by Debra Vogler, senior technical editor, Solid State Technology/Advanced Packaging

September 28, 2009 – Earlier this month, Süss MicroTec launched its PA300PS 3D probe station targeting 300mm electrical probing of 3D stacked structures at the wafer-level. (The company already has wafer bonders and lithography equipment for 3D integration.) Among the probe’s features are an alignment function for vertical probe card technologies (MicroAlign), with an automated thermal management (ATM) system for active thermal compensation at various test temperatures. The mechanical stability of the chuck system enables the 3D application.

With automated testing at multiple temperatures in relation to small targets, one must consider thermal expansion and movements in the entire system when probing them, explained Stojan Kanev, director of marketing and product management at Süss MicroTec. "The ATM system adapts the probe station automatically to the different temperatures using sensors that tell the machine to control the right amount of dew ambient air and air purging, which minimizes thermal expansion," he told SST/AP. The ATM also enables the system to get to thermal equilibrium more quickly because stage and chuck target temperatures can be set independently, he noted; this feature is "especially useful in long-term measurements," and increases productivity by saving time with shortened settling periods through thermal stability, he added.

According to the company, using high pin count vertical probe cards in combination with its MicroAlign technology enables damage-free probing of small test pads and minimizes pad probe marks. Regarding the z-theta chuck, Kanev told SST/AP that vertical probe cards have the disadvantage of the operator not being able to see from the top. "This is important for engineering lab applications," he explained. "High pin count vertical probe cards are usually very expensive, so being able to view from the side [(via ContactView technology, another product feature] ensures that the expensive probe cards are protected during the operation."

Kanev also emphasized the importance of having a stable, accurate z-axis design. "Working with vertical probe cards to contact many micro-bumps at the same time usually leads to a high pin count and a high load capacity," he said, so the system needs to provide "minimal deflection independent of the load." The wedge design supporting the whole wafer area as well as the z-axis feature enables simultaneous control of overtravel and contact quality on the pads, he added.