JPH0332223B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to improvement of a multi-chip semiconductor module using a closed circulation type water cooling method, and in particular, the present invention relates to the improvement of a multi-chip semiconductor module using a closed circulation type water cooling method. Concerning maintenance techniques to protect water from water leakage.

[Background of the Invention] In recent multi-chip semiconductor modules, the amount of heat generated from one chip element continues to increase with the development of semiconductor technology, and forced air cooling cannot cool semiconductor chips sufficiently. In fact, the cooling performance of the air-cooled type has almost reached its limit. For this reason, especially regarding semiconductor modules in high-speed data processing devices and similar devices, the immersion boiling cooling method as disclosed in Japanese Patent Application Laid-open No. 57-159050 and the method disclosed in Japanese Patent Publication No. 56-31743 are particularly important. Cooling devices that use liquid, such as the closed circulation water cooling system shown in

Although the former immersion boiling cooling method has lower cooling efficiency than the latter water cooling method, it only requires a dielectric cooling medium to be enclosed in a sealed container that seals the semiconductor module, and its structure is lower than that of the latter water cooling method. It has the advantage of being simpler than . however,
Even when using perfluorocarbon-based low-boiling coolant, which is currently the most stable against decomposition, it still reacts with water, albeit in a small amount, to generate hydrogen fluoride.
There are problems in that there is a risk of damaging the wiring material and the semiconductor element itself, and that the cooling medium itself is a type of organic solvent, making it impossible to use an organic multilayer wiring board.

On the other hand, the latter closed circulation water cooling method has the advantage of having the highest cooling efficiency and no direct negative impact on wiring or semiconductor elements, but the cooling structure is complex and requires the use of thin materials. There are problems in that the long-term reliability of the cooling structure is poor due to corrosion, etc., and there is a high possibility of circuit malfunction or damage to semiconductor elements due to leakage of cooling water.

In this way, the immersion boiling cooling method and the closed circulation water cooling method each have their own problems.
The latter water cooling method can solve practical problems by increasing the reliability of the cooling structure and taking measures against water leakage, and is considered more promising than the former boiling cooling method. However, to date, although various proposals have been made regarding liquid cooling methods and structures, particularly for semiconductor modules in ultra-high-speed large-scale computers, no concrete ideas have been proposed regarding maintenance management to prevent water leakage. Not yet.

In order to predict in advance when a water leak will occur so that countermeasures can be taken in advance, a method of monitoring the corrosion state of the cooling structure may be considered. Possible methods for this include detecting the amount of metal ions eluted into the cooling water or measuring the electrical resistance of the cooling water, but these methods can only determine the overall average corrosion state, and do not cause intermittent corrosion or It is difficult to monitor the progress of localized corrosion such as pitting corrosion.
It is difficult to say that this is sufficient to prevent water leakage.

[Purpose of the invention]

An object of the present invention is to prevent water from rapidly entering the semiconductor module and to immediately remove the water when the cooling structure leaks water due to corrosion etc. in a multi-chip semiconductor module using a closed circulation water cooling method. The object of the present invention is to detect the occurrence of leakage and take maintenance measures, thereby preventing damage to the semiconductor module.

[Summary of the invention]

A semiconductor module according to the present invention includes a wiring board on which a plurality of semiconductor chips are mounted, a closed circulating water cooling structure for individually cooling the semiconductor chips, and a cooling structure for cooling the water cooling structure, the semiconductor chips, and at least the wiring board. A sealed housing that hermetically houses a semiconductor chip mounting side, and a metal oxide humidity sensor installed inside the sealed housing to detect temporal changes in absolute humidity in the space inside the sealed housing. It is characterized by

[Embodiments of the invention]

An embodiment of the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 is a diagram showing the configuration of a semiconductor module in which a water cooling structure using electrodeposited bellows is coated with an organic film, and a humidity sensor consisting of a metal oxide film on a Si chip is mounted together with an LSI chip. , and FIG. 2 is a diagram showing a maintenance system for a semiconductor device in which a plurality of semiconductor modules shown in FIG. 1 are mounted.

