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Reduction of solder paste usage

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Yngwie

#48159

Reduction of solder paste usage | 5 March, 2007

We are exploring ways to reduce the waste of solder paste. Here are some of the ideas I have in mind:

1) To use paste supplied in Syringe instead of jar. Paste that are opened more than 8 hours will normally be discarded, so we are looking for ways to eliminate this waste. 2) To order the paste in the smaller jar i.e. 125 gm instead of 500g or even 250 gram. 3) to move the balance paste from the line that only runs 8 hours a day to the line that runs 3 shifts.

The other idea that we came out with is to melt the expired paste to be a solid solder bar by heating the solder paste and form an ingot solder. The problem with this is, how to eliminate massive smoke that comes out from the burning flux in the solder paste during the process.

All please share your thought if any i.e.in the idea to save the solder paste usage, or reduce the amount of discarded paste or even prolong the shelf life of the opened solder paste.

Inputs are very much appreciated.

/yngwie

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Hussman

#48162

Reduction of solder paste usage | 5 March, 2007

Syringe is a good plan. You may need to buy some pnuematic guns to push ou the paste thuogh.

Instead of melting the paste down, have someone reclaim for you. They pay you for it. Sorry Maint Managers - gave away your secret.

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DC

#48163

Reduction of solder paste usage | 5 March, 2007

Any one have experience of MyData paste jet printing? I don't ave chance to take a look at Apex but it can reduce the paste, no stencil required and paste volume control by programming.

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#48179

Reduction of solder paste usage | 5 March, 2007

We buy our paste in Semco cartridges. You don't need a pneumatic gun to administer the paste to the stencil, just use a caulk gun which you should be able to purchase at your local hardware store. The cheap ones are about $2 (US).

We have green caulk guns for the Pb-free paste, blue for the Pb paste, and red for the SMT adhesive.

The Semco cartridges are available in various sizes. We buy ours in 600 gram or 250 gram tubes, depending on the paste.

By the way, I have all your albums.

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Rob

#48195

Reduction of solder paste usage | 6 March, 2007

Yes, looks great - had a play at one of their roadshows. Could turn into an amazing product if they can scale it down enough.

However, it's slow and costs more than a large house. More than a screen printer and a huge number of stencils.

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#48219

Reduction of solder paste usage | 7 March, 2007

First, don't put solder paste in a wave solder pot, the 50% by volume of organics and volatiles will gas off in an astonishing amount of fume, leaving a dismaying mess of spent resin and molten plastic in your pot.

Second, when you say, "Paste that are opened more than 8 hours will normally be discarded ...". Are you saying that you toss 500 gm jars, if they are not used in 8 hours? If so, your paste sale-type must love you. Does he/she take you to lunch often? You could eliminate that waste by putting the cover on the jar and using the remainder the next day.

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Yngwie

#48385

Reduction of solder paste usage | 14 March, 2007

Thanks for the reply Dave. :) No, we dont toss in 500g on the stencil.

Have you heard of any method to convert the solder paste to solder bar, just in case someone have done that before?

Thanks.

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#48390

Reduction of solder paste usage | 14 March, 2007

So, you toss whatever is on the stencil every 8 hours. Correct? How long has it been on the stencil? * If that particular paste has been on the stencil for 8 hours, we'd agree to toss it too. * If paste has been on the stencil for less than 8 hours, it probaly shouldn't be tossed.

Do you have a problem with paste drying-out that makes you want to throw-out paste?

If you cannot give-up the itea of throwing-out paste, here's what to do: * Add 100 ml of a mixture of IPA and Butyl-Acetate 1:1 to the paste * Stir the paste, liquid mixture * Pour the overlaying liquid in your organic waste bin * Repeat * Let the remaining paste, liquid mixture dry in open air * Melt the dryed solder in your wave solder pot without much fuming or spattering

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Cmiller

#48392

Reduction of solder paste usage | 14 March, 2007

We use cartridges, that way nobody can mix back in paste off the stencil and no air can get in period. Any paste that is still good to use when removed from a stencil at the end of a job is put into a small pink zip-lock baggy with the date written on it. Most EMS have these bags around for kitting parts. You can squeeze pretty much all the air out of the bag before sealing and you can "peel" the bag in half at the seams when using the paste for easy removal. We only use the "used" paste on boards that have no fine pitch parts since we can not determine exactly how old it was or how it will print. Have been doing this for 10 years. So far, so good.

We have tried to reclaim the solder in our wave. Dave's description is quite accurate and I can still remember the smell and smoke from a decade ago. You can just throw the stuff in with your wave solder dross to be recycled. Even still in the cartridges. With the system we have we have very little waste.

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Scotceltic

#48393

Reduction of solder paste usage | 14 March, 2007

Have you thought about switching to either automatic paste dispensers or rhemoetric pumpheads in order to contain the paste and only dispense what is needed during your shift ?

I am not sure what type of printers you have, but I know both of these options are available on Dek and MPM screenprinters.

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