JPS63150945A - Package for integrated circuit - Google Patents

Abstract

PURPOSE:To promote the removal of a gas generated at the time of brazing heating, and to prevent the generation of a blowhole by forming a juction structure, in which a grooved Ag buffer is applied, in the brazing joining section of an SiC group insulating board and an alumina substrate. CONSTITUTION:Radiation fins 1 are fixed to an SiC insulating board 21 through a fitting 13. Input-output pins 4 set up to an alumina substrate 3 are conducted with pads 8. Leads 7 connect the pads 8 and a semiconductor element 6. A cap 5 protects the semiconductor element 6 from the outside. Cr metallized layers 10 are shaped to the SiC insulating board 21 as foundations, and Ni plating layers 9 are executed to the layers 10. The nickel plating layer 9 is executed to the alumina substrate 3, a grooved Ag buffer 12 is held as a thermal stress relaxing material, and the substrate 3 is joined with the insulating board 23 through silver solder layers 11. The discharge of a gas generated from the Ni plating layer 9 at the time of brazing heating is facilitated by grooves in the grooves Ag buffer 12. The removal of a gas generated from molten and solidified silver solder is also promoted through the grooves.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an integrated circuit package, and more particularly to a bonding structure between an alumina substrate and a silicon carbide insulating plate that is suitable for high reliability and airtightness.

[Conventional technology]

A conventional integrated circuit package is shown in FIG. Second
Fig.-1 is a schematic cross-sectional view of an integrated circuit package to which a conventional flat Ag buffer is applied, and Fig.2-2 is a partially enlarged cross-sectional view of Fig.2-1, where 1 is a radiation fin, and 2 is an insulating plate. , S is the alumina board, M is the input/output pin, 5 is the cap,
6 is a semiconductor element, 7 is a lead wire, 8 is a pad, 9 is N1
plating layer, 10 is Or metallized layer, 11 is silver solder layer,
12 means Ag buffer. As shown in FIG. 2-1, 1 an insulating plate 2 with excellent thermal conductivity for dissipating the heat generated in the semiconductor element 6;
A pad 8 is fixed to the heat dissipating fin 1 with a bonding layer such as solder, mu-8i5S, Rirui or Ag paste, and connects the input/output pin 4 with the heat dissipating fin 1 which is fixed via the insulating plate 21C and the bonding layer. In recent years, as the density and speed of semiconductor devices have increased, problems have arisen in semiconductor devices. In order to effectively dissipate heat and maintain the functionality of semiconductor elements, there is a need for highly reliable packages that are highly hermetically sealed and do not deteriorate due to cooling/heating cycles.

In other words, in order to effectively dissipate the heat of the semiconductor element and prevent the semiconductor element from peeling off due to cooling/heating cycles, etc.
The insulating plate has a thermal expansion coefficient of semiconductor element B1 &5X10''''
A material with a coefficient of thermal expansion of 5x1o-
SIC (
containing a small amount of BeO) is selected.

On the other hand, the cap and insulating plate bonded to the alumina substrate are
It is required to bond to the alumina substrate in a highly airtight manner. For this reason, the cap is usually made of Kovar, which approximately matches the thermal expansion of the alumina substrate. However, the insulating plate E whose thermal expansion is similar to that of the semiconductor element? 10, on the other hand, differs from the thermal expansion coefficient of the alumina substrate, 6~ax 1o-'/°C.

As a result, when directly bonded, either alumina or SiO is damaged during brazing or during cooling/heating cycles, resulting in loss of airtightness. Therefore, a thermal stress relief material is generally applied between the alumina and the 1C.

As a suitable bonding structure between 1 alumina substrate and SIC,
As shown in Fig. 2-1, an Or metallized layer 10 is provided as a base on an insulating plate 2, and a N1 plating layer 9 is applied thereto, and similarly, a nickel plating layer 9 (base metallization is usually W or Mo) is applied to an alumina substrate. After applying Ag as a thermal stress relaxation material,
A method of sandwiching a buffer 12 and bonding via a silver solder layer 11 is described in Japanese Patent Application No. 60-206950. However, in industrial applications based on mass production, it is required to improve the manufacturing yield of semiconductor packages and increase the reliability of the joints, including the thermal stress caused by the radiation fins. However, no particular consideration has been given to this point in the past.

