JPS6232631A - Integrated circuit package - Google Patents

Abstract

PURPOSE:To enhance reliability in preventing cracks in a glass layer, by forming a lead piece with an iron alloy, which includes nickel and cobalt and has martensite transformation temperature of less than -55 deg.C. CONSTITUTION:A chamber is formed by a ceramic insulating substrate 4 including silicon carbide, a cap 5 and a sealing glass 6 in an airtight manner. A semiconductor element 1 is mounted on the substrate. The end parts of lead pieces 3 are introduced from the outside. Wires 2 electrically connect the lead pieces and the element 1. Those parts are contained in an integrated circuit package. The lead piece 3 comprises an iron alloy, which includes nickel and cobalt and has martensite transformation temperature of less than -55 deg.C. Out of the iron alloys, the alloy, in which the amount of Ni is 29-31wt% and the amount of Co is 12.5-15wt%, especially has the thermal expansion coefficient that is approximate to the thermal expansion coefficient of glass, therefore said ally is most suitable for the material of the lead piece 3.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to an integrated circuit package having a structure in which a semiconductor element is mounted on an insulating substrate made of silicon carbide ceramic and one periphery is hermetically covered with a cap. In particular, the present invention relates to an integrated circuit package having a structure in which a substrate and a cap are sealed with glass.

The present invention is suitable for use in electronic computers.

[Background of the invention]

The semiconductor element, the end of the lead piece introduced from outside, and the wire electrically connecting the semiconductor element and the lead piece are placed in a small chamber airtightly surrounded by a ceramic insulating substrate, a cap, and a sealing glass. Integrated circuit packages are known. For example, Tokukai Showa 5! ll
-134852 publication.

An example is shown in which silicon carbide ceramics are used as the insulating substrate in place of the conventional alumina sintered body.

In such an integrated circuit package, as described in the publication (page 2, lower right, line 117 to page 3, upper left column, line 2), cracks occur in the glass layer that seals the substrate and the cap. Easy to occur.

In order to prevent cracks in the glass layer, the publication describes that the cap is made of ceramic having a coefficient of thermal expansion similar to that of the silicon carbide ceramic insulating substrate.

[Purpose of the invention]

An object of the present invention is to provide an integrated circuit package that is more reliable in preventing cracks in the glass layer.

[Summary of the invention]

The present invention provides an integrated circuit package having a silicon carbide-based ceramic insulating substrate, in which lead pieces contain nickel and cobalt and have a martensitic transformation temperature of 155°C.
It is composed of the following iron alloys.

The present inventors have determined that one of the causes of cracks in the glass layer in integrated circuit packages having silicon carbide-based ceramic insulating substrates is due to the cooling process after glass sealing treatment or the life test performed by applying a cooling/heating cycle after package fabrication. It was determined that the glass layer was subjected to thermal stress.

Then, in order to avoid applying thermal stress to the glass layer, it was concluded that the thermal expansion and contraction of the material of the lead piece should be approximately the same as the thermal expansion and contraction of the glass, leading to the invention of 1+S.

The effects of the present invention were fully demonstrated by a life test using thermal cycles, and it was possible to obtain a highly reliable integrated circuit package with no cracks in the glass layer.

The present invention is even more effective when applied to the invention described in JP-A-59-134852.

(a) Structure of lead piece; The lead piece in the present invention is made of a material having a phase transition temperature, specifically, a martensitic transformation temperature of 155°C or less. The thermal cycle life test of integrated circuit packages is
Generally, it is repeated between -55℃ and +150℃,
It is necessary to have a phase transition temperature of -55°C or lower.

Iron alloys containing nickel (Ni) and cobalt (Co2) are examples of materials that have extremely low phase transition temperatures and low thermal expansion. Among this iron alloy, especially the Ni content is 2.
An alloy in which the amount of Go is in the range of 9 to 31% by weight and 12.5 to 15% by weight has a coefficient of thermal expansion close to that of glass, and is optimal as a material for the lead piece. F e -N i -C6f alloy ingot material having such a composition is 1
When stress relief annealing is performed at a temperature between 100 and 600℃ after 0 to 60% cold working, the thermal expansion coefficient is 40
It was found that the temperature was 10-7/°C or less. Practically speaking, the above composition includes carbon (C) of 0.1% by weight or less, silicon (Si) of 0.5% by weight or less, and manganese (Mn) of 0.1% by weight or less.
It can be contained in a range of 5% by weight or less. Other components include phosphorus (P) and sulfur (S) that are mixed in during dissolution.
etc. may be included as unavoidable impurities in amounts that are included in ordinary melted alloys.

