JPH0697347A - Semiconductor device - Google Patents

Abstract

PURPOSE:To provide a semiconductor device in which reliability is enhanced at the time of mounting. CONSTITUTION:Since a lead pin 15 planted on an enclosure 12 has a rectangular cross section where the flexural rigidity varies depending on the direction, relative deformation between a circuit board 17 and the enclosure 12 is absorbed through deformation of the lead pin 15 in same direction as the relative deformation, i.e., the direction of the long side face 16 where the flexural rigidity on the cross section is low, at the time of mounting the enclosure 12 on the circuit 17 thus suppressing thermal stress at a brazed part 20 of the lead pin 15. Consequently, fracture due to thermal fatigue is suppressed at the brazed part 20 resulting in the enhancement of reliability at the time of mounting.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device having improved reliability during mounting.

[0002]

2. Description of the Related Art As is well known, with the sophistication and multi-functionalization of equipment in which semiconductor devices are mounted, semiconductor chips are becoming highly integrated and large-scaled. The number of lead pins connected to a circuit board is extremely large, and the envelope is large. Then, for example, PGA (PinG
In the case of a rigid array package type semiconductor device or the like, there is a problem that reliability is deteriorated when it is mounted on a device or the like due to a larger envelope shape, a larger number of lead pins, a smaller pin pitch, and an increase in heat generation. There is a possibility that it will occur.

A conventional technique will be described below with reference to FIGS. 4 and 5. FIG. 4 is a plan view showing a schematic standing state of the lead pin, and FIG. 5 is a partially enlarged perspective view at the time of mounting.

In FIGS. 4 and 5, a semiconductor device 1 has a semiconductor chip 3 mounted inside a rectangular envelope 2, and the envelope 2 is made of, for example, a ceramic material or an epoxy resin material. It is configured by stacking a plurality of substrates. In addition, a large number of lead pins 5 having a circular cross-sectional shape are erected on each edge portion of the lower surface 4 of the envelope 2 so as to form a plurality of rows parallel to each edge. Although not shown, the electrodes of the semiconductor chip 3 are connected to the lead pins 5 inside the envelope 2 by connecting wires inside the envelope 2, and the semiconductor corresponding to the lead pins 5 is thereby connected. The electrodes of the chip 3 are electrically connected.

On the other hand, the semiconductor device 1 thus configured
The circuit board 6 on which is mounted is formed of, for example, an epoxy resin material containing polyimide resin, glass filler, or the like. Further, in the portion of the circuit board 6 where the semiconductor device 1 is mounted, the connection portions 7 are arranged corresponding to the lead pins 5 at the same pitch as the lead pins 5. Then, the semiconductor device 1 is mounted on the circuit board 6 by brazing the ends of the lead pins 5 to the connecting portions 7 of the circuit board 6 with the brazing material 8.

However, in the device configured as described above, when the semiconductor device 1 mounted on the circuit board 6 is operated, the semiconductor chip 3 generates heat and the ambient temperature rises, so Relative deformation occurs between the circuit boards 6 due to the difference in linear expansion coefficient of the materials used, and the tip portion of the lead pin 5 and the connecting portion 7 having a substantially uniform diameter.
Thermal stress is generated in the portion where the brazing joint 9 is formed.

The coefficient of linear expansion is, for example, about 13 to 14 × 10 ⁻⁶ for the circuit board 6 made of epoxy resin, whereas it is about 4 to 8 × 10 for the ceramic envelope 2.
^It is as small as about ^−6, and in the case of the envelope 2 made of epoxy resin, it is as large as about 20 × 10 ⁻⁶ .
The stress generated in the portion where the solder joint 9 is formed is larger as the envelope 2 is larger, the amount of heat generated is larger, and the distance from the mounting portion of the semiconductor chip 3 is larger.
The greater the value, the greater the value.

Further, by using the mounted equipment, the semiconductor device 1 is repeatedly operated and stopped, and the temperature rises and falls. Along with this, the brazing 9 by repeated relative deformation occurs.
There is a high possibility that thermal fatigue failure will occur in the damaged part.
As a result, a crack 10 may occur in the brazing material 8 at the portion where the brazing is performed 9 with time. As a result, the reliability of mechanical and electrical connection at the portion where the brazing 9 is performed is reduced.

[0009]

When the semiconductor device is mounted on the circuit board as described above, thermal fatigue damage occurs in the brazing joint portion of the lead pin erected on the envelope due to repeated rise and fall of temperature. The cracking reduces the reliability of mechanical and electrical connection of the brazed joint. The present invention has been made in view of such a situation,
It is an object of the invention to provide a semiconductor device in which the occurrence of thermal fatigue fracture of a brazing joint portion is suppressed at the time of mounting and the reliability is improved.

[0010]

The semiconductor device of the present invention comprises:
In a semiconductor device in which a plurality of lead pins are provided upright in an envelope on which a semiconductor chip is mounted, at least a part of the lead pins is characterized in that the bending rigidity of the cross section of the lead pins differs depending on the direction. In addition, at least a part of the lead pins has a rectangular cross-sectional shape, and further, at least a part of the lead pins has a lateral cross-section of the lead pin in a direction in which the bending rigidity decreases. The feature is that it is erected so as to face the center.

[0011]

In the semiconductor device configured as described above, since at least a part of the lead pin erected on the envelope has a shape in which the bending rigidity of the cross section varies depending on the direction, it is mounted on a circuit board and operated. The relative deformation between the circuit board and the envelope that occurs at that time is absorbed by the bending deformation of the lead pin in the direction in which the bending rigidity of the cross section is small, and the thermal stress at the brazing portion of the lead pin is reduced. As a result, the occurrence of thermal fatigue fracture of the brazing joint is suppressed, and the reliability during mounting is improved.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 1 is a side view, FIG. 2 is a plan view showing a schematic standing state of lead pins, and FIG. 3 is a partially enlarged perspective view at the time of mounting.

