Method for packaging semiconductor chilling plate by using high-thermal-conductivity metal substrate

Abstract

The invention provides a method for packaging a semiconductor chilling plate by using a high-thermal-conductivity metal substrate, and belongs to the technical field of substrate packaging, the high-thermal-conductivity metal substrate is a thermal conductive adhesive film, the thickness of the thermal conductive adhesive film is 40-80 microns, and the thermal conductivity is greater than 3.5 W by D5470 actual test; placing the heat-conducting adhesive film on a metal plate, covering a layer of copper or aluminum on the heat-conducting adhesive film, and placing the metal plate in a vacuum hot press for hot pressing at the temperature of 205 DEG C for 2.5 hours; and after complete curing, cooling and taking out the material, checking the thickness of the plate surface and the adhesive film, and carrying out tension, tin bleaching and voltage resistance tests. The formula of the high-thermal-conductivity metal substrate adhesive film contains part of epoxy resin, the CTE value is matched with the CTE value of copper through special design, the thermal stress problem is solved, and the cold and hot impact aging performance is better; the metal (mainly aluminum, copper and stainless steel) is not easy to break, so that the problems of corner breakage and the like of the refrigeration sheet are solved.

Description

Technical Field

[0001] The present invention relates to the field of substrate packaging, and in particular to a method for packaging a semiconductor refrigeration chip using a high thermal conductivity metal substrate. Background Art

[0002] A semiconductor refrigeration chip is a thermoelectric device that becomes cold on one side and hot on the other side when DC current passes through it. Currently, most semiconductor refrigeration chips are packaged in alumina ceramics, and some are packaged in metal substrates.

[0003] The above two packaging methods in the prior art have the following disadvantages: 1. Alumina ceramic metal copper clad laminate packaging has disadvantages such as slow delivery, high cost of special shapes, and easy fragmentation during production and transportation.

[0004] 2. The measured thermal conductivity of ordinary metal substrates cannot meet the heat dissipation requirements, the temperature difference of thermoelectric devices is insufficient, and the performance is poor.

[0005] 3. DBC is made of copper and ceramic sintered at 1085° in a tunnel furnace. Due to the CTE mismatch between copper and ceramic, the DBC package substrate has poor weather resistance and its thermal shock performance does not meet the standards. Summary of the Invention

[0006] In order to make up for the above deficiencies, the present invention provides a method for packaging a semiconductor refrigeration chip using a high thermal conductivity metal substrate, aiming to improve the problems of alumina ceramic packaging and metal substrate packaging.

[0007] The present invention is achieved in that: A method for packaging a semiconductor refrigeration chip using a high thermal conductivity metal substrate comprises the following steps: S1. Prepare clean semiconductor refrigeration chips; S2. Prepare a thermally conductive adhesive film with a thickness of 40-80 μm and a thermal conductivity greater than 3.5 W / (m・K); S3. Prepare a metal substrate with a surface roughness of Ra ≤ 1.6 μm; S4. Prepare a covering metal layer with a thickness of 50-100 μm; S5. Equipment preparation: prepare vacuum hot press, constant temperature oven, tensile tester and thickness gauge; S6. Preparing a laminate of adhesive films and components: sequentially bonding the metal substrate, the thermally conductive adhesive film, the semiconductor cooling sheet, and the cover metal together to form a laminate; S7. Adjust the basic parameters of the vacuum hot press: temperature to 205°C, pressure to 0.3-0.5 MPa, vacuum degree less than or equal to 10 Pa, and time to 2.5 hours; S8, placing the laminate prepared in S6 into a carrier in a vacuum hot press and pushing it into the cavity; S9, evacuate the vacuum hot press in S7 to a vacuum level of less than or equal to 10 Pa, and start the heating program to 205°C; S10, after reaching 205°C in S9, keep the temperature and pressure for 2 hours; S11, after the components prepared in S10 are naturally cooled to room temperature, the pressure is released and the components are taken out; S12, cooling and visually inspecting the components removed from S11; S13. Test the components that have passed the inspection in S12.