If the Ni and CO contents are less than the above composition range, martensitic transformation occurs upon cooling from the completely annealed state, resulting in an increase in the coefficient of thermal expansion. Also, from the above composition range, Ni and Co
If the amount is large, austenite becomes chemically stable and the martensitic transformation point decreases, but the coefficient of thermal expansion increases and 40
10-7/°C becomes difficult to obtain. Regarding the degree of cold working, if the degree of cold working is less than 10%, stabilization of austenite cannot be obtained by working. Also, depending on the composition, when the degree of cold working exceeds 160%, the coefficient of thermal expansion increases, and when the degree of cold working exceeds 90%, emulsion martenside is generated, and the coefficient of thermal expansion increases significantly. It is preferable to apply a cold working degree of 12 to 50%, and stabilization of austenite can be obtained by applying this working. Stress relief annealing should be performed at a temperature below the recrystallization temperature of the material, and is suitably 100 to 600°C. At temperatures below 100°C, sufficient strain removal cannot be achieved, and there is a risk that the leads may be deformed due to glass sealing. When annealing is performed at a temperature of 600° C. or higher, the stabilizing effect of austenite due to processing is lost and martensitic transformation is likely to occur.

Next, the allowable amount of elements added as deoxidizing and desulfurizing agents and elements unavoidably mixed during production will be explained. C is necessary as a strong deoxidizing agent to improve the cleanliness of the material, but as its content increases, the coefficient of thermal expansion increases, so C should be kept at 0.1% by weight or less. Si is also used as a deoxidizing agent, but as the content increases, the toughness decreases and lead breakage is caused, so the content is preferably 0.5% by weight or less. Mn is used as a desulfurizing agent, but as the content increases, the coefficient of thermal expansion increases, so it is limited to 0.5% by weight or less. Since p and s deteriorate the toughness of the material, P+
It is desirable that the amount of S be 0.01% by weight or less.

Table 1 shows Ni-Fe alloy, Ni-Go-F
The phase transformation temperature determined from the change in thermal expansion coefficient and electrical resistance of the e-alloy is shown.

Table 1, Figure 2 shows the material of the lead according to the present invention, i.e. 29.5
wt% Ni-14, 5 wt% Co-Fs alloy,
Ni-Co-Fe, showing the thermal expansion properties of the 42 wt% Ni-Fe alloy and glass shown for comparison.
Alloys have less thermal expansion than glass.

(b) Composition of the insulating substrate: The insulating substrate is composed of silicon carbide ceramics. By using silicon carbide ceramics in place of the conventional alumina sintered substrate, it is possible to improve the dissipation of heat generated in the semiconductor element.

The silicon carbide ceramic substrate can be manufactured by a sintering method that is commonly used as a means for manufacturing ceramic molded products.

A preferred insulating substrate is a silicon carbide ceramic containing 0.05 to 5% by weight of at least one selected from beryllium (Be) and beryllium compounds, and containing silicon carbide as a main component. and a sintered body having a relative density of 90% or more of the theoretical density. The coefficient of thermal expansion of such a sintered body is 35 to 40 x 10-'/''
C, which has a thermal expansion coefficient close to that of silicon, and its thermal conductivity is 0.2 caΩ/am-s·°C or more.

This thermal conductivity value of 0.2 caQ/cx-s・℃ has a negative effect on electrical insulation (resistivity of 107 Ω-1 or more) and thermal expansion coefficient when silicon carbide ceramics are made by sintering. This means the lower limit of the thermal conductivity that can be obtained with good reproducibility without giving rise to a loss of heat, and moreover, it is about four times the thermal conductivity of conventional alumina ceramic substrates. Furthermore, the coefficient of thermal expansion is close to that of silicon used in semiconductor devices, and when a semiconductor device is bonded to a substrate, the thermal stress caused by the difference in thermal expansion between the two is small.

(c) Structure of the cap; It is desirable that the cap for covering and enclosing the semiconductor elements, wiring, etc. on the substrate be made of a material having a coefficient of thermal expansion of 20 to 55 Xl0-7/°C. The material is silicon carbide ceramics.

°Mullite ceramics, zircon ceramics,
Silicon nitride ceramics and the like can be used.

When a cap material with the above thermal expansion coefficient value is used, conventional alumina ceramics (thermal expansion coefficient value 65X 10-
7/° C.), the expansion differential between the silicon carbide insulating substrate and the silicon carbide insulating substrate is reduced by at least 173, and therefore the thermal stresses that may occur between the substrate and the cap are reduced accordingly.

(d) Composition of the sealing glass; Ideally, the sealing glass material should be a material with a coefficient of thermal expansion close to that of the silicon carbide ceramic used for the substrate, with a value of 30 to 55 x 10-7/ In particular, a temperature of 40 to 55 x 10-f/°C is appropriate. Glass sealing is performed after bonding the semiconductor element onto an insulating substrate, so glass with a high melting point is not suitable for use.
It is desirable to select glass that can be sealed at temperatures below 0°C.

In order to satisfy these conditions, it is desirable to use β-eucribtite, lead titanate, or lead borate glass containing these.

By configuring as above, even when cooling from the sealing temperature to room temperature, and when repeating the cooling/heating cycle between -55 and +150°C.