[Problem that the invention seeks to solve]

As shown in Figure 2-2, the alumina substrate 5 and the insulating plate 2 are
It also has excellent wettability with silver wax. By forming the N1 plating layer 9, which has wettability with silver solder, on both the ninth insulating plate and the alumina substrate, silver soldering becomes possible, and a bonding structure via an Ag buffer becomes possible. However, when heating the components of these joints, ao, C01N
1. Horse, H! Adsorbed or occluded gases such as O are generated, and as a result, these gases cause defects, that is, blowholes, at the joints of silver solders, resulting in poor airtightness at the joints between alumina and SiC. Therefore, the member is made gas-free by vacuum degassing treatment or the like. However, when setting the joining members, they are exposed to the atmosphere and adsorption of H and O is virtually avoided, but although there are differences in degree, blowholes are unavoidable, and as a result, brazing reduces the subsequent joining yield. It is not always possible to be satisfied with this point. Furthermore, if there is a blowhole defect, the defective portion will be fatigued by the cooling and heating cycles after joining, resulting in poor airtightness and deteriorating reliability in terms of thermal fatigue resistance.

An object of the present invention is to provide a highly reliable integrated circuit package that ensures the integrity of the joints formed by silver brazing, has excellent heat dissipation, and is highly reliable.

[Means for solving problems]

To summarize the present invention, the present invention relates to an integrated circuit package, which has pads for connecting lead terminals of integrated circuit elements and a plurality of input/output pins electrically connected to the pads on the same surface. , and an alumina substrate with a through hole in the center, a silicon carbide-based insulating plate with high thermal conductivity on the back side, and heat dissipation fins made of metal material are soldered to the insulating plate, and an integrated circuit element and a silicon carbide-based insulating plate are soldered to the insulating plate. In an integrated circuit package in which an insulating plate is fixed, a nickel plating film is interposed between each soldering surface of the alumina substrate and the silicon carbide insulating plate, and a grooved Ag buffer is further provided between the nickel plating film. It is characterized by being in close contact with each other.

The blowhole caused by silver brazing due to gas released from the component is controlled by many factors such as the amount and type of gas released from the component itself, and the brazing conditions such as temperature, time, atmosphere, heating and cooling rate, etc. In fact, it is difficult to inhibit prohol generation solely by controlling these factors, ie, by controlling these processes.

That is, in addition to controlling the process, it is necessary to create a bonding structure that effectively releases gas generated from the members during bonding and ensures wetting of the silver solder to the members. This bonding structure eliminates the factor of blowhole generation, making it possible to improve bonding yield and reliability.

The present inventors focused on the fact that the Ag buffer has good workability among the members constituting the joint structure, and developed the shape of the Ag buffer into a second material.
-1 from the conventional flat Ag buffer 12 shown in Figure 1.
It has been found that the above object can be achieved by using a grooved Ag buffer 12 as shown in the figure.

Fig. 1-1 is a schematic cross-sectional view of an integrated circuit package to which a grooved Ag buffer is applied, which is one example of current collection according to the present invention, and Fig. 1-2 is a partially enlarged cross-sectional view of Fig. 1-1. , 1 and S to 12 have the same meanings as above, 21 is the SiO-based insulation plate edge plate 3 is a heat dissipation fin attachment, 14 is a silver solder layer, 15
It means waxy layer.

The amount of gas generated from a single member during heating during brazing increases as the temperature rises, and gas adsorbed on a member such as a cylindrical member is durable at high temperatures and decreases, but does not completely disappear. Special K Ni-plated SiO-based insulation plate edge plate 21 Gas generation from the alumina substrate is caused by A, which is a pure metal.
Generates more gas than g-buffer.

