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silver pads, reflow charateristics??

#23021

silver pads, reflow charateristics?? | 15 January, 2003

we have recently been trying silver composition on our pads with our PCB boards. I am wondering what if any characteristics are different from tin etc... I have found with profiling the board it to be about the same temps. but getting granular looking joints, is this the norm or? would I expect to reflow hotter etc for the silver? Also our paste is no-clean without silver..would the addition of the silver in the paste cause better bonding (silver and silver etc..etc...).

Any thoughts?

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Vijay

#23028

silver pads, reflow charateristics?? | 15 January, 2003

Grainy finish of the solder joint also caused by higher reflow temp.So far we have observed grainy structure in case of gold plated board.

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Vijay

#23029

silver pads, reflow charateristics?? | 15 January, 2003

Grainy finish of the solder joint also caused by higher reflow temp.So far we have observed grainy structure in case of gold plated board.

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Lee

#23037

silver pads, reflow charateristics?? | 16 January, 2003

I have been using silver coated boards for over 3 years and with a Qualitek No-clean solder paste and have used primarily the same convection reflow profiles as Hasl boards.

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#23038

silver pads, reflow charateristics?? | 16 January, 2003

I have heard that the profiles are pretty much the same but I have a visible solder joint difference... might half to start looking at the plating, might be something with that?

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#23039

silver pads, reflow charateristics?? | 16 January, 2003

Ren´┐Ż

#23052

silver pads, reflow charateristics?? | 16 January, 2003

Hi burb , reflow temps are same than other profiles just follow your solder paste recomendations , Will help you a lot a solder paste with Silver , or if you want to eliminate completely the granular looking , use nitrogen with your oven ( You will see the diference) .But no matter granular looking , important is the solderability and pin contact.

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#23077

silver pads, reflow charateristics?? | 20 January, 2003

Hi Burb, I think you should try with paste which consist Ag.Or it might be other:Ag has different thermal characteristics, so you probably stay too long in the reflow zone.That's one reason for granular joints. good luck!

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JohnW

#23139

silver pads, reflow charateristics?? | 24 January, 2003

I fyour just using Sn/Pb in your paste even using nitrogen will lave you with slightly grainy joints. The silver from your PCB will disolve into the Sn/Pb at 'uncontrolled' rate what I mean is depending on the temperature and time above liquidous the disolution rate will vary. The addition of the silver to the solder paste add's the additional silver molecules in the Sn/Pb atomic structure which basically prefill the gap's that the silver from the board will take up. This should stop the grainyness.

John

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MA/NY DDave

#23157

silver pads, reflow charateristics?? | 24 January, 2003

Hi

Don't really know what "your grainy" means. It could be good, marginal, or bad. You need to get some photos or micrographs of what is normal and off-normal. Compared to Sn/Pb 63/37 on mostly Sn it should look visually different.

Every time you change materials the resultant joint is going to visually, under SEM, and other techniques appear different. The question is always am I observing something within the normal range. It gets tough sometimes.

If you don't have books or reports, try going back to the material supplier for your solder or paste.

YiE, DDave

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