JPH01149379A - Lead mounting mechanism for ceramic base substance - Google Patents

Abstract

PURPOSE:To see that cracks do not occur in a ceramic base substance by arranging the constitution that the major part of a solder material may be replaced with a member which exists inside the solder material and has a thermal expansion coefficient smaller than that of the solder material. CONSTITUTION:The major part of a solder material 4 to solder a lead 3 terminal directly to the terminal 2 of a circuit pattern on the surface of a ceramic base substance 1 is replaced with a member which is put between the lead 2 lower end and the terminal 2 inside the solder material 4 and is smaller in thermal expansion coefficient than the solder material 4 and has the same outside diameter as that of the terminal 2 or a little smaller outside diameter than that outside diameter. Accordingly, when soldered to the terminal 2, the shrinkage stress which acts directly on the ceramic base substance, of the solder material 4 which cools and solidifies at the surface of the ceramic base substance 1 can be sharply weakened. Hereby, it can be soldered without causing cracks in the ceramic base substance 1.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention connects lead ends to terminals of circuit patterns on the surface of ceramic substrates such as ceramic packages and ceramic substrates by brazing using a brazing material such as silver solder. Regarding the lead attachment structure when

[Prior Art] As shown in FIG. 3, a terminal 2 of a circuit pattern consisting of a metallized layer on the surface of a ceramic substrate 1 such as a ceramic package or a ceramic substrate that houses and mounts electronic components such as semiconductor elements, The ends of the metal leads 3 made of 42 alloy (iron-nickel alloy), Kovar (iron-nickel-cobalt alloy), etc., which electrically connect the terminal 2 of the circuit pattern and the electric circuit of the external device, are soldered with silver solder, etc. Connect using brazing material 4.

Incidentally, in recent years, as the integration of semiconductor elements made of silicon chips housed and mounted on the ceramic base i has progressed further, and as the size of these elements has increased, the difference between the ceramic base l and the semiconductor elements housed and mounted on the base has increased. Ceramic substrate l
Adverse effects on semiconductor devices due to the difference in coefficient of thermal expansion between semiconductor devices and semiconductor devices have become a problem.

Therefore, in order to eliminate the adverse effect on semiconductor elements due to the difference in thermal expansion coefficient between the ceramic substrate I and the semiconductor element, recently, alumina ceramic substrates with a large thermal expansion coefficient formed by ordinary high temperature firing have been used. Instead, ceramic substrates (hereinafter referred to as A ceramic substrate (simply referred to as a ceramic substrate with a small coefficient of thermal expansion) has been developed, and semiconductor devices using this substrate are being put into practical use.

[Problems to be Solved by the Invention] However, ceramic substrates with a small coefficient of thermal expansion, such as ceramic substrates and mullite ceramic substrates formed by low-temperature firing, have a lower thermal expansion coefficient than alumina ceramic substrates formed by ordinary high-temperature firing. , vulnerable.

That is, an alumina ceramic substrate formed by ordinary high-temperature firing has a transverse rupture strength of 30 to 40 kg/cm', whereas a ceramic substrate with a small coefficient of thermal expansion has a transverse rupture strength of 30 to 40 kg/cm'.
Its transverse rupture strength is only 20kg/cm.

In addition, while the thermal expansion coefficient of the ceramic substrate with a small thermal expansion coefficient is 4 to 7X10-@/℃, the thermal expansion coefficient of the silver brazing material is 18 to 20Xl (I@/℃ and its thermal expansion coefficient is 4 to 4 of the thermal expansion coefficient of the ceramic substrate with a small thermal expansion coefficient.
About 5 times larger.

Therefore, as shown in FIG. 3, the ends of the leads 3 are brazed to the terminals 2 of the circuit pattern made of the metallized layer etc. on the surface of the ceramic substrate with a small coefficient of thermal expansion using a brazing material 4 such as silver solder. When connected, the brazing material 4, such as silver solder, which has a large coefficient of thermal expansion, shrinks greatly on the surface of the fragile ceramic base 1, which has a small coefficient of thermal expansion, and solidifies by cooling. As a result, a large shrinkage stress of the brazing material 4 such as silver solder which is cooling and solidifying is applied to the ceramic base 1 having a small coefficient of thermal expansion, and this stress causes the ceramic base 1 having a low coefficient of thermal expansion to crack. As a result, the airtightness of the substrate I was impaired, and the connection strength of the ends of the leads 3 brazed to the terminals 2 of the circuit pattern made of the metallized layer on the surface of the ceramic substrate 1 became unstable.

