Hi Rex - there are a couple of different failure phenomena associated with the use of gold finishes: 1) gold embrittlement - the formation of a AuSn4 microstructure phase which induces solder joint degradation by a brittle fracture in the solder joint bulk or in the Au/Sn phase. This is a soldering process root cause; 2) black pad - the formation of a corroded Au/Ni interface region which induces solder joint degradation by brittle fracture at the nickel interface region. this is a plating root cause.; 3)solderability failure - the oxidation of the nickel plating which prohibits the formation of good solder joint wetting at the nickel interface region. This is a plating root cause or a storage environment root cause. Gold isn't a bad surface finish - it just has some disadvantages that need to be recognized and dealt with in a proactive manner. Dave Rex Waygood <[log in to unmask]> Sent by: TechNet <[log in to unmask]> 01/17/2008 02:41 AM Please respond to TechNet E-Mail Forum <[log in to unmask]>; Please respond to Rex Waygood <[log in to unmask]> To [log in to unmask] cc Subject Re: [TN] Solderability of Tin-Gold Intermetallic The thread has drifted into brittle fracture due to 'gold embrittlement'. We have experienced 'gold embrittlement' at levels (0.25%) which are well below the threshold said to be 'safe'. Maybe Murphy did his bit to ensure that the gold didn't distribute evenly through the joint and therefore the failure initiated at concentration points. In our situation the important thing was to solve the problem quickly so we made an assumption it was 'gold embrittlement' and took to double dipping to get rid of the plated 'excess' gold. The joints stopped failing after double dipping. I would now say that we tend to have a belief that gold in solder joints should be avoided. Rex Waygood Technical Manager PartnerTech Poole Ltd Benson Road Poole Dorset BH17 0RY United Kingdom Tel: +44 (0)1202 674333 Fax: +44 (0)1202 678028 DDI: +44 (0)1202 338222 Mob: +44 (0)7887 997403 [log in to unmask] www.PartnerTech.co.uk -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Bev Christian Sent: 16 January 2008 13:52 To: [log in to unmask] Subject: [TN] Solderability of Tin-Gold Intermetallic Technetters, We all know that the tin-copper intermetallic has terrible solderability. I also know there are high melting tin-gold solders. My question is: what is the solderability of surfaces of tin with small amounts of gold (<4%) in it? As good as 100% tin, better, worse? If worse, how much so? 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