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Temporary Stencil for MPC555 PBGA

Carol Stirling


Temporary Stencil for MPC555 PBGA | 27 May, 2002


I'm looking for Temporary Stencils to assist placement using a Sniper Rework Station.

The PBGA is a MPC555 Motorola with 272 pins. The ball map shows 4 populated outer rows, then 16 balls in the centre of an open, unpopulated area.

Could I get the name of a Supplier or two please?

Thank you,


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Temporary Stencil for MPC555 PBGA | 28 May, 2002

Does this PBGA have eutectic balls? If so and the PCB is HASL finish, or has solder on the lands from BGA removal, you may not have to apply solderpaste. Check with you flux supplier to see if they offer a NC "flux paste" product, otherwise I know Multicore does. This is great for soldering BGA devices with eutectic balls to a PCB with solder on the lands. It greatly simplifies the process. You apply a thin coating of the paste flux to the PCB solder lands and a thin coat on the tips of the balls then solder in the usual manner. Check with your paste flux supplier to confirm the correct application. I've used this process with excellent results. BGA devices with non-eutectic balls will require solderpaste.

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David R


Temporary Stencil for MPC555 PBGA | 30 May, 2002

If I get you right and you are looking for a micro stencil for bga rework, then you should try They are offering a free sample of their Flextac micro stencils in a wide range of sizes. The thing with these ones is that they are self adhesive, and apparently leave no residue. This leads to excellent gasketing and less fiddling about while you paste. I have looked and if your BGA is 27 x 27mm square with balls on a 1.27mm pitch (as i suspect it is), then it is one of the stencils that they offer as a free sample. Thier part number for this one is B6-272-2727-127.

I hope this helps.


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Temporary Stencil for MPC555 PBGA | 30 May, 2002

Consider NOT getting involved in those little POS chunks of sheet metal. * They're expensive. * You never have the one you need. * Even if you DO have the item you need, you probably will not be able to locate it. * It's all but impossible to control paste deposition with them.

As an alternative, consider using tacky flux. Just: * Dip the BGA into a precisely leveled glob of tacky flux [Search the fine SMTnet Archives for an innovative approach to the precision leveling of tacky flux]. * Place the part. * Reflow the solder. * Live well, live long.

While you're perusing the fine SMTnet Archives, * Keep an eye out for a reference to a paper on BGA rework by Earl Moon that was published in the SMTnet Newsletter, circa maybe, maybe not late summer / fall 1999 or some other time. * Determine if reballing and reusing BGA is appropriate for you product end-use application. [The Archives may contain a reference to a Motorola position that they do not reuse BGA in shippable product, because of reduced reliability in BGA with multiple heat cycles.] * Recognize that following this suggestion of using tacky flux, in lieu of solder paste, would reduce the amount of solder that ends-up as solder attachments under your component. While this reduced amount of solder potentially lowers the reliability of your product, we have never found anything that supports this theory.

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David R


Temporary Stencil for MPC555 PBGA | 31 May, 2002

The Flextac micro stencils I mentioned are not metal, but rather laser cut polymer, so not as easily damaged. As for cost, Even if you only re-use them 5 times and not the 10 that another company I know does, they only cost around �36 for a pack of ten (about 70 pence per use which is nothing to us when we consider the cost of mucking up the rework). If they can improve the paste deposition then it's money well spent. If you have to paste, as we do then, this may be the way forward....

As for losing the stencils.. there is always the possibility of losing engineering equipment if you don't look after it, however It would just be plain stoopid to let this put you off a potential solution to your problems!


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Temporary Stencil for MPC555 PBGA | 4 June, 2002

One thing that has worked for us is to get the full size stencil for the board. Then we put a bit of paste on it, then someone holds the BGA on the other side and we apply paste to the BGA. It can be awkward. We only use this technique for if we are reworking one or two BGA's. You don't get lots of paste on the balls because they tend to poke into the holes but we do get paste on them and then they reflow in the rework station.


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