阅读说明：本技术 用于to-252封装的金属陶瓷外壳及制备方法 (Metal ceramic shell for TO-252 packaging and preparation method ) 是由 侯杰 黄璐 杨旭东 张振兴 相裕兵 于 2021-08-27 设计创作，主要内容包括：本发明公开一种用于TO-252封装的金属陶瓷外壳及制备方法,所述金属陶瓷外壳包括壳体、底板、盖板、无氧铜压焊区、陶瓷绝缘体、无氧铜引线和陶瓷承托柱,底板和盖板分别封装在壳体的底部和顶部,无氧铜压焊区位于壳体内部,通过陶瓷承托柱焊接在底板上,陶瓷绝缘体镶嵌在壳体上并通过焊接实现密封,陶瓷绝缘体为一整体,陶瓷绝缘体上开有多个引线孔,无氧铜引线一端焊接在无氧铜压焊区,另一端穿过引线孔延伸至壳体外。本发明可以原位替换塑封器件,具有可靠性高、抗恶劣环境性能高、抗机械冲击和热冲击性能好的优点。(The invention discloses a metal ceramic shell for TO-252 packaging and a preparation method thereof, wherein the metal ceramic shell comprises a shell body, a bottom plate, a cover plate, an oxygen-free copper pressure welding area, a ceramic insulator, an oxygen-free copper lead and a ceramic bearing column, wherein the bottom plate and the cover plate are respectively packaged at the bottom and the top of the shell body, the oxygen-free copper pressure welding area is positioned in the shell body and is welded on the bottom plate through the ceramic bearing column, the ceramic insulator is embedded on the shell body and realizes sealing through welding, the ceramic insulator is an integral body, a plurality of lead holes are formed in the ceramic insulator, one end of the oxygen-free copper lead is welded on the oxygen-free copper pressure welding area, and the other end of the oxygen-free copper lead passes through the lead holes and extends out of the shell body. The invention can replace the plastic package device in situ, and has the advantages of high reliability, high resistance to severe environment, and good mechanical impact resistance and thermal shock resistance.)

1. A cermet shell for TO-252 encapsulation characterized in that: the ceramic insulator is embedded on the shell and sealed through welding, the ceramic insulator is a whole, a plurality of lead holes are formed in the ceramic insulator, one end of the oxygen-free copper lead wire is welded in the oxygen-free copper pressure welding area, and the other end of the oxygen-free copper lead wire penetrates through the lead holes and extends out of the shell.

2. The cermet package for TO-252 of claim 1, further comprising: the oxygen-free copper pressure welding area extends along the transverse direction of the shell.

3. The cermet package for TO-252 of claim 1, further comprising: the ceramic insulator is 92% Al₂O₃And (3) high-temperature co-firing the ceramic.

4. The cermet housing for TO-252 package according TO claim 1 or 3, characterized in that: the ceramic insulator and the ceramic supporting column are provided with surface metallization layers at positions needing welding and sealing, the surface metallization layers comprise tungsten slurry layers and nickel plating layers, the tungsten slurry layers are printed in the ceramic insulator preparation process, and the nickel plating layers are carried out after the ceramic insulator is prepared and formed.

5. The cermet package for TO-252 of claim 4, further comprising: the thickness of the nickel plating layer is more than or equal to 3 mu m.

6. The cermet package for TO-252 of claim 1, further comprising: the shell is made of kovar alloy, the bottom plate is made of tungsten copper, the cover plate is made of iron-nickel alloy, the shell, the bottom plate, the cover plate, the oxygen-free copper pressure welding area and parts of the oxygen-free copper lead wire needing to be welded are all plated with nickel, and the thickness of the nickel plating is larger than or equal to 3 mu m.

7. The cermet package for TO-252 of claim 1, further comprising: the metal surface of the shell is plated with a layer of gold, and the thickness of the gold plating layer is more than or equal to 0.5 mu m.

