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Stencil Thickness

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Stencil Thickness | 15 June, 2007

We have not processed very much 0402 size components in the past. We are finding that alot of our customers are upgrading their circuits and going with 0402 size parts. We recently processed one such circuit and odered a paste stencil 6 mil in thickness. We found that this thickness was okay in the past dealing with our mostly 0603 (and up) size components, but found that on our 0402 size parts was depositing too much paste. Does anyone know what stencil thickness would be appropiate for a 50/50 mix of 0603 and 0402 size components? Thanks

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Stencil Thickness | 18 June, 2007

Good morning,

5mil stencil or less would be appropriate. We deal with 0402's daily and 5mil works.

BR, Pavel

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Stencil Thickness | 18 June, 2007


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Stencil Thickness | 18 June, 2007

5mil should work fine. Some stencil manufacturers charge more if you go less than 5mil so stick with 5mil.

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Stencil Thickness | 21 June, 2007

5 mil is perfect for 0402's.

If you are printing SnPb solder use apeture reduction such as home plating the pads.

However, if youre using SAC, we've found that printing the entire pad works best due to poor wetting compared to SnPb paste.


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Stencil Thickness | 22 June, 2007

5mil works great. Just make sure that you screen alignment is dead on.

We're using a SAC305 with a home plate design. I ran a test a couple of months back and found that the home plate design works the best with 0402s.

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Stencil Thickness | 27 June, 2007

5 mil will treat you just fine. Do some research on stencil area ratio and aspect ratio if you ever reduce your aperture sizes any further.

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Stencil Thickness | 28 June, 2007

Laser cut 0.13mm stencil thicknes works great for us. BTW, are we talking RoHS solder paste? We do reduce the stencil apertures to 88 % of the pads when we go for the RoHS solder paste. Otherwise we go fo 96% reduction in general with some excemptions.

The reason for that is, the RoHS paste we use have a much better release from the stencil apertures. Except for the 0402:s and 0603:s where we use rounded corners on the stencil apertures, just for the paste release. On the very same boards we also have QFP: 0.5mm pitch and some heavy DC/DC converters (we overprint these bastards) along with BGA and front PTH connectors with paste in hole or P.I.P process. At the very same stencil! We have in a long term adjusted our stencil printing process/stencil design/reflow profife so it will work on almost every mixed scenario that we have to deal with and still to be able to fulfill the IPC/customer req.

Now, if You feel that the 0402:s gets to much solder and you don't want reduce the stencil thicknes, then I would recomend you to reduce the apertures to somewhat 75 -80 % and make them like this: if You know what I mean.

Haha, I tried to use some special characters on the keyboard to give You an idea what I mean, but hey, this lousy new regulation would not allow me to do so. It is hard to explain, but 0402:s works best with tis type of un-square aperture shape, where it should be; well I try again: No the SMTnet forum does not allow me to use special characters on the keyboard. Scheisse... I am trying to use the left and right "arrows" to illustrate what i mean. As a bonus, this will also help the small ones to center on their pads. Sorry for my poor english & grammar. /Sincerly Ps. This is my third and last try to post. Grrr. Grrr. Ds.

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