JPH0363239B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical field to which the invention pertains] The present invention relates to a method for cooling a package in which at least one heating element is mounted on a wiring board made of alumina or the like and the whole is hermetically sealed. be.

[Prior art and its problems]

In recent years, demands for electronic equipment to be smaller, lighter, and more reliable have been increasing in various fields. A so-called multi-chip packaging technology is being developed in which the entire chip is mounted and hermetically sealed. In such a package,
Due to the demand for smaller size and lighter weight, there is a trend toward higher density and higher integration in the future. As a result, the amount of heat generated per unit area of packages tends to increase more and more, and the development of cooling technology for high-density packages has become essential.

A cross-sectional view of a conventional method for cooling such a high-density package is shown in FIG. On the surface of the multilayer wiring board 1-1 made of alumina or the like, an adhesive such as solder or epoxy is used to hermetically seal the semiconductor chip 1-2, which is a heat generating element, and the entire plurality of elements. Alternatively, a metal cap 1-3 made of, for example, Kovar or Fe/Ni42 alloy, which has approximately the same coefficient of thermal expansion as the wiring board 1-1 made of alumina or the like, is supported and fixed by welding or the like. Here, the semiconductor chip 1- which is the heating element is
It is necessary to cool the package in order to keep the junction temperature of 2 below its maximum rated operating temperature. Conventionally, as shown in FIG.
4 is supported and fixed on the back surface of the wiring board 1-1 made of alumina or the like using solder or an adhesive 1-5 such as epoxy, thereby significantly increasing the surface area of the entire package and reducing the thermal resistance between the package and air. In addition, if necessary, the metal cooling fins 1-4 may be forced to cool by sending air through the metal cooling fins 1-4, or the metal cooling fins 1-4 may be screwed to the system housing to cool the package. By dissipating the heat generated in the casing, the junction temperature of the semiconductor chip 1-2, which is a heat generating element, is reduced to below the maximum rated operating temperature.

However, with this method, for example, there are restrictions on the overall size of the system and there is no space to install a cooling fan, or the entire system is exposed to a very bad environment, and the system casing itself is a heat generating element. In cases where the maximum rated operating temperature of a certain semiconductor chip 1-2 is close to or above the maximum rated operating temperature, the junction temperature of the semiconductor chip 1-2, which is the heating element of the package, is set to be below its maximum rated operating temperature. It has become almost impossible to design and manufacture such a high-density, highly integrated package. It was no longer able to fulfill its function and had to become meaningless. In other words, this heat problem has resulted in the limit of miniaturization and weight reduction of electronic devices.

[Purpose of the invention]

The present invention was made in consideration of such circumstances, and its purpose is to solve problems when there is no space to install a cooling fan or the like in the entire system.
Or, because the entire system is exposed to extremely harsh environments, even if the temperature of the system casing itself is close to or even higher than the maximum rated operating temperature of the semiconductor chip, which is the heating element, there will be no problem. The goal is to make it possible to cool the junction temperature of a semiconductor chip, which is a heat generating element in a high-density package, to below its maximum rated operating temperature, and to make it possible to promote high density and high integration to a certain extent indefinitely. It's about tightening.

[Summary of the invention]

The present invention is based on the maximum rated operating temperature (commercial standard = 70℃, MIL standard = 125℃ to 150℃), the substance itself undergoes a state change such as from solid phase to liquid phase or from liquid phase to gas phase, and its own heat of fusion or vaporization It is characterized by cooling the package by supporting and fixing a substance that absorbs heat to the wiring board of the package, such as alumina.

