CN112679220A - Silicon nitride ceramic copper-clad substrate and preparation method thereof - Google Patents
Silicon nitride ceramic copper-clad substrate and preparation method thereof Download PDFInfo
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- 239000000919 ceramic Substances 0.000 title claims abstract description 168
- 229910052581 Si3N4 Inorganic materials 0.000 title claims abstract description 158
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 title claims abstract description 158
- 239000000758 substrate Substances 0.000 title claims abstract description 102
- 238000002360 preparation method Methods 0.000 title claims abstract description 25
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims abstract description 110
- 239000011889 copper foil Substances 0.000 claims abstract description 89
- 229910000679 solder Inorganic materials 0.000 claims abstract description 79
- 238000003466 welding Methods 0.000 claims abstract description 69
- 238000000034 method Methods 0.000 claims abstract description 59
- 230000008569 process Effects 0.000 claims abstract description 44
- 238000004519 manufacturing process Methods 0.000 claims abstract description 19
- 239000000126 substance Substances 0.000 claims abstract description 13
- 238000005516 engineering process Methods 0.000 claims abstract description 5
- 229910052802 copper Inorganic materials 0.000 claims description 17
- 239000010949 copper Substances 0.000 claims description 17
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 16
- 239000000243 solution Substances 0.000 claims description 16
- 239000011800 void material Substances 0.000 claims description 12
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 8
- 239000010445 mica Substances 0.000 claims description 7
- 229910052618 mica group Inorganic materials 0.000 claims description 7
- 238000005406 washing Methods 0.000 claims description 5
- 229910017945 Cu—Ti Inorganic materials 0.000 claims description 4
- 239000003929 acidic solution Substances 0.000 claims description 4
- 239000012670 alkaline solution Substances 0.000 claims description 4
- 238000001035 drying Methods 0.000 claims description 3
- 230000000694 effects Effects 0.000 abstract description 9
- 239000012535 impurity Substances 0.000 abstract description 9
- 238000004806 packaging method and process Methods 0.000 abstract description 9
- 239000002994 raw material Substances 0.000 abstract description 9
- 238000009736 wetting Methods 0.000 abstract description 7
- 230000009467 reduction Effects 0.000 description 14
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 11
- 239000010439 graphite Substances 0.000 description 11
- 229910002804 graphite Inorganic materials 0.000 description 11
- 238000011160 research Methods 0.000 description 4
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 3
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 3
- 230000008859 change Effects 0.000 description 3
- PMHQVHHXPFUNSP-UHFFFAOYSA-M copper(1+);methylsulfanylmethane;bromide Chemical compound Br[Cu].CSC PMHQVHHXPFUNSP-UHFFFAOYSA-M 0.000 description 3
- 230000017525 heat dissipation Effects 0.000 description 3
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 description 3
- 239000001301 oxygen Substances 0.000 description 3
- 229910052760 oxygen Inorganic materials 0.000 description 3
- FERIUCNNQQJTOY-UHFFFAOYSA-N Butyric acid Chemical compound CCCC(O)=O FERIUCNNQQJTOY-UHFFFAOYSA-N 0.000 description 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 2
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 2
- 230000002411 adverse Effects 0.000 description 2
- 238000000576 coating method Methods 0.000 description 2
- 239000001257 hydrogen Substances 0.000 description 2
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- 239000007788 liquid Substances 0.000 description 2
- 230000007246 mechanism Effects 0.000 description 2
- 239000011224 oxide ceramic Substances 0.000 description 2
- 229910052574 oxide ceramic Inorganic materials 0.000 description 2
- 238000005476 soldering Methods 0.000 description 2
- 239000004480 active ingredient Substances 0.000 description 1
- 230000003044 adaptive effect Effects 0.000 description 1
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- 238000005253 cladding Methods 0.000 description 1
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Abstract
The invention provides a silicon nitride ceramic copper-clad substrate and a preparation method thereof, belonging to the technical field of ceramic copper-clad substrates for power modules, wherein the preparation method comprises the following steps: pretreating a silicon nitride ceramic bare board, a copper foil and a solder sheet by using a chemical solution; reducing the pretreated silicon nitride ceramic bare board, copper foil and solder piece by adopting a reducing atmosphere; clamping the copper foil, the solder sheet, the silicon nitride ceramic bare board, the solder sheet and the copper foil in a tool clamp according to the stacking sequence of the copper foil, the solder sheet, the silicon nitride ceramic bare board, the solder sheet and the copper foil; placing the tool clamp in a vacuum furnace; and welding the copper foil and the silicon nitride ceramic bare board into an integrated substrate by adopting an AMB (advanced manufacturing technology) process to obtain the silicon nitride ceramic copper-clad substrate. The technical effects are as follows: the method can activate and reduce the fresh surface of the raw material, avoid the influence of the existence of impurity elements on the reaction wetting between the silicon nitride ceramic bare board and the solder sheet, reduce the generation of covering surface cavities, improve the reliability and meet the high-reliability packaging requirement of a high-power module.
