JP2000012749A - Semiconductor package heat sink - Google Patents

Abstract

PROBLEM TO BE SOLVED: To miniaturize and make a heat sink light-weight by a method, wherein carbon fibers are arrayed in one direction, and this array is laminated, and a carbon fiber orientation of a carbon composite material obtained by impregnating a resin therein is structured so as to increase the thermal conductivity in a planar direction. SOLUTION: A carbon fiber has satisfactory thermal conductivity in a fiber direction. Thereby, the carbon fibers are arrayed in one direction, and this array is laminated and by having a resin impregnated therein solidified, a carbon composite material is obtained which has one orientation for the thermal conductivity. Such a carbon composite material having the orientation in thermal conductivity is cut out in a desirable magnitude so that the direction of the carbon fiber is set in a planar direction, and this is used as a heat spreader. If a heat sink composed of this carbon composite is used, namely using a heat spreader, radiation effects of the same level as copper are attained, and it is possible to constitute a package lighter than that when a copper plate or an aluminum plate is used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat sink used for a semiconductor package.

[0002]

2. Description of the Related Art In recent years, semiconductor packages are required to have higher density and higher integration, and the scale itself is becoming smaller and lighter. However, on the other hand, the amount of heat generated per unit area of the semiconductor package is significantly increased, and the semiconductor package itself may be broken in the conventional resin package. As a result, a heat spreader called a heat spreader is used for the semiconductor package to release the heat of the semiconductor package and protect the semiconductor package.

Since it is necessary to efficiently dissipate the heat generated by the semiconductor chip to the outside of the package, a metal radiator is usually used. However, although the metal plate is good in that it has excellent thermal conductivity, it has a drawback that it is heavy, which is against the miniaturization and weight reduction.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a novel heat sink which can be reduced in size and weight.

[0005]

SUMMARY OF THE INVENTION The present invention for solving the above-mentioned problems is to arrange carbon fibers in one direction, and to laminate this arrangement,
This is a heat radiating plate configured by using a carbon composite material obtained by impregnating a resin with the carbon composite material so that the carbon fiber orientation of the carbon composite material becomes higher in the thermal conductivity in a plane direction.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Carbon fibers have good thermal conductivity in the fiber direction. Therefore, if the carbon fibers are arranged in one direction, the arrangement is laminated, and the resin is impregnated and solidified, a carbon composite material having directionality with respect to thermal conductivity can be obtained.

In the present invention, such a carbon composite material having directionality in thermal conductivity is cut out to a desired size and the direction of the carbon fibers becomes a plane direction, and this is used as a heat spreader.

In the present invention, the heat spreader is arranged so that the direction of the carbon fibers is in the plane direction because the heat conductivity is good in the direction of the carbon fibers, so that the heat spreads quickly throughout the package and the heat dissipation is reduced. This is because it will be performed in. That is, by dissipating heat in the entire package, a local increase in heat load near the semiconductor chip is suppressed.

Next, the present invention will be further described with reference to a study example.

[0010] As a heat spreader material, a carbon composite material is cut out in various directions and produced, and it is assumed that the 84 PLCC type MCM-L shown in FIG. 1 is produced.
The thermal resistance of the heat spreader in an equilibrium state at a speed of m / s and a wind speed of 1 m / s was determined.

In this case, the fiber directions of the carbon fibers constituting the heat spreader are X direction, X and Y directions, X and Z directions.
Direction and Z direction. Then, as a comparison, the thermal resistance was similarly calculated on the assumption that a heat spreader of the same size made of a copper plate was used. The program used is a commercially available program for thermal analysis.

The X and Y directions are in-plane directions of the heat spreader, and the Z direction is a thickness direction of the heat spreader. The results are shown in Table 1.

[0013] From Table 1, it can be seen that in the case of 3), 4) and 5) having the direction of the carbon fiber in the plane, that is, the direction of high thermal conductivity in the plane, a low thermal resistance equivalent to a copper plate can be achieved. Therefore, in the cases of 3), 4), and 5), it can be estimated that the same heat radiation effect as that of the copper plate is obtained.

Next, 1), 3), 4), and
MCM-L of 5) was prepared and the heat dissipation efficiency was compared. As a result, it was found that the transitions of the package temperature immediately above the semiconductor chip mounting portion were not significantly different, and that the carbon composites 3), 4) and 5) exhibited a high thermal conductivity function similarly to the copper plate.

The carbon composite has a density of 1.75 g / cm ³ and a copper density (8.96 g / cm ³ ).
It is about 1/5 of ³ ). From this point, the trial calculation of the weight reduction effect in various packages is as follows.

P-BGA (31 mm square, Cu heats
Weight with existing package = 4.80 g Heat spreader volume = approx. 0.24 cm^Three (31
mm × 31 mm × 0.25 mm thick) Weight of heat spreader = about 2.15 g This was put into a carbon composite (0.4
2 g)
The weight reduction effect of 2.15-0.42 = 1.73 grams as the absolute value of the weight, and the ratio of 1.73 / 4.80 × 100 = 36.0% to the total weight It can be seen that weight reduction can be achieved.

A 160-pin PQFP (28 mm square,
In the case of (with aluminum heat slag), the average weight of the existing package = 5.96 g The volume of the heat slag = about 0.73 cm^Three (24mm ×
24mm x 1.27mm thickness) Weight of heat slag = about 1.97 g This heat slag is carbon composite with specific gravity of 1.75.
Weight (1.28 grams)
The lightening effect of the entire body is as follows: 1.97-1.28 = 0.69 g as an absolute value of weight 0.69 / 5.96 × 100 = 11.6% as a ratio to the total weight. Become.

Therefore, the effect of reducing the weight is greater when exposed as a heat slag (= thick plate) than when embedded as a heat spreader (= thin plate). Also, when the tape-BGA is used as a stiffener and a heat spreader, the stiffener accounts for a large proportion of the entire package, so that the effect of reducing the weight is great.

[0019]

According to the present invention, if a heat radiating plate made of carbon composite having high thermal conductivity in at least one direction within a plane, that is, a heat spreader or a heat slag is used,
A heat radiation effect equivalent to that of copper can be obtained, and a lighter package can be configured than when a copper plate or an aluminum plate is used. The effect is greater when exposed as a heat slag (= thick plate) than when embedded as a heat spreader (= thin plate), and when used as a stiffener and heat spreader for T-BGA, the entire package Since the stiffener accounts for a large proportion, the weight reduction effect is large.

[Brief description of the drawings]

FIG. 1 is a diagram showing an MCM-L used in the study of the present invention.

Claims (1)

[Claims] 1. A heat radiating plate for a semiconductor package comprising a carbon composite material obtained by arranging carbon fibers in one direction, laminating the arrangement, and impregnating the carbon fiber with a resin. Characterized in that the carbon fiber orientation of (1) is such that the thermal conductivity is increased in the plane direction.