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Lead free Solder Paste troubles !!!!

We are printing on an assembly using SAC305 Alloy Sn96.5 Ag ... - Sep 23, 2004 by EMS-Engineer  

No comments ? ... - Oct 05, 2004 by Glenn Palmer  

#30668

Lead free Solder Paste troubles !!!! | 23 September, 2004

We are printing on an assembly using SAC305 Alloy Sn96.5 Ag 3 Cu .5 with a no clean flux and getting virtually NO spread with either a ramp to spike or straight ramp profile. We are printing to standard FR4 board with immersion Ag finish. I am trying both Indium and Senju pastes along with our normal No Clean paste which is an Aim no clean 293+ tin lead paste. The eutectic solder spreads fine, looks smooth and shiny, and wets fine to the lead free components, but we must use a no lead. Both lead free pastes are stiff, have poor release, stay put on the pad where printed and look very dull and very grainy. The indium stuff has tons of little solder balls on top of the joint on the flux residue. With the lead free both profiles are about 4 minutes with a peak of 245 C. Any suggestions ? We need to decide on a process and lead free paste for some proto boards which must ship next week.

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Bob R.

#30669

Lead free Solder Paste troubles !!!! | 23 September, 2004

We're just getting started in lead free, but the solder balling and poor wetting sounds like what we saw in some early experiments where we were investigating whether we needed nitrogen. Without nitrogen inerting we got just the kind of things you've described. Other factors played into it, but lack of nitrogen was the big driver.

Take this with a grain of salt though - we aren't in production yet.

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C Lampron

#30671

Lead free Solder Paste troubles !!!! | 23 September, 2004

EMS-Engineer,

Lead free alloys have a very low wetting creep. You probably will not ever get the same type of weting with a LF as opposed to SN 63/37. The question is if it is acceptable. Lead free solder joints cannot be inspected to the same criteria as leaded joints. They will be dull and grainy and have little to no spread. There is no official document like IPC-610 for lead free (yet) but everything you are experiencing is what I've been told would happen.

I believe that Kester and some of the other major manufacturers should have information that may help on thier web page.

Good Luck

Chris

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RDR

#30674

Lead free Solder Paste troubles !!!! | 23 September, 2004

Pb free pastes do not wet out like 63/37. Their are no claims from any manufacturers that I am aware of that say it will. Your "little solder balls" are likely caused from oxidization during reflow. What type paste are you using 3,4,5? What are the other temps and durations in reflow? You may want to try Alpha OM338 paste. I have used Indium and others and I find it odd that you say it is "stiff" The Indium and other manufacturers I have used is very "thin". Are you sure that you have good paste? It seems like it is garbage. No-Cleans tend to release and print much better than W.S. pastes from my experiences. We have never experienced the need for nitrogen atmosphere using lead free.

Russ

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KEN

#30680

Lead free Solder Paste troubles !!!! | 23 September, 2004

The LF pastes will have virtually NO wetting spread. This is normal. LF mobilities are virtually non-existant with SAC alloys. However, the addition of varrying amounts of silver can (and does) improve mobility but, this comes with a price (paste price increases and Silver related platelette formations which affects reliability).

Paste release is a function of your paste, stencil aperature design rules and your stencil material.

Solder balls may be an indication you need an extended drying period in your profile and/or reduced ramping rate.

As you're finding out LF is not a drop-in solution. Nitrogen is an excellent way to hide your real problems and drive up your manufacturing costs (all at the same time). Is your product consumer, Hi-REL, aerospace, what?

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#30719

Lead free Solder Paste troubles !!!! | 27 September, 2004

Your problem is easy. Lead free solder is like 63/37 solder paste when it was started. We make things complicated. We believed before that lead free has high melting temp and will not produce good fellet so on....