Description
Technical Field
The invention belongs to the technical field of ceramic copper-clad substrates for power modules, and particularly relates to a silicon nitride ceramic copper-clad substrate and a preparation method thereof.
Background
The power module is required to have high power, high heat dissipation and high reliability in the fields of military weaponry and civil vehicles (e.g., new energy vehicles, high-speed rails, etc.). The traditional power module packaging substrate mainly comprises an aluminum oxide copper-clad substrate and an aluminum nitride copper-clad substrate, on one hand, the heat conductivity of aluminum oxide ceramic and the bending strength of aluminum nitride ceramic are low, so that the temperature-resistant cycle times of the ceramic copper-clad substrate are lower than 500 times, and the high-reliability requirement cannot be met; on the other hand, the thickness of the copper foil covered and connected by the aluminum oxide and the aluminum nitride ceramics is less than 0.3mm, and the requirements of high power and large current cannot be met. Based on the structure, the silicon nitride ceramic copper-clad substrate with more temperature cycle resistance appears, has the excellent characteristics of high mechanical strength, moderate heat conductivity, capability of being covered with thick copper and the like, and is widely applied to high-reliability packaging of high-power modules.
Common ceramic Copper-coating processes mainly include a Direct Bonding Coater (DBC) process and an Active Metal welding (AMB) process. The DBC process is mainly used for oxide ceramics by using oxygen-containing eutectic liquid of copper foil at high temperature to bond the ceramics, and when the DBC process is applied to nitride ceramics, the process complexity is increased, and the problems of interface stress defect and the like exist. The AMB process realizes the cladding connection by utilizing the reaction of active ingredients in the solder and the ceramic at high temperature, forms a tough solder layer between the ceramic and the copper foil, and has higher bonding strength and better thermal stability. For the silicon nitride ceramic copper-clad substrate, the AMB process is more suitable, and can have higher bonding strength and better thermal stability.
However, in the process of preparing the silicon nitride ceramic copper-clad substrate by adopting the AMB process, a welding cavity often appears between the silicon nitride ceramic and the copper foil, so that the peeling strength of a substrate covering surface is reduced, the hidden danger of partial discharge exists, and the reliability of the silicon nitride ceramic copper-clad substrate is seriously affected.
Disclosure of Invention
The invention aims to provide a silicon nitride ceramic copper-clad substrate and a preparation method thereof, and aims to solve the technical problems that in the process of preparing the silicon nitride ceramic copper-clad substrate by adopting an AMB (advanced manufacturing technology) process, welding cavities often appear between silicon nitride ceramic and copper foil, the peeling strength of a substrate covering surface is reduced, the hidden danger of partial discharge exists, and the reliability of the silicon nitride ceramic copper-clad substrate is seriously influenced.
In order to achieve the purpose, the invention adopts the technical scheme that: the preparation method of the silicon nitride ceramic copper-clad substrate comprises the following steps:
pretreating a silicon nitride ceramic bare board, a copper foil and a solder sheet by using a chemical solution;
reducing the pretreated silicon nitride ceramic bare board, copper foil and solder piece by adopting a reducing atmosphere;
clamping the copper foil, the solder sheet, the silicon nitride ceramic bare board, the solder sheet and the copper foil in a tool clamp according to the stacking sequence of the copper foil, the solder sheet, the silicon nitride ceramic bare board, the solder sheet and the copper foil;
placing the tool clamp in a vacuum furnace;
and welding the copper foil and the silicon nitride ceramic bare board into an integrated substrate by adopting an AMB (advanced manufacturing technology) process to obtain the silicon nitride ceramic copper-clad substrate.
