11-09-2009 07:58 AM
Hey Guys, I have a query in regards to Virtex-5 devices. Hopefully you are able to share some of your experiences on it:
We are using Virtex-5 on our boards and the boards goes through a inline wash cleaning process. The boards are soldered using a No-clean solder paste and are washed in an inline cleaner using slightly alkaline cleaning agent (pH ~ 10). After the wash process, we noticed there is an interaction with the solder on the cap networks under the lid of the IC's. This resulted in formation of white powder like material as well as black spots on some of the capacitor leads.
Even in the case of DI-Water applications (no chemistry used), we noticed there was water getting trapped which was resulting in the failure of these parts.
The datasheet suggest that solvents and water could seep through the vents on these IC's and attack the organic materials and components inside the package. Could you kindly let me know what are these organic materials and why would it be attacking the heatspreader if its cured already?
Could you suggest an alternative over here if we need to clean these parts? How could we avoid this issue? Any suggestions or recommendations are highly appreciated.
03-06-2012 06:53 AM
The major concerns would be if a semi-aqueous cleaning chemistries are used to remove rosin (ROL0 type flux per J-STD-005). Saponifiers are basic organic materials that are designed to react with rosin in flux to form a saponified byproduct- soap- which is water soluble and can be rinsed off with DI water. In the case where the materials are trapped and cannot be rinsed off there might be some concerns. In most cases where you are worrying about corrosion, you need (1) moisture, (2) ionic residue and (3) a bias. If the residues are dry and the board is conformal coated to prevent moisture absorption - such as paralyene conformal coat- then I would think that the changes for later corrosion would be negligible.