30 micro inches of gold cannot be achieved through ENIG plating. From Coombs' Printed Circuits Handbook; "In this finish a layer of electroless nickel with a thickness of 120 to 240 micro inches is deposited on the copper surface. This is then followed by a thin coating (2-4 micro inches) of immersion gold. The nickel is a diffusion barrier to copper and is the surface to which the soldering occurs. The function of the immersion gold is to protect the nickel from oxidation or passivation during storage." Your specifications would require gold electroplate. The nickel thickness seems to be an order of magnitude too thin. 200-300 micro inches nickel plated with 30 micro inches of gold would seem to be a compromised gold thickness intended to have reasonable wear resistance and still allow for acceptable soldering process results. A word of caution. The gold would be too thick for most solder paste - surface mount applications, resulting in brittle solder connections. We worked out a rule of thumb some months ago, here on the TechNet. I think the number was 5 mil stencil - 10 micro inches max gold thickness. I am sure the thread is in the archives. This causes some problems in practice because it is difficult to protect the nickel with a 10 micro inch max on gold electroplate. It is a process thing. -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of David Harman Sent: Friday, December 29, 2006 1:09 AM To: [log in to unmask] Subject: [TN] Questions on ENIG VS gold plating I need some help in understanding. Are specified requirements are emersion gold plate per Mil-G-45204 type 2, gold plating thickness maximum of .00003 inches (30 micro inches) over minimum of .00005 inches (50 micro inches) nickel for our PCB Is this a standard that is used widely, any other recommendations? My supplier has indicated the following. The specifications you listed in your e-mail do not apply to the ENIG finish (Immersion Gold, electroless nickel) Mil -G- 45204 refers to Electroplated Gold, Type 2 is 99.0% purity IPC 6012B Table 3-2 requirements for ENIG are 1.97 u" minimum immersion gold and 118 u" minimum of electroless nickel. Which is a better specification? What would give better quality / reliability? Is there anyway to correlate the two different specifications. Can I correlate ENIG specs, to that of gold plating.? Dave --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 1.8e To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 ----------------------------------------------------- --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 1.8e To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 -----------------------------------------------------