Refrigeration – Using electrical or magnetic effect – Thermoelectric; e.g. – peltier effect
Reexamination Certificate
2002-06-26
2004-06-15
Bennett, Henry (Department: 3744)
Refrigeration
Using electrical or magnetic effect
Thermoelectric; e.g., peltier effect
Reexamination Certificate
active
06748746
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a device for controlling the temperature of a semiconductor module and a method of controlling the temperature of a semiconductor module. More particularly, the present invention relates to a device and a method for precisely controlling the temperature of a semiconductor module, which is a test sample on which an environmental temperature test is performed, to a test temperature.
A semiconductor module, such as an optical module having an optical semiconductor element, such as a laser, mounted therein is widely used as a key component of a high-speed communication network as typified by the internet. Among semiconductor modules, the demand for a small coolerless module for intermediate-distance optical communication is increasing.
Such semiconductor modules are often used in locations where high reliability is required of them as in a submarine repeater, or in locations where the temperature environment is severe such as outdoors, so that they are subjected to strict environmental temperature tests to guarantee their reliability.
In environmental temperature tests, the temperatures of semiconductor modules are changed in accordance with a predetermined temperature sequence, during which optical input/output characteristics are observed. Based on the temperature dependencies of the observed semiconductor modules, it is determined whether these observed semiconductor modules are good or defective modules. Therefore, in order to precisely measure the temperature dependencies, it is necessary to precisely control the temperatures of the semiconductor modules.
2. Description of the Related Art
Hitherto, in an environmental temperature test of a semiconductor module, such as an optical module, the temperature of the semiconductor module is kept at the test temperature by placing the semiconductor module on an temperature equalizing block controlled to a test temperature. Hereunder, a related test device will be described.
FIG. 1
is a side view of a related device used for an environmental temperature test of a semiconductor module. Referring to
FIG. 1
, in the related test device, a heat exchanger
53
, a Peltier element
51
, and an temperature equalizing block
52
are placed upon each other in that order on a device base
50
in contact with each other. The Peltier element
51
varies the temperature of the temperature equalizing block
52
by absorbing or discharging heat from the temperature equalizing block
52
which is placed in contact with the top surface of the Peltier element
51
. The temperature of the temperature equalizing block
52
is detected by a platinum resistance temperature sensor
54
placed inside a hollow near the top surface of the temperature equalizing block
52
. The Peltier element is driven so that the detected temperature of the temperature equalizing block
52
is equal to the test temperature, that is, an environmental temperature specified in a test specification.
In a semiconductor module
10
, a semiconductor laser element, a built-in Peltier element for controlling the temperature of the semiconductor laser element, and an optical part (none of which are shown) are incorporated in a package
13
including a heat-dissipating plate
12
, disposed at the lower portion of the semiconductor module
10
, and a cover
11
that covers the heat-dissipating plate
12
. In the semiconductor module
10
, which is a test sample on which an environmental temperature test is conducted, the bottom surface of the heat-dissipating plate
12
is placed in close contact with the top surface of the temperature equalizing block
52
, so that, by conduction of heat from the top surface of the temperature equalizing block
52
, the temperature of the semiconductor module
10
is kept equal to the temperature of the temperature equalizing block
52
. With the temperatures being kept equal to each other, characteristics of the semiconductor module, such as the light input/output characteristics, are measured.
In the above-described related environmental temperature test device, the temperature of the temperature equalizing block
52
is controlled at a predetermined temperature specified in the test specification. By placing the semiconductor module
10
, which is a test sample, on the temperature equalizing block
52
, the temperature of the semiconductor module
10
is caused to reach the predetermined temperature of the temperature equalizing block.
However, since the semiconductor module
10
is only placed on the temperature equalizing block
52
, heat resistance between the semiconductor module
10
and the temperature equalizing block
52
tends to become large due to contact failure. Considering heat dissipation, the top surface of the semiconductor module
10
(that is, the surface opposite to the surface that contacts the temperature equalizing block
52
) is ordinarily designed so that the heat resistance with the ambient atmosphere is small. As a result, a large amount of heat dissipation from the top surface of the semiconductor module
10
causes a large temperature difference to occur due to the heat resistance between the temperature equalizing block
52
and the semiconductor module
10
. Therefore, the temperature of the semiconductor module
10
is different by that amount of temperature difference from the predetermined temperature being specified in the test specification. In an ordinary specification of the environmental temperature test, the test temperature is set at the surface temperature of the semiconductor module
10
. In such a case, the difference between the temperatures of the temperature equalizing block
52
and the semiconductor module
10
cannot be ignored because it causes a reduction in the accuracy of the test temperature of the environmental temperature test.
To prevent such a temperature difference, an attempt has been made to carry out a method of monitoring the temperature of the semiconductor module
10
using a temperature sensor, such as a thermistor, which is attached to a surface of the semiconductor module
10
. However, in this method, the temperature distribution in the semiconductor module varies due to a considerable change in the heat transfer coefficient at the portion to which the temperature sensor is attached, consequently the temperature of the semiconductor module
10
cannot be precisely measured.
In addition, the semiconductor module
10
incorporates elements, including the semiconductor laser element and the Peltier element, which generate or absorb a large amount of heat. The generation and absorption of heat by these elements change the temperature distribution of a portion of the test device that contacts the semiconductor module
10
, such as the temperature distribution near the top surface of the temperature equalizing block
52
. The temperature sensor
54
of the temperature equalizing block
52
is not necessarily provided at a location where it can precisely detect this temperature distribution. Therefore, it becomes more difficult to precisely measure and control the surface temperature of the semiconductor module.
Another problem with the above-described related environmental temperature test device is that there is difficulty in controlling the temperature of the semiconductor module near room temperature.
Environmental temperature tests usually need to be carried out at ordinary temperatures. This ordinary temperature is generally specified as a temperature near 25 degrees, so that there are cases where there is very little difference between the ordinary temperature and the room temperature. In this case, the difference between the temperature of the temperature equalizing block
52
kept at ordinary temperature and the temperature of the ambient atmosphere at room temperature is small, consequently it is difficult to control the temperature. In addition, changes in the temperature of the ambient atmosphere surrounding the semiconductor package immediately changes the temperature of the surface of th
Armstrong Kratz Quintos Hanson & Brooks, LLP
Drake Malik N.
Fujitsu Quantum Devices Limited
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