recently bought smt boards from new supplier and mask openings were 20% larger than supposed to be.
this causes shorting problems between fine pitched pads.
should i insist they remake boards at no charge?

 

Before you do that, you need to double check the files you supplied to the PCB shop. They can only produce based on what you sent them.
View your gerber files on a gerber view to check the solder mask spacing.

 

Also, look to see if there are any sizing rules used by the board house.

 

already checked the gerbers twice, they were correct.
couldn't find mask size accuracy in their specs.

 

already checked the gerbers twice, they were correct.
couldn't find mask size accuracy in their specs.

Have you contacted them and asked what might be going on?

 

yes, they want pictures which would be worthless.
you can't see .010" in a picture.

 

If you order something and its not what you ordered then yes a refund or proper zero dollar replacement should be standard practice provided the mistake was theirs.

 

yes, they want pictures which would be worthless.
you can't see .010" in a picture.

How are you seeing the 20% error? Microscope, x-ray, etc?

Presumably you've measured this error in some way or another - can you get imagery of any kind from whatever you used to detect the error?

Working for a company that is on both ends of these sorts of accountability questions, I can understand where they're coming from. It's not unreasonable for them to request evidence of some sort - and not just because they don't trust you; often seeing the error makes it easier to identify the root cause of the problem and improve methods going forward. When we send out warranty parts, I often request the old parts be shipped back, not because I think the warranty claim is fraudulent, but because I want to learn what we've done wrong and how to avoid it in the future.

We've got a cheap USB "microscope" that has plenty of zoom and resolution to get a decent look at trace spacing, solder mask web thickness, etc. Images from it would be very helpful in a situation like yours. Maybe that's what they had in mind when they requested pictures.

As to your original question, assuming the mistake was on their end, I definitely agree that they should refund and/or replace the items... but I don't blame them for requesting evidence first.

 

measured a large pad with calipers.
and it's easy to see the pads are too close to each other when compared to gerbers.

 

measured a large pad with calipers.
and it's easy to see the pads are too close to each other when compared to gerbers.

So, snap a pic with the pad and calipers in the pic together.

Also if it's easy for you to see the difference by eye, without calipers, it should be easy for any modern camera to see the difference. Most digital cameras for many years now have been way better than my eyes!