JPH0629444A - Method of brazing - Google Patents

Abstract

PURPOSE:To provide a reliable method of brazing between Al-N alloy and Ni capable of preventing cracks. CONSTITUTION:Lead pins 6 of Ni alloy are bonded with brazing silver 5a to the underside of an Al-N alloy plate 3 of a semiconductor device. The wetting angle theta of brazing silver is set at 11 deg.-38 deg., while the amount of brazing silver is controlled so that it may flow beyond the normals extending from the ends of lead pin 6 to the base plate 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brazing method of aluminum nitride (hereinafter referred to as AlN) and a nickel alloy (hereinafter referred to as Ni alloy).

[0002]

2. Description of the Related Art A base (substrate) used for a semiconductor device or the like in which a semiconductor element is packaged is, for example, Al.
There are N, Al ₂ O ₃ , glass epoxy resin and the like, which are used properly according to the application. Of these, particularly AlN has excellent electrical characteristics, thermal conductivity, and environmental resistance, and is often used as a base for semiconductor devices and the like that are required to have high performance and high functionality.

Al used in semiconductor devices
When electrical connection is made between the surface wiring or internal wiring of the base made of N and an external element, a metal film is formed on this base by sputtering or the like, and a Ni alloy lead pin is soldered through silver solder. The contact method is generally used.

However, AlN and Ni alloys are essentially different in their chemical bonding modes and significantly different in chemical and physical properties, so that it is not easy to satisfactorily bond them to each other. Absent. In particular, AlN and Ni
Since the thermal expansion coefficients of the alloys differ greatly, the residual thermal stress depending on the thermal expansion difference due to the temperature change during brazing is A
There is a possibility that cracks may occur in AlN by being added to the brazing portion of 1N and Ni alloy.

Therefore, in a semiconductor device in which a lead pin made of a Ni alloy is brazed to a base made of AlN via a silver solder, cracks occur near the brazed portion between the base of AlN and the lead pin made of Ni alloy. Occurs, and the Ni alloy lead pin comes off.

In a conventional semiconductor device in which a lead pin made of a Ni alloy is brazed to a base made of AlN via silver brazing, the angle between the brazing end of the base and the silver brazing is about 55 degrees. Is.

[0007]

As mentioned above, Al
When N and Ni alloys are brazed via silver brazing, the coefficients of thermal expansion of the two are very different, so residual thermal stress is generated near the brazing part due to temperature change during brazing, and cracks occur in AlN. Therefore, there was a problem with the reliability of brazing.

The present invention has been made for the purpose of solving the above problems, and when AlN and a Ni alloy are brazed together through a silver braze, the AlN is prevented from cracking and a highly reliable brazing is performed. It is intended to provide a brazing method that can be used.

[0009]

In order to solve the above-mentioned problems, the present invention is such that, when brazing AlN and Ni alloy through silver brazing, the angle of the brazing end of AlN and silver brazing is The silver brazing amount is adjusted to be in the range of about 11 degrees to 38 degrees, and the amount of the silver brazing material is adjusted so that the silver brazing is almost completely protruded from the vertical line drawn from the end surface of the nickel alloy to the aluminum nitride side. It is characterized by brazing.

[0010]

When AlN and the Ni alloy are brazed with each other through silver brazing, residual thermal stress is generated due to the difference in the thermal expansion coefficient between the AlN and the Ni alloy due to the temperature change at the time of brazing. Between the residual thermal stress in the brazing of Al and Ni alloy and the angle of the brazing end of AlN and silver brazing (hereinafter referred to as the silver brazing angle) θ, the relationship between the amount of silver brazing and the silver brazing angle θ, etc. As a result of repeated diligent research on the above, it was found that there is a relationship as shown in FIGS.

FIG. 4 shows a base 10 made of AlN and Ni, for example.
FIG. 3 is a diagram showing a distribution of residual thermal stress in the case where an alloy pin 11 is brazed with a silver solder 12, and a maximum stress F is generated on the surface of the AlN base 10 near the skirt of the silver solder 12. A
There is a relationship between the maximum stress F on the surface of the base 10 made of 1N and the wetting angle θ of silver brazing as shown by the solid line A in FIG. Further, there is a relationship as shown by a broken line B in FIG. 5 between the silver brazing leak angle θ and the maximum stress G of the pin 11 when a tensile load is applied to the brazed Ni alloy pin 11.