8. A preparation method of a metal ceramic shell for TO-252 packaging is characterized by comprising the following steps: the method comprises the following steps:

s01), heating the nitrogen-hydrogen atmosphere protection chain type sintering furnace to the welding temperature of the silver-copper solder, introducing nitrogen-hydrogen mixed gas protection gas, and preheating for a period of time;

s02), welding the bottom plate and the shell together, welding the ceramic support column and the oxygen-free copper pressure welding area together, and welding the ceramic insulator and the oxygen-free copper lead together;

in order to realize the welding between the ceramic bearing column and the oxygen-free copper press welding area and between the ceramic insulator and the oxygen-free copper lead wire, surface metallization layers are arranged on the ceramic insulator and the ceramic bearing column at positions needing to be welded and sealed, each surface metallization layer comprises a tungsten slurry layer and a nickel plating layer, the tungsten slurry layers are printed in the preparation process of the ceramic insulator, and the nickel plating layers are carried out after the ceramic insulator is prepared and formed;

s03), final assembly welding, and welding and assembling the parts welded and formed in the step S02 together to form the metal ceramic shell as recited in claim 1.

9. The method of making a cermet housing for a TO-252 package as claimed in claim 8 wherein: the preparation process of the ceramic insulator comprises the following steps:

1. forming a ceramic blank layer by adopting a tape casting method, and punching holes at positions of the ceramic blank layer where wiring is needed;

2. the primary metallization is to print a layer of tungsten paste material slurry on the part of the ceramic insulator needing welding and sealing, the primary metallization comprises inner hole metallization and layer surface printing metallization, because the ceramic insulator is formed by laminating a plurality of layers of ceramic blanks, the metallization layer is distributed to the required layer, and then the following steps are carried out;

3. stacking materials, performing isostatic pressing, namely stacking multiple layers of ceramic blank materials, and then applying equal pressure to the ceramic chips in all directions by adopting isostatic pressing equipment so as to form the ceramic insulator;

4. separating into single products, and co-firing at high temperature;

5. nickel plating, wherein the thickness of the nickel layer is more than or equal to 3 μm.

10. The method of making a cermet housing for a TO-252 package as claimed in claim 8 wherein: the shell, the bottom plate, the cover plate and the oxygen-free copper pressure welding area are all plated with nickel, and the thickness of the nickel plating is larger than or equal to 3 mu m.

Technical Field

The invention relates TO the field of semiconductors, in particular TO a metal ceramic shell for TO-252 packaging and a preparation method thereof.

Background

At present, a large amount of TO-252 series standard-size device products are required in the fields of aerospace, aviation, ships, weapons and the like, the characteristics of low resistance, low thermal resistance, good impact resistance, high reliability and the like are required, and the guarantee is provided for improving the reliability of the whole machine. The plastic package TO-252 device shell is made of epoxy resin, the strength and the sealing performance are poor, and under a high-temperature and humid environment, the joint of the plastic package material and the lead frame is easy TO invade water vapor, so that the electric leakage of the device is large, and the plastic package TO-252 device shell cannot be used in the field of high-reliability devices. The metal ceramic shell device adopts metal material as main body and high-temperature co-fired Al₂O₃The ceramic is an insulator, the metal is Al₂O₃The strength and high temperature resistance of the ceramic shell are obviously higher than those of plastic package materials, so that the reliability of the metal ceramic shell is greatly improved. However, the metal ceramic shell and the packaging structure are complex, the production flow is complicated, and the technical difficulty is high; high temperature co-fired Al₂O₃The processing difficulty is high, the cost is high, and a high-reliability shell and a packaging device which can replace a plastic package TO-252 high-current device do not exist at home at present.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides the metal ceramic shell for the TO-252 package and the preparation method thereof, and the metal ceramic shell can replace a plastic package device in situ and has the advantages of high reliability, high severe environment resistance and good mechanical impact resistance and thermal shock resistance.