[0008] Preferably, the preparation of the semiconductor refrigeration sheet in S1 includes the following steps: A1. Fold the dust-free cloth into 4 to 8 layers and add a small amount of ethanol or isopropyl alcohol.

[0009] A2. Wipe the chip in a spiral motion from the center to the edge, changing the clean area of ​​the cloth each time to avoid repeated contamination.

[0010] A3. For the gaps or corners of the electrode pins, gently wipe them with a cotton swab dipped in solvent.

[0011] A4. When the chip is seriously contaminated, wipe it with acetone first, and then clean it again with ethanol.

[0012] Preferably, surface moisture is removed during the preparation of S3, and the removal of surface moisture includes the following steps: placing the metal substrate in a constant temperature oven and drying it at 80° C. for 30 minutes.

[0013] Preferably, laying the thermally conductive adhesive film in S6 includes the following steps: cutting the adhesive film according to the size of the semiconductor refrigeration chip, with a size larger than the chip; and laying the adhesive film flatly in the center of the metal substrate to avoid wrinkles or bubbles.

[0014] Preferably, placing the semiconductor refrigeration chip in S6 includes the following steps: placing the refrigeration chip at the center of the adhesive film to ensure that the chip is aligned with the substrate; and covering the surface of the refrigeration chip with another layer of adhesive film or directly attaching a covering layer of metal.

[0015] Preferably, cooling in S11 includes the following steps: natural cooling at room temperature, or cooling to room temperature in an oven at a rate of 50° C. / h.

[0016] Preferably, the appearance inspection in S11 includes the following steps: A1. Check whether the surface is flat, and whether there are bubbles, cracks or uneven film overflow; A2. Measure the film thickness with a micrometer and ensure it is within the range of 40-80 μm. Repeat three times and take the average value.

[0017] Preferably, S12 includes mechanical property testing, thermal property testing and environmental resistance testing; Mechanical performance testing includes the following steps: Using a universal material testing machine, apply a tensile force perpendicular to the substrate at the edge of the metal foil at a speed of 5 mm / min, and record the maximum force at the interface between the film and the metal. When the adhesion is ≥5 N / cm², the product passes the test. Thermal performance testing includes thermal conductivity verification and thermal resistance testing; Environmental resistance tests include tin float test and voltage resistance test.

[0018] Preferably, the thermal conductivity verification in the thermal performance test adopts the laser flash method to measure the thermal conductivity of the film after disassembly. When the measured thermal conductivity is greater than 3.5W / (m·K), the product is qualified. The thermal resistance test in the thermal performance test uses an infrared thermal imager or thermocouple to measure the junction temperature and substrate temperature of the cooling chip during operation, and calculate the thermal resistance: Rth=(Tj-Tb) / P; Where, Tj is the junction temperature, Tb is the substrate temperature, and P is the power consumption of the cooling chip.

[0019] Preferably, the tin-float test in the environmental resistance test comprises the following steps: immersing the package in a 260° C. solder solution for 10 seconds, and observing whether the adhesive film bubbles or falls off or the metal foil is deformed; The voltage resistance test in the environmental resistance test includes the following steps: using a voltage resistance tester, applying a 1000V DC voltage between the metal substrate and the covering metal for 1 minute, and measuring the leakage current; when the leakage current is less than or equal to 0.5mA, the product is qualified.

[0020] The beneficial effects of the present invention are: This high-thermal-conductivity metal substrate is a thermally conductive adhesive film with a thickness of 40 to 80 microns. The thermal conductivity is greater than 3.5W using a D5470 test. The thermally conductive film is placed on a metal plate, covered with a layer of copper or aluminum, and then placed in a vacuum hot press at a temperature of 205 degrees Celsius for 2.5 hours. After complete curing, the material is cooled and removed, and the board surface and film thickness are inspected. Tensile strength, solder float, and voltage resistance tests are then performed.

