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Solder resist in between pads of a 38 pin TSSOP package IC

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treez

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Hello,
Is it possible for PCB manufacturers to make the footprint of the LT3791-1 38 pin TSSOP and have a "sliver" of solder resist between each of its adjacent pads?

LT3791-1 datasheet (footprint on page 24)
http://cds.linear.com/docs/en/datasheet/37911fa.pdf

As you can see, there's only 0.25mm gap between each pad and the next, so is it impossible to have any solder resist in between the pads?
 

Let's see. The recommended pads are 0.315±0.05 mm wide. The center-to-center spacing is 0.50 mm. Now, 0.50 -(0.315 +.05) = 0.135 mm

Do you know a manufacturer that can do that? Why do you ask? Maybe a good project this week would be for you to research every other SMD that has such tight spacing. That list might be useful to someone.

JOhn
 
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Thanks, in that case, what method would be used to solder such a part on the board without getting pad to pad shorts?

The pin thickness is 0.17mm to 0.27mm.
As you say, the distance from centre of pin to the next is 0.5mm
The minimum distance between adjacent pins is 0.5-0.27mm = 0.23mm
 

I wonder if we looked at the same datasheet. This is from the Linear site:

Capture.PNG

In any event, the space is small.

John
 
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Use IPC-7351 recommended footprint, this uses 0.30mm wide pads, this gives 0.20mm between pads, this allows for 0.10mm solder mask sliver and 0.05mm clearance to pad. This is doable and will prevent solder bridging.
 
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