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Solder mask bridge issue

Eyal78

New Member
From what I understand, PCB manufacturing has a limitation on the minimum width of the solder resist—it cannot be too thin, typically not less than 5 mil. In many components, including those with a 0.65 mm pitch, the spacing between pads can become smaller than 5 mil.

This reduction in spacing is due not only to the proximity of the pads but also to the solder mask opening—the larger it is (e.g., a common value is 4 mil), the smaller the remaining solder mask bridge. However, this issue persists even when the solder mask opening is as small as 2 mil.

For example, I am currently working with the NCP730BMT280TBG (LDO, see below) and the PMPB15XP (P-channel MOSFET, see below). Both of these components have tight pad spacing, making it difficult to maintain a sufficient solder mask bridge between them.

Is my understanding correct? If so, how is this issue typically addressed?

Additionally, I'd like to clarify terminology: Does "SM bridge" mean the same as "SM sliver," and is this the issue I am describing here?

What are the recommended design practices for professional manufacturing (without strict compliance to specific standards)? What is commonly accepted in various industries?

Thanks in advanced for any answer,

Eyal

Onsemi - NCP730.jpg


NCP730 FP measurement.jpg


Nexperia - PMPB15XP.jpg
 

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  • Onsemi - NCP730BMT280TBG.pdf
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I would strongly suggest that you contact the board assembly house for guidance. Some are quite capable of doing very fine pitch… for a cost.
 
Thank you all for your responses!

I am working with PCBWay, and unfortunately, I haven't been able to fully understand their capabilities for the cheapest board option (which I assume is their "Standard" service). Their website seems somewhat unclear, and based on my correspondence with them, I’m still unsure.
Here is the correspondence:
What is the minimum solder mask sleeve/bridge (depending on color)?
--white, black, matte black, matte white, these 4 requires min 0.22mm IC spacing, all other colors can do with 0.19mm.

—could it really be that large?
From their website:
PCBWay Capabilities

Perhaps someone with experience working with them can clarify.

In any case, my original question was about common industry practices, and I’d like to add:
What are the typical values for the minimum solder mask sliver/bridge in standard PCB manufacturing (nothing special or high-end)?

To refine my question further:
At what pitch does a design become too fine for standard manufacturing and require special fabrication processes?

Additionally, are there alternative solutions? I’ve come across the option of removing the solder mask between pins, but I assume this is not ideal.
 
I have not used PCBWays in a long time.
It is common, when a PCB house gets new machines, they do not retire the older machines but use them for low-cost boards. It might be that the "low cost" boards are being made by old machines.

Most of these places will answer emails.
 

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