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stencil apertures for BGA

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#54352

stencil apertures for BGA | 11 April, 2008

I have a question concerning stencil apertures for BGA. In my case we have 0,8mm pitch BGA - plastic casing. I have found an information that paste reduction diameter should be 2mils. Is that correct ?

In my case aspect ratio = r/2t = 0,76 > 0,66 Is it ok ? Is it overprinted

r - radius of stencil aperture - 9mils ~ 230um t - stencil thickness - 150um

Other data :

diameter of soldermas - 26mils Diameter of pad - 18mils Diameter of stencil apertre - 18mils Pitch - 0,8mm ~ 31mils

What stencil aperture for BGA do you recommend ?

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#54358

stencil apertures for BGA | 11 April, 2008

Hi Andrzej,

We are using for BGA (0.8 pitch) square apertures size 0.4 mm (rounded corners r = t) and stencil thickness t=5 mils. So area ration-> w/4t=0.8

Regards Jan

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#54359

stencil apertures for BGA | 11 April, 2008

> Hi Andrzej,
>
> We are using for BGA (0.8 pitch)
> square apertures size 0.4 mm (rounded corners r =
> t) and stencil thickness t=5 mils. So area
> ration-_ w/4t=0.8
>
> Regards Jan

Hello Jan,

I understand that you have the same pad dimensions for BGA balls ?

In regards to my calculations looks like we print 20% more paste then in your solution.

What is yield in your case ? Did you develope this stencil apertures based on your own needs and experience or did you obtain this stencil design according to common rules for 0,8mm pitch?

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#54380

stencil apertures for BGA | 14 April, 2008

Hello,

That is working for us.

If you have a look at the Indium or Cookson recommendation they are very similar.

Just make few diffrent patterns of the BGA and find out what is workin for you.

Regards

Jan

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#54396

stencil apertures for BGA | 16 April, 2008

Thanks Jan for hints

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