The present invention has been made to solve such problems, and its purpose is to provide leads using a brazing material 4 such as silver solder to the terminals 2 of the circuit pattern on the surface of the ceramic substrate 1 having a small coefficient of thermal expansion. The third end is attached to the ceramic substrate l.
An object of the present invention is to provide a lead attachment structure for a ceramic base that can be connected by brazing without causing cracks.

[Means for Solving Problems] In order to achieve the above object, the lead attachment structure of the ceramic base of the present invention, as shown in FIG. 1 and FIG. In a ceramic substrate in which the ends of the leads 3 are brazed and connected to the terminals 2 of the circuit pattern on the surface of the ceramic substrate 1 such as a substrate using the brazing material 4, the brazing material 4 between the lower end of the lead 3 and the terminal 2 is The present invention is characterized in that a member 5 having a coefficient of thermal expansion smaller than that of the brazing filler metal 4 and having an outer diameter that is the same as or slightly smaller than the outer diameter of the terminal 2 is interposed.

In the electronic component substrate of the present invention, the member 5 may be constructed separately from the leads 3 or may be constructed integrally with the leads 3.

[Function] In the ceramic substrate lead attachment structure of the present invention, a large portion of the brazing material 4 that directly connects the ends of the leads 3 to the terminals 2 of the circuit pattern on the surface of the ceramic substrate 1 is connected to the brazing material 4. A wire having a lower coefficient of thermal expansion than the brazing filler metal 4 and having an outer diameter that is the same as or slightly smaller than the outer diameter of the two-legged terminal 2 is interposed between the lower end of the lead 3 and the terminal 2. The ends of the leads 3 are connected to the terminals 2 of the circuit pattern on the surface of the ceramic substrate 1 by brazing.

Furthermore, since the outer diameter of the member 5 interposed inside the brazing filler metal 4 is set to be the same as or slightly smaller than the outer diameter of the terminal 2, the periphery of the disc-shaped member 5 and the surface of the ceramic base 1 are The amount of brazing filler metal 4 that forms a meniscus shape and adheres to the terminal 2 can be extremely reduced.

Therefore, when the ends of the leads 3 are brazed and connected to the terminals 2 of the circuit pattern on the surface of the ceramic substrate 1, the shrinkage stress of the brazing filler metal 4 that cools and solidifies on the surface of the ceramic substrate 1 directly applied to the ceramic substrate 1 is greatly weakened. be able to.

Furthermore, in the case where the member 5 interposed inside the brazing filler metal 4 is structured separately from the lead 3, the member 5 is not limited to the same material as the metal material for forming the lead 3; You can select materials with the optimal coefficient of thermal expansion according to various situations.

In addition, in the case where the member 5 interposed inside the brazing material 4 is integrated with the lead 3, the lead 3 and the member 5 are integrated, and the ends of the lead 3 are connected to the circuit pattern on the surface of the ceramic substrate 1. Since the number of parts for brazing connection to the terminal 2 is reduced, the end of the lead 3 can be brazed to the terminal 2 using the brazing material 4 without any trouble.

Examples] Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows a preferred embodiment of the lead attachment structure for a ceramic substrate according to the present invention, and in detail is a partially broken front view of a mullite ceramic substrate using the lead attachment structure. The embodiment shown in the above figure will be described below.

In the figure, l is a mullite ceramic substrate having a coefficient of thermal expansion of about 4.5xlO-'/°C, which is a ceramic substrate with a small coefficient of thermal expansion.

Leads 3 are formed on the surface of this mullite ceramic substrate 1 and are connected in series to a circuit pattern (not shown) made of a tungsten metallized layer provided inside the substrate 1 or on its surface.
It is integrally equipped with a terminal 2 having a circular circuit pattern made of a tungsten metallized layer whose ends are connected by brazing.

Then, the surface of the terminal 2 made of the tungsten metallized layer is plated with nickel 6 by electroless plating.
was applied.