On the other hand, regarding the wettability of silver solder, Ag buffer has greater N1 adhesion and wetting spread. This difference largely depends on the surface condition of the member, and also depends on the solid-liquid and surrounding atmosphere, as well as the reaction of the solid-liquid and the presence or absence of solid solution, and is generally determined by experiment. The above results demonstrate that BAg-7 (Ag-(!u-Zn-a
N1 plating on the 1iM edge plate and alumina substrate and on the surface of the Ag buffer at 700°C, N, -
These are the results determined from the wetted and spreading area of BAg-7 in 10H gas.

As mentioned above, Fig. 1-1 shows the details of the joint part from the gas generation from plating and the wettability of Ag buffer.
The joining structure shown in Figure 2 can be explained. In other words, the gas generated from N1 plating is easily released by the grooves in the Ag buffer, and when the silver solder melts, the grooves are filled with silver solder, which prevents poor wetting of the silver solder to the Ag buffer. At the same time, the gas generated from the silver solder melting and solidifying is also promoted to be removed through the groove.

On the other hand, by providing grooves for the Ag buffer, the joint diameter is the same, and by expanding the area of brazing, the thermal stress can be kept constant, and by expanding the area of brazing, airtightness can be maintained. .

As described above, the bonding structure using the grooved Ag buffer promotes the removal of gas generated from the members and prevents the occurrence of blowholes, resulting in stable bonding of SiO-based insulating board edge boards and lumina substrates. becomes possible.

〔Example〕

Hereinafter, embodiments of the present invention will be described in more detail with reference to FIG. 1, but the present invention is not limited to these embodiments.

Example 1 240 pins brazed with BAg-8 (Mug-(!u system) and pads connected to them on the same surface,
And on the back side of the 12 x 121 penetration source, an outer diameter of 16 x 16-1
An alumina substrate 5 having an inner diameter of 12×12− and having a W metallized base and a ring-shaped N1 plating layer 9 applied to the surface thereof was prepared.

On the other hand, Or containing 5 μmar powder and ethyl cellulose
Separately prepare a powder paste and prepare B with a thermal conductivity of 2.7 W/cm °C with an outer diameter of 1 & 5 × 1 & 5 ■ and a thickness of 1 ■.
A ring (alumina substrate joint) with the same dimensions as the N1 plated part of the alumina substrate was placed on the aO-containing BiO insulating board, and on the back side of the ring (Ou fin joint) with dimensions of 15 x 15 g was coated with the above (3r powder paste). Printed.

The above 810 series insulating board printed with this Or powder paste was
It was baked in argon gas at 0°C for 3 minutes to remove the Or powder on the surface and to remove the Cr powder generated on the 81c-based insulating board.
A υN1 plating layer 9 (thickness 1.5 μm) was applied to the printed surface of the Or metallized layer 10 by the reaction of 1c using a Watts bath,
An N1-plated 131c type insulating board that can be brazed was manufactured.

On the other hand, BAg with the same dimensions as the ring at the alumina substrate joint
A silver solder foil ring of No.-7 was produced by punching.

Furthermore, a pure Ag ring having the same outer and inner diameters as the silver solder foil ring and a thickness of 1L5 m was produced by punching, and a flat Ag buffer (see FIG. 2-2) was prepared.

Also, on both surfaces of this flat plate, width (1.5 mm, depth Q,
Grooved A with a groove of 15 dew formed by a die or cutter
g buffer 12 (see FIG. 1-2) was prepared.

In addition to the above-mentioned bonding material between the alumina substrate and SiC-based insulating board,
Heat dissipation fin foam attachment diameter 8-1 height 7cm pure Cu 15
A silver solder foil for joining a BAg-7 heat dissipation fin fitting for a door with a diameter of 7-1 and a thickness of 80 μm was prepared.

For graphite brazing, use a jig to braze the graphite to the N1 plating ring on the back side of the alumina substrate 3 with pins and pads. The foil, the Ni-plated SiC insulating board 21, the silver solder foil for joining the heat dissipation fin fixture, and the heat dissipation fin fixture pure 0u15 (7) were laminated in this order, and set in an N, -10 temperature furnace.

