of a shielding plate or an auxiliary cathode during electroplating can reduce edge current concentration and improve the uniformity of the thickness of the copper plating layer. For example, sodium polydisulfide dipropylene glycol sulfonate, an inhibitor of a high molecular weight polymer surfactant, such as polyethylene glycol, a leveler of a nitrogen-containing heterocyclic compound and its derivatives, such as tetrahydrothiazolidinethione, etc., and the use of a shielding plate or an auxiliary cathode during electroplating to ensure the uniformity of the copper plating thickness.

[0017] Furthermore, in step (4), the thickness of the copper layer is 10-300 μm.

[0018] Furthermore, in step (5), the chemical solution is an organic solution, such as acetone; and the etching solution is FeCl3 etching solution.

[0019] Furthermore, in step (6), in the nickel-palladium-gold layer, the nickel layer has a thickness of ≥2 μm, the palladium layer has a thickness of 0.05-0.5 μm, and the gold layer has a thickness of ≥0.05 μm.

[0020] Beneficial effects: Compared with the prior art, the present invention has the following significant effects: (1) The thermal conductivity of aluminum nitride material is generally 170-250W / (m·K), while the thermal conductivity of copper is about 398W / (m·K). Compared with traditional copper-based metal composite materials, the aluminum nitride-copper composite substrate based on the DPC process of the present invention can increase its thermal conductivity to 220-330W / (m·K) by densely punching and copper plating in the chip welding area and copper plating on the surface; (2) The aluminum nitride-copper composite substrate based on the DPC process of the present invention has lower cost than the mainstream copper-based metal composite materials, and can be used in conjunction with the nickel-palladium-gold process compared with the traditional nickel-gold process. The thickness of the gold layer is greatly reduced, which has obvious price advantages; (3) by controlling the punching density, aperture, and surface copper layer thickness of the aluminum nitride-copper composite substrate, the thermal conductivity and expansion coefficient of the material can be adjusted; (4) the present invention densely punches holes in the chip welding area to provide an efficient heat dissipation channel for the chip, and no holes are required in other areas. While improving the heat dissipation capacity, it also reduces the impact of punching on the substrate strength, thereby improving the reliability of the aluminum nitride-copper composite material substrate; (5) the aluminum nitride-copper composite substrate based on the DPC process of the present invention can prepare high-precision patterns on the surface to achieve electrical interconnection between the internal circuits of the device and between the device and the external circuits, which is particularly suitable for high-power device packaging applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a schematic diagram of a typical structure of an aluminum nitride-copper composite material substrate with a circuit on its surface in Example 1;

[0022] Figure 2 The aluminum nitride substrate in Example 1;

[0023] Figure 3 The aluminum nitride substrate after punching the chip bonding area in Example 1;

[0024] Figure 4 The aluminum nitride substrate after copper plating in Example 1;

[0025] Figure 5 A single aluminum nitride-copper composite material substrate cut into corresponding sizes in Example 1;

[0026] Figure 6 This is a schematic diagram of welding chips and bonding gold wires to a single aluminum nitride-copper composite material substrate in Example 1;

[0027] Figure 7 This is a schematic diagram of a typical structure of an aluminum nitride-copper composite material substrate with a circuit on its surface in Example 2;

[0028] Figure 8 The aluminum nitride substrate in Example 2;

[0029] Figure 9 The aluminum nitride substrate after punching the chip bonding area in Example 2;

[0030] Figure 10 The aluminum nitride substrate after copper plating in Example 2;

[0031] Figure 11 A single aluminum nitride-copper composite material substrate cut into corresponding sizes in Example 2;

[0032] Figure 12 This is a schematic diagram of welding chips and bonding gold wires to a single aluminum nitride-copper composite material substrate in Example 2. DETAILED DESCRIPTION

[0033] The present invention is further described in detail below with reference to the embodiments and accompanying drawings.

[0034] Example 1: The method for manufacturing an aluminum nitride-copper composite substrate for power devices based on the DPC process described in this embodiment is based on the packaging application of a certain type of P-band RF power chip. An aluminum nitride-copper composite substrate suitable for chip packaging is prepared, comprising four chips. The chips are bonded to the center of the composite substrate and interconnected by bonding gold wires. Specifically, Figure 6 shown. Figure 1 Here, 1 refers to the upper surface pattern layer, 2 refers to the copper via, 3 refers to the bottom copper layer mounting surface, 4 refers to the aluminum nitride substrate, 5 refers to the upper surface pattern layer bonding area, and 6 refers to the upper surface pattern layer chip welding area.

