Martin Muendlein, ESCATEC's Engineering Manager, explained, "Until now, PoP has only been used in high volume applications such as mobile phones, where it provides high density packaging, low power and high performance. We believe that we are one of the first contract manufacturers in Europe to offer this as a low volume option to customers. It is ideal for customers wanting to make portable devices that need high performance processors and where space is tight. We already have one customer wanting to use PoP for their next generation of a hand held terminal."
The company has invested in a special dipping unit for its new Siplace assembly line that will enable it to do PoP. The dipping unit wets about 50% of each ball of the Ball Grid Array with paste/flux. Before reflow, both components are stacked on each other and then both are soldered in one process step. During the soldering the upper device sinks down so that, in the final assembly, there is virtually no gap between the two stacked chips. Verification of accurate bonding between the layers of the PoP stack is checked using X-Ray inspection. The darker balls are from the upper BGA and the lighter balls are from the lower BGA.
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