JPH07297530A - Wiring substrate - Google Patents

Abstract

PURPOSE:To provide a wiring substrate capable of firmly fitting an external lead terminal on an insulating basic without generating a crack or a fracture in the insulating basic. CONSTITUTION:In this wiring substrate, on a surface of an insulating base 1 made of a ceramic having a metallized wire layer 2, a connection pad 7 connecting electrically with the metallized wire layer 2 is provided, and also an external lead terminal 3 is soldered in the connection pad 7. The connection pad 7 is formed so that a plurality of metallized layers 7a, 7b having different outer dimensions are laminated and adhered to the surface of the insulating base 1 according to the descending order of the outer dimensions.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wiring board used for a semiconductor element housing package, a hybrid integrated circuit device, or the like.

[0002]

2. Description of the Related Art Conventionally, a wiring board, for example, a wiring board used for a semiconductor element housing package for housing a semiconductor element is generally an aluminum oxide sintered body, a mullite sintered body, a glass ceramics sintered body, An insulating base made of an electrically insulating ceramics such as an aluminum nitride sintered body and having a recess for accommodating a semiconductor element in a substantially central portion of its upper surface, and a portion extending from the periphery of the recess of the insulating base to the lower surface. From a metallized wiring layer made of a refractory metal powder such as tungsten, molybdenum, or manganese, and an iron-nickel-cobalt alloy or an iron-nickel alloy attached to the lower surface of the insulating substrate and electrically connected to the metallized wiring layer. The semiconductor element is formed on the bottom surface of the concave portion of the insulating substrate by glass, resin,
The electrodes are bonded and fixed via an adhesive such as a brazing material, and each electrode of the semiconductor element is electrically connected to a metallized wiring layer located in the periphery of the recess via a bonding wire. A lid made of ceramics or the like is bonded via a sealing material made of glass, resin, brazing material, etc. so as to cover the recess of the insulating base, and the semiconductor element is hermetically housed in the recess of the insulating base to obtain a final product. As a semiconductor device.

As shown in FIG. 3, the external lead terminals are attached to the insulating base by circular connection pads, a part of which is electrically connected to the metallized wiring layer 12 on the lower surface of the insulating base 11. This is done by depositing 13 and brazing one end of the external lead terminal 14 to the connection pad 13 via a brazing material 15 such as silver brazing.

[0004]

However, in this conventional wiring board, the brazing material for brazing the external lead terminals to the connection pads is bonded to substantially the entire surface of the connection pads and greatly contracts during solidification, and the insulating substrate. Is fragile and is formed of ceramics that has low mechanical strength against pulling force. Therefore, when external lead terminals are brazed to a connecting pad via a brazing material such as silver brazing, the brazing material is solidified and shrinks. The tensile force largely acts on the outer peripheral portion of the connection pad to cause cracks or breaks in the insulating substrate located on the outer peripheral portion of the connection pad, which may lead to reliability of hermetic sealing of the semiconductor element and attachment of the external lead terminal to the insulating substrate. It has a drawback that the reliability of the clothes is greatly reduced.

[0005]

SUMMARY OF THE INVENTION The present invention has been devised in view of the above-mentioned drawbacks, and an object thereof is to firmly attach an external lead terminal to an insulating substrate without causing cracks or breaks in the insulating substrate. To provide a wiring board.

[0006]

According to the present invention, a connection pad electrically connected to the metallized wiring layer is provided on the surface of a ceramic insulating substrate having a metallized wiring layer, and an external lead terminal is provided on the connection pad. A wiring board formed by brazing, wherein the connection pad is formed by depositing and laminating a plurality of metallized layers having different outer dimensions on the surface of an insulating substrate in order from the outer layer having the largest outer dimension. To do.

[0007]

According to the wiring board of the present invention, the connection pads to which the external lead terminals are brazed are formed by laminating a plurality of metallized layers having different outer dimensions on the surface of the insulating substrate in order of increasing outer dimensions. Therefore, when the external lead terminal is brazed to the connection pad via the brazing material, the brazing material is bonded to the metallization layer having the smallest outer dimension and directly contacts the insulating substrate having the largest outer dimension. As a result, the tensile force due to the solidification shrinkage of the brazing material does not significantly act on the outer peripheral portion of the connection pad, and cracks or cracks occur in the insulating substrate located on the outer peripheral portion of the connection pad. By omitting this, the reliability of hermetically sealing the semiconductor element and the reliability of attaching the external lead terminal to the insulating substrate can be made extremely high.