[0035] The specific implementation method includes the following process steps:

[0036] (1) Laser drilling: according to Figure 2 As shown in the figure, an aluminum nitride substrate is prepared. The thermal conductivity of the aluminum nitride substrate is 180W / (m·K). The chip bonding area is punched by infrared laser technology. The substrate thickness is 0.5mm, the punching hole diameter is 100μm, and the center spacing between adjacent array holes in the chip bonding area is 500μm. The infrared laser is used for drilling three times. The state after drilling is as follows Figure 3 As shown;

[0037] (2) Sputtering seed layer: a Ti / Cu metal seed layer is sputtered on the substrate surface, where the Ti layer thickness is 400 nm and the Cu layer thickness is 3 μm;

[0038] (3) Photolithography and development: A 25 μm thick dry film is applied to the seed layer, exposed through a photolithography mask, and developed to form the desired circuit pattern;

[0039] (4) Electroplating copper thickening: Immerse the substrate in the electroplating solution, add the accelerator sodium polydisulfide dipropane sulfonate, the inhibitor polyethylene glycol and the leveling agent tetrahydrothiothione, thicken the copper layer in the exposed seed layer area, and fill the via hole to form a conductor line. The thickness of the copper layer on the upper and lower surfaces is 100μm. The final surface pattern is as follows Figure 4 As shown;

[0040] (5) Stripping and etching: Use acetone organic solvent to dissolve the dry film, and FeCl3 low-temperature etching solution to remove the exposed seed layer;

[0041] (6) Nickel-palladium-gold plating: chemically treat the copper surface of the aluminum nitride substrate to electrolessly plate a nickel-palladium-gold layer with a nickel layer thickness of 3-6 μm, a palladium layer thickness of 0.1-0.3 μm, and a gold layer thickness of 0.2-0.5 μm, meeting the process requirements of RF power chip bonding and welding;

[0042] (7) Cutting: Cutting into individual substrates with the required size of 20.58×9.78 mm by scribing, as shown in the following example: Figure 5 .

[0043] Four RF power tube cores are soldered with gold-tin or conductive silver paste and wire-bonded onto the cut single aluminum nitride-copper composite substrate to complete the power device packaging. The device input and output functions are implemented through the bonding area. Based on actual chip junction temperature testing, the aluminum nitride-copper composite substrate prepared using the DPC process in Example 1 has a thermal conductivity of ≥240 W / (m·K), effectively reducing the chip junction temperature and providing a more efficient heat dissipation channel.

[0044] Example 2: The manufacturing method of the aluminum nitride-copper composite substrate for power devices based on the DPC process described in this embodiment is based on the packaging application of a certain type of L-band RF power chip. An aluminum nitride-copper composite substrate suitable for chip packaging is prepared, comprising two chips, which are bonded to the center of the composite substrate and interconnected by bonding gold wires. Specifically, Figure 12 shown. Figure 7 11 refers to the upper surface pattern layer, 12 refers to the copper via, 13 refers to the bottom copper layer mounting surface, 14 refers to the aluminum nitride substrate, 15 refers to the upper surface pattern layer bonding area, and 16 refers to the upper surface pattern layer chip welding area.

[0045] The specific implementation method includes the following process steps:

[0046] (1) Laser drilling: according to Figure 8 As shown in the figure, an aluminum nitride substrate is prepared. The thermal conductivity of the aluminum nitride substrate is 220W / (m·K). The chip bonding area is punched by infrared laser technology. The substrate thickness is 0.5mm, the punching hole diameter is 100μm, and the center spacing between adjacent array holes in the chip bonding area is 500μm. The infrared laser is used for drilling three times. The state after drilling is as follows Figure 9 As shown;

[0047] (2) Sputtering seed layer: a Ti / Cu metal seed layer is sputtered on the substrate surface, where the Ti layer thickness is 400 nm and the Cu layer thickness is 3 μm;

[0048] (3) Photolithography and development: A 25 μm thick dry film is applied to the seed layer, exposed through a photolithography mask, and developed to form the desired circuit pattern;

[0049] (4) Electroplating copper thickening: Immerse the substrate in the electroplating solution, add the accelerator sodium polydisulfide dipropane sulfonate, the inhibitor polyethylene glycol and the leveling agent tetrahydrothiazolidinethione, thicken the copper layer in the exposed seed layer area, and fill the via hole to form a conductor line. The thickness of the copper layer on the upper and lower surfaces is 80μm. The final surface pattern is as follows Figure 10 As shown;

