I can offer two other alternative explanations: (1) When PCB's were hand assembled, a great many of the operators found the green colour 'more restful' on the eyes than other colours used. (2) A more likely explanation is that the green colour is usually from a copper phthalocyanine pigment, which at the time of the first boards, was the only heat-stable organic colour. David Albin Project Leader Coates Circuit Products -----Original Message----- From: Arturo Aguayo [mailto:[log in to unmask]] Sent: 16 February 2000 08:14 To: [log in to unmask] Subject: [TN] Why are soldermasks green? I was recently asked by a college student working on a research project, "why are printed circuit boards green?". The short answer to that is that they are green because of the soldermask color. Which led to the next question "is there a reason why soldermasks are green?" To this question I had no answer and therefore turn to this forum to see if anybody might know the reason (I wouldn't want a student to not graduate because of me). regards Art Aguayo ############################################################## 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 Gayatri Sardeshpande at [log in to unmask] or 847-509-9700 ext.5365 ############################################################## ############################################################## 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 Gayatri Sardeshpande at [log in to unmask] or 847-509-9700 ext.5365 ##############################################################