[0021] Furthermore, the high-thermal-conductivity metal substrate film formulation of this application contains some epoxy resin, and its CTE is specifically designed to match that of copper, eliminating thermal stress issues and improving thermal shock aging performance. Because metals (primarily aluminum, copper, and stainless steel) are resistant to fracture, this eliminates issues such as cracked edges and corners of the cooling fins. Furthermore, using a high-thermal-conductivity metal substrate for packaging accelerates customer R&D efforts and is less expensive than existing ceramic packaging. The cooling fins themselves become lighter overall, and cracked edges and corners are completely eliminated. Customers can eliminate the need for polishing the ceramic during packaging, improving production efficiency and quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0023] Figure 1 It is a structural schematic diagram of a method for packaging a semiconductor refrigeration chip using a high thermal conductivity metal substrate provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0024] To make the purpose, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. 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 shall fall within the scope of protection of the present invention.

[0025] Example Reference Figure 1 A method for packaging a semiconductor refrigeration chip using a high thermal conductivity metal substrate comprises the following steps: S1. Prepare a clean semiconductor refrigeration chip. In some embodiments, the semiconductor refrigeration chip needs to be cleaned when it is prepared. The cleaning includes the following steps: A1. Fold the dust-free cloth into 4 to 8 layers and add a small amount of ethanol or isopropyl alcohol.

[0026] A2. Wipe the chip in a spiral motion from the center to the edge, changing the clean area of ​​the cloth each time to avoid repeated contamination.

[0027] A3. For the gaps or corners of the electrode pins, gently wipe them with a cotton swab dipped in solvent.

[0028] A4. When the chip is seriously contaminated, wipe it with acetone first, and then clean it again with ethanol.

[0029] Through the above cleaning, grease and impurities on the surface of the semiconductor refrigeration chip are removed.

[0030] S2. Prepare a thermally conductive adhesive film, wherein the thermally conductive adhesive film has a thickness of 40 to 80 μm and a thermal conductivity greater than 3.5 W / (m·K).

[0031] Furthermore, the thermal conductive adhesive film is an epoxy resin thermal conductive adhesive film; specifically, the material of the thermal conductive adhesive film includes organic polymer materials and insulating thermal conductive powder; the proportion of insulating thermal conductive powder is greater than or equal to 85%; the organic polymer is one or more mixtures of epoxy resin, acrylic resin, silicone resin, and polyurethane; the insulating thermal conductive powder is one or more mixtures of aluminum oxide, aluminum nitride, boron nitride, silicon carbide, silicon nitride, and magnesium oxide.

[0032] S3. Prepare a metal substrate with a surface roughness of Ra ≤ 1.6 μm; the main materials of the metal substrate are aluminum, copper, and stainless steel.

[0033] In some embodiments, to remove moisture from the metal substrate, the following method may be used: place the metal substrate in a constant temperature oven and dry it at 80° C. for 30 minutes, ie, evaporate the moisture from the metal substrate by drying.

[0034] S4. Prepare a covering metal layer with a thickness of 50-100 μm; S5. Equipment preparation: prepare vacuum hot press, constant temperature oven, tensile tester and thickness gauge; S6. Preparing a laminate of adhesive films and components: sequentially bonding the metal substrate, the thermally conductive adhesive film, the semiconductor cooling sheet, and the cover metal together to form a laminate; In some embodiments, laying the thermally conductive adhesive film includes the following steps: cutting the adhesive film according to the size of the semiconductor refrigeration chip, so that the size is larger than the chip; and laying the adhesive film flatly in the center of the metal substrate to avoid wrinkles or bubbles.

[0035] In some embodiments, placing the semiconductor refrigeration chip includes the following steps: aligning the refrigeration chip with the center of the adhesive film to ensure that the chip is aligned with the substrate; and covering the surface of the refrigeration chip with another layer of adhesive film or directly attaching a covering layer of metal.

