Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


glue size

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i want to learn from u

#46400

glue size | 27 December, 2006

Most of pcb have white/black printing at bottom side of them to indicate the chip location. Normally, this printing are the same location to the place that glue will be mount. My problem are the glue size between the point that have printing and not printing are difference. Point without printing will be smaller. It is possible that this printing can effect the glue size? Just to let you know, i'm using time/pressure dispensing system.

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#46401

glue size | 28 December, 2006

Tough call without seeing the board, but here's my best guess. You don't say if the glue dot is greater in height or diameter in the locations where you have printing (silkscreen), but I would guess that you might get either, or both, depending on needle height, shot duration, etc..

You're dispensing the same amount of glue into less space where you're dispensing on to the silkscreen, so the glue has to go somewhere...either up (which would probably show up in buildup around the needle tip) or out.

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#46402

glue size | 28 December, 2006

I know our glue looks different when applied over different color solk screen. Maybe it's just an optical illusion?

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#46403

glue size | 28 December, 2006

So I'm the only one that's had crappy piles of silkscreen between pads?

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i want to learn from u

#46410

glue size | 28 December, 2006

i just thought that it because of difference thickness between the silkscreen and without silkscreen. if we apply the same pressure and dispense time to this two difference location, the glue size will be difference. location with silkscreen will reach the nozzle first. Then, it's size will be larger due to longer dispence time.

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#46416

glue size | 29 December, 2006

Crappy piles? Weren't they a hard rock band in the 80's? I know on most of our boards the little silk screen dot is just the component identifier in really small font when looked at in Gerber. But this dot isn't very big, so I see how it can affect the volume of glue?

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#46432

glue size | 2 January, 2007

We had a supplier that put a [fuzzy and of variable height) line of ss between all chip R and C pads. Of course we were in low cost mode and had purchased a year's worth of boards.

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#46433

glue size | 2 January, 2007

Chalk this one up to semantics. Regardless of when you start pumping (do you use a needle with a foot? In that case the pump will run when the foot touches the board), your volume of epoxy is the same. You just have less room for it where there is silkscreen so it spreads or piles up.

You'll have to reduce your shot duration in those locations to reduce volume.

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#46434

glue size | 2 January, 2007

But that's how Purchasing is supposed to work, right? Then boast how they saved 50 bucks that day on buying slightly plemmed boards. Then you spend thousands of dollars over the course of the year reworking thru the plems. All the while management is asking why you can't be more cost conscious, like Purchasing!

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#46435

glue size | 2 January, 2007

Not to mention the couple hunnert they save by NOT getting an air ride truck to ship a new inline printer. You'd be amazed at what an E5 can do to a pallet in 3000 miles. I can't believe the thing worked.

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SMT in-printer dispensing