Agree with you, Dave. One benefit is that we can now combine soldering, glueing and wire bonding on one and the same card. The Pd is very thin compared with the traditional 5 micron Ni (save material) and the hardness properties of Pd is sort of compromise so that you can wire bond (Ni is not very good for fine wire gold ball bonding, aluminium heavy wire acceptable) with good result. We tried Pd in combination with epoxies, Teflon and other dielectrics (you know, Taconic, Arlon and like) and the result was good in many cases, but not all. So, Pd doesn't seem to be a universal miracle tool, as said Dave. Ingemar Hernefjord Ericsson Microwave Systems -----Original Message----- From: David Hillman [mailto:[log in to unmask]] Sent: den 30 juni 2000 15:13 To: [log in to unmask] Subject: Re: [TN] Palladium query Hi TechNet! This discussion on Pd has been wonderfully fun from a metallurgical viewpoint! One segment of information that has not come to light but really links the various responses together is the thickness of the Pd plating. Early test programs and investigations used relatively thick coating thicknesses (greater than 20 microinches) which promoted the formation of Pd/Sn intermetallic phases. The Pd/Sn intermetallic phases are brittle and resulted in solder joint crack failures (as documented in early TechNet posts). However if the Pd thickness is specified in the 9-12 microinch range the formation of the brittle intermetallics can be avoided and solder joint reliability is not compromised. The use of Pd is very similar to Au - there is a specific region of the phase diagrams which we need to reside in to avoid solder joint reliability problems. The use of Pd as a surface finish will find its place in electronics assembly because it is both wirebondable/solderable - but due to cost and process considerations it will not be the next 'universal' finish. Its just another surface finish option in our design/assembly 'tool' boxes. Dave Hillman Rockwell Collins [log in to unmask] To: [log in to unmask] cc: Subject: Re: [TN] Palladium query Hi Terry, TI publish a useful "Palladium Finish User's Manual" which may give you more information on palladium lead finish on components. According to this, the finish is as follows (viewed with Cu leadframe at bottom of list/outer layer at top): Palladium min 3u" (0.075micron) Nickel Plate 40 - 60u" (1.0 - 1.5micron) Palladium/Nickel Strike max 5u" (0.125micron) Nickel Strike max 5u" (0.125micron) Cu. Base Leadframe The key role of the palladium is to protect the underlying layer of nickel from oxidation during storage/assembly. The palladium dissolves into the solder joint, and these joints can look significantly different to those made to a solder dip finish leadframe. The exact role of the underlying Palladium/Nickel Strike and Nickel Strike layers I am not sure. Perhaps other TechNet Minds can advise? Hope this helps, Clive ffitch Matra BAe UK Stevenage, England -----Original Message----- Fellow TechNetters, Can someone please enlighten me as to the purpose of a Palladium Barrier on components / PCBs. Best regards Terry Exell BAE SYSTEMS, Plymouth, UK ############################################################## 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 ##############################################################