In order TO solve the technical problem, the invention firstly discloses a metal ceramic shell for TO-252 packaging, which comprises a shell, a bottom plate, a cover plate, an oxygen-free copper pressure welding area, a ceramic insulator, an oxygen-free copper lead and a ceramic bearing column, wherein the bottom plate and the cover plate are respectively packaged at the bottom and the top of the shell, the oxygen-free copper pressure welding area is positioned in the shell and is welded on the bottom plate through the ceramic bearing column, the ceramic insulator is embedded on the shell and is sealed through welding, the ceramic insulator is an integral body, a plurality of lead holes are formed in the ceramic insulator, one end of the oxygen-free copper lead is welded on the oxygen-free copper pressure welding area, and the other end of the oxygen-free copper lead passes through the lead holes and extends out of the shell.

Furthermore, the oxygen-free copper bonding area extends transversely along the shell, so that the bonding area can be increased as much as possible in a limited space, and a large-current chip mounting space and a circuit leading-out structure can be designed in a TO-252 small-size appearance limiting space.

Further, the ceramic insulator is 92% Al₂O₃The high-temperature co-fired ceramic has high resistance and high strength.

The ceramic insulator and the ceramic support column are made of ceramic, the surface welding wettability is avoided, in order to enable the ceramic insulator and the ceramic support column to have the surface wettability (welding performance), surface metallization layers are arranged on positions needing welding sealing on the ceramic insulator and the ceramic support column, the surface metallization layers comprise a tungsten slurry layer and a nickel plating layer, the tungsten slurry layer is printed in the preparation process of the ceramic insulator, and the nickel plating layer is carried out after the ceramic insulator is prepared and formed.

Furthermore, the thickness of the nickel plating layer is more than or equal to 3 μm.

In this embodiment, the casing is made of kovar alloy, the bottom plate is made of tungsten copper, the cover plate is made of iron-nickel alloy, the casing, the bottom plate, the cover plate and the oxygen-free copper pressure welding area are all nickel-plated on the part of the oxygen-free copper lead needing to be welded, and the thickness of the nickel-plated is greater than or equal to 3 μm.

The casing is made of kovar alloy, has good matching performance with ceramic materials, and can realize a thin-wall structure. The bottom plate is made of tungsten copper, the tungsten copper bottom plate is used as a chip heat sink, and the heat conducting performance is good and the matching performance with a ceramic material is good. The reason for nickel plating is that some metal materials do not have solder wettability either, and the surface nickel plating provides solder wettability.

Furthermore, the surface of the shell metal is plated with a layer of gold, and the thickness of the gold plating layer is more than or equal to 0.5 mu m. Gold plating is the last step in the housing fabrication process for device package die bonding and pressure bonding and to prevent surface corrosion.

A preparation method of a metal ceramic shell for TO-252 encapsulation comprises the following steps:

s01), heating the nitrogen-hydrogen atmosphere protection chain type sintering furnace to the welding temperature of the silver-copper solder, introducing nitrogen-hydrogen mixed gas protection gas, and preheating for a period of time;

s02), welding the bottom plate and the shell together, welding the ceramic support column and the oxygen-free copper pressure welding area together, and welding the ceramic insulator and the oxygen-free copper lead together; the ceramic insulator and the ceramic support column are made of ceramic, and have no surface welding wettability, in order to enable the ceramic insulator and the ceramic support column to have surface wettability (welding performance), the ceramic support column and the oxygen-free copper pressure welding area and the ceramic insulator and the oxygen-free copper lead wire are welded together, a surface metallization layer is arranged on the ceramic insulator and the ceramic support column at the position needing welding sealing, the surface metallization layer comprises a tungsten slurry layer and a nickel plating layer, the tungsten slurry layer is printed in the preparation process of the ceramic insulator, and the nickel plating layer is carried out after the ceramic insulator is prepared and formed;

s03), final assembly welding, and welding and assembling the parts welded and formed in the step S02 together to form the metal ceramic shell as recited in claim 1.

