If water residue from the cleaning process causes real shorts, there is a processing problem that must be solved prior to looking at coating. I suspect that water is under the microBGA and not properly dried. Coating will only trap the remaining moisture, if it even covers the water residue. I do not recommend water washing SMD, especially fine pitch. I have never worked with BGAs. It is difficult to dry under the parts and you cannot tell whether flux residue is trapped under fine pitch without destroying the panel, until its too late. This failure can exist even when the Omega Meter says the panel is clean. I suggest that you have your supplier either bake dry the panels to ensure all water is removed from under the SMD or use a no clean process and see if you even need coating. If its not trapped water, read on. If water residue interferes with your RF, how long will it last in any environment. I suggest you use either a robotic spray or vapor deposition for your coating. Dip will not provide even and repeatable coverage thickness relative to the above conditions. Tunnel spray has higher operating expenses. The coating material chosen depends upon your end environment and circuit design. All coatings have some capacitance and moisture permeability. Depending upon the final environment, system capacitance, sytem inductance...., different coatings will be recommended. I know of one material that worked fine at one environment, but at high humidity, absorbed enough moisture to change dielectric constants and changed the response characteristic of a sensor (at another company). I expect some coatings to do this to RF circuits. Also, you must tune your circuits after coating to compensate for the above reason. ARIC PARR Sr. Manufacturing Engineer Eaton Corp 1400 S. Livernois P. O. Box 5020 Rochester Hills, Mi 48308-5020 [log in to unmask] 248 608 7780 Fax: 248 656 2242 ------------- Original Text From: C=US/A=INTERNET/DDA=ID/TechNet(a)IPC.ORG, on 7/29/98 2:29 AM: To: Aric Parr@01635@Lectron_RH, EatonWHQ@CorpMail@WHQCleveOH[C=US/A=INTERNET/DDA=ID/TechNet(a)IPC.ORG] Dear Net member, We have a hybrid PCB with microBGA and some resistors/capacitors. It is a through hole component for data transmitting. When the customer insert the component to a PCB and finish the wave soldering. It is necessary to clean the board. Due to its application in high frequency, the residue of water after cleaning will cause short of the circuit. To solve the problem, we like to try the conformal coating the PCB. Do anyone can recommend the conformal material and the process? Eden ################################################################ TechNet E-Mail Forum 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's web site (http://www.ipc.org) "On-Line Services" section for additional information. For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312 ################################################################ ################################################################ TechNet E-Mail Forum 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's web site (http://www.ipc.org) "On-Line Services" section for additional information. For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312 ################################################################