In FIG. 1, a two-stage water supply and drainage passage 23, 24 formed by a ceiling plate 3, a partition plate 4, and a bottom plate 5 is provided on the top wall of the housing 6, and an LSI chip 14 is installed inside the module of the housing 6. An electroplated bellows 8 opening into the drainage passage 24 is brazed to the corresponding position, and the tip of the electroplated bellows 8 is made up of a metal cap 9 and a ceramic plate 10 that has good thermal conductivity and is an electrical insulator. The cooling block is brazed. A pipe 7 branching from the water supply passage 23 is provided inside the electrodeposited bellows 8.
Cooling water is efficiently sent from the water supply port 19 to the cooling block through the water supply passage 23 and the pipe 7,
The structure is such that the cooling water is discharged from there through the electrodeposited bellows 8 and the drain passage 24 to the drain port 20. The ceramic plate 10 of the cooling block and the LSI chip 14 are connected by solder 12 via metallized films 11 and 13. The LSI chip 14 is mounted on a multilayer wiring board 18 by solder connection, 15 and 17 are terminals, and 16 is solder. Several humidity sensors 2 are mounted in the open spaces on the multilayer wiring board 18 by soldering like the LSI chip 14. Humidity sensor 2 is 1ppm
This is a high-sensitivity metal oxide-based humidity sensor that can detect moisture in the air, and has a metal oxide film formed on a Si chip, and a metal pad for soldering is formed on the back side of the Si chip. , it is preferable that the electrode of the humidity sensor and the pad be electrically connected. The lower end of the skirt of the housing 6 is hermetically bonded to the multilayer wiring board 18 with a low melting point solder 21. Inside the module, the surface of the cooling structure composed of the housing 6, electrodeposited bellows 8, and cooling block is coated with a moisture-permeable organic thin film 1 formed by vacuum deposition. In addition to the vacuum evaporation method, organic thin films can be coated using an electrode method in which the material is immersed in a monomer solution and polymerized by applying a voltage, or a method in which it is immersed in a monomer solution diluted with a solvent and then heated and polymerized. be. Furthermore, the sealed space A inside the module is once brought to a vacuum state and then filled with high-purity He gas with a moisture content of 1 ppm or less.

Next, in FIG. 2, as described above, the wiring board 18
Stack several layers (three layers in the figure) of semiconductor modules made by hermetically sealing the housing 6 on the motherboard 2.
7 and 30 to form a semiconductor device, and the whole is housed in an airtight container 28. Cooling water is sent by a water pump 31 from a water supply pipe 34 to the water supply port 19 of each semiconductor module, and water from the drain port 20 is cooled by a heat exchanger 39 and regenerated by a pure water purification device 43 containing an ion exchange resin. The water is returned to the water pump 31 and circulated. Output of humidity sensor 2 of each semiconductor module and airtight container 28
The output of the humidity sensors 29 installed inside the room is monitored by the monitoring control device 36, and if these humidity sensors detect an increase in the absolute humidity in each closed space, the data currently being processed is immediately stored. transfer it to the device 37, stop the power supply,
Further, the water supply pump 31 is stopped, and the suction pump 40 is simultaneously driven to cool the cooling water circulation pipes 34, 35.
Control so that there is negative pressure inside. Further, the alarm device 38 warns the worker.

According to this embodiment, even if water leaks from the cooling structure due to corrosion or other reasons, the organic thin film 1 prevents the amount of water leakage from increasing rapidly and temporarily removes the exposed LSI chip. The organic film can prevent water droplets from falling on top. Furthermore, since semiconductor modules are normally used at humidity levels around 50°C,
If only a small amount of water leaks from the cooling structure, most of it will evaporate. Therefore, the slight change in absolute humidity that occurs is immediately detected as a water leak by the highly sensitive metal oxide humidity sensor 2 that can detect moisture from 1 ppm, and maintenance measures as described above are taken. It is possible to prevent semiconductor modules from being damaged due to exposure to water or high humidity on bare LSI chips. Also,
Since a humidity sensor made of metal oxide formed on a Si chip is used, there is no need for a special mounting process for the humidity sensor when assembling the semiconductor module, and its electrical wiring can be pre-wired within the multilayer wiring board. Therefore, it is possible to assemble a semiconductor module incorporating a humidity sensor using a soldering process that is exactly the same as a conventional semiconductor module mounting process. In addition, in a high-purity He gas atmosphere, the sensor has high stability over a long period of time, and therefore has high reliability as a semiconductor device.

FIG. 3 shows the present invention in the case of a semiconductor module using a cooling structure that circulates cooling water using two micro bellows 8 ₁ and 8 ₂ in one cooling block (consisting of 9 and 10). An example is shown. The same reference numerals as in FIG. 1 indicate the same parts as described above. In this embodiment, the water supply and drainage passages 2 of the two-stage structure shown in Fig. 1 are used.
3 and 24, horizontal water supply and drainage passages 64 and 65 are formed on the top wall of the housing.
Moreover, instead of the humidity sensor 2 shown in FIG. 1, a humidity sensor 45 having an electrode and a porous alumina film formed on a ceramic plate is mounted on the inner surface of the skirt portion of the housing 6. In addition, the input/output lead wire 5 of the humidity sensor
9 and 60 are led out from the skirt portion by a hermetic seal 58.

