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Lead free tin copper only

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#39345

Lead free tin copper only | 27 January, 2006

Kester is offering a tin/copper alloy for lead free. Any comments regarding using just tin/copper as opposed to tin/silver/copper or tin/nickel/copper? the price is low but why wouldn't everyone else offer just this alloy as opposed to the standard SAC305?

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#39513

Lead free tin copper only | 3 February, 2006

Kester offers Tin-Copper AND Tin-Copper-Nickel. The Kester K100 alloy is a Tin-Copper-Nickel material that is very similar to SN100C.

Straight Tin-Copper isn't tremendously popular but can be used in low-cost, consumer-electronics applications where reliability is not the most important factor. SAC is considered the more reliable material but certainly costs more.

The Tin-Copper-Nickel materials are lower cost than SAC305 and do have some advantages (shininess, Cu dissolution, pot leaching, etc.) but the SAC305 is still considered the most reliable lead-free alloy. It is important to know the differences between SAC and Tin-Copper-Nickel materials and to select the appropriate one for your application. In general, most high rel users are qualifying SAC305. When reliability is not as critical (but cost is), Tin-Copper-Nickel is often the more attractive option.

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Cmiller

#39516

Lead free tin copper only | 5 February, 2006

Are you refering to reflow soldering or wave soldering?

Brian, do you have any data to support that SAC305 is more reliable than Tin-Copper-Nickel?

NEMI reccomended SAC type alloys for reflow and Tin-Copper for wave. See: http://circuitsassembly.com/pdf/0404/0404nemi.pdf See third paragraph.

SAC305 creates a lot of dross in wave applications and disolves copper much faster. The dross issue in itself is a major problem and I have headr a number of complaints that the dross is so bad it ends up in the joints. I have seen no data to support SAC is a better choice for wave. Because of the lower melting temperature and better wetting it does seem to make a better choice for reflow soldering. But if all your components can take the heat and you use the right board laminate and you can control your process well enough Im still not convinced SAC305 is any more reliable in reflow either but the cost difference does not seem to make up for the luxury of the lower temp and better wetting characteristics. It seems people think SAC305 is more reliable because it costs more. Tin/Lead is very cheap, does that mean the boards that I make with it are low reliability? Tin/Copper is also eutectic. I believe thats why we were all using 63/37 Tin/Lead.

I agree with NEMI. If anyone has any good data to support another conclusion please post it here.

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Cmiller

#39517

Lead free tin copper only | 5 February, 2006

Look at: http://thor.inemi.org/webdownload/newsroom/Presentations/09.pdf

Page 47 shows both alloys to be similar in reliability although its a little troublesome that the particular defects are not isolated as I feel there is a big difference between reflow and wave with these two alloys.

We are using SAC305 for reflow, SN100C for Selective and will be filling a Vectra with SN100C as soon as they send us some tin to clean the pot out-Nihon does this for free, but we have been waiting a month. I am not trying to push my own agenda here and we did not make our decisions based on cost. If there are people out there using SAC305 in wave and selective applications and think its great, please speak up!! I cant remember hearing one single positive comment about SAC305 in a wave. There must be somebody out there using it.

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#39536

Lead free tin copper only | 6 February, 2006

Hi all, I just wave soldered 40 boards (20 if Imm Sn and 20 of Imm Ag) using SAC 305 (in this case the wave machine manufacturer (electrovert) suggested the alloy too). plan to carry out x-sectioning to see the results. overall, just from the visual inspection, there was good hole fill and topside wetting.....curious to see what the x-sections show.

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#39561

Lead free tin copper only | 7 February, 2006

You can use straight forward Tin/Copper but it flows very poorly so solderability is an issue. Dosing with Phos improves this but need to stay on top of it. We have supplied some 3.8%Ag alloys for flow they work well but you get a small 'chill point' on the joint not bad but biggest issue is with cost and dross formation. Other Tin/Copper alloy pushed in Europe is the 0.3% Ag doped as a good reliable NON PATENTED alloy that works very well in flow and is very popular here in the UK producing less dross than 63/37 while improving soldering results generally when compared to 63/37, especially through hole penetration and bridging which results are comparable to Patented higher Ag loaded more expensive alloys. There is a report avaiable for Tin/Cu/Ni alloys which should be studied carefully when making your choice for both wave soldering and HASL soldering. This is published in the SMT magazine under 'Lead Free Solder Alloy Selection:- Reliability is the key' Best of luck Greg York BLT Circuit Services Ltd England

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#39572

Lead free tin copper only | 8 February, 2006

Hello Greg, I agree with you that the article in SMT Magazine should be studied very carefully as it contains many errors in respect to SN100C. The testing performed was a DOE and was not an optimized run. There is also a statement on dross generation, which was incorrect as confirmed by the author from the assembly company. If X0307 or its �cousins� being sold in Europe is so good, why were there over 30 machines converted from them to SN100C in Europe in the last 12 months? The article also does not discuss SN100CL HASL so do not make statements you can not support with facts. SN100CL HASL is the most popular HASL coating in Europe, America and Asia, which add up to the world�s leader. Continuing to play the �PATENT� card illustrates pure desperation.

Good luck, Bob Gilbert FCT Assembly, Inc. Bgilbert@fctassembly.com

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