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What exactly is an apect ratio?

Antonio A. Medina

#2776

What exactly is an apect ratio? | 11 October, 2000

Hello all,

I'm new at this so forgive me if my question seems common knowledge to everyone else. I've searched the archives but found no clear answer to what exactly is aspect ratio and what the best ratio is. All I really know is that it has to do with solder paste size/stencil thickness. Is this correct?

tony

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#2777

Re: What exactly is an apect ratio? | 11 October, 2000

Hello Antonio ASPECT RATIO = the ratio of one dimension to another as in the ratio of the thickness of a stencil to the width of the aperture. For instance, a 10 mil aperture in a 5 mil stencil will have an aspect ratio of 2. This is aperture width divided by stencil thickness. It is generally accepted that if the ratio gets below 1.5 you're asking for trouble. The problem is poor release of the paste from the stencil because the surface tension of the paste to board cannot overcome the paste to stencil surface tension. I know the archives can be trying sometimes but if you try enough terms you will find information on the subject. While you're there you can search for a good book or two. Everybody had to start somewhere. Good luck

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