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SMT before through-hole

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#51399

SMT before through-hole | 14 August, 2007

I have posted earlier on a UIC Radial inserter machine. We have the machine running after repair of the CnC head.

However, I now have a process problem with a board that has 256x3 LED parts (768 LEDs in three colors) where only 50% of the LEDs can be placed if we run the SMT parts first due to clearance issues.

Would it be possible to run the board through the Radial inserter - putting all 768 LEDs in so that they are clinched - then running the Surface Mount process and reflow before masking and soldering the LEDs using a wave?

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#51400

SMT before through-hole | 14 August, 2007

standard procedure for this would be to solder SMDs on the bottom side and the LEDs all at once on the wave - if the layout is ok for the wave. You would have to glue the SMD components, for this you would have to use a glue dispenser or a special higher stencil for the printer with space on the bottom side of the stencil for the LED pins.

Hope that helps,

Erhard

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#51401

SMT before through-hole | 14 August, 2007

Should be do-able.

Check out a couple of things: 1. Temperature tolerance of the LED's. If they can't withstand reflow, then you won't be able to do it. 2. Height of the LED's versus the travel of your pick/place. If your pick/place head won't travel over the LED's, then you won't be able to proceed.

If the LED's can withstand reflow, you may want to check out intrusive reflow. Paste the board, including the holes for the LED's, place the LED's, place the SMT, then reflow the whole thing.

cheers ..rob

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#51405

SMT before through-hole | 14 August, 2007

> pick/place head won't travel over the LED's, then you won't be able to proceed.

I wasn't clear in describing my board layout; It is LEDs on one side and SMT components on the other side.

I don't think we can get around the problem of stenciling the SMT side after the LED leads are sticking through.

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#51407

SMT before through-hole | 14 August, 2007

I've never seen them used or even heard of them being used like this but you might want to look at http://www.sipad.com/

You will still have to work out other issues like how to keep the SMT on while you wave the LEDs.

Maybe you can get these boards, and use intrusive reflow for the LEDs?

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#51408

SMT before through-hole | 14 August, 2007

So it's a C-n-C clearance issue? Could you go with the other cutnclinch unit...which ever you have, get the other one (one's right angled, one's offset at 45�)? Yeah, I know, they're not cheap.

Other than that, hand place some of the SMT in chip bonder (of course then you have to cure, but your LEDs can probably handle that temperature) or hand solder them after you do wave. That's all I got.

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#51409

SMT before through-hole | 14 August, 2007

I see...said the blind man.

If you've got the LED's on one side, and the SMT on the other...and you have the clearance, I'd go with the previous suggestion of gluing the SMT, and waving the whole assembly...

As for stenciling....use a glue dispenser, rather than stenciling the glue on...

..rob

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