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

Printed Circuit Board Assembly & PCB Design Forum

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Silver Thru' Hole

Scott Davies

#4346

Silver Thru' Hole | 27 April, 2000

Our R&D people are looking at the possibility of "Silver Through Hole" as an alternative to "Plated Through Hole" for our future PCB specification. Do any of you have any experience of this, advantages/disadvantages, etc. I'm told that the main reason for going down this route is that a lower grade of PCB material (FR1 instead of FR4) can be used, signifcantly reducing the cost of the PCB. But, at what price?

Thanks Scott

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Jim L

#4347

Re: Silver Thru' Hole | 27 April, 2000

How will you be applying this? Will it be comparable to a screen printing operation?

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RDR

#4348

Re: Silver Thru' Hole | 27 April, 2000

Scott, I am a little confused, when you mention "silver thru hole vs. plated through hole what do you mean. A silver "immersion" type finish vs. HASL (Tin lead)on your PCB? Or are you talking about using silver solder to perform intrusive reflow of through hole parts? We currently use some silver immersion PCBs in our processes and have not noticed any process impact. I have heard of tarnish problems with silver but do not have any details.

Russ

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PeterB

#4349

Re: Silver Thru' Hole | 27 April, 2000

Russ,

We also use 'immersion silver' and have not had any impact on our processes. In fact there are a number of benefits i.e very flat pads (as good as electroless nickel/immersion gold but much cheaper and less unfriendly to the environment), good solderability etc.

We have not had any tarnish issues. The PCB manufacturer we use for this finish guarantees a minimum of 12 months shelf life.

Pete B.

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#4350

Re: Silver Thru' Hole | 27 April, 2000

Scott: I�m not familiar with some of the things you�re talking about, but let me: * Agree with Russ & Peter regarding immersion silver. * Give some snips of information on the substrate side of things that might help you to tie this together. � FR-1 is cheaper than FR-4. In fact no substrate material is cheaper than FR-1. � FR-1 is a phenolic / kraft paper laminate. (FR-4 is a resin/glass laminate). � FR-1 has no plated through holes. It has plated trace on a single side. (FR-4 can have plated through holes and more than one layer). � FR-1 is a punch grade material. Over 50% of the world market is punch grade. � Part of the price you pay for being able to punch is tg. FR-1 has a tg of 90�C. So, it�ll sag during wave soldering, but punch grade ain�t at 50% �cause no one can work with it � Following on with that, FR-1 will blister on a 260�C solder pot after 80 seconds (FR-4 will last for a coupla minutes. � Most people size the through holes on single sided boards to provide support of the component leads. � Most electrical properties of FR-1 are not superior to other substrates.

Good luck Dave F

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