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Printed Circuit Board Assembly & PCB Design Forum

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Paste Push-Out In PP Assembly

#6415

Paste Push-Out In PP Assembly | 20 July, 2000

Bob: On "paste push-out" (when inserting a component lead into a through hole pushes the paste out of the hole) in pin & paste assembly: * What factors affect paste push-out? * What techniques reduce this effect, given a board design and component lead size?

Continuing, how do different solder paste formulations and mesh sizes perform in pin & paste assembly? What is the preferred paste formulation and mesh size for pin & paste assembly?

Thanks

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Bob Willis

#6416

Re: Paste Push-Out In PP Assembly | 20 July, 2000

So far on all my trials on PIHR I have only used standard products as the paste is defined by the printing requirements for fine pitch etc. As most people will have seen you just get a heap more residues with this process and even more with lead free Paste push out does occur and seems to be mostly related to the reduced hole size whish we need to do.

Solder paste reflows back up a pin and in to the hole with little problem provided the pins are not too long, 1-1.5mm below the board. The plating on the pins can be a minor problem if the surface is slow to wet. When trying out the process with different pastes place a piece of white paper under your assembly jig and see if any paste drops down.

In the case of reflow put a copper foil under each of your trial boards on the mesh conveyor with the board on the rails and look for solder spots after reflow, its simple but works.

For people who have been on my PIHR workshops they may like to comment on the video clips I use to show all these things happen.

Bob

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#6417

Re: Paste Push-Out In PP Assembly | 20 July, 2000

Bob, I attended your PIHR workshop at Nepcon a few years back. At the risk of making a shameless plug, I must say that the presentation and the materials used were some of the best I have seen in my many (20+) years in the industry. The video that is included in the presentation is invaluable as both a supplement to the printed materials, and an educational aid in enlightening others (such as management) as to the technolgy and advanatges of PIHR

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Bob Willis

#6418

Re: Paste Push-Out In PP Assembly | 20 July, 2000

Many thanks the beer is in the post !

Thanks for that I spend a lot of time doing my video clips, to show a point as I believe if you see it happen it must be true. I would get bored listening to me if I did not use them.

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