JPH0320072B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method of manufacturing a cooling element for semiconductor devices that has excellent durability and cooling ability.

Some semiconductor devices consist of a single element such as a diode or transistor, but IC
There are also devices with multiple element configurations such as LSI and LSI, and the latter devices are often used for applications such as computers that rapidly process or store large amounts of information. As a way to increase processing capacity, use a configuration with more elements than LSI.
VLSI has been put into practical use.

The present invention relates to a method of manufacturing a cooling element used in a semiconductor device having such a multi-element configuration.

[Conventional technology]

Until now, semiconductor devices such as ICs and LSIs had fins placed on top of the package in which the elements were stored.
In addition, a forced air cooling system is used in which a fan blows air to cool the fins, thereby suppressing the temperature rise of the chip.

However, as the number of elements in a chip increases, there is a limit to the cooling method using air cooling.

That is, when mounting various components including semiconductor devices on a printed wiring board, there are limitations on the area occupied by the components and at the same time there are limitations on the mounting height of the components.

For this reason, the size and height of the fins are limited, which naturally limits the amount of heat dissipation, making it difficult to maintain the chip below the maximum operating temperature.

For this reason, attempts have been made to use liquid cooling or water cooling methods instead of air cooling methods.

Liquid cooling systems for superconducting elements and the like are well known, and liquid nitrogen (N ₂ ), liquid helium (He), and the like are used as refrigerants, and are stored in a bottle-type container.

However, cooling semiconductor devices does not require such low temperatures, except for special applications such as gallium arsenide (GaAs) transistors that utilize high electron mobility, and it is not necessary to use such low temperatures for cooling semiconductor devices such as computers. Due to the large scale of the semiconductor devices used, such a cooling method is currently not practical.

For these reasons, we installed a cooling element on top of the semiconductor device instead of the conventional fins.
The most practical and reliable method is to circulate water through the system for water cooling.

Here, conventional cooling elements with bellows are made by soldering a bellows made of flexible beryllium copper (hereinafter referred to as Be/Cu) or stainless steel copper to a cooling plate made of a copper-based metal with good thermal conductivity. The bellows was manufactured by either joining the bellows by welding or by using the same metal as the cooling plate for the bellows.

However, while the former provides a high cooling capacity, there are problems with the durability and corrosion resistance of the joints formed by methods such as soldering in water.

On the other hand, in the case of the latter, for example, when Be.Cu is used for the cooling plate, there is a problem that sufficient cooling capacity cannot be exhibited because the thermal conductivity is as low as 1/5 compared to pure copper (hereinafter referred to as pure Cu).

[Problem that the invention seeks to solve]

As described above, when using a water-cooled cooling element equipped with bellows as a method of cooling semiconductor devices, the cooling plate is made of a metal material with good thermal conductivity,
Further, although it is desirable to form the bellows using a flexible metal, there are problems with the durability and corrosion resistance of the joint portion in water.

[Means for solving problems]

The problem mentioned above is that the outer periphery of the cooling plate is made by integrally molding the same metal as the flexible bellows material on the outer periphery and a metal with good thermal conductivity in the center. This problem can be solved by a method of manufacturing a cooling element characterized by forming the bellows by welding.

[Function] The present invention focuses on experimental results showing that when a bonded body made of dissimilar metals is placed in an aqueous solution, corrosion resistance may deteriorate, but when the two are joined by welding, there is less corrosion. Developing pure Cu inside
A cylindrical metal body is made with Be/Cu or stainless steel clad on the outside, and this is crimped and integrated, and then cut into thin plates to make a cooling plate.
By welding bellows made of Be/Cu or stainless steel, the above problem is solved and a highly reliable cooling element is obtained.

〔Example〕

FIG. 1 is a sectional view showing a state in which a cooling element according to the present invention is mounted on a semiconductor device, and FIG. 2 is an enlarged sectional view showing the configuration of a cooling plate and a bellows.

That is, a semiconductor device 2 is mounted on a wiring board 1 made of ceramic or the like by a method such as face-down bonding, and a cooling element 3 according to the present invention is closely attached thereon.

Here, the cooling element 3 has a cooling plate 4 on the bottom.
Welded to this is a bellows 5, which is welded to a metal lid 8 having a cooling water inlet 6 and an outlet 7.

In the case of the present invention, the bellows 5 is formed of a flexible thin plate made of Be.Cu, phosphor bronze, stainless steel, or the like.

As shown in FIG. 2, the cooling plate 4 has a metal 9 with good thermal conductivity (for example, pure Cu) in the center part, or a flexible metal 10 (for example, in the peripheral part).
Be/Cu, phosphor bronze or stainless steel) should be used.

Here, the reason why pure Cu is used for the central part is that the thermal conductivity is 0.93cal/cm・sec・℃ and 0.17~ for Be・Cu.
0.26cal/cm・sec・℃ and stainless steel
This is because it is much better than 0.038cal/cm・sec・℃.

Here, the method for integrating Cu and Be/Cu will be explained as follows.

A clad rod with pure Cu on the inside and Be/Cu on the outer periphery is made, which is crimped until the diameter reaches 20 mm, then cut to make a 2 mm thick disk, which is then subjected to precipitation hardening treatment to harden both metals. Cooling plate 4 with integrated
is made.

A bellows 5 made of the same kind of metal, such as Be or Cu, is attached to the outer periphery of the cooling plate 4 made in this way.
are welded using a laser or electron beam.

Note that when stainless steel is used for the outer peripheral portion of the cooling plate 4, the material of the bellows 5 is stainless steel.

If the bottom surface of the cooling plate 4 is made of Cu and the outer peripheral part and the bellows are welded using Be.Cu or stainless steel, a cooling element with good corrosion resistance can be produced.

As described above, a cooling element as shown in FIG. 1 is formed by using the joining of the cooling plate 4 and the bellows according to the present invention, and the semiconductor device 2 is brought into close contact with the semiconductor device 2 under slight pressure, and cooling water is supplied from the injection port 6. By circulating the water through the drain port 7, semiconductor devices can be efficiently cooled.

〔Effect of the invention〕

As described above, by carrying out the present invention, it becomes possible to form a cooling element with good cooling efficiency and excellent durability.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a cooling element brought into close contact with a semiconductor device, and FIG. 2 is a cross-sectional structure showing the relationship between a cooling plate and a bellows of the cooling element. In the figure, 2 is a semiconductor device, 3 is a cooling element, 4 is a cooling plate, and 5 is a bellows.

Claims (1)

[Claims] 1. The flexible bellows is attached to the outer periphery of a cooling plate made by integrally molding the same metal as the flexible bellows material to the outer periphery and a metal with good thermal conductivity to the center. A method for manufacturing a cooling element, characterized in that the cooling element is formed by welding.