Further, the step of pretreating the silicon nitride ceramic bare board, the copper foil and the solder sheet by using the chemical solution specifically comprises the following steps:
pretreating a silicon nitride ceramic bare board, a copper foil and a solder piece by adopting an acidic solution and an alkaline solution;
washing the pretreated silicon nitride ceramic bare board, copper foil and solder piece with water and ethanol;
and drying the silicon nitride ceramic bare board, the copper foil and the solder sheet which are washed by water and ethanol.
Further, in the step of reducing the pretreated silicon nitride ceramic bare board, the copper foil and the solder piece by adopting the reducing atmosphere, the reducing temperature is 300-500 ℃.
Further, before the step of clamping the copper foil, the solder sheet, the silicon nitride ceramic bare board, the solder sheet and the copper foil in the tool clamp according to the stacking sequence, the method comprises the following steps:
and pasting mica paper on the inner surface of the tool clamp.
Further, in the step of welding the copper foil and the silicon nitride ceramic bare board into an integrated substrate by adopting the AMB process to obtain the silicon nitride ceramic copper-clad substrate, the welding temperature and the welding pressure of the copper foil and the silicon nitride ceramic bare board are controlled by changing the temperature of the vacuum furnace and the weight of the tool clamp.
Further, in the step of welding the copper foil and the silicon nitride ceramic bare board into an integrated substrate by adopting the AMB process to obtain the silicon nitride ceramic copper-clad substrate, the welding temperature range is 800-950 ℃.
Further, in the step of welding the copper foil and the silicon nitride ceramic bare board into an integrated substrate by adopting the AMB process to obtain the silicon nitride ceramic copper-clad substrate, the welding pressure is in a range of 100 g-2000 g.
Further, after the step of welding the copper foil and the silicon nitride ceramic bare board into an integrated substrate by adopting the AMB process to obtain the silicon nitride ceramic copper-clad substrate, the method further comprises the following steps:
and testing the void ratio of the silicon nitride ceramic copper-clad substrate.
Furthermore, the strength of the silicon nitride ceramic bare board is not less than 700MPa, the thermal conductivity is not less than 60W/(m.K), and the thickness is 0.1-1 mm; the copper foil is made of oxygen-free copper, the purity of the oxygen-free copper is more than or equal to 99.99%, and the thickness of the oxygen-free copper is 0.1mm-2 mm; the solder sheet is an Ag-Cu-Ti solder sheet with a thickness of 0.01 mm-0.2 mm.
The preparation method of the silicon nitride ceramic copper-clad substrate provided by the invention at least has the following technical effects: compared with the prior art, the preparation method of the silicon nitride ceramic copper-clad substrate provided by the invention has the advantages that before the silicon nitride ceramic bare board and the copper foil are connected in a covering manner by adopting the AMB process, the silicon nitride ceramic bare board, the copper foil and the solder sheet are pretreated by using the chemical solution, and then the silicon nitride ceramic bare board, the copper foil and the solder sheet are subjected to reduction treatment by using the reduction atmosphere, so that the fresh surfaces of the silicon nitride ceramic bare board, the copper foil and the solder sheet can be activated and reduced, and the reaction wetting between the silicon nitride ceramic bare board and the solder sheet due to the existence of impurity elements is avoided, thereby reducing the generation of holes at the covered surface, improving the peeling strength of the covered surface, reducing the hidden danger of local discharge, improving the reliability of the silicon nitride ceramic copper-clad substrate and meeting the high-reliability packaging requirement of a high-power module.
The invention also provides a silicon nitride ceramic copper-clad substrate which is prepared by adopting the preparation method of the silicon nitride ceramic copper-clad substrate.
The silicon nitride ceramic copper-clad substrate provided by the invention is prepared by adopting the preparation method of the silicon nitride ceramic copper-clad substrate described in any embodiment, the covered surface has lower void ratio, and the high-reliability packaging requirement of a high-power module can be met.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed for the embodiments or the prior art descriptions will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.
FIG. 1 is a flow chart of a method for manufacturing a silicon nitride ceramic copper-clad substrate according to an embodiment of the present invention;
fig. 2 is a clamping schematic diagram of a method for manufacturing a silicon nitride ceramic copper-clad substrate according to an embodiment of the present invention.
In the figure:
100. silicon nitride ceramic bare board 200, copper foil 300, solder sheet
400. Work fixture
Detailed Description
In order to make the technical problems, technical solutions and advantageous effects to be solved by the present invention more clearly apparent, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
It will be understood that when an element is referred to as being "secured to" another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present. When an element is referred to as being "disposed on," "disposed on" another element, it can be directly on the other element or intervening elements may also be present. "plurality" means two or more.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.
