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Very thin laminate substrate problem with solder printing

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#76937

Very thin laminate substrate problem with solder printing | 26 January, 2017

Hi all,

Am new to SMT here.

I have a very thin laminate substrate which around 120um thickess. Being that thin, warpage is constantly an issue for us.

For the solder printing part, we have a number of problems.

Being so thin and warped, we need to have a carrier to support the substrate while it is being printed. Since it needs to be totally flat when printed, we will need to vacuum hold it down.

The problem is the substrate is so warped to begin with that vacuum can't hold it down unless we press the substrate down manually.

That is not feasible so we used a window magnetic clamp to clamp it down at the sides. That came with another set of issues as the window clamp added extra height to the entire structure which then our screen cannot contact fully onto the substrate for printing.

To work around that, we trialed this MagicResin that something like a reflowable and reuseable double sided tape which we applied onto the carrier to hold the substrate down without the window clamp. That came with another set of problem as it is either too sticky, or not not sticky enough or the resin lost its stickiness after a number of reflows which forces us to replace sooner than what its tech specs stated.

Anyone encountered similar issues and how do you work around it?

Thanks for any advice!

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#76948

Very thin laminate substrate problem with solder printing | 27 January, 2017

Consider that printing may not be the only approach to getting paste on to your board. Would a dispenser work better?

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Rob

#76951

Very thin laminate substrate problem with solder printing | 30 January, 2017

> Hi all, > > Am new to SMT here. > > I have a very > thin laminate substrate which around 120um > thickess. Being that thin, warpage is constantly > an issue for us. > > For the solder printing part, > we have a number of problems. > > Being so thin > and warped, we need to have a carrier to support > the substrate while it is being printed. Since it > needs to be totally flat when printed, we will > need to vacuum hold it down. > > The problem is > the substrate is so warped to begin with that > vacuum can't hold it down unless we press the > substrate down manually. > > That is not feasible > so we used a window magnetic clamp to clamp it > down at the sides. That came with another set of > issues as the window clamp added extra height to > the entire structure which then our screen cannot > contact fully onto the substrate for > printing. > > To work around that, we trialed this > MagicResin that something like a reflowable and > reuseable double sided tape which we applied onto > the carrier to hold the substrate down without > the window clamp. That came with another set of > problem as it is either too sticky, or not not > sticky enough or the resin lost its stickiness > after a number of reflows which forces us to > replace sooner than what its tech specs > stated. > > Anyone encountered similar issues and > how do you work around it? > > Thanks for any > advice!

Hi Joshua,

We have had similar issues with very thin flex in the past. This may not work for you, but we have done the following:

Route the substrate profile into durastone carriers so the pcb sits flat for printing. Spray the pallet with 3M spray mount and push the substrate down onto it. Add Kapton tape for the corners.

Or, pin it down in a carrier and dispense instead of print as Dave asuggests. However you have to make sure the placement head doesn't hit the carrier.

Hope that helps, Rob.

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#76955

Very thin laminate substrate problem with solder printing | 30 January, 2017

so, why are your laminates warped? What needs to be done to correct that issue?

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#76957

Very thin laminate substrate problem with solder printing | 30 January, 2017

Thanks Rob.

I'm not so sure in a mass production environment that using the mount spray and kapton tapes are going to be efficient.

For solder paste dispensing, any idea what is the smallest solder dot size the machine can dispense?

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#76958

Very thin laminate substrate problem with solder printing | 30 January, 2017

I just assume when you have laminates that thin, it will invariably be warped in some degree. I have worked on a few and I have never seen one that is not warped consistently.

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#76962

Very thin laminate substrate problem with solder printing | 30 January, 2017

Tacsil is another product you might try.

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#76963

Very thin laminate substrate problem with solder printing | 30 January, 2017

Looks like a similar product to magic resin.

Thanks I'll check it out.

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Rob

#76974

Very thin laminate substrate problem with solder printing | 31 January, 2017

Hi Joshua,

We ran 150K per week this way, you just need a lot of pallets.

Regarding dispensing I've seen 0201 (Imperial)paste dispensed, so about 0.4ish mm dots. I'm sure the Mydata printer is also pretty high resolution too, but not too quick.

Rob.

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#76983

Very thin laminate substrate problem with solder printing | 31 January, 2017

Hi Rob,

So do you have to constantly remove the old adhesive and spray on new ones? Is that an automated process?

Also for the kapton tape removal and application, is that automated as well?

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#76985

Very thin laminate substrate problem with solder printing | 31 January, 2017

Dispensing: You can dispense for 0201 and above

Warped laminates: Ask your laminate fabricator what's ausing the warping and how to make it go away

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Rob

#76989

Very thin laminate substrate problem with solder printing | 1 February, 2017

Hi Joshua,

No, the adhesive lasts 2 or 3 runs. The adhesive is put on manually as is the kapton. It's a big panel for a flex - nearly 300 x 210, so the operator loading the boards onto the pallet and fixing them (then into a buffer) stays well ahead of the printer.

Rob.

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