JPH0936280A - Package structure for resin encapsulation - Google Patents

Abstract

(57) Abstract: [PROBLEMS] To provide a package structure for resin encapsulation that can prevent the generation of voids during resin encapsulation and can improve heat conductivity and hygroscopicity. A cavity 37 for housing a chip 33 is provided in a base frame 21, and a resin 39 is injected into the cavity 37 to seal the chip 33 in a resin sealing package structure. A tapered cavity inner wall surface 23 formed with an obtuse angle is formed on the base frame 21.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a resin encapsulation package, and more particularly to improvement of a cavity shape of a chip accommodating portion.

[0002]

2. Description of the Related Art One of the ceramic packages that are resin-sealed is a ceramic DIP (dual in-line package) used for a linear sensor. As shown in FIG. 3, a conventional ceramic DIP uses a base frame 1 made of Al ₂ O ₃ or the like, and a concave cavity 5 for accommodating a chip 3 is formed in the base frame 1. The bottom surface of the cavity 5 serves as a chip attach surface 7, and the inner wall surface 9 of the cavity serves as an upright surface formed perpendicularly to the chip attach surface 7. N for base frame 1
Lead frame 11 made of i-Fe alloy or the like, and A
The window frame 13 made of l ₂ O ₃ or the like is brazed by the low melting point glass 15. Then, after the chip mounting, the resin 17 such as silicone resin is injected into the concave cavity 5 and the chip 3 is resin-sealed, thereby completing the packaging.

[0003]

However, in the conventional package structure, since the inner wall surface 9 of the cavity 5 is formed perpendicular to the chip attach surface 7, the corner portion between the chip attach surface 7 and the inner wall surface 9 is formed. In some cases, there was a void portion 19 that was not completely filled with the resin 17. When the package 20 is subjected to thermal stress under such a condition, the hole portion 1 is affected by the thermal stress difference between the package 20 and the resin 17.
There was a risk that stress would occur in the resin 9 and the resin 17 would be cracked. On the other hand, if the filler contained in the resin is reduced in order to reduce the viscosity of the resin 17 at the time of injection, the pores 19 are less likely to occur, but the thermal conductivity of the resin 17 itself is reduced. In addition, since the hygroscopicity also increases, heat dissipation and reliability of the chip are reduced. The present invention has been made in view of the above situation, and provides a package structure for resin encapsulation that can prevent generation of holes during resin encapsulation, and can also have good thermal conductivity and hygroscopicity. However, the purpose is to prevent the occurrence of cracks and improve reliability.

[0004]

In order to achieve the above object, the structure of a package structure for resin encapsulation according to the present invention is such that a cavity for housing a chip is provided in a base frame, and a resin is injected into the cavity. A package structure for resin encapsulation for encapsulating the chip, characterized by comprising a tapered cavity inner wall surface formed on the base frame and having an obtuse angle with respect to a chip attachment surface. Is.

When the resin is injected into the cavity, the air in the cavity is likely to move upward along the tapered inner wall surface of the cavity, and the generation of air pockets which are the cause of the holes is suppressed. Will be. In addition, by virtue of such an action, it becomes possible to use a resin having a higher viscosity that contains a larger amount of filler than in the past, and by this,
It is also possible to improve thermal conductivity and hygroscopicity.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of a resin sealing package structure according to the present invention will be described in detail below with reference to the drawings. FIG. 1 is a sectional view of a resin sealing package structure according to the present invention, and FIG. 2 is an explanatory diagram comparing the present invention and a conventional example with respect to viscosity / heat conductivity and moisture absorption. In the resin sealing package structure according to the present embodiment, the base frame 21
The cavity inner wall surface 23 is formed with an obtuse angle with respect to the chip attachment surface 25 which is the bottom surface of the cavity. That is, the cavity inner wall surface 23 has a taper shape that gradually expands from the chip attachment surface 25 toward the upper opening. Further, the window frame 29 is arranged on the base frame 21 with the lead frame 27 interposed therebetween, and the inner wall surface 31 of the window frame 29 also has a taper shape that gradually expands toward the upper opening. Has become. In the figure, 33 is a chip and 35 is a low melting point glass.

In the resin sealing package structure thus constructed, when the resin 39 is injected into the cavity 37, the air in the cavity 37 moves upward along the tapered cavity inner wall surfaces 23 and 31. This facilitates the movement, and suppresses the generation of air pockets that have caused the holes.

Therefore, due to such an action, in the package structure of this embodiment, the resin 39 having a higher viscosity than before can be used. That is, in the conventional package structure, in order to prevent the generation of the holes 19 (see FIG. 3), the amount of the filler contained in the resin 39 is kept small so that the viscosity of the resin 39 does not increase. Therefore, as shown in FIG. 2, the resin that can be used in the conventional structure is limited to the range A in which the amount of the filler is small, a sufficient thermal conductivity cannot be obtained, and the hygroscopicity is good. I couldn't do it. On the other hand, in the package structure of the present embodiment, it is possible to suppress the generation of voids even if the filler is increased, so that the resin 39 in the range B having a large amount of filler can be used, and Increasing the amount of agent will improve the thermal conductivity and hygroscopicity.

According to the above-mentioned package structure, the inner wall surfaces 23 and 3 of the base frame 21 and the window frame 29 are formed.
Since 1 has a tapered shape that allows air to easily escape, voids do not occur, and as a result, the occurrence of cracks due to voids can be prevented. In addition, since it is possible to use the resin 39 with an increased filler, it is possible to improve the thermal conductivity and the hygroscopicity.
Further, according to this embodiment, the resin sealing can be carried out without any trouble, so that the cost can be reduced as compared with the case where the sealing glass product is carried out.

In this embodiment, the inner wall surfaces 23 and 3 of both the base frame 21 and the window frame 29 are arranged.
Although 1 is tapered, the effect of the package structure of the present invention can also be exhibited by tapering the inner wall surface 23 of only the base frame 21. That is, the present invention also includes a structure in which the inner wall surface 31 of the window frame 29 is a surface perpendicular to the chip attachment surface 25 and only the inner wall surface 23 of the base frame 21 is tapered.

[0011]

As described above in detail, according to the package structure for resin sealing according to the present invention, the inner wall surface of the base frame is tapered so that air can easily escape, so that the air trap at the time of resin injection is not generated. No holes are formed. In addition, since the air easily escapes, it is possible to use a resin with an increased filler, which can improve the thermal conductivity and the hygroscopicity. As a result, it is possible to prevent the occurrence of cracks due to the holes and improve the reliability of the package.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a resin sealing package structure according to the present invention.

FIG. 2 is an explanatory diagram comparing the present invention and a conventional example with respect to viscosity / heat conductivity and moisture absorption.

FIG. 3 is a cross-sectional view of a conventional resin sealing package structure.

[Explanation of symbols]

 21 Base Frame 23, 31 Inner Wall Surface 25 Chip Attached Surface 29 Window Frame 33 Chip 37 Cavity 39 Resin

Claims (2)

[Claims] 1. A resin-sealing package structure, wherein a cavity for housing a chip is provided in a base frame, and a resin is injected into the cavity to seal the chip with a resin. On the other hand, a package structure for resin encapsulation, comprising a tapered cavity inner wall surface formed with an obtuse angle. 2. A tapered cavity inner wall surface formed on a window frame disposed on the base frame and having an obtuse angle with respect to a chip attachment surface. The package structure for resin sealing described.