Then, as shown in FIG. 1, the top surface of the terminal 2 made of the tungsten metallized layer with the nickel plating 6 is heated to a temperature close to the thermal expansion coefficient of the mullite ceramic substrate l, which is smaller than the thermal expansion coefficient of silver solder (described later). A disc-shaped member 5 made of molybdenum having a coefficient of expansion and having a metal plating such as nickel plating or gold plating on the surface to which the silver solder is accurately adhered is mounted.

Here, the disk-shaped member 5 made of molybdenum has an outer diameter that is the same as or slightly smaller than the outer diameter of the circular terminal 2 on the surface of the mullite ceramic substrate 1. did.

Then, the lower end of the thin cylindrical lead 3 made of Kovar mentioned above was brought into contact with the upper surface of the member 5 made of molybdenum mounted on the upper surface of the terminal 2, and the lead 3 was made to stand above the member 5.

With the lead 3 standing above the member 5 made of molybdenum, the lower part of the lead 3, the member 5 made of molybdenum with which the lower end of the lead 3 is brought into contact, and the terminal 2 made of a tungsten metallized layer on which the member 5 is mounted. , the mullite ceramic substrate around the terminal is heated to 800°C.
After preheating back and forth, the silver solder 4a is heated and molten and adhered around the lower part of the lead 3, around the molybdenum member 5, and over the terminal 2 on the surface of the mullite ceramic substrate 1, The silver solder 4a was cooled and solidified together with the lower part of the lead 3, the member 5 made of molybdenum, the terminal 2 on the surface of the mullite ceramic substrate 1, and the mullite ceramic substrate 1 around the terminal.

The lead attachment structure for the mullite ceramic substrate shown in FIG. 1 was constructed as described above.

FIG. 2 shows another lead attachment structure for a ceramic substrate according to the present invention, and in detail is a partially cutaway front view of a mullite ceramic substrate using the lead attachment structure.

The embodiment shown in the above figure will be described below. In Figure 2,
The same members as those of the mullite ceramic substrate shown in FIG. 1 described above are given the same reference numerals, and their explanations will be omitted.

FIG. 2 shows a mullite ceramic substrate l which is integrally equipped with a terminal 2 having a circuit pattern made of a circular tungsten metallized layer on its surface similar to that shown in FIG. 1, and whose surface is nickel plated 6. It is shown.

The lower end of the lead 3 which is brazed and connected to the terminal 2 on the surface of the mullite ceramic substrate 1 is made of the same material as the lead and has a coefficient of thermal expansion close to that of the mullite ceramic substrate l, which has a coefficient of thermal expansion of 4 to 7X10-@/''C. A thin disk-shaped member 5 made of the aforementioned Kovar or 42 alloy to which silver solder (described later) is adhered accurately is integrally provided, and the member 5 protruding from the lower end of the lead 3 is attached to the surface of the mullite ceramic substrate 1. The lead 3 was brought into contact with the upper surface of the terminal 2 and erected above the terminal 2.

Here, the thin disk-shaped member 5 integrally provided at the lower end of the lead 3 has an outer diameter that is the same as or greater than the outer diameter of the circular terminal 2 on the surface of the mullite ceramic substrate 1. It was made a little smaller in size.

Then, with the lead 3 standing above the terminal 2, the disc-shaped member 5 at the lower end of the lead 3, the terminal 2 in contact with the member 5, and the mullite ceramic substrate l around the terminal are heated to around 800°C. At the same time as preheating, the silver solder 4a is heated and melted and applied to the lower part of the lead 3, the member 5 at the lower end of the lead 3, and the terminal 2 on the surface of the mullite ceramic substrate 1. Silver solder 4a is attached to the lower part of the lead 3, the member 5 at the lower end of the lead 3,
The terminal 2 on the surface of the mullite ceramic substrate 1 and the mullite ceramic substrate 1 around the terminal were cooled and solidified.

The lead attachment structure for the mullite ceramic substrate shown in FIG. 2 was constructed as described above.

Next, the operation of each of the above-mentioned embodiments will be explained.

In the lead attachment structure of each of the above embodiments, the ends of the leads 3 are attached to the terminals 2 on the surface of the mullite ceramic substrate 1.
Many parts of the silver solder 4a that are directly soldered to the
Interposed between the lower end of the board 3 and the terminal 2 inside the silver solder 4a, it has a coefficient of thermal expansion smaller than that of the silver solder 4a and close to that of the mullite ceramic substrate l;
A disc-shaped member 5 made of molybdenum whose outer diameter is the same as or slightly larger than the outer diameter of the circular terminal 2, and whose surface is metal-plated and has a separate structure from the lead 3. , or is replaced with a disc-shaped member 5 at the lower end of the lead 3 made of 4270I, which is the same material as the lead 3 and has an integral structure, and the end of the lead 3 is brazed and connected to the terminal 2 on the surface of the mullite ceramic substrate 1. It will be done.

