Circuit board solder replacement medical devises going green.

I'd have thought gold wires would be standard in implants, welded as per IC internal connections.? Solder has been lead free for a couple of years now...

Adhesives are tricky...dunno what dentists use for sticking crowns on, but I wish I could get some to fix my own. I reckon the average dentist has the mechanical skills of a blind Baboon.

Del

The United Baboon Association would like to have a word with you over your recent libelous remark.

I read an article recently about the development of a conductive plastic. Of course the word "conductive" is relative... as compared to silver?... a 1 Megohm resistor?

I like Dels answer... welding. Conductivity implies metals for the most part... with few electrons in the outer valence ring of the atoms.

Bill

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I wish the government would quit trying to protect me from myself... but this protection insures a future source for new politicians.

"Going green means eliminating anything harmful to the human body from implantable devises." No it doesn't.

No going green means environmentally sustainable. Eliminating anything harmful from the human body from implantable devices isn't "green;" its protecting the public health by assuring the safety, efficacy, and security of human implantable devices.

There are a whole host of FDA, ASTM standards http://www.astm.org/BOOKSTORE/BOS/1301.htm

and protocols on this subject.

The idea of lead solder being an issue is a red herring, The solder will be contained in a sealed container of suitable material to not be biotoxic.

Or are you envisioning soldered circuit boards wetted by biological fluids in the patient?

You might want to familiarize your self with the travails of other electronic manufacturers going down this path by searching for material regarding the EU's WEEE regulations.

https://www.iod.com/intershoproot/eCS/Store/en/pdfs/weeed.pdfThey haven't solved the solder issue yet.

http://www.allbusiness.com/technology/computer-hardware/871999-1.html

Your real issue is the survival of the solder bonds over time; failure means surgery for replacement.

The lead leaching is a non issue.

milo

http://www.globalspec.com/FeaturedProducts/Detail/EpoxiesEtc/Electrically_Conductive_Epoxy/48102/0

google 'conductive epoxy' for similar products.

conventional lead free solder is a reliability problem waiting to happen. for implantable equipment, you will kill someone if you use the stuff. most lead free solders are basically pure tin or alloys of tin and bismuth. both have some serious problems in long term use. tin will grow whiskers (actually conductive tin crystals) that can and will short out the equipment eventually. tin/lead solder came to be not just because it has a lower melting point than tin but also because the lead prevents the growth of tin whiskers. lead also vastly improves the alloy's ductility and toughness. The higher melting point of tin also means that semiconductors and boards must be exposed to much higher temperatures during soldering which means more thermal stresses and potentially shortening the device's life. Tin Bismuth does not grow whiskers, but it has it's own problems in that the solder is brittle and over time grows brittle intermetallic crystals in the grain boundaries. The solder joints will crack and become intermittent over time. brittleness is a big problem for surface mount components because the device is supported entirely by the solder connections. differentials in the CTE of the device and the board material will eventually shear the connections and cause either an intermittent connection or loss of the device completely, especially if vibration or thermal cycling is an issue. strength of both alloys is quite low as well. pure tin also forms a tin oxide which can be brittle as well.

The only solder that I am aware of that does not suffer from these problems (but has it's own processing problems including high melting point and potential issues with brittle intermetallics) is an alloy made by the Indium corp. called Indalloy 182. It is essentially 18k gold. And yes it is expensive as hell, but it is ten times stronger than other solders and more ductile as well and if processed correctly does not have issues with intermetallics.

You can read about the problems posed by lead free solders here.

remember, going green usually has huge hidden costs. In your case that cost may be in lives. Be very careful which system you choose.

I will add that this is yet another case of politicians with absolutely NO knowledge of the subject trying to solve a non-problem and instead causing a much larger problem in it's place.

The next time you see a EU politician, just shoot the bastard and save the world a lot of misery.