JP3068224B2 - Semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

 [Object of the invention]

[0001]

The present invention relates to, for example, PGA (Pin Gr)
id semiconductor package).

[0002]

2. Description of the Related Art As is well known, with the increase in density and scale of integrated circuits, ceramic substrates having excellent thermal conductivity and electrical characteristics have been used in semiconductor devices. I have. On the surface of the ceramic substrate, metal lead pins and lead wires for connection to an external circuit, pin fins for cooling, and the like are brazed and used.

As one of the semiconductor devices using such a ceramic substrate, a PGA type semiconductor device will be described with reference to the drawings. FIG. 6 is a sectional view, and FIG. 7 is a sectional view of a main part. In the figure, reference numeral 1 denotes a multilayer ceramic substrate provided with internal wiring, which is formed of, for example, aluminum nitride (AlN). Reference numeral 2 denotes a semiconductor element provided in the concave portion 3 on the lower surface side of the substrate 1, and the electrode portion of the semiconductor element 2 is connected to a terminal of the internal wiring of the substrate 1 by a bonding wire 4. On the lower surface of the substrate 1, a cap 5 for closing the recess 3 so as to enclose the semiconductor element 2 is fixedly provided with a seal ring 6 provided therearound.

Reference numeral 7 denotes a connecting portion of a metal film formed on the upper surface of the substrate 1 by sputtering or the like, which is connected to a via hole of an internal wiring. And connection part 7
A shaft lead pin 10 in which a large-diameter head 8 at the end is brazed using a brazing material 9 is implanted. The lead pin 10 is made of a metal material, and its surface is plated with a metal having a high affinity for the brazing material in order to increase the wettability to the brazing material.

[0005] However, in the above prior art,
When the lead pins 10 are implanted on the substrate 1, the head 8 is soldered to the connection portion 7. In the soldering, the molten brazing material 9 reaches a state determined by the surface condition of the lead pins 10.
It flows and solidifies without restraint. At this time, the lead pin
The surface of 10 is plated so that the brazing material flows and solidifies farther from the brazing portion, and the wetting angle of the brazing material with respect to the surface of the connection portion 7 is large. .

[0006] The implantation of the lead pins 10 on the substrate 1 is as follows.
Despite the connection portion 7 of the metal film, it was not easy because the ceramics of the substrate and the metal of the shaft had different physical properties and the like. In particular, the coefficient of thermal expansion differs greatly between ceramics and metals, and the temperature changes due to brazing, that is, heating and cooling from room temperature to a temperature of about 800 ° C, depend on the difference in the coefficient of thermal expansion. The applied thermal stress is applied to the soldered portion of the substrate 1, and the implanted lead pins 10 fall off the substrate 1 while being soldered to the connection portion 7, or crack the substrate 1 near the soldered portion. Or has occurred. Further, the substrate 1
When the cracks occur, the fixing strength of the lead pins 10 to the substrate 1 is reduced, and an electrical connection failure or non-contact may occur over time, which may reduce the reliability of the semiconductor device.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described situation where a problem caused by thermal stress due to a difference in thermal expansion coefficient occurs in a brazed portion between a ceramic and a metal as described above. It is an object of the present invention to provide a semiconductor device in which the thermal stress applied to a substrate is reduced to solve problems such as dropping and cracking of a shaft fixed on the substrate and reliability is improved.

[Structure of the Invention]

[0009]

According to the present invention, there is provided a semiconductor device comprising:
A substrate on which semiconductor elements are mounted and a substrate formed on the surface of the substrate;
It is a connecting portion of the metal film, the made and a shaft which is fixed the end in contact with the wax on the top surface of the connecting portion, wherein
Shaft includes a shaft portion, which has a large-diameter plate-shaped head from the shaft portion provided on the connecting end portion of the shaft portion, said head
From the end to a predetermined position of the end
To the brazing material between the plated and unplated parts.
It is characterized by a difference in wettability
You.

