JP3441170B2 - Wiring board - Google Patents

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 in which semiconductor elements are housed and mounted, 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 made of an electrically insulating material such as alumina ceramics, and the semiconductor element is mounted on a substantially central portion of its upper surface. An insulating substrate having a mounting portion for mounting, a metallized wiring layer made of a refractory metal powder of tungsten, molybdenum, manganese, etc. derived from the periphery of the semiconductor element mounting portion of the insulating substrate to the outer periphery, and a bowl shape The semiconductor element is adhered and fixed to the semiconductor element mounting portion of the insulating substrate with an adhesive such as glass or resin, and each electrode of the semiconductor element is bonded to the metallized wiring layer with a bonding wire. Then, a bowl-shaped lid is joined to the upper surface of the insulating base so as to accommodate the semiconductor element therein, A semiconductor device as a final product by accommodating hermetically a child to the container interior made of an insulating base and the lid.

In the wiring board used for the package for housing the semiconductor element, a metallized pad is provided at a portion of each metallized wiring layer provided on the insulating substrate, the portion being led to the outer peripheral portion of the insulating substrate. External lead terminals made of iron-nickel-cobalt alloy, iron-nickel alloy, etc. are brazed and attached to the pads via a brazing material such as silver braze, and the external lead terminals are connected to an external electric circuit to connect the semiconductor element. Each electrode is a metallized wiring layer,
It will be electrically connected to the external electric circuit via the bonding wire and the external lead terminal.

Further, the insulating substrate having the metallized wiring layer is formed into a sludge by adding a suitable organic binder, a plasticizer and a solvent to a raw material powder such as aluminum oxide, silicon oxide or magnesium oxide and mixing them together. A green sheet (green sheet) of alumina ceramics is obtained by using tape forming technology such as the doctor blade method and calendar roll method, and then the green sheet is an organic binder suitable for refractory metal powder such as tungsten and molybdenum. A metal paste obtained by adding and mixing a plasticizer and a solvent is applied in a predetermined pattern by printing, and finally the green sheet is baked at a temperature of about 1600 ° C. in a reducing atmosphere.

Further, the external lead terminals are brazed to the metallized pads provided on the metallized wiring layer by connecting the other end of each external lead terminal, one end of which is joined to the frame at a predetermined interval, onto the metallized pad with silver between them. It is carried out by placing a brazing material such as wax between them, and then heating the brazing material to a temperature of about 850 ° C. to melt the brazing material.

[0006]

However, in recent years,
The number of electrodes in the semiconductor element has increased to several hundreds due to the rapid increase in the degree of integration and density, and along with this, the number of metallized wiring layers provided on the insulating substrate has also grown to several hundred and formed on the metallized wiring layers. The width of the metallized pad is about 0.25 mm or less, the distance between adjacent metallized pads is about 0.35 mm or less, and a green sheet of alumina ceramics with a metal paste such as tungsten or molybdenum printed and applied in a predetermined pattern is applied. When an insulating substrate having a metallized wiring layer is obtained by firing, unevenness in shrinkage of the green sheet causes variations in the spacing between the metallized wiring layer and the metallized pads formed on the metallized wiring layer. For example, when brazing and attaching each external lead terminal to each metallized pad, the metallized pad located on the outer peripheral portion of the insulating substrate is attached. When the other end of each external lead terminal, one end of which is joined to the frame at a predetermined interval, is placed with a brazing material such as silver solder interposed therebetween, the other end of each external lead terminal is placed on each metallized pad. As a result, the external lead terminals cannot be firmly brazed and attached to the metallized pads, or the metallized pads adjacent to the external lead terminals are electrically short-circuited. It had the drawback of losing its function as.

Further, although the alumina ceramics constituting the insulating substrate and the iron-nickel-cobalt alloy or the iron-nickel alloy constituting the external lead terminals have a thermal expansion coefficient of approximately 350 from room temperature to approximately 350.degree. When the temperature exceeds ℃, the coefficient of thermal expansion of iron-nickel-cobalt alloy or iron-nickel becomes larger than that of alumina ceramics. If the brazing material is heated to a temperature of about 850 ° C during brazing and mounting via the brazing material, the external lead terminals expand more thermally than the insulating base material and the metallized pad formed on the outer peripheral part of the insulating base material and the external lead. Misalignment occurs between the terminals and the metallized pads, so that the external lead terminals can be brazed and attached accurately and firmly. Drawback that can not be had.

[0008]

SUMMARY OF THE INVENTION The present invention has been devised in view of the above-mentioned drawbacks, and an object of the present invention is to provide a wiring board in which external lead terminals are accurately and firmly attached to metallized pads.

[0009]

A wiring board of the present invention comprises an insulating substrate having a plurality of metallized pads arranged in a staggered pattern in two rows on the outer peripheral surface of an upper surface, and a melting point of each metallized pad of 400 ° C. or less. A plurality of external lead terminals to be brazed via the brazing material, and a mold resin material covering the brazing part of the external lead terminals, wherein the metallized pad and the external lead terminals are provided on either side. The gold plating is tin-plated on the other side, and by heating the gold plating and the tin plating to form a gold-tin eutectic solder between the metallized pad and the external lead terminal, The external lead terminal is brazed to the metallized pad.

