1 Wafer test probe burn modeling and characterization Baha Zafer Mehdi H. Vishkasougheh İstanbul University - Dept. of Mechanical Engineering İstanbul Şehir University - Dept. of Industrial Engineering, İstanbul, Türkiye / baha.zafer@istanbul.edu.tr İstanbul, Türkiye / mehdi@sehir.edu.tr Bahadır Tunaboylu İstanbul Şehir University - Dept. of Industrial Engineering, İstanbul, Türkiye / btunaboylu@sehir.edu.tr Abstract This study investigates the wafer probe temperature distribution along a probe body in order to model probe burn phenomenon by using computational mechanics techniques. The finite volume software is used to study the effects of different materials and different geometrical factors on the temperature along a special design vertical/spring and cantilever probe. The computation shows higher temperatures towards the probe tip region as a result of Joule heating. The probe burn is also observed at the tip region of spring and cantilever probes in wafer testing. This is believed to be due to very low heat dissipation rates resulting from very small sizes compared to the probe body. 1. Introduction Recent advances in semiconductor process technologies have enabled the design of complete electronic systems on a single chip. In order to handle the complexity and satisfy the increasing demand for a shorter time to market, design engineers typically use computational mechanics techniques in their designs especially for structural analysis and thermal management [1]. Wafer level test is the first step in the manufacturing test process, where the chip in bare wafer form is tested by using the input/output (I/O) terminals of the chip for manufacturing defects. The devices are subjected to standardized parametric and functional tests such as electrical excitations and thermal cycles [2]. In the wafer level test, an individual chip is tested using a probe card with probe card needles as shown in Figure 1. (a) (b) Figure 1: Images of a) probe card for higher pin counts and b) detailed view of cantilever probe needles and wafer pad contacts. In this paper, the 3D thermal conduction equation with Joule heating as a source term is used to compute temperature distribution on the probe body. A special design spring beam and cantilever probe was selected as the probing technology for this study. A computational model is used for the probes for predicting temperature rise along a probe body in order to investigate probe burn effects. The effects of different probe materials such as Tungsten (W) and Nickel-Manganese (Ni- Mn) on the temperature distribution and performance is investigated. 2. Probe Burn Phenomenona A probe will burn during wafer test when its probe current carrying ability (I max ) is exceeded. The maximum allowable probe current carrying capability is a function of probe material, probe wire diameter, and the probe tip diameter. In addition, the continuous (steady state) or pulsed currents are important parameters for the study of probe burn. Probes are usually the weakest link in the test architecture and therefore first to burn during test due to the constriction resistance. Therefore, in many applications the crucial point is how much current can be handled by a spring probe tip. Increasing wafer probe current beyond its limit can drastically reduce life span by deforming or burning the probe tip. Experimental study results showing probe burn locations [3,4] for vertical and cantilever type of probes are shown in Figure 3a and 3b, respectively. (a) (b) Figure 2: Probe burn effects on (a) the vertical probe at the middle curved section of the probe and (b) the cantilever probe at the tip due to Joule heating. 978-1-4673-6139-2/13/$31.00 ©2013 IEEE 2013 14th International Conference on Thermal, Mechanical and Multi-Physics Simulation and Experiments in Microelectronics and Microsystems, EuroSimE 2013 — 1 / 4 —