Marcel R. wrote:
> *minimum trace-to-trace distance is 3.5mil

Marcel R. wrote:
> the spacing between traces is too small ,we need Min.0.25mm spacing .

Many manufacturers have different classes and different prices for them 
- smaller design rules result in higher prices. May be you ordered PCBs 
with 0.25 mm spacing and you could also have 3,5 mil spacing, but for a 
substantially higher price.

But the correct answer you can only get from the manufacturer himself.

Georg

For a prototype I needed a 6 layer PCB (with a BGA 0.8mm on it) and 
decided to give JLC a try (in the past I ordered several 2L-designs and 
was satisfied with the quality).

They accepted my design (4 mil spacing), but when I got the boards I 
first realised that all the thermals on the pads were removed.

After further investigation it seems that they just increased the 
isolation distance to about 8 mil?
Some ground plane connections on the top and bottom layer are now 
missing, I think I don't want to know what how they messed up the inner 
layers.

I filed a complaint and got the answer that the minimum gap is 10 mil.

Actually, this is not what they write on the website.


Conclusion:
Good for simple 2L-boards,
crap for designs with tight tolerances.
And dont't trust the specs on the website!

Alex

Marcel R. wrote:
> I assume they measure from mid trace to mid trace)

I would not agree. Distance is from copper to copper in my opinion. We 
really need to see the picture.
I ordered already 4 layer PCBs from JLCPCB at the edge of their 
specifications without any problem.

Had just a couple of months ago a design with 3.5mil tracks and 3.5mil 
spacing.

The only thing which they didn't like was less than 3.5mil spacing to a 
plated through-hole. But they changed the restring of the hole.

It was a 4-layer board.

Everyting worked fine and they didn't complain further.

My design passed their checks without any error,
they charged for a 3.5mil design,

and still they say the min. clearance is 10 mil...

Alex