Next, the furnace was heated and held at 700° C. for 50 minutes, and then cooled as it was to obtain an integrated circuit package assembly to which a grooved Ag buffer was applied, with the radiation fins removed.

On the other hand, among the parts of the above package, grooved person g/
(The other parts and bonding conditions were the same as those for the grooved Ag buffer, and an integrated circuit package assembly to which the flat Ag buffer was applied was separately obtained.)

As described above, after fabricating 50 integrated circuit packages each using two types of bonding structures, namely, a flat Ag buffer and a grooved Ag buffer, Tle +7 of the bonding portion was fabricated.
- As a result of conducting tests, it was found that an integrated circuit package using a flat plate Ag buffer has a performance of 10-16 Torrs1/I!
The pass rate of 1lilc or less is 15,150 pieces, whereas the integrated circuit package to which the grooved Ag buffer is applied has only 29/So pieces.In addition, the above integrated circuit package that passed the bonding was tested at a temperature of -55°C to After 24 cycles of heating and cooling from room temperature to 150°C, the results of a He IJ test were as follows:
The acceptance rate for integrated circuit packages of flat plate Ag buffers is 1.
The number was 1/15, and that of the grooved Ag buffer was 29,729, and a clear significant difference was observed, and most of the leak points in the flat Ag buffer were caused by blowholes at the silver soldering area.

Au plating was applied to the bonded body to which the grooved Ag buffer was applied, and then a semiconductor element 6 and a Kovar cap 5 were attached using an A/A affine 1 and an Au-8i solder 15, and an additional 24 cycles of a thermal cycle test were conducted. It was confirmed that adding other parts such as fins had no particular effect on the airtightness of the joint.

As can be seen from the above embodiments, by applying a grooved Ag buffer to the aluminum substrate and the SiC insulation board edge plate, the manufacturing yield of the joint and the reliability of the thermal cycle test can be improved.

In addition, in this example, the bonding structure of the SiC insulating plate was described in detail using a 240-pin integrated circuit package as an example, but this example shows that the same effect can be obtained for integrated circuit packages with other pin numbers. This is more obvious than the example.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to prevent blowholes from occurring at the joint, thereby improving the manufacturing yield and reliability of integrated circuit packages.

[Brief explanation of the drawing]

FIG. 1-1 is a schematic cross-sectional view of an integrated circuit package to which a grooved Ag buffer according to an embodiment of the present invention is applied;
Figure 2 is a partially enlarged sectional view of Figure 1-1, Figure 2-1 is a schematic cross-sectional view of an integrated circuit package that uses a conventional flat Ag buffer, and Figure 2-2 is a portion of Figure 2-1. It is an enlarged sectional view. 1: Heat dissipation fin, 2 Insulating board, 21: SiC insulating board, 3: Alumina substrate, 4: Input/output pin, 5: Cap, 6: Semiconductor element, 7 Lead wire, 8: Pad, 9: N
1 plating layer, 10: Or metallized layer, 11 and 14:
Silver wax decoy, 12: Ag buffer, 15: Wax layer /-/Figure 1-2Figure 2-7Figure 2-2

Claims (1)

[Claims] 1. An alumina substrate that has a pad that connects the lead terminal of an integrated circuit element and multiple input/output pins that are electrically connected to the pad on the same side and a through hole in the center, and a high-temperature substrate on the back side. In an integrated circuit package having a structure in which an integrated circuit element and a silicon carbide insulating plate are fixed to each other by a conductive silicon carbide insulating plate and a heat radiation fin made of a metal material being soldered to the insulating plate, the alumina substrate and the silicon carbide insulating plate are bonded to each other. An integrated circuit package characterized in that a nickel plating film is interposed on each soldering surface of the silicon carbide-based insulating plate, and a grooved Ag buffer is further soldered between the nickel plating films.