Cantagallo, Hope this helps. A nominal thickness of 4µm provides enough thickness to prevent leaching, in most cases. The ±2µm provides the plating operation with a readily achievable process window, thereby keeping your/their costs down. Even at 2 µm one should have good leach resistance and durability. Three possible issues come to mind. 1 - Even though the rate of dissolution of Ni in the solder is quite slow [function of temp and alloy], at 0.5µm of Ni you may run into Ni leaching issues. Some thick film Cu pastes are fritted, meaning that they bind to the Al2O3 substrate by mechanical [glass] means. Some of these pastes can/do have an excess of frit [glass] at the surface, which makes them difficult to solder to. Plating over this surface provides a uniform surface to solder to. If your plated surface is in poor condition and you expose the underlying Cu, the solderability of the Cu may not be all that good. There are a lot of "it depends" - on the exact Cu used, Cu firing conditions, plating control, solder alloy, and solder reflow conditions. 2 - At 0.5µm, the Ni layer may not totally/uniformly cover the underlying Cu. If the substrate is subjected to elevated temperatures, the Ni may diffuse through the thin Ni layer and into the Au layer. If the substrate is then allowed to 'sit around' in this condition for prolonged periods of time, the exposed Cu may oxidize and render the surface only partially solderable. 3 - Even though you did not ask, if the Ni layer is thin [by accident?], it is possible that the Au layer is also very thin [plating process not in control] - making item 2 even worse. This can also result in oxidized Ni, which is also hard to solder to. If you are thinking about reduced Ni thickness as a cost savings - I would not do it. The Ni plating is cheap. Likely cost you more as a 'special process'. If you are asking about reduced Ni thickness because a shipment came in that way - I would send it back and request they ship what you asked for. Best wishes, Steve Creswick Sr Associate - Balanced Enterprise Solutions http://www.linkedin.com/in/stevencreswick 616 834 1883 -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of [log in to unmask] Sent: Monday, September 05, 2011 5:52 AM To: [log in to unmask] Subject: [TN] Fw: Electroless Ni plating thickness Hello Technetters. We use a ceramic substrate covered with Cu layer. This Cu layer is plated with ENIG process. We solder SMD's on it with SnPb process (vapor phase and iron). The ASTM specifications give a thickness of Ni 4 ± 2 µm. Where comes from this value ? What could be an issue with thinner Ni layer like 0.5 µm ? Thanks to answer. Best regards, CANTAGALLO Luigi ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. For more information please contact helpdesk at x2960 or [log in to unmask] ______________________________________________________________________ --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 16.0 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 For additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 ----------------------------------------------------- ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. For more information please contact helpdesk at x2960 or [log in to unmask] ______________________________________________________________________ --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 16.0 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 For additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 -----------------------------------------------------