Further, the preparation process of the ceramic insulator comprises the following steps:

1. forming a ceramic blank layer by adopting a tape casting method, and punching holes at positions of the ceramic blank layer where wiring is needed;

2. the primary metallization is to print a layer of tungsten paste material slurry on the part of the ceramic insulator needing welding and sealing, the primary metallization comprises inner hole metallization and layer surface printing metallization, because the ceramic insulator is formed by laminating a plurality of layers of ceramic blanks, the metallization layer is distributed to the required layer, and then the following steps are carried out;

3. stacking materials, performing isostatic pressing, namely stacking multiple layers of ceramic blank materials, and then applying equal pressure to the ceramic chips in all directions by adopting isostatic pressing equipment so as to form the ceramic insulator;

4. separating into single products, and co-firing at high temperature;

5. nickel plating with a thickness of 3 μm or more.

Furthermore, the shell, the bottom plate, the cover plate, the oxygen-free copper pressure welding area and the part of the oxygen-free copper lead wire needing to be welded are all plated with nickel, and the thickness of the nickel plating is larger than or equal to 3 mu m.

Drawings

FIG. 1 is a schematic structural view of a cermet housing without a cover plate;

FIG. 2 is a schematic side view of the cermet housing without a cover plate;

FIG. 3 is a cross-sectional view of FIG. 2;

FIG. 4 is a schematic bottom view of the cermet housing without a cover plate;

FIG. 5 is a schematic structural diagram of a front view of a cover plate encapsulated by a cermet housing;

FIG. 6 is a schematic side view of a cover plate with a cermet housing;

in the figure: 1. the welding structure comprises a tungsten copper base plate, 2, a kovar alloy shell, 3, a ceramic supporting column, 4, an oxygen-free copper pressure welding area, 5, a ceramic insulator, 6, an oxygen-free copper lead, 7, a hole of the ceramic insulator and a welding area of the oxygen-free copper lead, 8, a welding area of the base plate and the shell, 9, a welding area of an upper plane of the ceramic insulator and the shell, 10, a welding area of an inner vertical surface of the ceramic insulator and the shell, 11, a welding area of a lower plane of the ceramic insulator and the shell, 12 and an iron-nickel alloy cover plate.

Detailed Description

The invention is further described with reference to the following figures and specific embodiments.

Example 1

The embodiment discloses a ceramic metal shell for TO-252 packaging, which comprises a tungsten copper base plate 1, a kovar alloy shell 2, a ceramic supporting column 3, an oxygen-free copper pressure welding area 4, a ceramic insulator 5, an oxygen-free copper lead 6 and an iron-nickel alloy cover plate 12, wherein the tungsten copper base plate 1 and the iron-nickel alloy cover plate 12 are respectively packaged at the bottom and the top of the kovar alloy shell 2, and the oxygen-free copper pressure welding area 4 is positioned in the kovar alloy shell 2 and transversely extends along the kovar alloy shell 2, as shown in FIGS. 1-6. The tungsten copper bottom plate 1 is used as a chip heat sink, a ceramic supporting column 3 is arranged between the tungsten copper bottom plate and the oxygen-free copper pressure welding area 4, and the ceramic supporting column 3 ensures the installation strength of the pressure welding area. The ceramic insulator 5 is embedded on the kovar alloy shell 2 and sealed by welding, the ceramic insulator 5 is a whole, a plurality of lead holes are formed in the ceramic insulator 5, one end of the oxygen-free copper lead 6 is welded in the oxygen-free copper pressure welding area 4, and the other end of the oxygen-free copper lead passes through the lead holes and extends out of the kovar alloy shell 2.

According to the embodiment, the ceramic metal shell is designed according to the external dimension and the pad distance of the original plastic package device, in-situ replacement is guaranteed, kovar alloy is used as the shell, the matching performance with the ceramic insulator 5 is good, and the thin-wall shell design can be realized. The thin-wall shell and the oxygen-free copper pressure welding area 4 transversely extend along the kovar alloy shell 2, so that a large-current chip installation space and a circuit leading-out structure can be designed in a small-size appearance limiting space based on TO-252.

In this embodiment, 92% Al is used for the porcelain insulator 5₂O₃The high-temperature co-fired ceramic has the bending strength of 400MPa and the bulk resistance of more than or equal to 1 multiplied by 10¹²Omega (measured by 500 VDC) meets the requirements of high-reliability devices on the mechanical strength and the insulating property of the shell.