[0010]

The semiconductor device constructed as described above has a
At the end of the shaft that is brazed upward, between the head and the shaft
By applying a plating having a high affinity to the brazing material to a predetermined position of the end portion , a difference is made in the wettability to the plating portion and other portions, so that the wetting angle of the brazing material to the brazing surface is reduced. I have. And, since the wetting angle of the brazing material is reduced, the residual thermal stress applied to the brazed portion with the temperature change after joining is also reduced. Can be reduced, the shaft fixed to the substrate does not fall off, and the substrate does not crack, and the reliability can be improved. Also, from the head to the shaft
Since the brazing material is filled in the space between the beam and the end portion up to a predetermined position, the bending rigidity at the end portion of the shaft body is high.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. The present invention is based on the knowledge obtained by experiments of the inventors, and according to this knowledge, a shaft such as a pin is formed on a ceramic substrate by brazing, and a metal formed on a substrate surface is formed. When fixed through a thin film, the residual thermal stress applied to the ceramic substrate changes depending on the wetting angle of the brazing material with respect to the ceramic substrate surface, that is, the metal thin film surface. As a result, the residual thermal stress applied to the ceramic substrate at the brazing portion is reduced.

First, a first embodiment will be described with reference to FIG. FIG. 1 is a cross-sectional view of a main part. In the figure, reference numeral 11 denotes a multilayer ceramic substrate provided with internal wirings, which corresponds to the substrate 1 in the above-described conventional technique, and is formed of, for example, aluminum nitride (AlN). A semiconductor element on which predetermined wiring is performed by a bonding wire or the like is provided in a concave portion formed on the lower surface side, and the concave portion is closed by a cap. Reference numeral 12 denotes a thin film formed on the upper surface of the substrate 11 by sputtering in the order of nickel (Ni), titanium (Ti), and gold (Au).
A connection portion of a metal thin film formed by plating, and this connection portion 12 is connected to a via hole of an internal wiring.

Reference numeral 13 denotes a shaft lead pin formed of a nickel (Ni) -iron (Fe) alloy. The lead pin 13 has a round bar-shaped shaft portion 14 and a head portion 15 at one end. For example, the surface is plated with Au or Ni. Also, the head 15 is smaller than the connecting portion 12, has a larger diameter than the shaft portion 14, has a substantially arc-shaped outer peripheral surface in the axial cross section, and is provided at an intermediate portion of the head 15 in the axial direction. Is formed with a circumferential groove 16 having a rectangular cross-sectional shape, whereby flanges 17a and 17b are formed on both circumferential edges of the groove 16.

A lead pin 13 is implanted in the connection portion 12 by brazing using a silver braze 18 as a brazing material, with the end face of the head 15 of the lead pin 13 facing the upper surface of the connection portion 12. In addition, between the surface of the connection portion 12 and the end surface of the head portion 15, and the outer peripheral edge of the connection portion 12 and the flange portion 17 on the end surface side of the head portion 15.
The space formed between a and silver is filled with the silver solder 18 melted at the time of soldering by flowing due to surface tension. 19 is
The wetting angle of the silver solder 18 with respect to the surface of the connection portion 12 at this time. If the amount of the silver solder 18 during brazing is further increased, the silver solder 18 flows so as to fill the groove 16 of the head 15.

According to the present embodiment constructed as described above, the groove 16 is formed in the head 15 provided at the end of the lead pin 13 as means for reducing the wetting angle of the brazing material. The position of the silver solder 18 filled in the space around the flange 17a at the time of soldering at the lead pin 13 is the position of the periphery of the flange 17a. In addition, the wetting angle 19 with respect to the upper surface of the connection portion 12 is substantially determined by the thickness of the flange portion 17a of the head portion 15, and is constant until the silver braze 18 finishes filling the groove 16. Since the wetting angle 19 at this time has the groove 16 as a means for reducing the wetting angle, it has a smaller value than that shown in the above-mentioned prior art.

