---"[log in to unmask]" <[log in to unmask]> wrote: > > Has anyone any experience of blisters (delamination) of solder resist on copper > planes at hot air solder levelling. > > We have been through a range of checks and tests to find the cause, including:- > > Surface conditioning before resist application. > Water rinses on the brushing machine. > Surface moisture. > Predrying before exposure. > In line resist filter. > Quality of electroplated copper. > Final resist cure. > > We are curtain coating liquid photoimageable solder resist. Hasl is carried out > at 250 deg.C dwell time is 6 seconds. The boards are allowed to cool before post > cleaning. There is minimal hold time between final cure and hasl. We have been using the > same solder resist and hasl process for years. Now we have this problem. > > Screen printing the same boards with photoimageable resist, containing more > epoxy, we do not get blisters. > Any response would be appreciated. > > Roger Hammond. > > ############################################################## > TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c > ############################################################## > To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: > To subscribe: SUBSCRIBE TECHNET <your full name> > To unsubscribe: SIGNOFF TECHNET > ############################################################## > Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information. > For the technical support contact Dmitriy Sklyar at [log in to unmask] or 847-509-9700 ext.311 > ############################################################## > From my experience, most of the resist breakdown problems are due to improper final curing. I suggest you to check the temperature distribution in your oven. The min. temperature should be 145 deg C. (different LISM has different setting). Temperature up to 165 deg C is O.K. Air circulation should be 10 CFM or above. The space between panels is very critical. It should be 15 mm or higher. Do not open the oven door during the curing. If you still have resist breakdown problem at HAL, I suggest you pre-bake panels at 150 deg C for 10-20 min. and HAL with 10 min. I hope it can help. [log in to unmask] _____________________________________________________________________ Sent by RocketMail. Get your free e-mail at http://www.rocketmail.com ############################################################## TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c ############################################################## To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TECHNET <your full name> To unsubscribe: SIGNOFF TECHNET ############################################################## Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information. For the technical support contact Dmitriy Sklyar at [log in to unmask] or 847-509-9700 ext.311 ##############################################################