In this embodiment, the ceramic insulator 5 is integrally designed with a plurality of lead holes, so that a solid lead can be directly led out. The metal ceramic high-power large-current shell generally adopts a structure that each lead is provided with a ceramic insulator, and the TO-252 shell of the invention adopts HTCC high-temperature co-fired ceramic as an integral insulator because of small volume and small lead spacing and cannot adopt a plurality of independent insulators.

In the embodiment, a solid lead is adopted to directly lead out a circuit process, particularly a low-resistance oxygen-free copper lead, so that the overcurrent capacity can be improved to the maximum extent within a limited size. The TO-252 shell leads have 2, 3 or 5 leads, and the number of leads is set according TO the requirements of the device. Because the invention is suitable for high-current devices, a general ceramic printing metallization circuit can not meet the high-current requirement, and an entity low-resistance lead is required to directly penetrate through the ceramic to lead out an internal circuit. At present, the experience of directly leading out solid leads from HTCC high-temperature co-fired ceramics, particularly low-resistance material leads, does not exist in China.

The solid lead designed by the invention adopts a low-resistance material, passes through the ceramic and is directly led out of a circuit process, and the welding matching performance of the low-resistance lead and the ceramic insulator is well solved through an innovative structure on the premise of ensuring the sealing reliability.

In order to realize the welding matching of the low-resistance lead and the ceramic insulator, a surface metallization layer is arranged on the part, needing welding and sealing, of the ceramic insulator, the surface metallization layer comprises a tungsten slurry layer and a nickel-plated layer, the tungsten slurry layer is printed in the preparation process of the ceramic insulator, and the nickel-plated layer is formed after the ceramic insulator is prepared and formed.

Specifically, the thickness of the nickel plating layer is more than or equal to 3 μm.

Because the ceramic surface has no welding wetting property, a layer of metallization layer, namely metal tungsten paste and nickel plating layer, is added at the welding position of the ceramic insulator. The metallization layer can realize the sealing welding of metal parts and ceramic parts, and the silver-copper solder is wetted and filled at the welding part after being melted to realize sealing. The metallization layer also serves to form the conductive circuit of the device.

In this embodiment, the casing is made of kovar alloy, the bottom plate is made of tungsten copper, the cover plate is made of iron-nickel alloy, the casing, the bottom plate, the cover plate and the oxygen-free copper pressure welding area are all nickel-plated on the part of the oxygen-free copper lead needing to be welded, and the thickness of the nickel-plated is greater than or equal to 3 μm.

The casing is made of kovar alloy, has good matching performance with ceramic materials, and can realize a thin-wall structure. The bottom plate is made of tungsten copper, the tungsten copper bottom plate is used as a chip heat sink, and the heat conducting performance is good and the matching performance with a ceramic material is good. The reason for nickel plating is that some metal materials do not have solder wettability either, and the surface nickel plating provides solder wettability.

The metal surface of the shell is plated with a layer of gold, and the thickness of the gold plating layer is more than or equal to 0.5 mu m. Gold plating is the last step in the housing fabrication process for device package die bonding and pressure bonding and to prevent surface corrosion.

Example 2

A preparation method of a metal ceramic shell for TO-252 encapsulation comprises the following steps:

s01), heating the chain type sintering furnace protected by the nitrogen-hydrogen atmosphere to the welding temperature of the silver-copper solder of 830 ℃, introducing a nitrogen-hydrogen mixed gas protective gas (the introduced gas amount is based on that the parts and the solder are not oxidized in the whole sintering process), and preheating for more than or equal to 30 min;

s02), welding the bottom plate and the shell together, welding the ceramic support column and the oxygen-free copper pressure welding area together, and welding the ceramic insulator and the oxygen-free copper lead together;

the linear expansion coefficient of the ceramic is 6.8 multiplied by 10^-6About/° C, the linear expansion coefficient of tungsten copper is 6.3-7.0 x 10^-64J29 kovar alloy has a linear expansion coefficient of 5.7-6.2 x 10 at/° C^-6The linear expansion coefficients of the materials are similar at/DEG C, and the materials belong to matched welding.