Referring to fig. 1 and fig. 2 together, a silicon nitride ceramic copper clad substrate and a method for manufacturing the same according to an embodiment of the present invention will now be described.
Referring to fig. 1 and 2, an embodiment of the invention provides a method for preparing a silicon nitride ceramic copper-clad substrate, including the following steps:
s100, pretreating a silicon nitride ceramic bare board, a copper foil and a solder sheet by using a chemical solution.
The surface impurities of the silicon nitride ceramic bare board 100, the copper foil 200 and the solder sheet 300 can be removed through the chemical solution, so that the fresh surface of the raw material can be activated, and the influence of impurity elements can be avoided.
S200, reducing the pretreated silicon nitride ceramic bare board, the copper foil and the solder piece by adopting a reducing atmosphere.
The reducing atmosphere comprises hydrogen or a mixture of hydrogen and inert gas and the like, the fresh surface of the raw material can be reduced, the influence of impurity elements is avoided, the purity and the cleanliness of the raw material can be further ensured on the basis of pretreatment of the chemical solution, and the influence of the raw material on the generation of a covering surface cavity is reduced.
S300, clamping the copper foil sheets, the solder sheets, the silicon nitride ceramic bare plates, the solder sheets and the copper foil sheets in a tool clamp according to the stacking sequence.
Referring to fig. 2, in the embodiment, the silicon nitride ceramic copper-clad substrate is a double-sided copper-clad substrate, and is sequentially clamped in the tooling fixture 400 according to the stacking sequence of the copper foil sheet 200, the solder sheet 300, the silicon nitride ceramic bare board 100, the solder sheet 300, and the copper foil sheet 200, the tooling fixture 400 may specifically adopt a graphite fixture, the graphite fixture has two graphite clamping plates symmetrically arranged to respectively clamp the two copper foil sheets 200, and the graphite fixture can provide a matched welding pressure for the AMB process. Typically, one of the graphite clamping plates is used to support the silicon nitride ceramic copper clad substrate and the other graphite clamping plate is used to apply the bonding pressure.
S400, placing the tool clamp in a vacuum furnace.
The tooling fixture 400 may be disposed in a vacuum furnace through a clamping mechanism, a support mechanism, etc., and the vacuum furnace is configured with a temperature control system, which may provide a matched welding temperature for the AMB process.
S500, welding the copper foil and the silicon nitride ceramic bare board into an integrated substrate by adopting an AMB (advanced manufacturing technology) process to obtain the silicon nitride ceramic copper-clad substrate.
In the AMB process, the scattering performance of the solder sheet 300 under the high-temperature condition can be changed by adjusting different welding temperatures and welding pressures, so that the solder sheet can not only fill the interface cavity between the silicon nitride ceramic bare board 100 and the copper foil sheet 200, but also can not scatter outside the silicon nitride ceramic bare board 100, a silicon nitride ceramic copper-clad substrate with the cavity rate of less than 1% can be prepared, the flatness of the silicon nitride ceramic copper-clad substrate is less than 3 per thousand, the temperature resistant cycle times (-65-150 ℃) is more than or equal to 3000, and the high-reliability packaging requirement of a high-power module can be met.
The preparation method of the silicon nitride ceramic copper-clad substrate provided by the embodiment of the invention at least has the following technical effects: compared with the prior art, the preparation method of the silicon nitride ceramic copper-clad substrate provided by the embodiment of the invention, before the AMB process is adopted to connect the silicon nitride ceramic bare board 100 and the copper foil 200 in a covering manner, the silicon nitride ceramic bare board 100, the copper foil 200 and the solder piece 300 are pretreated by using a chemical solution, and then the silicon nitride ceramic bare board 100, the copper foil 200 and the solder piece 300 are subjected to reduction treatment by using a reducing atmosphere, so that fresh surfaces of the silicon nitride ceramic bare board 100, the copper foil 200 and the solder piece 300 can be activated and reduced, the influence of reaction wetting between the silicon nitride ceramic bare board 100 and the solder piece 300 due to the existence of impurity elements is avoided, therefore, the generation of cavities on the covered surface is reduced, the peeling strength of the covered surface is improved, the hidden danger of partial discharge is reduced, the reliability of the silicon nitride ceramic copper-clad substrate is improved, and the high-reliability packaging requirement of a high-power module is met.
