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Kester Paste = Dirty Oven?

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#40432

Kester Paste = Dirty Oven? | 15 March, 2006

About a year ago we switched from another vender to Kester 256HA paste. As we've switched assemblies from the old paste to our Kester paste, we've seen a need to increase the frequency of our oven cleanings. It has been very noticeable. After only two weeks they are a pretty big mess.

Just yesterday I was in a facility that used yet another brand of paste (but they haven't used Kester), and their ovens were pretty much spotless. When I asked about cleaning frequency the tech at me kind of funny and said they clean them "about every 6 months or so".

I've spoken with a couple of other people from different facilities and they've seen the same increase in residue when switching to a Kester product. I'm wondering if anyone else has noticed this?

Just in case you're curious, the reason I'm not mentioning the other brand names is so nobody gets the idea that I'm a "paste XYZ" guy bashing the competition

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Chunks In Cebu

#40455

Kester Paste = Dirty Oven? | 15 March, 2006

Yes, different pastes will cause ovens to become "dirty". I believe you are talking about flux build-up. I've switched from one paste to another based on sample studies, only to find an increase in oven cleaning. During most solder paste evaluations, this always seems to get over looked. Talk to Kester about it, maybe they can help by adjusting your profile. Maybe you need more exhaust? Hard to say without details.

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#40477

Kester Paste = Dirty Oven? | 16 March, 2006

Is it possible that the other facility you were at was running a WS paste more or exclusively? We found that the nc Kester left us with a lot more sticky mess than the ws.

That said, are you sure you're also getting enough exhaust airflow?

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#40488

Kester Paste = Dirty Oven? | 16 March, 2006

Well I honestly can't say that I have enough flow, so that's a good point. We don't have a flow meter or manometer on our reflow exhaust.

How do you measure that? Or, is it just that you make sure your exhaust path is clean and the blower is working properly?

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#40489

Kester Paste = Dirty Oven? | 16 March, 2006

Find out what the exhaust draw requirements are and talk to a HVAC expert. They should be able to tell you what size fans and duct work you need for your oven.

They can also calculate how much draw you have with your current set up.

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#40491

Kester Paste = Dirty Oven? | 16 March, 2006

The right way is to know what velocity numbers would net you the required flow for your oven and then measure with a manometer. The required velocity is primarily a function of pipe diameter (and blower rpms) but length and how bendy it is contributes too.

Sniffing the exit end for stinky flux vapor is the other way. :)

How your oven cools and routes exhaust gasses also effects how quickly things get sticky and/or covered in flux dirt.

Are there filters in the system, or on the oven, that might be clogged and slowing things down?

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Chunks In Cebu

#40502

Kester Paste = Dirty Oven? | 17 March, 2006

Just thought of something while on the beach. We made a paste change several years ago when we installed another surface mount line. At around that same time, our maint. crew changed chain oil and about 2 months later changed when they oiled the chains. The result was sending non-approved oil on the chains WHILE running the ovens. The oil would evaporate and then settle and cling to the first cool spot. I spend the next year trying to explain that the "flux" dripping from the vents was non flux at all. My first clue was only the reflow ovens were dripping.

Any-who, you might want to verify that nothing else has changed just to cover all your ducks (not sure what that means - time for more beach).

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