Plasma Clean to Reduce Wire Bond Failures
Wire bond failures, their causes, and ways to eliminate them
Concord, California, USA - 7 July 2014 - Nordson MARCH announced that the white paper, Plasma Clean to Reduce Wire Bond Failures, is now available on the Nordson MARCH website at http://bit.ly/PlasmaWP. The article discusses the two areas of wire bonding: the wire bonding process itself (wire bond "statistics") and the long-term reliability of the device.
"In an ideal world we would be bonding onto clean metal surfaces on both the semiconductor device and the substrate or leadframe we are connecting it to," explained John Maguire, business manager, Nordson MARCH and author of the white paper. "In practice, there are a number of sources of surface contamination which influence the wire bond statistics and the device reliability. These contaminants cover the surface we want to bond to, preventing us from making a good bond. A bonding process can run for hours or days without encountering any issues and suddenly go out of control for no apparent reason. Decreases in bonded area, average shear strength, and pull strength are all indicators that when the bond is made, the area of contact between the bond wire and the pad will be sub-optimal. This is due to the surface contaminant impeding the process of "welding." Surface contamination will lead to a bond which does not reach its maximum potential strength."
The article shows that plasma cleaning results in:
- Reduction or elimination of non-stick on pads (NSOPs).
- Reduction or elimination of lifts.
- Increase in average shear strength.
- Increase in bonded area.
- Increase in average wire-pull strength.
- Increase in process window for the bonding process.
- Reduction or elimination of cratering and other damage arising from a too aggressive bond process.
The introduction of an appropriate plasma process prior to wire bonding will always deliver a cleaner surface to bond to. The article describes wire bond failures, their causes, and ways to eliminate them. Potential benefits are improved wire bond statistics, improved device reliability, and the elimination of excursions caused by non-systemic influences such as random pollution of the surfaces to be bonded by uncontrolled factors.
For more information, visit www.nordonmarch.com.