In addition, the outer diameter of the disc-shaped member 5 made of molybdenum interposed inside the silver solder 4a or the disc-shaped member 5 made of 42 alloy made of the same material as the board 3 is determined by the circular shape of the surface of the mullite ceramic substrate 1. Since the outer diameter of the terminal 2 is the same as or slightly smaller than the outer diameter of the terminal 2, the end of the lead 3 is inserted through the disc-shaped member 5 as shown in FIGS. Of the silver solder 4a to be brazed and connected to the terminal 2 on the surface of the mullite ceramic substrate 1, it is attached in a meniscus shape between the periphery of the disk-shaped member 5 and the terminal 2 on the surface of the mullite ceramic substrate 1. The amount of silver solder 4a can be extremely reduced.

Therefore, most of the silver solder 4a directly attached to the upper surface of the terminal 2 on the surface of the mullite ceramic substrate 1 is replaced with the disc-shaped member 5, and the silver solder 4a is replaced with the disc-shaped member 5.
When connecting the ends of the leads 3 to the terminals 2 on the surface of the mullite ceramic substrate 1 by using the It can be weakened.

In addition, a member 5 with which the brazing filler metal is tightly adhered to the inside of the brazing filler metal 4 is also provided.
As a result, the ends of the leads 3 are brazed and connected to the terminals 2 on the surface of the mullite ceramic substrate 1.
The connection strength is not significantly weakened by the member 5 interposed inside the brazing filler metal 4.

Furthermore, in the case where the member 5 interposed inside the silver solder 4a has a separate structure from the lead 3 as shown in FIG. You can select the member 5 that has .

In addition, in the case where the member 5 interposed inside the silver solder 4a is integrated with the lead 3 as shown in FIG. 2, the end of the lead 3 can be easily connected to the surface of the mullite ceramic substrate 1. It can be connected by brazing to the terminal 2 of the terminal 2 using silver solder 4a.

According to the experimental results, when the lead 3 ends were brazed and connected to the terminal 2 of the circuit pattern made of the tungsten metallized layer on the surface of the mullite ceramic substrate 1 using silver solder 4a using the lead attachment structure of each of the above-mentioned examples, the mullite It was confirmed that no cracks were formed on the ceramic substrate 1 that would impair the airtightness of the substrate 1 or destabilize the connection strength of the ends of the leads 3 brazed to the terminal 2 on the surface of the substrate 1. .

Furthermore, with the lead attachment structure of each of the above embodiments, the ends of the leads 3 can be connected to the terminals 2 on the surface of the mullite ceramic substrate 1.
When the tensile strength of the lead 3, which was connected by brazing using silver solder 4a, was measured, it was found to be over 6 kg.
It was confirmed that the connection strength to the terminal 2 was sufficient for practical use.

In each of the above-mentioned embodiments, a silver-copper eutectic solder, a gold-germanium solder, or the like is used as the brazing material 4, a low-temperature fired alumina ceramic substrate is used as the ceramic substrate 1, and the circuit pattern in which the leads 3 are connected by brazing is used. terminal 2 of
Alternatively, a terminal 2 made of a silver metallized layer or the like whose surface is not plated may be used, and a lead attachment structure having substantially the same functions and effects as those of the above-mentioned embodiments can be obtained.

Moreover, the member 5 interposed inside the brazing material 4 such as silver solder is
In addition to the above-mentioned metal members such as tungsten and titanium oxide, which have a coefficient of thermal expansion smaller than that of the brazing filler metal 4, an inorganic member whose surface is metallized and which has a coefficient of thermal expansion smaller than that of the brazing filler metal 4, to which the brazing filler metal 4 adheres precisely, is used. (It is possible to obtain a lead attachment structure that has the same functions and effects as those of the above-mentioned embodiments.