In addition, referring to fig. 1, after step S500 of welding the copper foil and the silicon nitride ceramic bare board into an integrated substrate by using the AMB process to obtain the silicon nitride ceramic copper-clad substrate, the method further includes step S600 of: and testing the void ratio of the silicon nitride ceramic copper-clad substrate. And if the void ratio meets the preparation requirement, storing and storing the corresponding silicon nitride ceramic copper-clad substrate, and if the void ratio does not meet the preparation requirement, recovering the corresponding silicon nitride ceramic copper-clad substrate.
The specific step of the pretreatment with the chemical solution is not limited, and as a specific embodiment, the step S100 of pretreating the silicon nitride ceramic bare board, the copper foil and the solder sheet with the chemical solution specifically includes the following steps: pretreating the silicon nitride ceramic bare board 100, the copper foil sheet 200 and the solder sheet 300 by adopting an acidic solution and an alkaline solution; washing the pretreated silicon nitride ceramic bare board 100, the copper foil sheet 200 and the solder sheet 300 with water and ethanol; and drying the silicon nitride ceramic bare board 100, the copper foil sheet 200 and the solder sheet 300 which are washed by water and ethanol.
In this embodiment, the chemical solution includes an acid-base solution such as a sodium hydroxide solution, hydrochloric acid, or butyric acid. The acidic solution, the alkaline solution, the water washing and the ethanol washing are utilized to remove impurity elements as much as possible, the influence on the reaction wetting between the welding material sheet 300 and the silicon nitride ceramic bare board 100 is reduced, and the generation of covering surface cavities is reduced. The silicon nitride ceramic bare board 100, the copper foil 200 and the solder sheet 300 which are washed by water and ethanol are dried by hot air, so that the influence of impurity liquid is reduced, and the dryness is kept.
In order to improve the effect of the reduction treatment, as a specific embodiment, in step S200 of reducing the silicon nitride ceramic bare board, the copper foil sheet and the solder sheet which are pretreated by using a reducing atmosphere, the reduction temperature is 300 to 500 ℃. In this embodiment, in the reduction treatment process, the temperature needs to be optimally designed to improve the reduction treatment effect, and specifically, adaptive matching can be performed according to factors such as the type of the reduction atmosphere and the reaction time. The inventor researches and finds that the reduction temperature is in the range of 300-500 ℃, the reduction treatment of different preparation requirements can be matched, and the higher reduction treatment effect is ensured. The reduction temperature may be, for example, 300 ℃, 310 ℃, 320 ℃, 330 ℃, 340 ℃, 350 ℃, 360 ℃, 370 ℃, 380 ℃, 390 ℃, 400 ℃, 410 ℃, 420 ℃, 430 ℃, 440 ℃, 450 ℃, 460 ℃, 470 ℃, 480 ℃, 490 ℃, or 500 ℃, and is not limited thereto, and may be selected adaptively according to the preparation requirements. It can be understood that, in the pretreatment process of the raw materials, i.e., the silicon nitride ceramic bare board 100, the copper foil sheet 200, and the solder sheet 300, a reduction temperature may be set, or the reduction temperature may be adjusted according to the soldering process, which is not limited to this.
In order to avoid adhesion between the tool fixture 400 and the copper foil 200, as a specific embodiment, before the step S300 of clamping the copper foil, the solder sheet, the bare silicon nitride ceramic board, the solder sheet, and the copper foil in the tool fixture in the stacking order, the method includes the following steps: mica paper is attached to the inner surface of the work fixture 400. In this embodiment, the mica paper separates the inner surface of the tool fixture 400 from the copper foil 200, so as to prevent the solder pieces 300 from being melted and overflowing from the gap between the bare silicon nitride ceramic board 100 and the copper foil 200 and flowing to the inner surface of the tool fixture 400 under a high temperature condition, further prevent the copper foil 200 from being adhered to the inner surface of the tool fixture 400, and prevent the prepared copper-clad silicon nitride ceramic substrate from being adhered to the tool fixture 400 and being unable to be separated.
The fixture 400 may specifically adopt graphite clamping plates arranged in pairs, and mica paper is pasted on the inner surfaces of the graphite clamping plates. It can be understood that the mica paper selected in the embodiment can resist high temperature, and the high temperature resistance of the mica paper is higher than the welding temperature in the vacuum furnace, so that poor welding caused by failure is prevented.