Then, the wetting angle of the silver solder 18 at the soldered portion
Since 19 can be maintained at a small value, the thermal stress applied to the substrate 11 is small, no crack is generated in the substrate 11 near the connection portion 12, and the lead pins 13 brazed to the connection portion 12 do not fall off. Further, the amount of the silver solder 18 to be brazed is between the surface of the connection portion 12 and the end surface of the head portion 15, and the outer peripheral edge of the connection portion 12 and the flange portion 17a.
The wetting angle 19 can be maintained at an almost constant small value even if the amount of space fills the groove 16 from the amount filling the space formed with the peripheral edge of the silver braze 18. The small thermal stress of the substrate 11 does not change with the change,
No cracks occur in the substrate 11 near the
There is no dropping of the lead pin 13 soldered to. As described above, in the present embodiment, in addition to the fact that the manufacturing variation in the amount of the silver solder 18 can be absorbed by the groove 16, the bending rigidity of the lead pin 13 can be increased by filling the silver solder 18 in the groove 16. Can be. Then, high reliability of the semiconductor device can be maintained without causing electrical connection failure or non-contact over time.

Next, a second embodiment will be described with reference to FIG. FIG. 2 is a cross-sectional view of a main part. In FIG.
A shaft lead pin formed of an Fe alloy,
The lead pin 21 has a shaft portion 22 and a connection portion at one end.
Two flanges 23a smaller than 12 and larger in diameter than the shaft 22;
And a head portion 24 which is formed so as to be spaced apart from each other in the axial direction. The two flanges 23a and 23b have different thicknesses, and the thinner flange 23a is located on the outermost end side to form an end face. Between the flanges 23a and 23b, A circumferential groove 25 having an arc-shaped cross section is formed. And the lead pin 21
In the same manner as in the first embodiment, brazing is performed by using a brazing material such as silver brazing material so that the end surface of the head portion 24 faces the upper surface of the connecting portion 12. 27 is the connection part
This is the wetting angle of the silver solder 26 on the 12 faces.

Also in the present embodiment having the above-described structure, the flange 24a and the groove 25 are formed in the head 24 as means for reducing the wetting angle of the brazing material. The same operation and effect as described above can be obtained. Since the thickness of the flange portion 23a is reduced, the wetting angle 27 of the silver solder 26 can be reduced, which is effective in reducing the thermal stress applied to the substrate 11.

Next, a third embodiment will be described with reference to FIG. FIG. 3 is a cross-sectional view of a main part.
A shaft lead pin formed of an Fe alloy,
The lead pin 28 has a round bar-shaped shaft 29 and a head 30 at one end. The head portion 30 is a thick disk having a smaller diameter than the connecting portion 12 and a larger diameter than the shaft portion 29 and having an arc-shaped outer peripheral surface in an axial cross-sectional shape. An outer surface 31 plated with Ni is provided from the position to the end surface.

The lead pins 28 are provided on the brazing material such that the end surfaces of the heads 30 face the upper surfaces of the connecting portions 12.
It is planted by brazing using 32. The space formed between the surface of the connection portion 12 and the end surface of the head 30 and the space formed between the outer peripheral edge of the connection portion 12 and the plated outer surface 31 of the head 30 are filled with soldering. The molten silver solder 32 flows and is filled. 33 is a wetting angle of the silver solder 32 with respect to the surface of the connection portion 12.

In the above-mentioned structure, the head 30 provided at the end portion is Ni-plated on a silver braze 32, for example, which has a high affinity with the brazing material, for example, partially to a predetermined position. The outer surface 31 is formed, and when soldering, the silver brazing between the plated outer surface 31 and other unplated surfaces
From the difference in wettability with respect to 32, the position where the silver solder 32 flows is first determined in a range up to the periphery of the outer surface 31. Then, the solder angle 32 of the soldered silver 32 with respect to the upper surface of the connection portion 12 is determined by the plating position of the head 30. As described above, the wetting angle 33 is smaller than that shown in the above-described prior art because the partially plated outer surface 31 is provided as means for reducing the wetting angle.

As described above, also in this embodiment, since the wetting angle 33 of the silver solder 32 at the soldered portion can be maintained at a small value,
The thermal stress applied to the substrate 11 is small, and
No cracks occur, and the lead pins 28 brazed to the connection portion 12 do not fall off. Then, high reliability of the semiconductor device can be maintained without causing electrical connection failure or non-contact over time.

Next, a fourth embodiment will be described with reference to FIG. FIG. 4 is a cross-sectional view of a main part.
A shaft lead pin formed of an Fe alloy,
The lead pin 34 has a round bar-shaped shaft 35 and a head 36 at one end. The head 36 has a truncated cone shape smaller in diameter than the connection portion 12 and larger in diameter than the shaft portion 35, and has a large diameter surface of the truncated cone as the outermost end surface. And an outer surface 37 plated with Ni.