As is clear from this figure, the maximum stress F on the surface of the base 10 made of AIN becomes smaller as the leakage angle θ of the silver brazing becomes smaller, and when the tensile load is applied to the pin 11 made of Ni alloy. The maximum stress G of the pin 11 is as the silver brazing angle θ becomes smaller.
Although it becomes small like the maximum stress F on the surface, it becomes larger when the silver brazing leak angle θ becomes about 11 degrees.

Further, as shown in FIG. 6 to FIG.
When the Ni alloy pin 11 is brazed to the base 10 made of silver through the silver solder 12, the leak angle θ of the silver solder changes depending on the amount of the silver solder 12, and as the amount of the silver solder 12 decreases, the silver solder leaks. If the angle θ becomes smaller and becomes smaller than a certain amount, it becomes large conversely. That is, the relationship between the silver brazing amount and the silver brazing leak angle θ is as shown in FIG. As is clear from this figure, the minimum value of the silver braze leak angle θ was about 11 degrees.

The solid line C in FIG. 11 indicates the amount of silver braze when the Ni alloy pin 11 is brazed to the above-mentioned AIN base 10 via the silver brazing filler 12 and the maximum of the surface of the AIN base 10. The relationship with the stress F, the broken line D shows the relationship between the amount of silver brazing and the maximum stress G of the pin 11 when a tensile load is applied to the brazed Ni alloy pin 11.

As is apparent from FIGS. 10 and 11, when the amount of silver brazing is reduced, the maximum stress F on the surface of the base 10 made of AIN at the time of brazing when the brazing angle θ is small.
And the maximum stress G at the time of pulling the pin 11 made of Ni alloy is almost the same. However, when the amount of silver brazing is reduced when the silver brazing leak angle θ is large, the maximum stress G when pulling the pin 11 made of Ni alloy is much larger than the maximum stress F on the surface of the base 10 made of AIN. growing.

That is, as shown in FIGS. 8 and 9, the maximum stress G at the time of pulling the pin 11 made of Ni alloy is such that the silver solder 12 is from the end face of the pin 11 made of Ni alloy to the base 10 made of AIN. It is small when it sticks out almost completely from the perpendicular L drawn to the side (FIG. 8), and it becomes large when the silver solder 12 bites inside the perpendicular L (FIG. 9).

FIG. 12 shows the relationship between the occurrence rate of fracture and the leakage angle θ of the silver solder when a tensile fracture test is performed on the Ni alloy pin 11 brazed to the AIN base 10 with the silver solder 12. Is shown.

As is apparent from FIGS. 5 and 12, the silver braze leak angle θ is approximately 38 degrees or less, and as described above, the silver braze 12 is from the end surface of the pin 11 made of Ni alloy to the base made of AIN. If it is made to protrude completely from the perpendicular line drawn to 10, the residual thermal stress of the AIN base 10 becomes less than the maximum stress F (50 MPa) of this base 10, and the fracture occurrence rate at the brazing portion is almost the same. It becomes zero.

The present invention sets the silver brazing angle based on the relationship between the amount of silver brazing and the silver brazing angle found by the above experimental results, and the silver brazing is drawn from the end surface of the Ni alloy to the aluminum nitride side. By adjusting the amount of silver brazing so that the brazing can be almost completely protruded from the vertical line, it is possible to prevent cracking of AlN and perform highly reliable brazing.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to an embodiment shown in the drawings.

1 and 2 are enlarged cross-sectional views showing a brazing portion of the semiconductor device shown in FIG. 3, respectively. In a semiconductor device 1 shown in FIG. 3, a cap 4 made of a Ni alloy is bonded to an upper portion of a base (substrate) 3 made of AlN on which a semiconductor chip 2 is mounted so as to cover the semiconductor chip 2, and a base 4 is formed. At the bottom of 3, the lead pin 6 made of Ni alloy
Are brazed via the silver brazing 5a. As shown in FIG. 2, the lower surface of the cap 4 is formed by laser bonding or Au-Sn.
The Ni alloy seal ring 7 is joined by joining or the like, and the lower surface of the seal ring 7 is connected to the base 3 via the silver solder 5b.
It is touched by a sword.

To braze the base 3 made of AlN and the lead pin 6, a ball-shaped silver solder 5 is placed on the brazing surface of the lead pin 6 on the base 3 side, and the lead pin 6 is coated with a metal film. Set it to the specified position on the base 3
It is performed by heating the silver solder 5 to a predetermined temperature. In addition, brazing of the seal ring 7 joined to the base 3 and the cap 4 is performed in the same manner.

