Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


low thermal emf solder & paste - SAC 405

Views: 3110

#72099

low thermal emf solder & paste - SAC 405 | 12 May, 2014

Hello - I am looking for a source to supply low thermal EMF solder - can anyone provide pointers ? In the past a cadmium - lead alloy was used for this, but these are banned (RoHs) ... - the aim is to minimize thermo-couples on a very sensitive 4 layer printed circuit board - 0.1ppm / K on a 10V full scale - so every 100nV we can reduce is taken under consideration (preventive actions) Could SAC405 (Ag4% 95.5%Sn 0.5%Cu) a silver based alloy be a suitable product ? Thank you for all feedback !

Michel (Belgium)

reply »

#72103

low thermal emf solder & paste - SAC 405 | 12 May, 2014

I've never used SAC405. Not for nothing ...

Other low temperature solder alloys that you should consider are: * Sn42/Bi58 [138*C]: Alloy for low temperature applications. Attention should be paid to potential embrittlement issues and poor thermal fatigue properties. * Sn42/Bi57/Ag1 [138*C]: Similar characteristics to Sn42/Bi58 with improved fatigue characteristics. * In97/Ag3 [143*C]: Alloy for low temperature applications. Costly due to high indium and silver contents. Attention should be paid to corrosion, joint strength and fatigue issues. These points were made in an excellent, although maybe somewhat dated paper [http://www.smtnet.com/library/index.cfm?fuseaction=view_article&article_id=1975] ]

BR ... davef

reply »

#72109

low thermal emf solder & paste - SAC 405 | 13 May, 2014

What is the product for? If you share more information maybe there is another way of dealing with the issue, like removal of the joints by a different circuit design.

sarason

reply »

#72110

low thermal emf solder & paste - SAC 405 | 13 May, 2014

> What is the product for? If you share more > information maybe there is another way of dealing > with the issue, like removal of the joints by a > different circuit design. > > sarason

Hello - it is a highly stable reference source - exactly 10,000.000.0xV generated and < 0.2ppm total drift / YR (target) - it is not a question of solving issues, it is a question of avoiding them by design & mfg. - so we take all details into account - one of those is using appropriate low thermal emf solder, correct materials and appropriate PCB Lay Out. Thanks - Michel

reply »

#72111

low thermal emf solder & paste - SAC 405 | 13 May, 2014

Hello davef - could it be you are confusing low thermal emf (Seebeck coefficient) with low temperature solder ? I am looking after solder wire and paste with low Seebeck coefficient - cadmium based alloy was OK but banned in europe due to RoHs directive - so looking for substitute. classic Sn Pb is around 1.5µV/K - low thermal emf is around 160nV/K - everything < 0.3µV/K can be considered. material should be RoHs compliant Thank You - Michel

reply »

#72112

low thermal emf solder & paste - SAC 405 | 13 May, 2014

Hello Michel...this might be a bit of a battle finding the low thermal EMF material that you are looking for. The first one that comes to my mind is Bismuth Selenium Telluride, with either a nickel or cobalt doping agent. Silver went away from this process early on. There is a Company called Marlow Industries in or around Dallas Texas that might be able to give you more information on RoHS compliant materials that are used in their process for the Peltier Effect.

Cheers, Anvil

reply »

#72113

low thermal emf solder & paste - SAC 405 | 13 May, 2014

Hello Anvil - Thank you for the info ! I will contact Marlow ...

Have a nice day ! Michel

reply »

reflow oven profiler

Used SMT machines