FIG. 4 shows still another embodiment of the present invention. In this embodiment, as a cooling structure, a flexible metal thin film 68 that forms a cooling water passage 67 between the top wall of the housing 6 and a fin 86 is provided at one end. A block-shaped thermal conductive medium 70 with good thermal conductivity is brazed, and the other end of this thermal conductive medium 70 is connected to the LSI chip 1.
4, cooling water 85 flows through the passage 67 from the water supply port 81, and the chip 14 is cooled through the block 70. A moisture-permeable organic thin film 1 is applied to the surfaces of the housing 6, the metal thin film 68, and the block 70, as in the previous embodiment. In the figure, the same reference numerals as in FIG. 1 indicate the same parts. In this embodiment, a humidity sensor including a metal oxide sensor circuit 79, electrodes, and solder terminals 75 is mounted on the bottom surface of a Si chip 80, similar to the LSI chip.

In the embodiments shown in FIGS. 3 and 4 above, it is possible to prevent damage to semiconductor modules by suppressing water leakage from the cooling structure, immediately detecting water leakage, and taking maintenance measures. be effective,
In this case, it goes without saying that a maintenance system similar to that shown in FIG. 2 may be used.

Note that the semiconductor module in FIG. 2 may be installed upside down. If you do that,
Even if a water leak occurs in the cooling structure, water will not directly splash onto bare LSI chips, reducing the possibility of damage to the semiconductor module.

〔Effect of the invention〕

In the present invention, in a semiconductor module that employs a closed circulation water cooling method, a metal oxide humidity sensor is installed in a sealed container in which the semiconductor module is sealed, and detects slight temporal changes in absolute humidity within the container. Since the system also monitors the humidity, if there is a slight water leak in the closed circulation type cooling structure due to corrosion or destruction, this will be immediately detected as a change in the absolute humidity, and the bare LSI chip will be immediately detected. At the very beginning of a water leak, before the semiconductor module is damaged due to water splashing on it or high humidity, turn off the power switch of the electrical circuit or control the cooling system to reduce the water pressure to negative water pressure. It becomes possible to take measures to suppress leakage, maintain the semiconductor module, and prevent damage to it.

Furthermore, by covering the entire surface of the water-cooled structure inside the sealed container with a moisture-permeable organic film, even if the water-cooled structure leaks due to corrosion or other reasons, the bare LSI chip can be temporarily removed. It is possible to prevent water droplets from falling on top of the device, while a humidity sensor can detect water leaks and take maintenance measures, ensuring reliable maintenance of the semiconductor module.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of one embodiment of the present invention, FIG. 2 is a diagram of a maintenance system for a semiconductor device configured using the semiconductor module of FIG. 1, and FIGS. It is a sectional view of an example. DESCRIPTION OF SYMBOLS 1... Organic thin film, 2... Humidity sensor, 6... Housing, 7... Pipe, 8, 8 ₁ , 8 ₂ ... Bellows, 9... Cap, 10... Ceramic plate,
11, 13...Metallized film, 12...Low melting point solder, 14...LSI chip, 18...Multilayer wiring board, 19...Water inlet, 20...Drain port, 21...
Low melting point solder, 22... Metallized film, 23...
Water supply passage, 24... Drain passage, 27, 30... Motherboard, 28... Airtight container, 29... Humidity sensor, 31... Water pump, 32, 33... Solenoid valve, 34... Water supply pipe, 35... ...Drain pipe, 36
...Monitoring control device, 37...Storage device, 38...
Alarm device, 39... Heat exchanger, 40... Suction pump, 41... Suction pipe, 42... Power supply device, 43...
...Pure water purification device, 45...Humidity sensor, 64...
Water supply duct, 65...Drainage duct, 67...Cooling water passage, 68...Flexible thin metal plate, 70...
...Heat transfer medium, 79...Sensor circuit, 80...Si
Chip, 81... Water supply port, 86... Cooling fin.

Claims (1)

[Claims] 1. A wiring board on which a plurality of semiconductor chips are mounted;
a closed circulating water cooling structure for individually cooling the semiconductor chips; a closed housing that seals and accommodates the water cooling structure, the semiconductor chips, and at least the semiconductor chip mounting side of the wiring board; and a space inside the closed housing. 1. A semiconductor module comprising: a metal oxide humidity sensor installed within the sealed housing to detect temporal changes in absolute humidity. 2. The semiconductor module according to claim 1, wherein the metal oxide humidity sensor is formed on a Si chip and mounted on the wiring board by solder connection like other semiconductor chips. 3. The semiconductor module according to claim 1, wherein the surface of the water cooling structure facing the space within the hermetic housing and the inner surface of the hermetic housing are covered with a moisture permeable organic thin film. 4. The semiconductor module according to claim 1, wherein the space within the hermetically sealed housing is filled with an inert gas whose water content does not exceed 1 ppm at most.