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Lead Free paste

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#44939

Lead Free paste | 7 November, 2006

We are using Kester Type R520A, Alloy SN96.5/A63.0/CU.5 paste which is applied using an MPM Accuflex machine. Our plant Humidity is 38 degrees. We are seeing insufficient paste post stencil on fine pitch parts. Could this be an environment issue? In the past we have not seen this issue.

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RDR

#44940

Lead Free paste | 7 November, 2006

here are my thoughts on kester,

I have rec'd a sample to qualify here and we cannot even get it out of the cartridge it is so dryed out. Rep informed me that Kester has a problem with its chemistry right now. Product is Mfgr'd in off shore location in country I would be very suspect of as far as repeatable quality

Was there a recall? nope

I will not be switching to Kester products

Russ

Russ

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aj

#44941

Lead Free paste | 7 November, 2006

Hi,

I trialled 4 or 5 of the main suppliers including Kester.

I went with Alpha OM338 SAC305 - exceeded all expectations and actually performs better than PB Paste in my opinion.

aj...

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#44951

Lead Free paste | 8 November, 2006

hi...

try evaluating eco solder paste Sn96.5/Ag3.0/Cu0.5 from Senju...

output is good and i suggest your stencil's apperture ratio with the pad 1:1 when it comes to fine pitches...and BGA pads

regards,

janry

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Amol Kane

#44954

Lead Free paste | 8 November, 2006

well, if in the past you havent seen this issue, then something in the process has changed......as any good process engineer should do, investigate it.....new batch of paste?, expired paste?, clogged stencil?, change in programming parameters?, change in wipe cloth?, change in environmental parameters? etc. etc........the purist approach is to do a controlled DOE to find out the root cause

we use R520A, and have not seen any issues so far........ and are getting good results even with SnPb print parameters(not affiliated with Kester in any way)

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RDR

#44955

Lead Free paste | 8 November, 2006

I also am using the alpha OM338, great product

Russ

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aj

#44960

Lead Free paste | 8 November, 2006

Russ,

Have you incorporated any stencil modifications in particular since switching to LF?

aj...

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cuculi54986@yahoo.com

#45301

Lead Free paste | 20 November, 2006

We evaluated the OM338 from Alpha and it worked great! Looked like crap, though, compared to the other products out there.

When I set the boards out in front of the Alpha sales guy to show him the difference in appearance between his boards and the competitors, he asked sarcastically if we had a "shiny-meter" somewhere in house to measure the difference. Which of course, we do.

I understand that looks don't really matter... what matters is the quality of the solder joint. We saw no significant difference in solder joint physical strength between the SAC305's we evaluated. All else being equal, I'm going to go with the better looking one.

When we began evaluating Kester EM907, the cold storage expiration date was 6 months from manufacture. Now I believe it has been shortened to 4 months.... That makes me wonder if they are having some quality control issues. The last two tubes we opened were pretty well dried up. We had to kneed the paste with about 50 squeegee passes to make it roll. Around the end of the summer this year we had problems with the paste turning into soup and the print bridging across IC pads....

Hmmm, on second thought, maybe OM338 didn't look all that bad.... Maybe our shiny-meter was just out of calibration.

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RDR

#45303

Lead Free paste | 20 November, 2006

Ahh the old Kester dry product EM907 just had major thicjener issues, we wer quailifying the kester product and could not get out of tube. needless to say it failed the qual. I was informed by Kester rep that all lots were recalled for this? was your product not recalled? our was not because we were told that samples were of an uncontrolled nature. In seeing that they are shortening the shelf life of this product I would tend to guess that the viscosity is very unstable and the product becomes unusable quite fast.

Anyway, we use OM338 and we have good shiny meter results? 5 zone and no nitrogen.

Russ

Russ

Just curious, if I should further explore Kester for lead free paste.

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Earl Jr

#45639

Lead Free paste | 27 November, 2006

Jeff, I suspect you are just the guy running the line. The things you asked are not anything out of the norm. Go into your manufacturing engineering's office, grab that video game out of their hands and tell them you're not giving it back to them until they come out and help you solve your problems.

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Bob B

#46020

Lead Free paste | 6 December, 2006

Attention Alpha users: I just read Alpha is going to close the US paste factories and move them to Mexico. Be on the lookout for quality issues when they do. I am sorry to see them go in this direction.

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wrong way

#46022

Lead Free paste | 6 December, 2006

Im using kester easy profile 256 and just this week started seeing problems with the paste being to thick sticking to the sqeeges and not going thur the screen this is not a lead free paste but it is a keester product

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SWAG

#46023

Lead Free paste | 6 December, 2006

Check your expiration/storage/shipping conditions. We've been using EP256 for a couple of years and it works excellent. Never had any problems with it.

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#46025

Lead Free paste | 6 December, 2006

Assuming you meant 38 percent humidity - I would have to say your environment is only part of the problem. When you experience this problem, is because the paste has set idle for a period of time? If you knead the paste does the fine pitch print OK? If so you probably have a paste problem. Problem being short stencil life. Shop around for some other paste that offer long stencil life. Then run a side by side comparison. If this yields no difference then you can rule out paste and try messing around with your humidity.

If you DID mean 38 degrees, then your shop floor is just too fricken cold! Spend $30 bucks on a space heater and put it in your screen printer. The penguins may complain but at least your paste will start to roll on your stencil!

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#46028

Lead Free paste | 6 December, 2006

I would have to say it was a month from experation but we have ben using it as well for years with no poblems we left multi-core when they started having there problems paste being to thick they wouldnt admit anything until 6 months after we quit using them

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RDR

#46059

Lead Free paste | 7 December, 2006

Seriously folks Kester has some major issues with their thickeners. Do not spend time fixing your process that is the same as it has been.

As a post here stated, Alpha is going to Mexico, we will see probs form them here pretty soon as well.

Kester went to mexico recently and look what happened

Russ

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Reflow Oven

McDry Ultra-Low Humidity Storage Cabinets