In this case, the silver brazing angle θ of the base 3 and the seal ring 7 of the cap 4 and the brazing portion of the base 3 and the lead pin 6 is in the range of about 11 to 38 degrees as described above. Thus, the amount of silver solder 5 (in this case, the amount of silver solder is about 0.07 to 0.16 mg, as shown in FIG. 10) is adjusted and brazing is performed.

As the silver brazing wetting angle θ becomes smaller as shown in FIG. 5, the maximum stress becomes smaller.
It is better to have a low angle (for example, about 12 to 25 degrees in consideration of manufacturing accuracy error) in the range of degrees. Further, the thickness of the brazing portion between the base 3 and the cap 4 and between the base 3 and the lead pin 6 is several microns.

Further, as described above, the base 3 made of AIN is used.
Since it is possible to reduce the stress acting on the Ni alloy lead pins 6 to be brazed to the lead pins, when the lead pins are mounted at high density in a semiconductor device, the lead pin joining area is reduced by narrowing the lead pin intervals. Even
No problem occurs in the bonding strength of the lead pin.

Further, in the above embodiment, the brazing of the base 3 and the cap 4 and the base 3 and the lead pin 5 of the semiconductor device 1 was described, but other than this, AlN and the Ni alloy are brazed. It is applicable to brazing in all devices.

In the above embodiment, the brazing of AlN and Ni alloy was described.
_{Even in the combination of 2} O ₃ , glass epoxy resin, copper alloy, Si, etc. It is possible to perform brazing with high quality.

[0028]

As described above in detail with reference to the embodiments, according to the present invention, the residual thermal stress at the brazing portion between AlN and Ni alloy is reduced to prevent the cracking of AlN. As a result, reliable brazing can be performed.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a method of soldering a semiconductor device according to the present invention.
It is an expanded sectional view showing an example applied to brazing of a base made of N and a lead pin made of Ni alloy.

FIG. 2 is a schematic view showing a method for soldering a semiconductor device according to the present invention.
It is an expanded sectional view showing an example applied to brazing of a base made of N and a cap made of Ni alloy.

FIG. 3 is a cross-sectional view showing a semiconductor device.

FIG. 4 is a diagram showing a distribution of residual thermal stress on an AlN surface of a brazed portion of AlN and a Ni alloy.

FIG. 5 shows the relationship between the silver braze leak angle at the brazing part of AlN and the Ni alloy and the maximum stress of the AIN surface, and the silver braze leak angle and the maximum stress of the Ni alloy when a tensile load is applied to the Ni alloy. It is a figure which shows a relationship.

FIG. 6 is an explanatory diagram showing an example of a wetting angle of silver brazing material in a brazing portion of AlN and Ni alloy.

FIG. 7 is an explanatory diagram showing an example of a wetting angle of silver brazing material in a brazing portion of AlN and Ni alloy.

FIG. 8 is an explanatory diagram showing an example of a wetting angle of silver solder in a brazing portion of AlN and Ni alloy.

FIG. 9 is an explanatory diagram showing an example of a wetting angle of silver brazing material in a brazing portion of AlN and Ni alloy.

FIG. 10 is a diagram showing a relationship between a silver brazing amount and a brazing angle of silver brazing in a brazing portion of AlN and Ni alloy.

FIG. 11: Silver brazing amount and A at brazing part of AlN and Ni alloy
It is a figure which shows the relationship with the maximum stress of the IN surface, and the relationship between the amount of silver brazing when a tensile load is applied to the Ni alloy, and the maximum stress of the Ni alloy.

FIG. 12 is a diagram showing a relationship between a fracture occurrence rate at a brazing portion of AlN and a Ni alloy and a silver brazing angle.

[Explanation of symbols]

 1 semiconductor device 2 semiconductor chip 3 base 4 cap 5 silver solder 6 lead pin

Claims (1)

[Claims] 1. When brazing aluminum nitride and a nickel alloy through a silver braze, the angle of the brazing end of the aluminum nitride and the silver braze is in the range of about 11 degrees to 38 degrees. A brazing method in which the amount of the silver brazing is adjusted so that the silver brazing sticks out almost completely from a vertical line drawn from the end surface of the nickel alloy to the aluminum nitride side, and brazing is performed.