JPH077815B2 - Semiconductor device cooling method - Google Patents

Description

DETAILED DESCRIPTION [Overview] In order to improve the liquid cooling effect of a semiconductor device, a piezoelectric vibrator is installed on a wiring board on which the semiconductor device is mounted, and high frequency vibration generated by the piezoelectric vibrator causes the semiconductor device to generate the vibration. A cooling method that removes air bubbles to improve cooling efficiency.

[Industrial application field]

The present invention relates to a semiconductor device cooling method with improved cooling efficiency.

As a method for improving the processing capacity of an information processing apparatus, a semiconductor device including a large number of semiconductor elements is being miniaturized as a unit element and the number of elements is being increased.

That is, the size of the electrodes and the width of the conductor pattern forming the unit element are extremely reduced, while the number of elements is increased and
VLSI has been put to practical use.

In addition, the mounting method on the wiring board has also been improved, and conventionally it was stored in each hermetically sealed package for each semiconductor chip, and this was mounted on the printed wiring board, but in the future, due to the progress of passivation technology, Mount multiple LSI chips on a circuit board such as ceramic
A method has been adopted in which an SI module is created and mounted on a wiring board as a replacement unit.

As described above, as the miniaturization and high density of the unit element progress, the amount of heat generated by the semiconductor device also becomes enormous, and it becomes impossible to keep the element temperature within the maximum operating temperature range by the conventional air cooling method.

In other words, the heat generated by LSI chips has been about 4 watts at the maximum, but it is about 30 watts by VLSI, which is a tendency to increase further.

From the above, the cooling method of the semiconductor device requires liquid cooling instead of conventional air cooling or forced air cooling, but the cooling capacity is insufficient by just immersing it in the refrigerant, and forced liquid cooling is required. It has become to.

[Conventional technology]

The inventor is applying for several utility model registrations regarding a liquid cooling method for a semiconductor device in which a large number of LSIs are mounted on a multilayer wiring board.

For example, Japanese application Sho 59-016496, Japanese application Sho 59-019428, Japanese application Sho 59-099
389, Japanese Patent Application No. 59-099390, Japanese Patent Application No. 59-15752, etc. The gist of these applications is a semiconductor chip (hereinafter abbreviated as a chip).
A circuit board on which is mounted is non-corrosive and non-dissociative, and has a boiling point of 85 ° C or lower, which is the maximum operating temperature of the chip, such as fluorocarbons such as C ₅ F ₁₂ (boiling point 30 ° C), C ₆ F ₁₄ (boiling point 56
(° C) and soak it in a hermetically sealed medium, and connect the circuit board to an external circuit through a connector provided inside the container, or use the circuit board as a side wall and insert the connector into the lead pin drawn from the back surface. The circuit is connected.

Then, during operation, the refrigerant vaporized at the contact interface due to the heat generation of the chip is effectively cooled in the liquid or by the heat exchanger (condenser) arranged in the void portion of the upper part of the container to be liquefied,
It has a structure in which a refrigerant is forcedly circulated and a heat exchanger is provided on the way to cool the refrigerant.

However, such a liquid cooling structure is suitable when the power consumption of the chip is less than 10 watts, but when the power consumption of the chip is higher than this, boiling from the chip becomes intense and the surface of the chip vaporizes. The liquid cooling effect is lost because it is covered with the bubbles.

That is, the vaporized gas covers the surface of the chip and interrupts the contact of the refrigerant, resulting in an adiabatic state.

On the other hand, the semiconductor has a negative temperature coefficient of resistance, so that the resistance value decreases as the temperature rises, and the current value increases, causing a runaway state and destruction.

Therefore, a more effective liquid cooling method than before has been required.

[Problems to be solved by the invention]

As described above, the conventional liquid cooling method lacks the ability to cool a chip that consumes a large amount of power, and it is a problem to find a more effective forced cooling method.

[Means for solving problems]

The above-mentioned problem is that the wiring board mounted in the liquid cooling container by the connection terminal and having the plurality of semiconductor devices mounted therein has the piezoelectric vibrator at one end of the wiring board, and the piezoelectric vibrator causes high-frequency vibration to the wiring board. It can be realized by a cooling method of a semiconductor device in which a cooling is performed with a refrigerant while being applied.

[Action]

The present invention has been made as a result of studying an effective method for removing bubbles.

That is, it is desirable that the bubbles are released from the chip as soon as they are generated, but the detachment occurs only after the bubbles grow to a certain size determined by the viscosity and the specific gravity of the refrigerant, so no forced means is used. As long as it occurs, it cannot be disengaged.

That is, in a chip with high power consumption, the density of nuclei in which boiling occurs is high, so that the surface of the chip is covered with bubbles during the process of bubble growth.

Therefore, spraying a refrigerant or vibrating the substrate is effective as a method for removing the bubbles as soon as they are generated, but in this case, the case of vibrating was studied.

As a result, it was found that applying a high frequency vibration of 10 KHz or more is effective.

It should be noted that if the frequency is lower than this, the refrigerant will vibrate, and there will be no effect of removing the minute bubbles, and therefore the object of the present invention will not be met.

〔Example〕

10 x 10 mm square LSI chips arranged in a matrix of 10 x 10
A piezoelectric vibrator composed of PZT (lead zirconate titanate) as a dielectric was mounted on a ceramic multilayer substrate, and the substrate was vibrated horizontally at a vibration frequency of 40 KHz and a power of 30 watts.

The refrigerant used in this case is C ₆ F ₁₄ with a boiling point of 56 ° C,
The substrate was fixed in the coolant and the chip was rated.

As a result, as soon as the bubbles were generated, they were released from the chip, and the cooling capacity could be improved to 25 W / cm ² from the conventional cooling capacity of 15 W / cm ² .

It should be noted that when the vibration frequency is 10 KHz or less, the bubbles oscillate, and the bubbles continue to grow without detaching and the chip breaks into a runaway state as in the past.

〔The invention's effect〕

As described above, by carrying out the present invention, in the liquid cooling structure of the semiconductor device, the bubbles generated from the chip surface can be removed as soon as they are generated, so that the cooling capacity can be improved.

Claims (1)

[Claims] 1. A wiring board mounted in a liquid cooling container by a connection terminal and having a plurality of semiconductor devices mounted thereon, a piezoelectric vibrator being provided at one end of the wiring board, and the piezoelectric vibrator causes high-frequency vibration on the wiring board. A method for cooling a semiconductor device, which comprises cooling with a refrigerant while applying.