The wiring board of the present invention is characterized in that an epoxy resin or a polyimide resin is used as the mold resin material.

[0011]

In the wiring board of the present invention, the metallized pad to which the external lead terminal is brazed and attached is provided on the outer peripheral portion of the insulating substrate.
Since the metallized pads are arranged in rows in a zigzag manner, the width of each metallized pad and the distance between adjacent metallized pads can be widened. As a result, there is some variation in the position of the metallized pads due to uneven contraction of the green sheet. Even if it occurs, accurately connect the predetermined external lead terminal to the predetermined metallized pad,
In addition, the brazing can be surely performed.

In the wiring board of the present invention, the brazing of the external lead terminals to the metallized pads provided on the insulating base is
The thermal expansion coefficient of the insulating base and the external lead terminal is close to 400
Since it is performed at a temperature of ℃ or less, there is almost no positional deviation between the external lead terminal and the metallized pad during brazing, and as a result, the predetermined external lead terminal is accurately soldered to the predetermined metallized pad. Can be attached.

Further, in the wiring board of the present invention, since the brazing portion of the external lead terminal is covered with the molding resin material, even if the brazing strength of the external lead terminal is slightly weak, the strength is reinforced by the coating of the molding resin material. As a result, the external lead terminals can be firmly attached to the metallized pad.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a wiring board of the present invention will be described in detail with reference to the accompanying drawings.

FIGS. 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, wherein 1 is an insulating base and 2 is an external lead terminal.

The insulating substrate 1 is a substantially rectangular flat plate made of an electrically insulating material such as alumina ceramics, and has a mounting portion 1a for mounting the semiconductor element 3 in the center thereof, and the mounting portion 1a The semiconductor element 3 is attached and fixed to 1a via an adhesive.

When the insulating substrate 1 is made of, for example, alumina ceramics, a raw material powder such as alumina, silica, calcia, magnesia, etc. is mixed with an appropriate binder, a plasticizer, a solvent, etc. to form a slurry. Using a sheet forming technique such as the doctor blade method or calender roll method, a ceramic green sheet is obtained as a sheet, and then the ceramic green sheet is punched and cut, and a plurality of layers are laminated on top and bottom as necessary. Then, finally, the ceramic green sheet is manufactured by firing at a temperature of about 1600 ° C. in a reducing atmosphere.

A large number of metallized wiring layers 4 made of a refractory metal such as tungsten or molybdenum are deposited on the insulating substrate 1 from the periphery of the mounting portion 1a to the outer peripheral portion thereof. A bonding wire 5 electrically connected to the electrode of the semiconductor element 3 is connected to the peripheral portion of the mounting portion 1a, and an insulating substrate of the metallized wiring layer 4 is formed.
1 External lead terminals 2 are brazed to the outer periphery.

For the metallized wiring layer 4, the insulating substrate 1 is a metal paste obtained by adding and mixing a high melting point metal powder such as tungsten and molybdenum with an appropriate binder and solvent.
By applying a thick film method such as a conventionally known screen printing method to the ceramic green sheet to be printed and applied, a predetermined pattern is formed from the periphery of the mounting portion 1a of the insulating substrate 1 to the outer peripheral portion.

The metallized wiring layer 4 is also an insulating substrate 1.
A metallized pad 4a is formed on the outer peripheral portion of the metallized pad 4a.
And the metallized wiring layer 4 and the external lead terminal 2 are electrically connected to each other.

The metallized pads 4a formed on the outer peripheral portion of the insulating base 1 are arranged in two rows in a zigzag pattern along the outer peripheral edge of the insulating base 1 as shown in FIG. The width of 4a and the adjacent space are wide, and the ceramic green sheet is fired to form the insulating substrate 1.
Even if there is some variation in the position of the metallized pad 4a due to uneven contraction of the ceramic green sheet, the predetermined external lead terminals 2 should be brazed to each metallized pad 4a accurately and surely. It becomes possible to wear.

Like the metallized wiring layer 4, the metallized pad 4a is made of a refractory metal powder such as tungsten or molybdenum. It is formed so as to be electrically connected to the metallized wiring layer 4.

An external lead terminal 2 is brazed to the metallized pad 4a. The external lead terminal 2 is made of a metal of iron-nickel alloy or iron-cobalt-nickel alloy, and is placed on the insulating substrate 1. It serves to electrically connect the semiconductor element 3 to an external electric circuit.

Further, the external lead terminals 2 are brazed to the metallized pads 4a by a low melting point brazing material having a melting point of 400 ° C. or less. Specifically, one of the metallized pads 4a and the external lead pins 2 is plated with gold. , After the other is tin-plated, the external lead terminal 2 is placed on and abutted on the metallized pad 4a, and then this is heated to a temperature of about 350 ° C. to separate the metallized pad 4a and the external lead terminal 2 from each other. This is done by forming a gold-tin eutectic braze in between. As a result, since the low melting point brazing material having a melting point of 400 ° C. or less is used as the brazing material 7 for brazing the metallized pad 4a and the external lead terminal 2, the thermal expansion of the insulating substrate 1 and the external lead terminal 2 is made during brazing. The coefficients are close to each other, and there is almost no positional deviation between the external lead terminal 2 and the metallized pad 4a. As a result, the predetermined external lead terminal 2 is accurately brazed and attached to the predetermined metallized pad 4a. be able to.

