No solder resist allowed between LED pads...why?

[ocset]

Hello,
We have just found out that our LED footprint is wrong. We have had 200 LED MCPCB’s made up (100 LEDs on each one)  with solder resist between the LED pads. –Now we find out that  there should be no solder resist between the LED pads.
Do you think we must throw all these  LED MCPCBs away?
The LED is the WICOP2_Z8_Y19 LED   by Seoul Semiconductor.
Page 8 of the Seoul Semiconductor App Note called “Wicop” says that there should be no solder resist between the pads of the LED. They say that it is because flux residue can cause short circuit between the LED pads and the flux residue more readily settles on top of solder resist.

Page 8 of the following....("PSR" = Photo Solder Resist")
http://www.seoulsemicon.com/_upload/Goods_Spec/WICOP_Application_Note_Rev2.0.pdf

So Since when did solder resist *cause* short circuits?            

 

[ataradov]

I feel like it all will work just fine, assuming your board assembly house is competent.

Also, the same document "Figure 3 (b)" shows a PCB with solder resist between the pads.

[DerekG]

“Wicop” says that there should be no solder resist between the pads of the LED. They say that it is because flux residue can cause short circuit between the LED pads and the flux residue more readily settles on top of solder resist.

Most modern solder pastes leave almost most deposits behind. Pay a little more for one that is of high quality.

I think there is more to this than the manufacturer is letting on. I suspect the main reason the manufacturer does not want any solder mask between the pads is because it raises up the part on the board. If the solder paste is not thick enough it is possible to get open circuits (which is our experience), not short circuits.

Anyway, you can minimise the likelihood of open circuits by having a thicker solder paste stencil or minimise the likelihood of short circuits by having a thinner solder paste stencil. You can also adjust the openings in the stencil for the best reliability.

Give it a try. You have nothing to lose & everything to gain.

[donotdespisethesnake]

Also, the same document "Figure 3 (b)" shows a PCB with solder resist between the pads.

That is obviously demonstrating something else, doesn't mean anything.