In order to better reduce the void ratio of the clad surface, as a specific embodiment, in step S500 of welding the copper foil and the bare silicon nitride ceramic substrate into an integrated substrate by using the AMB process to obtain the silicon nitride ceramic copper-clad substrate, the welding temperature and the welding pressure of the copper foil 200 and the bare silicon nitride ceramic substrate 100 are controlled by changing the temperature of the vacuum furnace and the weight of the tool 400. In the embodiment, the scattering performance of the solder sheet 300 under the high-temperature condition can be changed by optimizing the welding parameters, so that the solder sheet can not only fill the interface cavity between the silicon nitride ceramic bare board 100 and the copper foil sheet 200, but also can not scatter outside the silicon nitride ceramic bare board 100, a silicon nitride ceramic copper-clad substrate with the cavity rate less than 1% can be prepared, the flatness of the silicon nitride ceramic copper-clad substrate is less than 3 per mill, the temperature resistant cycle times (-65-150 ℃) is more than or equal to 3000 times, and the high-reliability packaging requirement of a high-power module can be met. It is understood that the welding pressure corresponds to the weight of the tooling fixture 400, and generally the tooling fixture 400 comprises two graphite clamping plates symmetrically arranged, wherein one graphite clamping plate is used for supporting the silicon nitride ceramic copper-clad substrate, and the other graphite clamping plate is used for applying the welding pressure.
Specifically, the vacuum furnace is provided with a temperature control system, and the temperature generated by the temperature control system is controlled manually or automatically, so that the welding temperature can be controlled. It is understood that a welding temperature may be set for the same type of silicon nitride ceramic copper clad substrate, or the welding temperature may be adjusted according to the welding process, which is not limited thereto. A welding pressure can be set corresponding to the same type of silicon nitride ceramic copper-clad substrate, and the welding pressure can also be adjusted according to the welding process, which is not limited to this, when the self weight of the tool fixture 400 can be adjusted, for example, the tool fixture 400 has a plurality of different weight blocks or weight pieces, and the number of the weight blocks or the weight pieces is adjusted according to the change or the preset pressure in the welding process, so that the self weight of the tool fixture 400 can be adjusted.
In one embodiment, in step S500 of welding the copper foil and the silicon nitride ceramic bare board into an integrated substrate by using the AMB process to obtain the silicon nitride ceramic copper-clad substrate, the welding temperature ranges from 800 ℃ to 950 ℃. In the embodiment, the inventor researches and discovers that when the welding temperature ranges from 800 ℃ to 950 ℃, the welding performance can be more guaranteed, the voidage of the prepared silicon nitride ceramic copper-clad substrate is less than 1%, the flatness is less than 3 per thousand, and the temperature resistant cycle times (-65 ℃ to 150 ℃) is more than or equal to 3000. It can be understood that the welding temperature can be adjusted in time according to the change or preset temperature in the welding process, so that the void ratio is controlled at a lower level. The welding temperature can be 800 ℃, 810 ℃, 820 ℃, 830 ℃, 840 ℃, 850 ℃, 860 ℃, 870 ℃, 875 ℃, 880 ℃, 890 ℃, 900 ℃, 910 ℃, 920 ℃, 930 ℃, 940 ℃, 950 ℃ and other specific values, and the welding temperature is not limited, and can be selected adaptively according to the preparation requirements. It can be understood that, a welding temperature may be set for the same type of silicon nitride ceramic copper clad substrate, or the welding temperature may be adjusted according to the welding process, which is not limited to this, and in this embodiment, the welding temperature refers to the highest temperature.
In one embodiment, in step S500 of welding the copper foil and the silicon nitride ceramic bare board into an integrated substrate by using the AMB process to obtain the silicon nitride ceramic copper-clad substrate, the welding pressure is in a range of 100g to 2000 g. In the embodiment, the inventor researches and discovers that when the welding pressure ranges from 100g to 2000g, the reliability can be better ensured, the voidage of the prepared silicon nitride ceramic copper-clad substrate is less than 1%, the flatness is less than 3 per thousand, and the temperature resistant cycle times (-65 ℃ to 150 ℃) is more than or equal to 3000. It can be understood that the welding pressure can be adjusted in time according to the change or preset pressure in the welding process, so that the void ratio is controlled at a lower level. The welding pressure may be a specific value such as 100g, 200g, 300g, 400g, 500g, 600g, 700g, 800g, 900g, 1000g, 1100g, 1200g, 1300g, 1400g, 1500g, 1600g, 1700g, 1800g, 1900g, 2000g, etc., but is not limited thereto, and may be adaptively selected according to manufacturing requirements. It can be understood that a welding pressure may be set for the same type of silicon nitride ceramic copper-clad substrate, or the welding pressure may be adjusted according to the welding process, which is not limited to this.
