Beside gold thickness, the amount of solder applied should also be considered. Per IPC-D- 279, "Design Guidelines for Reliable Surface Mount Technology Printed Board Assembly", Section 5.4.4. where gold or palladium plating is used, the gold or palladium content in the solder joint should be approx 3 %wt. or less. Here are our thinkess rules for Gold. Electrolytic AKA hard gold: Mostly for Wire bond Elecrtroles AKA Soft gold: Common 15 to 25 u" as long as it follows the 3%wt rule Immersion: Common 5 to 10 u" (Preferred in SMT assemblies, except edge finger connector) To calculate the weigth factors, these number might help Density of Gold = 19,300 kg per m3 Density of Solder = 8,500 kg per m3 Please ensure to have at least 100 u" of Ni beneath the gold. Hope that helps Michael Yuen ################################################################ 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 web site (http://jefry.ipc.org/forum.htm) for additional information. For the technical support contact Dmitriy Sklyar at [log in to unmask] or 847-509-9700 ext.311 ################################################################