Patent Application
20160041202
The present invention relates to test fixtures for electronic/optoelectronic devices, and more particularly, to a test fixture with a thermoelectric cooler (TEC) and a spring-operated holding pin to provide a desired contact pressure between the device under test and the TEC.
Testing of electronic or optoelectronic devices or other components often involves thermal control of the device under test (DUT). This is particularly true when the device is a laser and the transmission wavelength of the laser may be dependent on the operating temperature of the laser, thus requiring relatively precise thermal control to obtain accurate test results. Many other types of electrical or electronic components may similarly require thermal control to a desired level of precision for proper testing.
Typically, a test fixture, or portion thereof, is enclosed in an oven or other type of environmental control chamber that attempts to regulate the temperature of the environment to a desired level for operation and testing of the device. An oven or other such device, however, is generally not able to maintain a uniform temperature distribution throughout the environment. In particular, each DUT typically generates heat during operation and may therefore raise the local temperature in the vicinity of the device, creating a varying temperature profile throughout the oven. Additionally, each DUT may draw a different operating current, as compared to another DUT, and therefore run at a different temperature. These varying temperatures may degrade testing results and lower production yields.
These and other features and advantages will be better understood by reading the following detailed description, taken together with the drawings wherein:
A test fixture, consistent with embodiments described herein, provides improved thermal control of a device under test (DUT). The test fixture generally includes a thermoelectric cooler (TEC) configured to regulate the temperature of the DUT. The test fixture may further include a device carrier configured to secure the DUT in a desired position relative to the TEC and a spring-operated pin configured to generate a desired contact pressure between the DUT and the TEC. The desired contact pressure may be selected to achieve a thermal coupling between the DUT and the TEC that maintains the temperature of the DUT at a desired operation level, while avoiding damage to the DUT that might result from excessive pressure.
The DUT may be any type of electrical, electronic or optoelectronic component, the operation of which is sensitive to temperature variation, including a laser or laser diode chip, such as, for example, a laser diode chip incorporated in a mini-coaxial laser.
As used herein, “wavelength” refer to the wavelengths associated with optical channels and may include a specified wavelength band around a center wavelength. In one example, the channel wavelengths may be defined by an International Telecommunication (ITU) standard such as the ITU-T dense wavelength division multiplexing (DWDM) grid. As used herein, “tuning to a channel wavelength” refers to adjusting a laser output such that the emitted laser light includes the channel wavelength. The term “coupled” as used herein refers to any connection, coupling, link or the like and “optically coupled” refers to coupling such that light from one element is imparted to another element. Such “coupled” devices are not necessarily directly connected to one another and may be separated by intermediate components or devices that may manipulate or modify such signals.
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In a relatively simpler embodiment, the force application module 202 and operator interface 206 may include a lever and/or handle mechanism through which an operator exerts downward pressure on the spring-operated pin 208 which is configured to compress by a pre-determined distance that generates a known spring force. The spring force may be calculated by the spring equation F=kx, where k is the spring constant and x is the compression distance. This spring force is selected or calibrated to provide pressure on the DUT that achieves a desired thermal coupling between the DUT and the TEC. The desired contact pressure and resulting thermal coupling may be associated with a desired operational temperature for the DUT. In some embodiments, for example where the DUT is a laser or laser diode, the desired operational temperature may be associated with a desired transmission wavelength (or tuned channel wavelength) of the laser.
In some relatively more complex embodiments, the force application module 202 may be an electric motor, a hydraulic operated device or other suitable device configured to generate force on the spring-operated pin 208 in a more automated manner, as opposed to the manual process described above. Force controller module 204 may be a closed loop feedback system configured to control the level of force generated by module 202 based on, for example, measurements of the compression distance or generated pressure of spring 208 obtained by distance/pressure monitor module 210 or other suitable sensor systems. In some embodiments, force controller module 204 may be implemented as software executing on a computer system or processor and operator interface 206 may include a computer display, keyboard, mouse and/or any other suitable input/output devices coupled to the computer system. For example, a user/operator may enter information about the DUT 106 (e.g., device classification, model number, serial number, etc.) and the computer system may retrieve previously stored data that is related, either directly or indirectly, to the desired force of the spring-operated pin.
TEC controller module 214 may be configured to control the level of cooling/heating that is to be provided to the DUT 106 by the TEC 108. The TEC configuration may be associated with parameters that are pre-determined or operator adjustable. In some embodiments, operator interface 206 or another computer system may be configured to enable operator adjustment of the TEC parameters. Base or heat sink 216 may be configured as both a stable platform for the TEC 108 and as a mechanism for heat dissipation, for example when the TEC is operating to cool the DUT 106.
Testing probes 212 may be configured to supply signals, to monitor and measure results and/or to provide power to the DUT 106 to enable operation of the DUT for testing purposes. In some embodiments, the DUT 106 may be a laser and an optical fiber may also be coupled to the laser during the test. In some embodiments, the DUT may be a mini-coaxial laser.
In some embodiments, a locking mechanism may be provided, for example as part of the operator interface 206, to lock the spring-operated pin 208 in its compressed position during the test so that the correct thermal contact may be maintained throughout the test.
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In this embodiment, the force application module 202 is implemented as cam box 304, which may be configured to translate rotational or linear motion of hand crank 302, for example by an operator, into downward motion of spring-operated pin 208. The cam box 304 may be secured to the base 216 by any suitable mounting hardware 306. A locking knob, or other locking mechanism (not shown), may be included to engage or fix the position of the cam box 304 during test.
In this illustration, cam box mounting hardware 306 is shown to include springs which are configured to push the cam box 304 back up to effect the separation of spring pin 208 and DUT 106 when the lock is released at the completion of the test. The cam box springs may be configured to avoid excessive pressure contact between spring pin 208 and DUT 106, in order to further reduce the risk of damage to the DUT 106 by the spring pin 208. In some embodiments, the locking knob may be part of the hand crank 302 (or other lever mechanism employed as part of the operator interface 206) or part of the cam box mounting hardware 306.
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Accordingly, a test fixture with thermoelectric cooler and spring-operated holding pin, consistent with embodiments described herein, may provide a desired contact pressure between the device under test and the TEC.
Consistent with one embodiment, a test fixture generally includes a thermoelectric cooler (TEC) configured to regulate temperature of a device under test (DUT). The test fixture may also include a device carrier configured to secure the DUT in a desired position relative to the TEC. The test fixture may further include a spring-operated pin configured to generate a desired contact pressure between the DUT and the TEC. The desired contact pressure may be associated with a desired thermal coupling between the DUT and the TEC.
Consistent with another embodiment, a method generally includes securing a device under test (DUT) in a position proximate to a thermoelectric cooler (TEC). The method may also include regulating the temperature of the DUT through operation of the TEC. The method may further include applying a spring-operated pin to the DUT to generate a desired contact pressure between the DUT and the TEC. The desired contact pressure may be associated with a desired thermal coupling between the DUT and the TEC.
While the principles of the invention have been described herein, it is to be understood by those skilled in the art that this description is made only by way of example and not as a limitation as to the scope of the invention. Other embodiments are contemplated within the scope of the present invention in addition to the exemplary embodiments shown and described herein. Modifications and substitutions by one of ordinary skill in the art are considered to be within the scope of the present invention, which is not to be limited except by the following claims.