It can be understood that for silicon nitride ceramic copper-clad substrates with different preparation requirements, the void ratio of the covered surface can be controlled at a lower level by matching different parameters such as welding temperature, welding pressure and the like. That is, the welding temperature and welding pressure may be selectively configured during the manufacturing process.
In one embodiment, the copper foil sheet 200 is made of oxygen-free copper, and the solder sheet 300 is made of an Ag-Cu-Ti based solder sheet 300. In this embodiment, the copper foil 200 is made of oxygen-free copper, which can reduce the presence of oxygen element on the basis of selecting raw materials, thereby reducing the presence of impurity elements, avoiding adverse effects on reaction wetting between the solder sheet 300 and the silicon nitride ceramic bare board 100, and further reducing the generation of voids on the bonding surface. The solder sheet 300 is an Ag-Cu-Ti solder sheet 300, and is an active metal solder conforming to the AMB process, and active components, such as Ti, are used to react with the silicon nitride ceramic bare board 100 for wetting, so that the silicon nitride ceramic bare board 100 and oxygen-free copper form a reliable overlay structure, and the soldering strength and reliability can be improved on the basis of selecting raw materials.
Furthermore, the strength of the silicon nitride ceramic bare board 100 is more than or equal to 700MPa, the thermal conductivity is more than or equal to 60W/(m.K), and the thickness is 0.1 mm-1 mm; the purity of the oxygen-free copper is more than or equal to 99.99 percent, and the thickness is 0.1mm-2 mm; the thickness of the solder sheet 300 is 0.01mm to 0.2 mm. In the embodiment, the inventor researches and discovers that the parameters of the silicon nitride ceramic bare board 100, the oxygen-free copper and the solder sheet 300 are optimally designed, so that the preparation requirements of different sizes can be met, the adverse effect of raw materials on the AMB process can be reduced on the basis, and the silicon nitride ceramic copper-clad substrate with low void ratio can be prepared by adopting the preparation method.
Specifically, the strength of the silicon nitride ceramic bare board 100 may be a specific value such as 700MPa, 720MPa, 740MPa, 760MPa, 780MPa, 800MPa, 850MPa, 900MPa, 950MPa, or 1000MPa, which is not limited thereto, but may be adaptively selected according to the production requirements. The thermal conductivity of the bare silicon nitride ceramic board 100 may be, but is not limited to, 60W/(m · K), 65W/(m · K), 70W/(m · K), 75W/(m · K), 80W/(m · K), 85W/(m · K), 90W/(m · K), 95W/(m · K), or 100W/(m · K), and may be selected adaptively according to production requirements. The thickness of the silicon nitride ceramic bare board 100 may be a specific value such as 0.1mm, 0.2mm, 0.3mm, 0.4mm, 0.5mm, 0.55mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, 1mm, etc., and is not limited thereto, and may be adaptively selected according to the production requirements.
The purity of the oxygen-free copper may be specific values such as 99.99%, 99.991%, 99.992%, 99.993%, 99.994%, 99.995%, 99.996%, 99.997%, 99.998%, 99.999% and the like, but is not limited thereto, and generally, the higher the purity is, the better the purity is, so that the presence of oxygen element can be reduced, and the influence on the reaction wetting between the solder sheet 300 and the silicon nitride ceramic bare board 100 can be reduced. The thickness of the oxygen-free copper may be a specific value such as 0.1mm, 0.3mm, 0.5mm, 0.7mm, 0.9mm, 1.05mm, 1.1mm, 1.3mm, 1.5mm, 1.7mm, 1.9mm, 2.0mm, etc., which is not limited thereto, and may be adaptively selected according to the production requirements.
The thickness of the solder sheet 300 may be a specific value such as 0.01mm, 0.03mm, 0.05mm, 0.07mm, 0.09mm, 0.10mm, 0.105mm, 0.11mm, 0.13mm, 0.15mm, 0.17mm, 0.19mm, and 0.20mm, which is not limited thereto, and may be adaptively selected according to the production requirements.
The embodiment of the invention also provides a silicon nitride ceramic copper-clad substrate which is prepared by adopting the preparation method of the silicon nitride ceramic copper-clad substrate.