The only thing you must do is to look for solder paste manufacturer which can provide minimal cost at a low melting point. No nitrogen needed, no expensive reflow oven or even your old reflow oven can be use. I suggest you ask the supplier of solder paste. If you can not find the right supplier, please feel free to come back to me and I will show you.

Arman

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KEN

#30735

Lead free Solder Paste troubles !!!! | 27 September, 2004

Minimal cost and low melting point??? Have you bought Indium or Bismuth based alloys lately? Tin/Silver, Tin silver coper-X you name it....there are trade-offs (cost / performance). Not all are exactly published or are suitable for all appliations. The lowest cost vs. melting point is Tin-Silver-Copper 217C. There is a reason why the industry is focusing on this alloy.

No other solder element is cheaper than lead. No LF alloy can compare to the cost of Tin/Lead solder. NONE Tin costs are rising, silver is rising....am I missing something here?

Easy....sounds a bit naieve.

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#30737

Lead free Solder Paste troubles !!!! | 28 September, 2004

You mean if I bought that material in USA or Europe It will be expensive. If you buy those material in places where labor is cheap then you get cheap prices with same capability. You are really missing something....

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#30742

Lead free Solder Paste troubles !!!! | 28 September, 2004

The lead free debates are getting more and more interesting Didn't know that low labor cost was also lowering melting temps of LF alloys

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#30743

Lead free Solder Paste troubles !!!! | 28 September, 2004

mostly we buy our solder paste in countries with high labor cost thus making it expensive.

Check out China. Won't you believe they sell LF paste at a fraction of a cost of a well known brand.

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DenisM

#30745

Lead free Solder Paste troubles !!!! | 28 September, 2004

Can anyone share with me the price you pay for LF solder paste? I have a chinese brand on hand that is purported to reflow well in air and leave shiny joints and minimal solder balls. It does not flow like lead based solder of course, nothing does. I have not inquired about the price but if it works well later this week I will get a quote and post it here if anyone is interested.

This message was posted Add this forum to your site! Click to learn more. the Electronics Forum @

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RDR

#30746

Lead free Solder Paste troubles !!!! | 28 September, 2004

Lets not forget about shipping costs,lead times, and bad lot recovery plan(s)on product rec'd from China.

We are paying $.096 per gram (SAC405)with 4kg per wk usage. Shipping is free, stock maintained locally with 2 hr. delivery if necessary.

Russ

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#30755

Lead free Solder Paste troubles !!!! | 28 September, 2004

Well known American,Japanese and European brand cost between US$75 TO US$150 PER KILO. China made cost at US$50 to US$75 per kilo.Free shipping and in stock.

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KEN

#30757

Lead free Solder Paste troubles !!!! | 28 September, 2004

If we are talking about Indium...then you will eventually be paying what everyone else is. The resource is diminishing especially with the application into the display markets. Same with silver. We are comming out of an all time low for silver....it can only rise from here!

Labor rates will eventually rise in China, Malaysia, Tiawan. As consumerism takes over and the cost of living increases, your labor advantage will cease. Then we will have a (more) level playing field. Now about that trade deficit....

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#30760

Lead free Solder Paste troubles !!!! | 28 September, 2004

yes, in the future prices of China product will increase by 10 - 20 percent, but other may increase double. So still China price will stay competative.

I am not for China,in fact most of our local companies went to China already, but hey, lets face it they are now provides the lowest wages. Indium is one of the best product I knew. The technology is far from competitor, but if you are cost cutting won't you like alternatives?

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habba

#30771

Lead free Solder Paste troubles !!!! | 29 September, 2004

Hi all ! I have a very simple ( maybe stupid ) question : Can we mix the lead-free components with 'Pb components' ? I mean, some component would lead-free, but it is only 5% of the whole. Will I have problems on wave and on reflow ?

Thanks for help. I am a beginner in this issue... habba

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#30772

Lead free Solder Paste troubles !!!! | 29 September, 2004

do you mean the parts like capacitor or solder paste/solder bar. If you mean solder paste/solder bar, yes you'll have big trouble. Why? because LF solder paste/solder bar has high melting point and different composition.

