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SMT electronics assembly manufacturing forum.


Costing new products - Qty of solder paste

rberry

#3294

Costing new products - Qty of solder paste | 16 August, 2000

Hi

Does anyone have a tried and tested method of estimating the mass of solder paste that will be used for an SMD assembly given only the type and quantity of components used. (As well as type of paste, stencil thickness etc) In other words is there some sort of formula that would say allocate ? grams of paste for an 0603 chip, ? grams for an SSOP-28 etc.

Richard

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Charles S

#3295

Re: Costing new products - Qty of solder paste | 16 August, 2000

Are you running high volume. If yes then what you propose may be relevant. If however you run low volume - lots of changeovers then your wastage/transfer will be equal if not greater than the amount put on the boards. Enclosed systems like DEK Proflow will greatly reduce this wastage.

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#3296

Re: Costing new products - Qty of solder paste | 16 August, 2000

Richard,

take a given volume and weigh it. For your parts you have already determined the aperture opening and stencil thickness and that gives you the volume for each lead of the component. This way you should be able to determine the amount of paste used for each board. But realize that only a part of the paste you need to produce a board actually sticks to the board. Depending on your printing, cleaning and handling process yopu will see that more or less paste is needed which is not found on the later product.

A good approach would be to determine the average consumption for a given board (or if you like for a component) taking the amount used over along period and the number of boards ( or used components ) and than calculate for a new product. In my experience the amount of used paste depends on the batchsize and the equipment and processes used and that for a good calculation the wastage should be taken into account.

Good luck

Wolfgang

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rberry

#3297

Re: Costing new products - Qty of solder paste | 18 August, 2000

Thanks Wolfgang / Charles

Have tried method suggested by Wolfgang on one product, and seem to be a bit over (perhaps density calculation was a bit out). Also, the volume of paste deposited must be less than the voume of the apetures on the stencil because of paste adhering to the sides of the apetures. We use Stainless squeegees so I presume the volume of paste would be less if a rubber squeegee was used. Batch sizes we are running are between 300 and 2000 panels - but I do agreee a lot of paste is wasted with changeovers. We are using standard squegees (i.e. not ProFlow). Will monitor actual usage compared to calculated usage over the next few batches we run and give feedback (Production guys don't like it when we waste their machine time with experiments so I have to be patient!)

Thanks again

Richard

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