It can be understood that the silicon nitride ceramic copper-clad substrate provided in the embodiment of the present invention is mainly applied to the circuit substrate, the heat dissipation substrate and other occasions of the high power module, and specifically can be the circuit substrate, the heat dissipation substrate and other occasions of the high power module such as the IGBT power module, and is not limited thereto.
The silicon nitride ceramic copper-clad substrate provided by the embodiment of the invention is prepared by adopting the preparation method of the silicon nitride ceramic copper-clad substrate described in any embodiment, the coating surface has lower void ratio, and the high-reliability packaging requirement of a high-power module can be met.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.
Claims (10)
1. The preparation method of the silicon nitride ceramic copper-clad substrate is characterized by comprising the following steps of:
pretreating a silicon nitride ceramic bare board, a copper foil and a solder sheet by using a chemical solution;
reducing the pretreated silicon nitride ceramic bare board, copper foil and solder piece by adopting a reducing atmosphere;
clamping the copper foil, the solder sheet, the silicon nitride ceramic bare board, the solder sheet and the copper foil in a tool clamp according to the stacking sequence of the copper foil, the solder sheet, the silicon nitride ceramic bare board, the solder sheet and the copper foil;
placing the tool clamp in a vacuum furnace;
and welding the copper foil and the silicon nitride ceramic bare board into an integrated substrate by adopting an AMB (advanced manufacturing technology) process to obtain the silicon nitride ceramic copper-clad substrate.
2. The method according to claim 1, wherein the step of pretreating the silicon nitride ceramic bare board, the copper foil sheet and the solder sheet with the chemical solution comprises the following steps:
pretreating a silicon nitride ceramic bare board, a copper foil and a solder piece by adopting an acidic solution and an alkaline solution;
washing the pretreated silicon nitride ceramic bare board, copper foil and solder piece with water and ethanol;
and drying the silicon nitride ceramic bare board, the copper foil and the solder sheet which are washed by water and ethanol.
3. The method according to claim 1, wherein in the step of reducing the pre-treated silicon nitride ceramic bare board, the copper foil sheet and the solder sheet in a reducing atmosphere, the reducing temperature is 300 ℃ to 500 ℃.
4. The method according to claim 1, wherein before the step of clamping the copper foil sheet, the solder sheet, the bare silicon nitride ceramic plate, the solder sheet and the copper foil sheet in the tool holder in the stacking order, the method comprises the steps of:
and pasting mica paper on the inner surface of the tool clamp.
5. The manufacturing method according to claim 1, wherein in the step of welding the copper foil and the bare silicon nitride ceramic board into an integrated substrate by using the AMB process to obtain the silicon nitride ceramic copper-clad substrate, the welding temperature and the welding pressure of the copper foil and the bare silicon nitride ceramic board are controlled by changing the temperature of the vacuum furnace and the weight of the tool holder.
6. The production method according to claim 1 or 5, wherein in the step of welding the copper foil and the silicon nitride ceramic bare board into an integrated substrate by using the AMB process to obtain the silicon nitride ceramic copper-clad substrate, the welding temperature is in a range of 800 ℃ to 950 ℃.
7. The production method according to claim 1 or 5, wherein in the step of welding the copper foil and the bare silicon nitride ceramic board into an integrated substrate by the AMB process to obtain the silicon nitride ceramic copper-clad substrate, the welding pressure is in a range of 100g to 2000 g.
8. The method according to claim 1, wherein after the step of welding the copper foil and the bare silicon nitride ceramic board into an integrated substrate by using the AMB process to obtain the silicon nitride ceramic copper-clad substrate, the method further comprises the following steps:
and testing the void ratio of the silicon nitride ceramic copper-clad substrate.
9. The preparation method according to claim 8, wherein the silicon nitride ceramic bare board has a strength of 700MPa or more, a thermal conductivity of 60W/(m.K) or more, and a thickness of 0.1mm to 1 mm; the copper foil is made of oxygen-free copper, the purity of the oxygen-free copper is more than or equal to 99.99%, and the thickness of the oxygen-free copper is 0.1mm-2 mm; the solder sheet is an Ag-Cu-Ti solder sheet with a thickness of 0.01 mm-0.2 mm.
10. The silicon nitride ceramic copper-clad substrate according to any one of claims 1 to 9, which is produced by the method for producing a silicon nitride ceramic copper-clad substrate.
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