[0008]

The present invention will now be described in detail with reference to the embodiments shown in the accompanying drawings. 1 and 2 show an embodiment in which the wiring board of the present invention is applied to a semiconductor element housing package for housing a semiconductor element, 1 is an insulating base, and 2 is a metallized wiring adhered to the insulating base 1. Layers 3 are external lead terminals brazed and attached to the metallized wiring layer 2 via a brazing material. The wiring board A is obtained by attaching the external lead terminals 3 to the metallized wiring layer 2 attached to the insulating substrate 1.
Becomes

The insulating substrate 1 is provided with a recess 1a at the center of its upper surface for forming a space for accommodating the semiconductor element 4, and the semiconductor element 4 is provided on the bottom surface of the recess 1a with glass, resin, brazing material or the like. The adhesive is fixed through the adhesive.

The insulating substrate 1 is made of an electrically insulating ceramic such as an aluminum oxide sintered body, a mullite sintered body, a glass ceramic sintered body, or an aluminum nitride sintered body. For example, an aluminum oxide sintered body. In the case of consisting of alumina, silica, calcia, a suitable organic solvent to a ceramic raw material powder such as magnesia, a solvent is added and mixed to form a sludge, and the sludge is subjected to a conventionally known doctor blade method or calendar roll method. By adopting ceramic green sheet (ceramic green sheet)
After that, appropriate punching processing is applied to the ceramic green sheet and a plurality of these are laminated,
It is manufactured by firing at a temperature of about 1600 ° C.

The insulating substrate 1 is covered with a plurality of metallized wiring layers 2 from the periphery of the recess 1a to the lower surface, and the electrodes of the semiconductor element 4 are bonded to the periphery of the recess 1a of the metallized wiring layer 2. An external lead terminal 3 which is electrically connected via a wire 5 and which is connected to an external electric circuit is electrically connected to a portion led out to the lower surface.

The metallized wiring layer 2 deposited on the insulating substrate 1 is made of a refractory metal powder such as tungsten, molybdenum, or manganese, and the metallized wiring layer 2 is connected to an external electric circuit by a semiconductor on an external lead terminal 3. It serves to electrically connect each electrode of the element 4.

For the metallized wiring layer 2, for example, a metal green paste, which is obtained by adding a suitable organic solvent or a solvent to a high melting point metal powder such as tungsten, and mixing the same, is conventionally known in advance on a ceramic green sheet serving as the insulating substrate 1. By printing and applying a predetermined pattern by the screen printing method, the insulating base 1 is attached at a predetermined position.

The metallized wiring layer 2 is coated with a metal, such as nickel or gold, which is excellent in corrosion resistance and has a good wettability with the brazing material, on the exposed outer surface by plating.
When the metallized wiring layer 2 is layered to a thickness of 0 μm, oxidative corrosion of the metallized wiring layer 2 can be effectively prevented and the electrical connection between the metallized wiring layer 2 and the bonding wire 5 can be strengthened. Therefore, the surface of the metallized wiring layer 2 has excellent corrosion resistance against nickel, gold, etc.,
In addition, the brazing material and the metal having good wettability are 1.0 by the plating method.
It is preferable that the layers are laminated to a thickness of 20.0 μm.

Further, the metallized wiring layer 2 is electrically connected at its portion led out on the lower surface of the insulating substrate 1 to the connection pad 7 formed on the lower surface of the insulating substrate 1 by means of the connection pad 7. The external lead terminals 3 are brazed via a brazing material 6 such as silver brazing.

The connection pad 7 serves to attach the external lead terminal 3 to the insulating substrate 1 and electrically connect the external lead terminal 3 to the semiconductor element 4 via the metallized wiring layer 2, and tungsten, molybdenum and molybdenum are used. , High melting point metal powder such as manganese.

As shown in FIG. 2, the connection pad 7 has two metallization layers 7a and 7b having different outer dimensions.
Is formed by depositing and laminating the metallization layer 7a having a large outer dimension on the surface side of the insulating substrate 1, and the metallized layer 7a having a large outer dimension is formed on the insulating substrate 1 side and the metallized layer 7b having a small outer dimension is formed. Since the external lead terminals 3 are located on the side to be brazed, when the external lead terminals 3 are brazed to the connection pads 7 via the brazing material 6, the brazing material 6 has only the surface of the metallized layer 7b having a small outer dimension. To the metallized layer 7a which has a large outer dimension and is in direct contact with the insulating substrate 1, and thus the tensile force due to the solidification shrinkage of the brazing material 6 largely acts on the outer peripheral portion of the connection pad 7. As a result, no cracks or cracks are generated in the insulating substrate 1 located on the outer peripheral portion of the connection pad 7.

The connection pad 7 is used as the insulating substrate 1 in the same manner as the metallized wiring layer 2, that is, a metal paste obtained by adding and mixing an appropriate organic solvent or solvent to a refractory metal powder such as tungsten. The ceramic green sheet is applied to a predetermined position on the lower surface of the insulating substrate 1 by applying a plurality of times to the ceramic green sheet by sequentially reducing the printing area by a conventionally known screen printing method.

