Executive Summary

The purpose of this project is to design a peripheral seal solution for our sponsor, Cohu, to implement into their existing semiconductor testing machines. Cohu is an industry leader in equipment and services for back-end semiconductor manufacturing, including test and handling equipment, thermal subsystems, test contacting, vision inspection and MEMS test solutions. It is necessary to research a variety of seal candidates in attempts to move the pickup mechanism for their pick and place handler to the periphery of the semiconductor chips their products handle. The reason for this is to extend the surface contact area of the thermal element that they use for the tests in order to increase the capability of their testing equipment. We have designed a preliminary seal that utilizes a bellow. We have verified its lifecycle using FEA software, and have tested the concept with prefabricated bellows. In order to test these bellows, we created a fixture that simulates a pick up cycle and tests whether the pickup was successful or not. It includes a airtight chamber that seats a heat sink and the seal. The setup is actuated by a stepper motor, controlled by a microcontroller. Air pumps create both the vacuum and blow-off, which are actuated by a 3 way valve, that are used to pick up and blow off the chip in different stages of the pick up cycle. There is a pressure sensor in this setup that sends pressure data to the microcontroller. The heat sink is heated up to the desired temperature for each test using cartridge heaters and an RTD controlled by the microcontroller. A successful pickup cycle satisfies that the chip was able to hold pressure in the pressure sensor in the upright position for a designated dwell time. This data is recorded over several cycles for analysis about the seal performance at certain temperatures.