Atul, You may have two problems causing this insulative fault. We have seen this in some other troubleshooting projects we have worked on. I believe that the insulative film that you are experiencing is a weak organic acid (WOA) from the no clean flux. Most low solids fluxes are WOA-activated. The WOAs are an insulating material when dried on a surface, but they are not a very durable film. That is why you get contact after 3-4 insertions, you have worn through the WOA film. The source of the film is two-fold. First, if you are spraying and wave fluxing, you are putting high amounts of flux on, probably flooding the area. As the no-clean fluxes usually have a high level of isopropanol, capillary action can carry the flux to places you never intend, such as the mating surfaces of a ZIF socket. We have had customers who have had the same problem inside of membrane switches. Secondly, you may be getting WOAs as a result of pyrolization. When a low solids flux burns off, either in pre-heat or in wave solder (or hand soldering), where to the evaporated / burned material go? In many cases, the smoke or fumes are very pervasive and can "vapor deposit" on the inner surfaces of components, such as sockets. Such deposited layers are also WOAs, but are usually more fragile, causing intermittant failures, rather than the more consistent layer you are experiencing. To combat these problems, you must be more careful about where, and in what amount, you are applying your flux. More is not better. Second, you need to be more efficient in your fume removal. Hope this was helpful. Doug Pauls [log in to unmask]