However if parts like capacitor,resistors etc. I don't think it will matter. LF components cost higher.

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RDR

#30776

Lead free Solder Paste troubles !!!! | 29 September, 2004

Make sure that you use lead paste and solder for this. (See Dave I listened)

Russ

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habba

#30779

Lead free Solder Paste troubles !!!! | 30 September, 2004

Yes, sorry I forget to mention it. SO only some capacitor will be lead-free. The rest remain 'Pb' parts. The solder paste also remain 'Pb'. You mean that if only this capacitor will change, we can solder that with no problem ? thanks ! habba

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#30785

Lead free Solder Paste troubles !!!! | 30 September, 2004

Habba,

I don't know why use lead free capacitors and a non LF components. I do not get the idea? Can you educate me? Is this customer driven or just your company. You must use leaded solder paste for this type of process.

Arman

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#30786

Lead free Solder Paste troubles !!!! | 30 September, 2004

Habba: Here is a thread from the fine SMTnet Archives from a couple of weeks ago, where we spoke about the topic of mixed lead-free solder with components that have lead-bearing solderability protection: http://www.smtnet.com/forums/Index.cfm?CFApp=1&Message_ID=30307

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#30787

Lead free Solder Paste troubles !!!! | 30 September, 2004

Armin

Habba could be considering a situation where: after they convert to no-lead they receive components with lead-bearing solderability protection from their component supplier. This could happen when: * Supplier has not converted to no-lead. * Older date code parts that are pre-no-lead end-up on the line.

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HOSS

#30799

Lead free Solder Paste troubles !!!! | 30 September, 2004

Habba,

I think I understand your question. Just to be sure.....you need to use some components that are LF in an otherwise Pb process?

If this is your question, then, yes, chances are good that you will not have a problem. Of course you should do your due dilligence and validate that your process can still produce your desired level of quality.

We are using many lead free ICs (no LF BGAs yet) and passive parts that are lead-free with our Pb process. We haven't needed to do any significant adjustments to accomodate these parts.

If this isn't what your question was regarding, nevermind.

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habba

#30802

Lead free Solder Paste troubles !!!! | 1 October, 2004

HOSS ! Yes, this was my question. You got it right. Thanks the information for everyone. Appreciate everyones help. habba

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#30807

Lead free Solder Paste troubles !!!! | 1 October, 2004

Well Thanks for all the good advise. Lots of different opinions on this one. I took the advise to contact my current supplier of solder paste. They sent in one of their tech people along with a sales guy and we ran without much trouble. Other than a slight increase in the soak zone and a recommendation to get rid of the standard reductions on my stencil, except for homeplates on 1206 and 805 parts, we were golden. Boards came out pretty well all things considered. I guess next time I have a problem I will call my supplier first. Kudos to aim solder for their help.

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#30809

Lead free Solder Paste troubles !!!! | 1 October, 2004

Thats why they hire process engineers at solder companies. We might as well benefit from em.

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#30811

Lead free Solder Paste troubles !!!! | 1 October, 2004

As long as they're good. Have you guys had any free "help" from so called engineers that turned into a costly waste of time (both in resources and line down). I have heard some real horror stories from former co-workers. I haven't heard this about the solder manufacturer you mentioned, but there are some out there to beware of.

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#30812

Lead free Solder Paste troubles !!!! | 1 October, 2004

I second that one Glenn. I have had really solid support from my paste company. Our guy is Kevin with Aimsolder. He is quick to respond and very knowledgable. We used a cheaper paste a while back, but never ever got any support. I wont make that mistake again either.

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#30832

Lead free Solder Paste troubles !!!! | 4 October, 2004

Haven't used aim solder products. Any good ?

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#30851

Lead free Solder Paste troubles !!!! | 5 October, 2004

No comments ?

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