Electricity: measuring and testing – Fault detecting in electric circuits and of electric components – Of individual circuit component or element
Reexamination Certificate
1999-09-29
2001-07-17
Metjahic, Safet (Department: 2858)
Electricity: measuring and testing
Fault detecting in electric circuits and of electric components
Of individual circuit component or element
C324S1540PB, C324S224000
Reexamination Certificate
active
06262584
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an IC device temperature control system which makes it possible to evaluate performance of an IC device correctly and an IC device inspection apparatus incorporating the IC device temperature control system.
2. Description of the Prior Art
Inspection of temperature characteristics of an IC device is carried out in an environment which is held at a predetermined temperature (thermostatic bath or chamber).
The temperature set point of the chamber is set e.g. at −50° C. to +150° C. according to inspection programs.
Further, electric current is supplied to the IC device under test in various patterns according to many different test items of an inspection program. As a result, the IC device generates heat by Joule's law in a different pattern, dependent on the test item. The heat generation is more conspicuous in the case of inspecting an IC device which has a high integration density, such as a microprocessor (MPU) installed in a computer.
In recent years, the processing capacity or speed of microprocessors has been markedly increased, and their integration density has also become higher, resulting in an increased watt density (W/cm
2
) of such a microprocessor under test. Therefore, IC devices including MPUs tend to generate a still larger amount of heat.
For example, when a microprocessor generates approximately 30 watts of heat during inspection, the temperature of the microprocessor becomes higher than the set point temperature of the chamber by 40° C. or so.
Further, the amount of heat generated by an IC device becomes larger as the frequency of an electric signal supplied thereto.
Moreover, it is reported that the maximum operating frequency of the microprocessor is lowered with an increase in the temperature of the same due to a lowered switching frequency of transistors, and that if the temperature of the microprocessor rises by 10° C., the maximum operating frequency of the same is reduced by 2%.
For example, when the temperature of a microprocessor capable of operating at a maximum operating frequency of 500 MHz becomes 40° C. higher than the set point temperature of the chamber, the actual maximum operating frequency of the microprocessor falls by no less than 40 MHz. Therefore, the microprocessor which should be ranked in itself in a class in which operation at 500 MHz is ensured is demoted by one grade or class as a microprocessor for operation on the order of 400 MHz.
As a result, yields of microprocessors for operation at high operating frequencies are unduly deteriorated, causing a serious loss.
Further, when there is an increase in heat generation, an IC device is in danger of destroying itself.
Conventionally, with a view to enhancing accuracy of inspection (i.e. yield of properly ranked IC devices) and preventing self-destruction of an IC device, the temperature of the IC device is monitored, and then the IC device is cooled to the set point temperature of the chamber.
The temperature of an IC device can be measured by a method using a contact temperature sensor such as a thermocouple or a non-contact temperature sensor such as an infrared sensor.
Further, another method can be employed in which a temperature sensor is incorporated in an IC device under test and the temperature of the IC device is measured by the temperature sensor, as disclosed in Japanese Laid-Open Patent Publication (Kokai) No. 6-188295.
However, the contact temperature sensor can scratch or soil a package surface of an IC device, causing degradation of the product.
On the other hand, the non-contact temperature sensor such as an infrared sensor cannot measure the temperature of an IC device having a metal surface accurately.
Further, the method using a temperature sensor incorporated in an IC device increases the size and weight of the IC device, resulting in a considerable increase in manufacturing costs of the product.
SUMMARY OF THE INVENTION
It is a first object of the invention to provide an IC device temperature control system which is capable of measuring the temperature of an IC device accurately without scratching or soiling the IC device which also it possible to evaluate performance of the IC device correctly even when a temperature sensor is not incorporated in the IC device.
It is a second object of the invention to provide an IC device inspection apparatus incorporating the IC device temperature control system.
To attain the first object, according to a first aspect of the invention, there is provided An IC device temperature control system for controlling a temperature of an IC device received in a chamber, for inspection, the IC device temperature control system, comprising:
magnetometric detection means for detecting a magnetic field generated around the IC device when electric current is supplied to the IC device;
temperature control means for controlling a temperature of the IC device; and
control means for controlling the temperature control means based on a signal delivered from the magnetometric detection means, to maintain the temperature of the IC device within a predetermined temperature range.
According to this IC device temperature control system, the magnetometric detection means detects a magnetic field which is generated by electric current supplied to an IC device under test in a manner momentarily varying in response to changes in the electric current. The control means issues an instruction to the temperature control means based on a detection signal delivered from the magnetometric detection means, and the temperature control means adjusts the temperature of the IC device according to the instruction (by cooling or heating).
Further, differently from an infrared sensor, the magnetometric detection means is capable of measuring the temperature of the IC device accurately even when the IC device has a metal surface. Also differently from a contact temperature sensor such as a thermocouple, the magnetometric detection means is not required to be brought into contact with the IC device, so that the IC device cannot be scratched or soiled. Moreover, since it is not required to incorporate a temperature sensor in the IC device as in the prior art, increases in size and weight of the IC device can be prevented.
A refrigerant used in the cooling means may be cold air produced e.g. by a refrigerator, cold air produced by adiabatic expansion caused by a difference in pressure between the inside and outside of a vortex of a gas rotating at an extremely high speed (i.e. cold air produced based on the vortex principle), gaseous nitrogen utilizing latent heat of vaporization of liquid nitrogen, or the like.
Preferably, the IC device temperature control includes conversion means for converting the signal delivered from the magnetometric detection means to information indicative of an amount of heat generated by the IC device, and the control means controls the temperature control means based on the information from the conversion means, to maintain the temperature of the IC device within the predetermined temperature range.
According to this preferred embodiment, the conversion means converts the detection signal delivered from the magnetometric detection means into information indicative of the amount of heat generated by the IC device. The control means issues an instruction to the cooling means based on the information, for cooling the IC device according to a change in the amount of the heat, and the cooling means cools the IC device according to the instruction.
More preferably, the control means adjusts an operating amount to be applied to the temperature control means to a predetermined value corresponding to a temperature change of the IC device, based on the information from the conversion means.
According to this preferred embodiment, the control means issues an instruction for adjusting the operating amount to be applied to the cooling means to a predetermined value corresponding to a change in temperature of the IC device, and the cooling means cools the IC device
Kawaguchi Kazuhiro
Kurosu Osamu
Frishauf, Holtz Goodman, Langer & Chick, P.C.
McElectronics Co., Ltd.
Metjahic Safet
Nguyen Jimmy
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