HASL REPLACEMENT - Immersion White Tin
It seems that everyone is searching for a viable alternative to hot air leveling these days. The reasons include HAL's inability to handle fine pitch applications, the issues involving lead, and its high labor and extensive maintenance. Omni has implemented one such alternative final coating - Omikron Immersion White Tin.
The Immersion White Tin can be run in either a vertical or horizontal application. The process is very straight forward. The exposed copper is first cleaned by an acid cleaner and micro-etch. The boards then go into a pre-dip for about one minute, an immersion tin bath at room temperature for about one minute, and then into a heated immersion tin bath at 60-65° C for six to eight minutes. The panels are then rinsed and warm air-dried.
After going through this process, the areas where copper was exposed on the boards is coated with a flat, uniform, and esthetically pleasing white tin. The tin thickness is approximately 0.7-1.0 micron (or about 44 micro inches). The appearance of the tin is white rather than the gray color of traditional tins.
Immersion White Tin is formulated to create a fine, dense grain structure that is stable and works to suppress the growth of an intermetallic layer. This distinguishes it from traditional tins, which have a porous structure that is unstable and insufficient to suppress the intermetallic layer. This fine grain structure allows Immersion White Tin to resist the dendritic growth or "tin whiskers" that can be a problem for other tins.
A board coated with Immersion White Tin will have a solderable shelf life of one year. Immersion White Tin is excellent for fine pitch applications, and can withstand multiple heat cycles. Moreover, rework for a board coated with Immersion White Tin is easy - simply strip it off with standard tin/solder strippers.
The Immersion White Tin baths have extremely long lives, and are controlled by measuring specific gravity and tin content. A concentrated replenisher is added to the bath when indicated by the measurements.
This process has been tested in the field with more than 35 PC fabricators using Immersion White Tin for their final coating. In addition, Immersion White Tin has been extensively tested in the laboratory to receive numerous OEM approvals.
If your company is interested in an alternative final coating, contact us and we can coat your panels with Immersion White Tin.
© 2000 Omni Graphics Ltd.