〔Effect of the invention〕

According to this method, by increasing the weight supported and fixed on the package of the substance that causes the state change and absorbs heat by its own heat of fusion or heat of vaporization, it is possible to increase the amount of heat absorbed by the heat generating element. It becomes possible to cool the junction temperature of a certain semiconductor chip to below its maximum rated operating temperature.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 shows an embodiment according to the present invention. 2-1 is a high-density wiring board made of alumina or the like, and 2-2 is a semiconductor chip, which is a heating element, supported and fixed on the surface thereof with solder or adhesive such as conductive epoxy. Reference numeral 2-3 indicates a metal cap for supporting and fixing to the back surface of the wiring board 2-1 made of alumina or the like in order to hermetically seal the entire semiconductor chip. In addition, 2-6 is a material such as wax, naphthalene, or fluorocarbon sealed in the metal tank according to the present invention, which is removed from the solid phase within a relatively low temperature range from room temperature to the maximum rated operating temperature of the semiconductor chip, which is the heating element. Causes a state change such as a liquid phase or from a liquid phase to a gas phase,
It is a substance that absorbs heat due to its own heat of fusion or heat of vaporization. Here, the metal tank 2-4
The thickness of the outer wall of the portion not in contact with the back surface of the wiring board 2-1 is relatively thin (0.1 to 0.25 mm),
A substance 2- such as wax or naphthalene sealed in metal tanks 2 to 4 that changes state from a solid phase to a liquid phase at a relatively low temperature and absorbs heat with the heat of fusion.
It is better if 6 is able to absorb the increase/decrease in its own volume or the increase/decrease in pressure to some extent when the state changes. In addition, if 2-6 is a substance such as fluorocarbon that changes state from a liquid phase to a gas phase at a relatively low temperature and absorbs heat due to the heat of vaporization, the wiring board 2-6 of the metal tank 2-4, such as alumina,
- form at least one relatively small through hole (diameter 0.2 to 1 mmφ) in the outer wall not in contact with 1;
In order to prevent the endothermic substance 2-6 such as fluorocarbon from increasing its boiling point and becoming no longer vaporized due to an increase in the atmospheric pressure in the gas phase due to the change in the state of the endothermic substance 2-6 from the liquid phase to the gas phase, It is sealed with a relatively soft resin adhesive such as epoxy or silicone, and as the pressure increases, the relatively soft resin adhesive such as epoxy or silicone is destroyed and the liquid phase changes continuously from the liquid phase to the gas phase. It is better to have a structure that allows for state changes to occur.

[Other embodiments of the invention]

FIG. 3 shows another embodiment according to the present invention, in which a wiring board 3-1 made of alumina or the like is bonded to the back side of the wiring board 3-1 made of alumina or the like by soldering, an adhesive such as epoxy, or a method such as welding. For example, Kovar or Fe/Ni42 with almost equal coefficient of thermal expansion
First, a metal cap 3-4 made of alloy or the like is supported and fixed. This figure shows the welding method, where 3-5 is the welded part and 3-13 is the wiring board 3-1.
For example, Kovar or
A metal ring for welding such as Fe/Ni42 alloy,
The welding metal ring 3-13 is connected to the wiring board 3-1.
Conductor pattern 3-11 metalized on the back side of
It is adhesively fixed on the top with an adhesive 3-12 such as silver solder. Metallic cap 3 according to the invention
-4 has a relatively small through hole 3-7 (1 to 2 mm in diameter) before it is supported and fixed to the wiring board 3-1.
φ) and the relatively small through hole 3-
7 (diameter 1 to 2 mmφ), the state changes from a solid phase to a liquid phase or from a liquid phase to a gas phase within a relatively low temperature range from room temperature to the maximum rated operating voltage of the semiconductor chip 3-2, which is a heating element. After pouring a substance 3-6 that absorbs heat due to its own heat of fusion or vaporization in a liquid state and filling it between the wiring board 3-1 and the metal cap 3-4 according to the present invention,
The relatively small through hole 3-7 (diameter 1-2 mmφ)
By sealing with an adhesive 3-8 such as solder or epoxy, the heat-absorbing substance 3-6 is supported and fixed to the back surface of the wiring board 3-1. Even in this case, the thickness of the metal cap 3-4 according to the present invention is the second
As in the case shown in the figure, the volume increases and decreases when a substance 3-6 that is formed relatively thin (0.1 to 0.25 mm) and absorbs heat undergoes a state change from a solid phase to a liquid phase at a relatively low temperature, such as wax or naphthalene. Alternatively, it would be better to absorb some stress due to increase or decrease in pressure. Furthermore, if the heat-absorbing substance 3-6 is a substance that changes state from a liquid phase to a gas phase at a relatively low temperature, such as fluorocarbon, the gas phase portion 3-6
At least one relatively small through hole ( Diameter 0.2
~1 mmφ) 3-9 is formed, and the heat-absorbing substance 3-6 is passed through the relatively small through hole (1~2 mm in diameter).
After pouring in liquid phase from φ) 3-7 and sealing the relatively small through hole (diameter 1 to 2 mmφ) 3-7 with adhesive 3-8 such as solder or epoxy,
The at least one relatively small through hole (diameter 0.2 to 1 mmφ) 3-9 is wiped with a relatively soft resin adhesive 3-10 such as epoxy or silicone, so that the heat-absorbing substance 3-6 undergoes a state change. The relatively soft resin adhesive, such as epoxy or silicone, is destroyed by the increase in pressure during the raising process, allowing the endothermic substance 3-6 to continuously change its state from the liquid phase to the gas phase. Good.