In the same manner as in the third embodiment, the lead pin 34 is implanted by brazing using a silver braze 38 as a brazing material so that the end surface of the head 36 is opposed to the upper surface of the connection portion 12. I have. In addition, spaces formed between the surface of the connection portion 12 and the end surface of the head portion 36 and between the outer peripheral edge of the connection portion 12 and the plated outer surface 37 of the head portion 36 have a The molten silver solder 38 flows and is filled. 39 is a wetting angle of the silver solder 38 with respect to the surface of the connection portion 12.

In the present embodiment having the above-described structure, the same operation and effect as those of the third embodiment can be obtained.

Further, a fifth embodiment will be described with reference to FIG. FIG. 5 is a cross-sectional view of a main part. In FIG.
A shaft lead pin formed of an Fe alloy,
The lead pin 40 has a round bar-shaped shaft portion 41 and a head 42 at one end.
The head portion 42 is formed in a disk shape having a relatively small thickness and a diameter smaller than the connecting portion 12 and larger than the shaft portion 41. An end portion of the lead pin 40 is formed from the head portion 42 to a predetermined position of the shaft portion 41 and provided with a Ni-plated outer surface 43.

As in the third embodiment, the lead pin 40 is implanted by brazing using a silver braze 44 as a brazing material with the end face of the head 42 facing the upper surface of the connection portion 12. I have. In addition, between the surface of the connection part 12 and the end face of the head part 42, between the outer peripheral edge of the connection part 12 and the peripheral edge of the head part 42, and further, the peripheral part of the head part 42 and the predetermined part of the plated shaft part 41 The space formed between the positions is filled with the silver solder 44 that has melted during the soldering. 45 is a silver solder 44 for the surface of the connection 12
Is the wetting angle.

In this embodiment configured as described above, the same operations and effects as in the third embodiment can be obtained. Further, since the space formed between the periphery of the head 42 and the predetermined position of the plated shaft 41 is filled with the silver solder 44, the bending rigidity at the end of the lead pin 40 can be increased.

The present invention is not limited to only the above embodiments, but may be changed as appropriate without departing from the scope of the invention, such as the material and shape of the shaft, the shape of the end and the shape of the groove. It can be implemented.

[0030]

As is apparent from the above description, the present invention is characterized in that the end of the shaft fixed to the ceramic substrate by brazing is provided with means for reducing the wetting angle of the brazing material. Further, it is possible to reduce the thermal stress applied to the substrate, to prevent the shaft fixed to the substrate from falling off, to prevent the substrate from cracking, and to improve the reliability.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part showing a first embodiment of the present invention.

FIG. 2 is a sectional view of a main part showing a second embodiment of the present invention.

FIG. 3 is a sectional view showing a main part of a third embodiment of the present invention.

FIG. 4 is a sectional view showing a main part of a fourth embodiment of the present invention.

FIG. 5 is a sectional view showing a main part of a fifth embodiment of the present invention.

FIG. 6 is a sectional view showing a conventional example.

FIG. 7 is a sectional view of a main part in FIG. 6;

[Explanation of symbols]

 11 Ceramic substrate 12 Connection part 13 Lead pin (shaft) 15 Head (end) 16 Groove (means for reducing wetting angle) 18 Silver solder (brazing material) 19 Wetting angle

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-61-96754 (JP, A) JP-A-63-116379 (JP, A) JP-A-63-91986 (JP, A) 43849 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) H01L 23/12 H01L 23/50

Claims (1)

(57) [Claims] 1. A substrate on which a semiconductor element is mounted, and the substrate
A connecting portion of a metal film formed on the surface of the connecting portion, and a shaft fixed to the upper surface of the connecting portion by brazing the end portion, wherein the shaft is a shaft, A plate-shaped head having a larger diameter than the shaft provided at the connection end of the portion, and the end portion between the head and the shaft.
Plating to the fixed position, plating part and non-plating part
It is characterized by the difference in wettability to brazing material between
Semiconductor device.