[0050] (5) Stripping and etching: Use acetone organic solvent to dissolve the dry film, and FeCl3 low-temperature etching solution to remove the exposed seed layer;

[0051] (6) Nickel-palladium-gold plating: chemically treat the copper surface of the aluminum nitride substrate to electrolessly plate a nickel-palladium-gold layer with a nickel layer thickness of 3-6 μm, a palladium layer thickness of 0.1-0.3 μm, and a gold layer thickness of 0.2-0.5 μm, meeting the process requirements of RF power chip bonding and welding;

[0052] (7) Cutting: Cutting into individual substrates with the required size of 16.55×7.36 mm by scribing, as shown in the following example: Figure 11 .

[0053] Two RF power tube cores are soldered with gold-tin or conductive silver paste and wire-bonded onto the cut single aluminum nitride-copper composite substrate to complete the power device packaging. The device input and output functions are implemented through the bonding area. According to actual chip junction temperature testing, the aluminum nitride-copper composite substrate prepared using the DPC process in Example 2 has a thermal conductivity of ≥260 W / (m·K), which can effectively reduce the chip junction temperature and provide a more efficient heat dissipation channel.

Claims

1. A method for manufacturing an aluminum nitride-copper substrate for power device packaging based on a DPC process, characterized in that: The following steps are involved: (1) Laser drilling: drilling holes on aluminum nitride substrates using a laser process; (2) Sputtering seed layer: magnetron sputtering a metal seed layer on the surface of the punched aluminum nitride substrate; (3) Photolithography and development: A dry film is applied to the metal seed layer, which is then exposed through a photolithography mask and developed to form the desired circuit pattern. (4) Electroplating copper thickening: Immerse the developed aluminum nitride substrate in an electroplating solution to thicken the copper layer in the exposed metal seed layer area and fill the vias to form a conductor circuit; (5) Stripping etching: Remove the residual dry film by chemical solution, and use etching solution to remove the seed layer not covered by the copper layer; (6) Nickel-palladium-gold plating: The copper layer on the surface of the aluminum nitride substrate after copper plating is chemically treated and plated with a nickel-palladium-gold layer to meet the requirements of power chip bonding, welding and bonding processes; (7) Cutting: Cut into individual aluminum nitride-copper substrates that meet size requirements through scribing or laser processing.

2. The manufacturing method according to claim 1, characterized in that In step (1), the thickness of the aluminum nitride substrate is 0.1-1.5 mm.

3. The manufacturing method according to claim 1, characterized in that In step (1), the laser drilling is performed by using an infrared laser process, with an average laser power of 10-50 W, a spot diameter of 10-50 μm, and a repetition number of ≥2 times.

4. The manufacturing method according to claim 1, characterized in that In step (1), in the laser drilling, the drilling density is such that the center distance between adjacent holes is ≥ 3 times the hole diameter, and the hole diameter size is ≥ 50 μm.

5. The manufacturing method according to claim 1, characterized in that In step (2), the metal seed layer is a Ti layer and a Cu layer, the thickness of the Ti layer is 200-600 nm, and the thickness of the Cu layer is 1-7 μm.

6. The manufacturing method according to claim 1, characterized in that In step (3), the thickness of the dry film is 10-100 μm.

7. The manufacturing method according to claim 1, characterized in that In step (4), an accelerator, an inhibitor and a leveler are additionally added to the electroplating solution, wherein the accelerator is a sulfur-containing compound, the inhibitor is a high molecular weight polymer surfactant, and the leveler is a nitrogen-containing heterocyclic compound and its derivatives. A shielding plate or an auxiliary cathode is used during electroplating to ensure uniformity of copper plating thickness.

8. The manufacturing method according to claim 1, characterized in that In step (4), the thickness of the copper layer is 10-300 μm.

9. The manufacturing method according to claim 1, characterized in that In step (5), the chemical solution is an organic solution, and the etching solution is FeCl3 etching solution.

10. The manufacturing method according to claim 1, characterized in that In step (6), in the nickel-palladium-gold layer, the nickel layer has a thickness of ≥2 μm, the palladium layer has a thickness of 0.05-0.5 μm, and the gold layer has a thickness of ≥0.05 μm.

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