Development of UV-LIGA contact probe

In recent years, as mobile equipment such as cellular phones and PDAs become drastically higher performance and downsized, semiconductor devices are rapidly becoming more integrated and higher speed. As a result of high integration, the pitches of electrode pads in chips are becoming smaller than 100 μm. In some devices, pad pitches are as small as 40 μm. Because the packing density of circuits has increased, the width of the probe and the space between each probe needs to be reduced. Therefore, in the field of IC testing, probe cards that contact the I/O pads of the devices are required to have more probes arranged in higher density. In order to achieve these small probes and narrow pitch probes, the fabrication processes have been studied. Microfabrication technique can be applied to develop probe cards with high-density and high pin-count by batch processing, such as probes have been reported to be fabricated by using the LIGA (Lithographie Galvanoformung, Abformung) process, the LIGA technology is the most popular as a result of low cost and batch production. The primary fabrication processes were photolithography, electroforming, and polishing technology. The material of the electro-plated probe tip was a Ni-Co alloy. In this study, we demonstrated the potential of 30×40 um tips (φ2 mil) cobra type contact probe by UV-LIGA process. The contact force is 4±1 gf with 100 μm over drive (O.D.) and lifetime is more than 300,000 touchdowns. The measured contact resistance is less than 640 mΩ and current carrying capability is 150 mA at room temperature.