In FIGS. 1 to 3, the semiconductor device 11 has a semiconductor chip 13 in a recess provided in the central portion of a quadrangular envelope 12, and the semiconductor chip 13 is mounted with a polyimide resin, an epoxy resin, or gold (Au). It is fixedly mounted with solder or the like. The envelope 12 is made of, for example, alumina (Al
₂ O ₃₎ , aluminum nitride (AlN), or another ceramic material or an epoxy resin material is laminated on a plurality of substrates. Many lead pins consisting of 15
Are erected by silver brazing on a thin film land provided on the lower surface 14 so as to form a plurality of rows parallel to each side.

Further, the lead pin 15 has the same cross-sectional area or outer peripheral length so that the electrical characteristics are the same as those of the conventional one, and the bending rigidity of the cross section differs depending on the direction, for example, the cross section has a rectangular shape. Further, each lead pin 15 has a surface in the direction in which the bending rigidity of the cross section is small, that is, a surface 16 on the long side of the rectangle, and
The two semiconductor chips 13 are erected so as to face toward the central portion where the semiconductor chips 13 are mounted. Although not shown, the electrodes of the semiconductor chip 13 are connected to the terminals inside the envelope 12 that are electrically connected to the lead pins 15 inside the envelope 12 by connecting wires, whereby the semiconductor corresponding to the lead pins 15 is connected. The electrodes of the chip 13 are electrically connected.

On the other hand, the semiconductor device 1 thus configured
The circuit board 17 on which 1 is mounted is similar to that of the prior art,
For example, it is formed of an epoxy resin material containing polyimide resin or glass filler, and the like, and in the portion where the semiconductor device 11 is mounted, the connection portions 18 corresponding to the lead pins 15 and arranged at the same pitch as the lead pins 15. Is provided.

To mount the semiconductor device 11 on the circuit board 17, the lead pin 15 is attached to the connecting portion 18 of the circuit board 17.
The tip portion of the brazing material 20 is brazed with the brazing material 19 by, for example, reflow soldering performed in an atmosphere of 200 ° C. or higher.

With this configuration, when the semiconductor device 11 mounted on the circuit board 17 is operated, the semiconductor chip 13 generates heat and the ambient temperature rises, so that the envelope 12 of the semiconductor device 11 and the circuit board 17 are heated. In the meantime, relative deformation due to the difference in linear expansion coefficient of each used material occurs mainly in the radial direction around the semiconductor chip 13 which is the heating source, and the temperature rises and falls due to the operation / stop of the semiconductor device 1. Repeatedly, the relative deformation is repeated along with this, and occurs in the same direction.

On the other hand, the rectangular lead pins 15, both ends of which are fixed to the envelope 12 and the circuit board 17, are arranged such that the surface 16 on the long side is directed toward the central portion where the semiconductor chip 13 is mounted. The surface 1 on the long side, which is erected and is more easily bent depending on the amount of the relative deformation between the envelope 12 and the circuit board 17 toward the central portion of the envelope 12.
It is absorbed by bending and deforming in the direction of 6.

As a result, the thermal stress generated in the portion where the lead pin 15 is brazed to the connecting portion 18 of the circuit board 17 is reduced, thermal fatigue fracture is less likely to occur, and cracks occur in the brazing material 19 at the joint over time. Less likely to occur. As a result, reduction in reliability of mechanical and electrical connection of the portion where the brazing 20 is performed is suppressed.

In the above embodiment, all the lead pins 15 provided upright on the envelope 12 have a rectangular cross-sectional shape, but the lead pins 15 have an elliptical shape in which the bending rigidity of the cross-section varies depending on the direction. Other shapes may be provided so that the direction in which the bending rigidity of the cross section is small matches the direction in which the relative deformation between the envelope 12 and the circuit board 17 occurs, and the lead pin 15 is not entirely installed. A part of the lead pin 15 at a portion distant from the mounting portion of the semiconductor chip 13 where the amount of relative deformation is large.
The shape can be changed as appropriate within the scope not departing from the gist of the invention, for example, the bending rigidity of the cross section varies depending on the direction.

[0021]

As is apparent from the above description, according to the present invention, at least a part of the lead pins erected on the envelope is configured so that the bending rigidity of the cross section differs depending on the direction. Occasionally, the occurrence of thermal fatigue fracture of the brazed joint is suppressed, and the reliability is improved.

[Brief description of drawings]

FIG. 1 is a side view showing an embodiment of the present invention.

FIG. 2 is a plan view showing a schematic standing state of the lead pin in the above.

FIG. 3 is a partially enlarged perspective view at the time of mounting in the above.

FIG. 4 is a plan view showing a schematic standing state of a lead pin of a conventional example.

FIG. 5 is a partially enlarged perspective view of the above-mentioned mounting.

[Explanation of symbols]

 12 ... Envelope 13 ... Semiconductor chip 15 ... Lead pin 16 ... Long side surface 17 ... Circuit board 18 ... Connection part 20 ... Brazing joint

Claims (3)

[Claims] 1. In a semiconductor device in which a plurality of lead pins are provided upright in an envelope on which a semiconductor chip is mounted, at least a part of the lead pins has different bending rigidity in a cross section of the lead pin depending on the direction. A semiconductor device characterized by the above. 2. The semiconductor device according to claim 1, wherein at least a part of the lead pins has a rectangular cross-sectional shape. 3. The at least part of the lead pin is erected so that the direction in which the bending rigidity of the cross section of the lead pin becomes smaller is directed toward the center of the envelope. Semiconductor device.