FIG. 4 shows another embodiment according to the present invention,
In FIGS. 2 and 3, substances 2-6 and 3-6 that undergo a state change and absorb heat according to the present invention are supported and fixed on the back surfaces of wiring boards 2-1 and 3-1 made of alumina, etc. However, in the embodiment shown in FIG. 4, the semiconductor chip 4-1, which is the heating element on the surface of the wiring board 4-1,
It is supported and fixed to the unmounted part of 2. In this case, a metal cap 4-4 having a relatively small through hole (1 to 2 mm in diameter) 4-7 according to the present invention is used with an adhesive 4 such as solder or epoxy.
-11, it is supported and fixed to a conductor pattern 4-5 metallized on a wiring board 4-1. The heat-absorbing substance 4-6 is passed through the relatively small through hole (1 to 2 mm in diameter) 4-7 in a liquid phase to the wiring board 4.
-1 and a metal cap 4-4, and a relatively small through hole 4-7 is sealed with an adhesive 4-8 such as solder or epoxy. The example shown in FIG. 4 will be particularly effective when the wiring board 4-1 has very good thermal conductivity, such as a SiC board. Note that 4-3 is a wiring board that is supported and fixed to the wiring board 4-1 using solder, an adhesive such as epoxy, or a method such as welding in order to hermetically seal the entire semiconductor chip 4-2, which is a heating element. Kovar or
It is a metal cap such as Fe/Ni42 alloy.

By adopting the present invention, it has become possible to solve the problem of heat in the package that accompanies high density and high integration, and it has become possible to develop high density and high integration packages without any problems. In addition, it is possible to cool high-density packages without any problems even if there is no space to install a cooling fan in the entire system, or if the entire system casing itself is exposed to harsh environments where the casing itself is exposed to high temperatures. Summer.

[Brief explanation of drawings]

FIG. 1 is a sectional view for explaining a conventional example, and FIGS. 2 to 4 are views for explaining an embodiment according to the present invention. 1-1, 2-1, 3-1, 4-1...Wiring board made of alumina, etc., 1-2, 2-2, 3-2, 4-2
...Semiconductor chip as a heating element, 1-3, 2-
3, 3-3, 4-3...metallic cap for hermetically sealing the semiconductor chip, 1-4...heat dissipation fan, 2-4...metallic tank according to the present invention, 3-
4,4-4...metallic cap according to the present invention, 3
-7, 4-7, 3-9...through hole formed in the metal cap according to the present invention, 2-6, 3-6, 4-6
...A substance that changes state from a solid phase to a liquid phase or from a liquid phase to a gas phase at a relatively low temperature and absorbs heat with its heat of fusion or vaporization, 1-5, 2-5, 4
-5...Adhesive such as epoxy or solder.

Claims (1)

[Claims] 1. In a method for cooling a package in which a heat generating element is mounted on a wiring board, a small through hole having a coefficient of thermal expansion approximately equal to that of the wiring board is provided on the back side or the front side of the wiring board where the heat generating element is not mounted. A metal cap is fixed, and through the holes in the metal cap, a substance that undergoes a state change from a liquid phase to a gas phase and absorbs heat with the heat of vaporization is brought into a liquid phase.
A method for cooling a package, characterized in that the space between the wiring board and the metal cap is filled, and the through hole of the metal cap is sealed with solder or adhesive.