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Midchip solderballs (MCSB) on pb-free

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#44114

Midchip solderballs (MCSB) on pb-free | 22 September, 2006

We are currently experiencing some MCSB's on 0603 components. I am looking into experimenting with the stencil thickness from 6 mil to 5 mil and also using Radiused inverted homeplate ( 20%60%20)to eliminate or reduced this problem.

We are using lead free paste and our current profile meets the recommended specs. Our current appertures are homeplate design.

Your ideas, experiences or thoughts about this issue (MCSB) are sure appreciated.

Thanks

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#44116

Midchip solderballs (MCSB) on pb-free | 22 September, 2006

Be careful of inverted homeplates if you hand clean your stencils. The "spikes" can easily catch on the wipe being used and bend up. Not to mention the nice slashing it does on your hand that immediately some how fills with solder paste.

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#44152

Midchip solderballs (MCSB) on pb-free | 25 September, 2006

For this inverted homeplate, the edges are rounded vs. spikes. Check image here :

http://www.emasiamag.com/article.asp?articleid=669

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#44154

Midchip solderballs (MCSB) on pb-free | 25 September, 2006

Yup, seen them too. Be care not to apply too much squeegee force or you could start to see these curl up as well.

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SWAG

#44155

Midchip solderballs (MCSB) on pb-free | 25 September, 2006

We are just getting into full production on a handful of lead-free builds. We are finding that the specific lead-free paste we are using is very susceptible to shelf life and dwell time. Much, much more than our experience with leaded. We have had problems with solder balls/beads and non-reflow and it seams to be directly related "old" paste. Our paste degrades quickly (compared to what we get away with-leaded) when not refrigerated. I'm sure it depends on what product you are using but just a caution...

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#44156

Midchip solderballs (MCSB) on pb-free | 25 September, 2006

Thnaks for the tips so far. I am currently reading our paste manufacturer's procedure for handling solder paste. I will try to adhere to it and control our old vs new paste.

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aj

#44161

Midchip solderballs (MCSB) on pb-free | 26 September, 2006

Have you tried an alternative paste supplier.

I have ran quite a few cards now with the homeplate design that I have used for the last few years and we are not experiencing any problems.

We experienced MCSB on one product but this card has oblong pads which were pasted 1:1. Now that I am on the topic of Oblong pads - has anyone else come across these and what mods do you use for leadfree?

aj...

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aj

#44164

Midchip solderballs (MCSB) on pb-free | 26 September, 2006

me and my big mouth.

we are currently running a leadfree product and I am getting MCSB on all 1210 caps.

Using homeplate with 10% reduction 6thou stencil.

I contacted my stencil supplier to ask for advice- they are looking into it but he did mention that they have been asked to go 1:1 from other customers?

aj...

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aj

#44168

Midchip solderballs (MCSB) on pb-free | 26 September, 2006

Just to update you on what I have found.

I was using Indium leadfree paste and I switched to Alpha OM338 Leadfree Paste.

Problem gone...no more MCSB.

aj...

I have no affiliation with either ofthe above mentioned companies.

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#44173

Midchip solderballs (MCSB) on pb-free | 26 September, 2006

We have solved our MCSB problems by using standard homeplate designs on all of our resistors and caps. I use a 50% taper and have achieved great results with 0402-1206 parts using both tin/lead and SAC305 paste. We use Amtech paste.

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#44362

Midchip solderballs (MCSB) on pb-free | 5 October, 2006

Good afternoon!

We are able to offer some insight into this and fix your issues.

A lot of the time, we are able to offer relief from MCSB using profiling. We have a Technical Paper and Application Note for the elimination of them. They can be found here:

http://www.indium.com/techlibrary/technicalpapers.php

Also, more information can be found at knowledge.indium.com. Plus, you can email me offline and I can send both of them to you. Should you have any further questions, please don't hesitate to ask. My contact information is below.

Regards,

Mario Scalzo, SMT CPE Technical Support Engineer - Southwest Region mscalzo@indium.com 315-853-4900

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