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Screen printing warped boards

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#41093

Screen printing warped boards | 20 April, 2006

Here is the problem :

We have 2 AP25 printers with dedicated tooling. After we run side one boards through reflow, we get some warpage in our boards occasionally.(Sometimes we get a lot of warp depending on the geometries of the substrate)

When the warped boards go into the AP25, the leading edge hops over the board stop(because of the warp) and then the camera proceedes to crash. The poor camera covers on our machines look like crunched beer cans from so may crashes.

Here is my question.....Is it possible to change something on my AP25's to fix this ? By the way, we have vacuum hold down, flippers and snuggers on our machines.

Is there another printer out there that handles warp better than AP25's? I thought I remember reading something about DEK printers being able to handle a substantial amount of warp somewhere ...

Any input is appreciated. Thanks

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#41096

Screen printing warped boards | 20 April, 2006

Sr.Tech,

Don't know about AP25's, we have a DEK. We have problems with some large board sagging in the middle, causing the board to slip under the board stop, but our DEK has the ability to program the board stop anywhere in the Y direction, allowing the board stop to locate outside of the board sagging area. It works, kind of a neat feature.

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dirk29

#41097

Screen printing warped boards | 20 April, 2006

We had that problem with our printers we just drill and tap the top end of the stop and put a short screw in to allow us to adjust the top height of the stop and catch the board. Be careful not to make it to long or to could restrict the board from leaving the printer or dent\tear the stencil when it comes up. Good luck

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Chunks

#41099

Screen printing warped boards | 20 April, 2006

The newer MPMs use the camera to find the board edge - no mechanical stops like AP and DEKs.

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PWH

#41100

Screen printing warped boards | 20 April, 2006

All our AP's have camera mounted board stop sensors (works like a conveyor sensor). You can also mount these sensors on or near the conveyor if you want. We do not have problems like you talk about. You should call MpM and ask them if it's possible to install a retro kit on your machines.

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RDR

#41102

Screen printing warped boards | 20 April, 2006

Can you run the first side on a mesh belt to keep it from warping?

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Geo

#41106

Screen printing warped boards | 20 April, 2006

When we have warpage issues we use Titanium Panel Stiffeners even though the stiffeners are mainly used for Wave we find little issue for reflow. Mind you the boards have to be large enough.

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#41110

Screen printing warped boards | 21 April, 2006

Good morning,

MPM AP25 we have is equipped with dedicated vacuum support only, no side snuggers. Also we had a lot of issues with fine pitch paste deposition due to this poor support. Vacuum support can�t fix wrapped boards properly causing a lot of headache. DEK support is designed in better way. It has side clamping blades with tooling fixing the board from underside. As far as I know, Speedline can offer you to replace your existing support system with newer one. Ask them for details.

BR, Pavel

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#41121

Screen printing warped boards | 21 April, 2006

A lot has changed since the AP25 was designed. What looks like a bad design today was cutting edge 10-12 years ago.

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#41122

Screen printing warped boards | 21 April, 2006

Chunks, I know about the board stopper in the camera. I forgot to mention that our 1 AP25 is a HI-E machine with that camera in it.

The HI-E still uses the dedicated tooling. When the snuggers engage the board pops over the mechanical stop.

We do run our boards on the mesh conveyor on side 1.

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#41152

Screen printing warped boards | 24 April, 2006

What you describe is the X snuggers fitted into the workholder which do need either a flat board or good vacuum to work. There are several solutions. One solution you can try yourself is to use Vacuum cups, ( bellows type) designed into the workholder. Run these off a venturi generator fed buy the snugger air supply instead of the snuggers. Later designs have a combination of clamping. Y clamping which incorpoates board warpage control before clamp. Advantage is the pcb is still in full contact with the stencil. Alternative platforms offer either Over top clamps, As adoted on a couple of the mid range MPM machines.Or Warpage control flippers and Y clamps. Talk to Speedline MPM about newer solutions to your problem.

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#41153

Screen printing warped boards | 24 April, 2006

Use the photo sensor to stop boards instead of the hard-stop. There is also an ultrasonic sensor upgrade. A little more robust than optical.

Y Snugger Tooling upgrade is kind of pricey and they like to do that in the plant. But, I've known that upgrade to be done in the field.

Contact MPM tech support for details and solutions- 800-737-8110.

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