It is possible to obtain an integrated circuit package that has stability, high reliability, and excellent heat dissipation characteristics without causing cracks in the sealing portion or abnormalities in electrical characteristics.

[Embodiments of the invention]

Next, the present invention will be explained by examples.

Embodiment 1 FIG. 1 illustrates a cross section of an integrated circuit package of the present invention. In the figure, a semiconductor element 1 is bonded to the center of one surface of an insulating substrate 4 made of silicon carbide ceramics through a metal solder layer 7.

A plurality of lead pieces 3 are bonded on the same surface through a sealing glass layer 6, and one end of the lead piece and the semiconductor element 1 are electrically connected by a bonding wire 2.

The other end of the lead piece 3 extends outward from the periphery of the insulating substrate 4. The ends of the semiconductor element 1° bonding wire 2 and lead piece 3 are surrounded by an insulating substrate and a cap 5,
The gaps between the cap 5, the insulating substrate 4, and the lead pieces 3 are hermetically sealed via a sealing glass layer 6.

The silicon carbide ceramic used for the insulating substrate is a sintered body having a density of 90% or more of the theoretical density.

This sintered body has electrical insulation with a resistivity (room temperature) of 10 aΩ-1 or more and a thermal conductivity of 0.2 to 0.7 caΩ/a1・S・℃
1 Bending strength 30 kgf/ma” or more, thermal expansion coefficient a
It has a characteristic of 5 x 10-7/°C.

The cap material is made of mullite ceramic (40 to 55 x 10
-7℃), silicon carbide ceramics (25~35
X 10-7/"C) etc. are used for the sealing glass. The sealing glass has a thermal expansion coefficient of 40 to 55X1 close to that of the silicon carbide ceramic of the insulating substrate and the cap material
07/°C is also required. Examples of glasses with a low sealing temperature and a low coefficient of thermal expansion include β-eucribtite, lead titanate, or lead borate glass containing both, which can be used as the sealing glass material in the present invention. It is.

The material of the lead piece has a thermal expansion coefficient of 40 from room temperature to 400°C.
Ni-Co-F with characteristics of X 10-'/℃ or less
e alloy with martensitic transformation below 155°C.
The lead pieces are made by blending the required amounts of Fa, Ni and Go, melting them in vacuum, hot rolling them, repeating cold rolling and annealing until the plate thickness is 0.18m, and then annealing them again to a thickness of 0.15mm. Finished by cold rolling. After that, about 400-5
A lead frame was fabricated from a plate that had been annealed to remove strain at 00°C, and an integrated circuit package as shown in FIG. 1 was fabricated.

As a result of the reliability test at -55 to +150°C, it was confirmed that there was no leakage failure at the glass sealing part.

〔Effect of the invention〕

As described above, according to the present invention, cracks do not occur in the glass sealing part when the glass sealing process is heated and then cooled to room temperature, and when a life test is performed in a cooling/heating cycle from -55 to +150°C. The result is a highly reliable integrated circuit package.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of an integrated circuit package of the present invention. FIG. 2 is a diagram showing the thermal expansion characteristics of the lead piece material and glass. 1... Semiconductor element, 2... Bonding wire, 3
...Lead piece, 4...Insulating substrate, 5...Cap, 6...Sealing glass layer, 7...Metal solder layer.

Claims (1)

[Claims] 1. In a chamber airtightly surrounded by a silicon carbide ceramic insulating substrate, a cap, and a sealing glass, a semiconductor element mounted on the substrate and a semiconductor device introduced from the outside An integrated circuit package that accommodates the ends of lead pieces and the wires that electrically connect them, wherein the lead pieces are made of an iron alloy containing nickel and cobalt and having a martensitic transformation temperature of -55°C or less. An integrated circuit package characterized by: 2. In claim 1, the composition of the iron alloy is 29 to 31% by weight of nickel and 12.5% by weight of cobalt.
An integrated circuit package comprising ~15.5% by weight and the remainder consisting essentially of iron. 3. In claim 2, the iron alloy is 10
An integrated circuit package characterized in that it is stress-relieving annealed in a temperature range of 0 to 600°C. 4. An integrated circuit package according to claim 1, wherein the substrate is made of a sintered body of silicon carbide. 5. Claim 4, wherein the composition of the sintered body is such that at least one of beryllium and beryllium compound is 0.05 to 5% by weight of beryllium, and the remainder is substantially silicon carbide. An integrated circuit package characterized by: 6. The integrated circuit package according to claim 1, wherein the cap is made of ceramic having a coefficient of thermal expansion of 20 to 55 x 10^-^7/°C. 7. The integrated circuit package according to claim 6, wherein the cap is made of any one of mullite ceramics, silicon carbide ceramics, zircon ceramics, and silicon nitride ceramics. 8. The integrated circuit package according to claim 1, wherein the glass has a coefficient of thermal expansion of 30 to 55 x 10^-^7/°C. 9. An integrated circuit package according to claim 8, wherein the glass is made of one of β-eucribtite, lead titanate glass, and lead borate glass.