Furthermore, the member 5 having a coefficient of thermal expansion smaller than that of the brazing filler metal to be interposed inside the brazing filler metal 4 is optimally a member 5 having a coefficient of thermal expansion close to that of the ceramic substrate l; The member 5 having a coefficient of thermal expansion close to zero may be used, and by interposing the member 5 inside the brazing filler metal 4, the shrinkage stress when the brazing filler metal 4 is cooled and solidified is reduced by the member 5, and the solder The shrinkage stress applied to the ceramic substrate 1 when the material 4 is cooled and solidified can be significantly weakened.

In addition, the terminal 2 of the circuit pattern on the surface of the ceramic substrate 1 is made of an aluminum nitride substrate, which is stronger than the alumina ceramic substrate but has a larger difference in coefficient of thermal expansion with the brazing filler metal 4 than the alumina ceramic substrate. Even when the leads 3 are brazed and connected to the aluminum nitride substrate, cracks may occur in the aluminum nitride substrate due to the difference in thermal expansion coefficient with the brazing material 4. If the leads 3 are connected by brazing using the lead attachment structure of the present invention, it becomes an effective solution to preventing the occurrence of cracks in the aluminum nitride substrate.

Furthermore, in each of the above-mentioned embodiments, the lead attachment structure of the ceramic substrate 1, which is the ceramic substrate 1, has been described. The same lead attachment structure as in each of the above-mentioned embodiments may be used for the lead attachment structure when the parts are brazed and connected using a brazing material, and in this case, the same functions and effects as in each of the above-mentioned embodiments can be obtained. Needless to say.

[Effects of the Invention] As explained above, in the ceramic substrate lead attachment structure of the present invention, many brazing materials such as silver solder are used to connect the lead ends directly to the terminals of the circuit pattern on the surface of the ceramic substrate. The part is interposed inside the brazing column between the lower end of the lead and the terminal, has a coefficient of thermal expansion smaller than that of the brazing filler metal, and has an outer diameter that is the same as or slightly smaller than the outer diameter of the terminal. It will be replaced with a new member.

In addition, since the outer diameter of the member interposed inside the solder pillar is the same as or slightly smaller than the outer diameter of the terminal, the area between the periphery of the member and the terminal on the surface of the ceramic substrate is The amount of brazing filler metal attached can be extremely reduced.

Therefore, when the lead ends are brazed and connected to the terminals of the circuit pattern on the surface of the ceramic substrate, the shrinkage stress directly applied to the ceramic substrate by the brazing material such as silver solder that cools and solidifies on the surface of the ceramic substrate can be significantly weakened. can.

Therefore, when the lead ends are brazed and connected to the terminals of the circuit pattern on the surface of the ceramic substrate, gel may form on the ceramic substrate, which may impair the airtightness of the ceramic substrate, or connect the terminals of the circuit pattern on the surface of the ceramic substrate with the leads. The connection strength with the end portions will not become unstable.

Further, in the case where the member interposed inside the solder column is constructed separately from the lead, a member having an optimal coefficient of thermal expansion depending on various situations can be selected as the member.

Furthermore, if the member interposed inside the solder pillar is integrally structured with the lead, the end of the lead can be brazed to the terminal on the surface of the ceramic substrate using a brazing material without any trouble.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway front view of a mullite ceramic substrate using the lead attachment structure of the present invention, and FIG. 2 is a partially cutaway front view of another mullite ceramic substrate using the lead attachment structure of the present invention. FIG. 3 is a partially cutaway front view of a ceramic substrate using a conventional lead attachment structure. l... Ceramic base, 2... Terminal, 3...
Lead, 4. Brazing metal, 4a. Silver solder, 5. Component. Patent applicant Shinko Electric Industry Co., Ltd.

Claims (1)

[Claims] 1. In a ceramic substrate in which a lead end is brazed and connected to a terminal of a circuit pattern on the surface of a ceramic substrate such as a ceramic package or a ceramic substrate using a brazing material, between the lower end of the lead and the terminal. A ceramic-based lead characterized in that a member having an outer diameter equal to or slightly smaller than the outer diameter of the terminal, which has a lower coefficient of thermal expansion than the brazing filler metal, is interposed inside the brazing filler metal. Mounting structure. 2. A lead attachment structure for a ceramic substrate according to claim 1, wherein the member is of a separate structure from the lead. 3. A lead attachment structure for a ceramic substrate according to claim 1, wherein the member is integrally constructed with the lead.