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

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Adhesive dispension

dszeto

#12457

Adhesive dispension | 1 March, 1999

We have customer requested machine dispension on adhesive of solder side components, however we are currently using stencil printing for adhesive. Have anyone evaluated and compared on dispension and screen printing of adhesive before? Thanks!

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#12458

Re: Adhesive dispension | 1 March, 1999

| We have customer requested machine dispension on adhesive of solder side components, however we are currently using stencil printing for adhesive. Have anyone evaluated and compared on dispension and screen printing of adhesive before? | Thanks! | Hey DS, give the customer what they want.

When we print adhesive on the second side, it's just to hold the components in-place during wave soldering and maybe PTH insetion. After waving, the solder holds them in-place and makes the electrical connection. Then the adhesive is about as useful as ... Not matter how it's put on the board. We can usually tell if a component is missing because there's big red blob of adhesive sitting there with no component trying to cover the blop up. So, I'm uncertain about the end item benefit of dispensing over printing adhesives. We print 'cause it cheaper, faster, and (we believe) produces an equivalent product.

Good luck

Dave F

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Erhan Kaya

#12459

Re: Adhesive dispension | 1 March, 1999

To me, customer always has a reason...

That reason may be the board requiring "smt primary" -> "DIP, VCD" -> "smt secondary" type of process flow. In that case, dispensing becomes a must. Dispensing needs less setup than printing, but takes longer. So, for a prototype manufacturer, dispensing becomes the best choice. Sometimes a machine dispenses glue and places the part simultaneously. Some people have a dedicated glue dispenser which is faster and more capable. When you have SOICs on the secondary side, you can dispense larger/higher glue dots while dispensing smaller ones for the chip resistors/caps. The last but not least; dispensing is a life saver during double sided reflow, if any top side parts need to be glued.

Good luck...

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James.L

#12460

Re: Adhesive dispension | 4 June, 2000

1) Adhesive dispensing -number of dot per component , what's the determined factor ? What's the distribution ? 2) What is the critical factor to monitor the consistacy of volume & profile per dot ? 3) What is the effect of temperature/balance of adhesive related to the volume of adhesive per dot ? 4) What is the thicknees of related to the opening ? 5) What is the method of cutting the opening of stencil? 6) How to measure the adhesive stregth or "green stregth" by cured ?

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