[0036] S7. Adjust the basic parameters of the vacuum hot press: temperature to 205°C, pressure to 0.3-0.5 MPa, vacuum degree less than or equal to 10 Pa, and time to 2.5 hours; S8, placing the laminate prepared in S6 into a carrier in a vacuum hot press and pushing it into the cavity; S9, evacuate the vacuum hot press in S7 to a vacuum level of less than or equal to 10 Pa, and start the heating program to 205°C; S10, after reaching 205°C in S9, keep the temperature and pressure for 2 hours; S11, after the components prepared in S10 are naturally cooled to room temperature, the pressure is released and the components are taken out; S12, cooling and visually inspecting the components removed from S11; In some embodiments, cooling comprises the following steps: natural cooling at room temperature, or cooling to room temperature in an oven at a rate of 50° C. / h.

[0037] In some embodiments, the visual inspection comprises the following steps: A1. Check whether the surface is flat, and whether there are bubbles, cracks or uneven film overflow; A2. Measure the film thickness with a micrometer and ensure it is within the range of 40-80 μm. Repeat three times and take the average value.

[0038] S13. Test the components that have passed the inspection in S12.

[0039] In some embodiments, the test in S12 includes a mechanical property test, a thermal property test, and an environmental resistance test.

[0040] The mechanical properties test includes the following steps: using a universal material testing machine, apply a tensile force perpendicular to the substrate at the edge of the metal foil at a speed of 5mm / min, and record the maximum force at the interface between the film and the metal. When the adhesion force is ≥5N / cm², the product is qualified. The thermal performance test includes thermal conductivity verification and thermal resistance testing. The thermal conductivity verification in the thermal performance test uses the laser flash method to measure the thermal conductivity of the film after disassembly. When the measured thermal conductivity is greater than 3.5W / (m・K), the product is qualified. The thermal resistance test in the thermal performance test uses an infrared thermal imager or thermocouple to measure the junction temperature and substrate temperature of the cooling chip during operation, and calculate the thermal resistance: Rth=(Tj-Tb) / P; Among them, Tj is the junction temperature, Tb is the substrate temperature, and P is the power consumption of the cooling plate. Furthermore, the smaller the Rth value, the better the thermal conductivity.

[0041] Environmental resistance tests include tin float test and voltage resistance test.

[0042] The tin-float test in the environmental resistance test includes the following steps: immersing the package in 260°C solder liquid for 10 seconds to observe whether the film bubbles or falls off or the metal foil is deformed; The voltage resistance test in the environmental resistance test includes the following steps: using a voltage resistance tester, applying a 1000V DC voltage between the metal substrate and the covering metal for 1 minute, and measuring the leakage current; when the leakage current is less than or equal to 0.5 mA, the product is qualified.

[0043] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for packaging a semiconductor refrigeration chip using a high thermal conductivity metal substrate, characterized in that: The following steps are involved: S1. Prepare clean semiconductor refrigeration chips; S2. Prepare a thermally conductive adhesive film with a thickness of 40-80 μm and a thermal conductivity greater than 3.5 W / (m·K); S3. Prepare a metal substrate with a surface roughness of Ra ≤ 1.6 μm; S4. Prepare a covering metal layer with a thickness of 50-100 μm; S5. Equipment preparation: prepare vacuum hot press, constant temperature oven, tensile tester and thickness gauge; S6. Preparing a laminate of adhesive films and components: sequentially bonding the metal substrate, the thermally conductive adhesive film, the semiconductor cooling sheet, and the cover metal together to form a laminate; S7. Adjust the basic parameters of the vacuum hot press: temperature to 205°C, pressure to 0.3-0.5 MPa, vacuum degree less than or equal to 10 Pa, and time to 2.5 hours; S8, placing the laminate prepared in S6 into a carrier in a vacuum hot press and pushing it into the cavity; S9, evacuate the vacuum hot press in S7 to a vacuum level of less than or equal to 10 Pa, and start the heating program to 205°C; S10, after reaching 205°C in S9, keep the temperature and pressure for 2 hours; S11, after the components prepared in S10 are naturally cooled to room temperature, the pressure is released and the components are taken out; S12, cooling and visually inspecting the components removed from S11; S13. Test the components that have passed the inspection in S12.