When the thickness t of the metallization layer 7b having a small outer dimension is set to 10 μm or more in the connection pad 7, a large step is formed between the metallization layer 7b having a small outer dimension and the metallization layer 7a having a large outer dimension. ,
When the external lead terminal 3 is brazed to the connection pad 7 via the brazing material 6 due to the step, the brazing material 6 does not flow out and join to the metallized layer 7a, and thus the brazing material 6
It is possible to prevent the occurrence of cracks or breaks in the insulating base 1 located on the outer peripheral portion of the connection pad 7 due to the tensile force caused by the solidification and contraction of the. Therefore, it is preferable that the thickness t of the metallized layer 7b having a small external dimension is 10 μm or more in the connection pad 7.

Further, the connection pad 7 is formed by depositing a metal such as nickel or gold having excellent corrosion resistance and good wettability with a brazing material to a thickness of 1.0 to 20.0 μm by a plating method. With this, the oxidative corrosion of the connection pad 7 can be effectively prevented, and the external lead terminal 3 can be firmly brazed and attached to the connection pad 7 via the brazing material 6. Therefore, on the surface of the connection pad 7, nickel,
It is preferable to deposit a metal such as gold having excellent corrosion resistance and good wettability with the brazing material to a thickness of 1.0 to 20.0 μm by a plating method.

Further, the external lead terminals 3 are brazed to the connection pads 7 attached to the insulating base 1 via the brazing material 6 such as silver solder, and the external lead terminals 3 are attached to the insulating base 1.
The semiconductor element 4 housed in the recess 1a has a function of connecting the semiconductor element 4 to the external electric circuit, and the external lead terminal 3 is connected to the external electric circuit. And, it is electrically connected to an external electric circuit through the external lead terminal 3.

The external lead terminal 3 is made of a metal material such as iron-nickel-cobalt alloy or iron-nickel alloy.
For example, an ingot (lump) of iron-nickel-cobalt alloy or the like is formed into a predetermined rod shape by using a conventionally known metal processing method such as a rolling processing method or a punching processing method.

Thus, according to the above-mentioned package for accommodating semiconductor elements, the semiconductor element 4 is adhered and fixed to the bottom surface of the concave portion 1a of the insulating substrate 1 via an adhesive such as glass, resin, or brazing material, and the semiconductor element 4 Each electrode is electrically connected to the metallized wiring layer 2 via the bonding wire 5,
Thereafter, the lid 8 is bonded to the upper surface of the insulating base 1 through a sealing material made of glass, resin, brazing material or the like so as to close the recess 1a of the insulating base 1, and the semiconductor is placed in the recess 1a of the insulating base 1. A semiconductor device as a final product is obtained by hermetically housing the element 4.

The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the gist of the present invention. For example, in the above-described embodiments, the wiring of the present invention is used. The example in which the substrate is applied to the semiconductor element housing package that houses the semiconductor element has been described, but the present invention can also be applied to the wiring board used in the hybrid integrated circuit device.

[0025]

According to the wiring board of the present invention, the connection pads to which the external lead terminals are brazed, the plurality of metallized layers having different outer dimensions, are attached to the surface of the insulating substrate in the order of increasing outer dimensions. Since they are formed by stacking, when the external lead terminal is brazed to the connection pad via the brazing material, the brazing material is bonded to the metallized layer having the smallest outer dimension and directly contacts the insulating substrate having the largest outer dimension. Does not bond to the metallization layer, resulting in
The tensile force due to the solidification shrinkage of the brazing material does not significantly affect the outer peripheral portion of the connection pad, and the insulating substrate located on the outer peripheral portion of the connection pad is completely free from cracks and cracks, and the semiconductor element The reliability of tight sealing and the reliability of attachment of the external lead terminals to the insulating substrate can be made extremely high.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an embodiment in which a wiring board of the present invention is applied to a semiconductor element housing package.

FIG. 2 is an enlarged sectional view of a main part of FIG.

FIG. 3 is an enlarged cross-sectional view of a main part of a conventional wiring board.

[Explanation of symbols]

 1 ... Insulating substrate 2 ... Metallized wiring layer 3 ... External lead terminal 6 ... Brazing material 7 ... Connection pad

Claims (1)

[Claims] 1. A wiring board comprising a ceramic insulating base having a metallized wiring layer, a connection pad electrically connected to the metallized wiring layer, and an external lead terminal brazed to the connection pad. The connection pad is formed by depositing and laminating a plurality of metallized layers having different outer dimensions on the surface of an insulating substrate in order of increasing outer dimensions.