The external lead terminal 2 brazed and attached to the metallized pad 4a via the brazing material 7 has the brazing portion attached to the surface of the insulating substrate 1 excluding the semiconductor element mounting portion 1a. Covered by 8.

The mold resin material 8 is the external lead terminal 2
It acts to reinforce the brazing strength to the metallized pad 4a, whereby the external lead terminal 2 is extremely firmly attached to the metallized pad 4a.

Since the molding resin material 8 is attached to the surface of the insulating substrate 1 excluding the semiconductor element mounting portion 1a, it also functions to form a recess for accommodating the semiconductor element 3, and thus the molding resin material 8 If the lid 9 is adhered via an adhesive so as to close the concave portion for housing the semiconductor element 3 on the upper surface of the semiconductor element 3, the semiconductor element 3 is hermetically sealed in the concave portion.

The mold resin material 8 is made of epoxy resin, polyimide resin, or the like. For example, an insulating substrate 1 in which external lead terminals 2 are brazed to a metallized pad 4a is loaded into a predetermined mold and a liquid is injected into the mold. Then, the epoxy resin is dropped, and then the epoxy resin is heat-cured to attach the epoxy resin at a predetermined position.

If the molding resin material 8 is made of epoxy resin or polyimide resin, the epoxy resin,
The polyimide resin has a very good bondability to the alumina ceramics forming the insulating base 1, and firmly bonds to the insulating base 1 and at the same time strongly reinforces the brazing portion of the external lead terminal 2. Therefore, it is preferable that the mold resin material 8 is formed of epoxy resin or polyimide resin.

Thus, according to the wiring board of the present invention, the semiconductor element 3 is attached and fixed to the mounting portion 1a of the insulating substrate 1 via an adhesive such as resin, and each electrode of the semiconductor element 3 is bonded with the bonding wire 5 It is electrically connected to the metallized wiring layer 4 via the above, and finally the lid 9 is joined to the upper surface of the covering material 8 via a sealing material such as resin to obtain a semiconductor device as a product.

The present invention is not limited to the above-described embodiments, but various modifications can be made without departing from the scope of the present invention. For example, the tip of the external lead terminal 2 can be bent. When the external lead terminals 2 are brazed to the metallized pads 4a arranged in a zigzag in two rows, it effectively prevents the external lead terminals 2 from contacting another metallized pad 4a and causing an electrical short circuit. be able to.

Although the semiconductor element 3 is sealed with the lid 9 in the above-mentioned embodiment, the semiconductor element 3 is sealed by filling a resin such as epoxy into the recess in which the semiconductor element 3 is accommodated. You may.

[0033]

In the wiring board of the present invention, the metallized pads to which the external lead terminals are brazed and attached are arranged in two rows in a zigzag pattern on the outer peripheral portion of the insulating substrate. As a result, even if there is some variation in the position of the metallized pad due to the non-uniform contraction of the green sheet, the predetermined external lead terminals can be accurately and accurately connected to the predetermined metallized pad. It can be securely brazed and attached.

In the wiring board of the present invention, the external lead terminals are brazed to the metallized pads provided on the insulating substrate.
The thermal expansion coefficient of the insulating base and the external lead terminal is close to 400
Since it is performed at a temperature of ℃ or less, there is almost no positional deviation between the external lead terminal and the metallized pad during brazing, and as a result, the predetermined external lead terminal is accurately soldered to the predetermined metallized pad. Can be attached.

Further, in the wiring board of the present invention, since the brazing portion of the external lead terminal is covered with the molding resin material, even if the brazing strength of the external lead terminal is slightly weak, the strength is reinforced by the coating of the molding resin material. As a result, the external lead terminals can be firmly attached to the metallized pad.

[Brief description of drawings]

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

FIG. 2 is a partially enlarged plan view of the insulating base of FIG.

[Explanation of symbols]

1 ... Insulating substrate 2 ... External lead terminal 3 ... Semiconductor element 4 ... Metallized wiring layer 4a ... Metallized pad 7 ... brazing material 8 Mold resin material

Claims (2)

(57) [Claims] 1. An insulating substrate having a plurality of metallized pads arranged in a zigzag pattern in two rows on the outer periphery of an upper surface, and a plurality of metallized pads which are brazed to each of the metallized pads through a brazing material having a melting point of 400 ° C. or less. number of the external lead terminals, Ri consists a molding resin material covering the brazing portion of the external lead terminals, wherein the metallization pad and the outer lead ends
The child is gold-plated on one side and tin-plated on the other.
In addition, the gold plating and the tin plating
By heating the metallized pad and the external
By forming a gold-tin eutectic solder with the lead terminals
The external lead terminals on the metallized pad.
Wiring board characterized in that it is U with. 2. The wiring board according to claim 1, wherein the mold resin material is an epoxy resin or a polyimide resin.