2. The method for packaging a semiconductor refrigeration chip using a high thermal conductivity metal substrate according to claim 1, characterized in that: The preparation of the semiconductor refrigeration sheet in S1 includes the following steps: A1. Fold the dust-free cloth into 4 to 8 layers and add a small amount of ethanol or isopropyl alcohol. A2. Wipe the chip in a spiral motion from the center to the edge, changing the clean area of ​​the cloth each time to avoid repeated contamination. A3. For the gaps or corners of the electrode pins, gently wipe them with a cotton swab dipped in solvent. A4. When the chip is seriously contaminated, wipe it with acetone first, and then clean it again with ethanol.

3. The method for packaging a semiconductor refrigeration chip using a high thermal conductivity metal substrate according to claim 1, characterized in that: During the preparation of S3, surface moisture is removed, and the removal of surface moisture includes the following steps: placing the metal substrate in a constant temperature oven and drying it at 80° C. for 30 minutes.

4. The method for packaging a semiconductor refrigeration chip using a high thermal conductivity metal substrate according to claim 1, characterized in that: Laying the thermal conductive adhesive film in S6 includes the following steps: cutting the adhesive film according to the size of the semiconductor cooling chip, so that the size is larger than the chip; laying the adhesive film flatly in the center of the metal substrate to avoid wrinkles or bubbles.

5. The method for packaging a semiconductor refrigeration chip using a high thermal conductivity metal substrate according to claim 1, wherein: Placing the semiconductor refrigeration chip in S6 includes the following steps: aligning the refrigeration chip with the center of the adhesive film to ensure that the chip is aligned with the substrate; covering the surface of the refrigeration chip with another layer of adhesive film or directly attaching a covering layer of metal.

6. The method for packaging a semiconductor refrigeration chip using a high thermal conductivity metal substrate according to claim 1, characterized in that: The cooling in S11 includes the following steps: natural cooling at room temperature, or cooling to room temperature in an oven at a rate of 50° C. / h.

7. The method for packaging a semiconductor refrigeration chip using a high thermal conductivity metal substrate according to claim 1, characterized in that: The appearance inspection in S11 includes the following steps: A1. Check whether the surface is flat, and whether there are bubbles, cracks or uneven film overflow; A2. Measure the film thickness with a micrometer and ensure it is within the range of 40-80 μm. Repeat three times and take the average value.

8. The method for packaging a semiconductor refrigeration chip using a high thermal conductivity metal substrate according to claim 1, characterized in that: The tests in S12 include mechanical performance test, thermal performance test and environmental resistance test; Mechanical performance testing includes the following steps: Using a universal material testing machine, apply a tensile force perpendicular to the substrate at the edge of the metal foil at a speed of 5 mm / min, and record the maximum force at the interface between the film and the metal. When the adhesion is ≥5 N / cm², the product passes the test. Thermal performance testing includes thermal conductivity verification and thermal resistance testing; Environmental resistance tests include tin float test and voltage resistance test.

9. The method for packaging a semiconductor refrigeration chip using a high thermal conductivity metal substrate according to claim 8, characterized in that: The thermal conductivity verification in the thermal performance test is to measure the thermal conductivity of the film by laser flash method after disassembly. When the measured thermal conductivity is greater than 3.5W / (m・K), the product is qualified. The thermal resistance test in the thermal performance test uses an infrared thermal imager or thermocouple to measure the junction temperature and substrate temperature of the cooling chip during operation, and calculate the thermal resistance: Rth=(Tj-Tb) / P; Where, Tj is the junction temperature, Tb is the substrate temperature, and P is the power consumption of the cooling chip.

10. The method for packaging a semiconductor refrigeration chip using a high thermal conductivity metal substrate according to claim 8, characterized in that: The tin-float test in the environmental resistance test includes the following steps: immersing the package in 260°C solder liquid for 10 seconds to observe whether the film bubbles or falls off or the metal foil is deformed; The voltage resistance test in the environmental resistance test includes the following steps: using a voltage resistance tester, applying a 1000V DC voltage between the metal substrate and the covering metal for 1 minute, and measuring the leakage current; when the leakage current is less than or equal to 0.5mA, the product is qualified.

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