Study on Microstructure of Vippo Desinged PCB in Lead Free ReworkAuthors: May Yan, Bendy Cai, Scott Priore
Company: Cisco Systems Ltd.
Date Published: 4/22/2014 Conference: SMTA China
The increasing usage of High Density Interconnect Printed Circuit Boards (HDI PCBs) makes the plugging of micro-vias becoming an inevitable subject for many manufactures of PCBs. Component pitch are going finer and the HDI design grows rapidly. In VIPPO design, via should be 100% plugged with thermal cured material. Via plugging is added after through hole copper plating and then add cap plating to be as a normal copper pad for further soldering in assembly. More and more lead free products adopt VIPPO design thus there are unexpected defects such as voids and bad soldering issues during reflow and even pad damaged in rework process due to the higher soldering temperature.
Different PCB supplier may have different VIPPO manu-facturing process and vary in PCB qualities. To study and understand the details of the VIPPO manufacturing process and the microstructure of the VIPPO would be good for the later SMT soldering and failure analysis. The purpose of this VIPPO soldering study is to find the impact of VIPPO PCB on lead free soldering as well as rework and to optimize the entire soldering process to en-sure the stable process and provide the higher reliable products.
This paper describes the microstructure of VIPPO, manu-facturing process for VIPPO in PCB factory and the sol-dering study in lead free rework for different designed VIPPO pads as well.
VIPPO (Via in pad and plated over), Capped plating, DOE
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