Abstract
Test Contact Pin is used for testing the functionality and quality of the micro-devices at extreme temperatures before shipping to customers. The contact pin transfers current & signal to the device tested through dynamic contacting where the material resistance of the pin and the contact resistance between the pin and the device plays a significant role in influencing the effectiveness of the test process. Available material specifications for these pins in the market are for ambient temperature only. The test contact pin was characterized across temperatures onto matte Sn leadframe for its contact resistance and force with respect to number of touchdowns. Contact resistance and pin force are the key variables used to understand the mechanism of the process which is also used for determining the lifespan of the contact pin. An automated and sophisticated contact tester tool (CTT) was used to characterize the test contact pin on the mattes Tin leadframe across temperatures (-43°C, 25°C and 150°C) and at fixed pin deflection. Based on the results, it was observed that the contact resistance was higher at higher temperatures. Further data analysis revealed that this phenomenon was due to influence of various factors such as temperature, leadframe material type and the material migration of Sn from leadframe to the test contact pin tip.
Highlights
Testing is a dynamic process in which the micro-devices are checked for their functionality and quality by pumping current and signal to the devices before shipment to the customer
Test contact pin that was run at ambient exhibited the trend of force and contact resistance (Cres) measurements as shown in the graph below (Figure 5)
It was observed that the contact resistance increased from 21mOhms to 78 mOhms after 1 million touchdowns
Summary
Testing is a dynamic process in which the micro-devices are checked for their functionality and quality by pumping current and signal to the devices before shipment to the customer. It is significantly smaller as compared with the overall circuit resist¬ance, the changes in the contact resistance can cause significant malfunctions of the device This is because the contact resistance can vary significantly with the changes in the real contact area, contact pressure variations, resistive film nonuniformity, and other factors. Perhaps the most important are electric (the transition voltage drop, commutation noise, erosion resistance), tribological (the wear resistance and friction coefficient) and chemical (corrosion resistance) Another important factor affecting the contact behavior is the presence of various films (such as oxides, contaminants, and reaction products). Since the electrical current lines are constricted to allow them to pass through the aspots, the electrical resistance increases. In the case of isotropic roughness topographies, the aspots are assumed to be circular or noncircular when the roughness has a directional characteristic
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