The linear expansion coefficient of the oxygen-free copper lead material is 16.0 multiplied by 10^-6The temperature per DEG C is not matched with the ceramic material, the linear expansion coefficients of the ceramic and the oxygen-free copper material are not matched, but the sizes of the welding areas of the ceramic and the oxygen-free copper material are small, and a large expansion difference cannot be formed. Even the stress that the difference of point expansion leads to also can not cause harmful effects, firstly because the oxygen-free copper material is very soft, can subdue the stress through self slight deformation, secondly ceramic strength can tolerate the residual stress completely. This is also why the ceramic insulator and oxygen-free copper lead wire can be non-matching soldered.

The ceramic insulator and the ceramic support column are made of ceramic, surface welding wettability is avoided, in order to enable the ceramic insulator and the ceramic support column to have surface wettability (welding performance), the ceramic support column and an oxygen-free copper pressure welding area and the ceramic insulator and an oxygen-free copper lead wire are welded together, surface metallization layers are arranged on the ceramic insulator and the ceramic support column, the portions needing welding sealing are provided with the surface metallization layers, the surface metallization layers comprise a tungsten slurry layer and a nickel plating layer, the tungsten slurry layer is printed in the preparation process of the ceramic insulator, and the nickel plating layer is formed after the ceramic insulator is prepared and formed.

Specifically, as shown in fig. 2 and 3, the portion of the ceramic insulator 5 to be metallized includes the hole of the ceramic insulator and the bonding region 7 of the oxygen-free copper lead, the bonding region 8 of the bottom plate and the case, the bonding region 9 of the upper plane of the ceramic insulator and the case, the bonding region 10 of the inner vertical surface of the ceramic insulator and the case, and the bonding region 11 of the lower plane of the ceramic insulator and the case.

S03), final assembly welding, welding and assembling the parts welded and formed in the step S02 together to form the metal ceramic shell described in the embodiment 1.

And the sintering of the step S02 lasts for about 1.5-2 hours, in the process, the sintering temperature and the nitrogen-hydrogen gas flow are ensured to be constant, the temperature error of each temperature zone does not exceed +/-3 ℃, and the flow error of the nitrogen-hydrogen mixture does not exceed +/-5L/min.

In this embodiment, the preparation process of the ceramic insulator is as follows:

1. forming a ceramic blank layer by adopting a tape casting method, and punching holes at positions of the ceramic blank layer where wiring is needed;

2. the primary metallization is to print a layer of tungsten slurry material slurry on the part of the ceramic insulator needing welding and sealing, the primary metallization comprises inner hole metallization and layer surface printing metallization, because the ceramic insulator is formed by laminating a plurality of layers of ceramic blanks, the metallization layer is distributed to the required layer, and then the next step is carried out;

3. stacking materials, performing isostatic pressing, namely stacking multiple layers of ceramic blank materials, and then applying equal pressure to the ceramic chips in all directions by adopting isostatic pressing equipment so as to form the ceramic insulator; the ceramic matrix produced by the isostatic pressing process has improved compactness and mechanical strength.

4. Separating into single products, and co-firing at high temperature;

5. nickel plating, wherein the thickness of the nickel layer is more than or equal to 3 μm.

In the embodiment, the shell, the bottom plate, the cover plate, the oxygen-free copper pressure welding area and the part of the oxygen-free copper lead which needs to be welded are all plated with nickel, and the thickness of the plated nickel is more than or equal to 3 microns. These metal parts are nickel plated because some metal materials also do not have solder wettability, which is provided by surface nickel plating.

According to the structural characteristics of the product, in order to ensure the long-term reliability of the product, after the product is molded, a plurality of tests related to matching are carried out, including 2000h power aging test, 100 times thermal shock (liquid-liquid) test (-55-125 ℃), 500 times temperature (-65-175 ℃) shock test, 10000 times intermittent life test and other tests, so that the product is qualified, and the high reliability of the product is proved to meet the national military standard requirement.

The foregoing description is only for the basic principle and the preferred embodiments of the present invention, and modifications and substitutions by those skilled in the art are included in the scope of the present invention.