Tri, Bob Furrow is correct. You need to remember the XRF doesn't measure thickness. In essence, the proportional detector measures atomic mass and the instrument is ususally calibrated with known thickness materials so that the results can be related to thickness. You can dip a copper sample into SnPb solder and blow off all of the solder leaving only the copper-tin intermetallic (Cu3Sn or Cu6Sn5) and when measured with an XRF calibarted to measure solder thickness will indicated that there is some solder present (0-40 microinches) and that it will have a high tin composition (70-100%). If you cross section the sample you'll more than likely find that there is only intermetallic left on the copper. -----Original Message----- From: Furrow, Robert Gordon (Bob) Sent: Tuesday, May 09, 2000 7:15 AM To: [log in to unmask] Subject: Re: [TN] HASL Tin-Lead component in thin coating Tri, I assume you are using X-Ray fluorescence to determine thickness and alloy composition. When you measure a thin pad (under 1 um), you are also picking up the tin from the CuSn intermetallic layer which is tin rich. The thinner the HASL coating, the higher the tin content expected since the intermetallic thickness relative to the bulk HASL coating is increased. Thanks, Robert Furrow SMT Process Engineer Lucent Technologies 978-960-3224 [log in to unmask] <mailto:[log in to unmask]> -----Original Message----- From: Le Dai Tri [SMTP:[log in to unmask]] Sent: Tuesday, May 09, 2000 4:16 AM To: [log in to unmask] Subject: [TN] HASL Tin-Lead component in thin coating TechNeter, We use horizontal HASL machine. When I measured the thickness of tin/lead if the thickness was over 1um, the component of tin was 64~69%, if the thickness was under 1um (0.8~0.9um), the component of tin was always over 70%. (Tin/lead made-up in solder pot was 63+/-3%; 37+/-3%; board thicness was 1.6mm) I did'nt know the reason why? In the case of component of tin was over 70%, what will happen in PCB Assembly manufacturing? Any help would be appreciated. Best regards, Tri'. _______________________________________ PWB Development section E-Mail : <mailto:[log in to unmask]> [log in to unmask] ############################################################## 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. If you need assistance - contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ############################################################## ############################################################## 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. If you need assistance - contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ##############################################################