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Prototyping PCB Minimum Spacing Limitation

Dave posted a video on the EEVBolg to talk about a mistake of our prototyping PCB service : “EEVblog #155 – ITead Studio PCB Prototype Goof”.  We didn’t get any feedback or complaint about this order, so we didn’t give any response until we saw a post in our forum that refer to this issue.

We have give out the official response on that post and reached an understanding with Dave. Now we remake the boards again with the same gerber file. Today the boards return, we can not wait to start checking the board, and the result make us very disappointed – the factory seems change the gerber again and the boards still not connect with that cooper where Dave use to building the GND connection.

We call to factory to confirm why they do this, and get the reason. So, maybe in the prototyping PCB page we didn’t make a very clear instructions about the minimum spacing limitation. So here below is the detailed limitation that we get back form the PCB department :

1. Line

The spacing between tow line should be more than 6mil (0.153mm), if the spacing less than 6mil this design can not be accept. But even the 6mil is not a save safe distance, we suggest you left more than 8mil distance.

 The minimum line width is 6mil(0.153mm) , if the width less than 6mil this line will not appear on your board. And also the 6mil will not a safe distance, more than 8mil is recommended.

2. Via

The minimum aperture for your via is 12mil (0.3mm), the aperture less than 12mil can not be drill because the factory have not the drill size less than 12mil.

3. PAD

The minimum aperture is the same as the via.

The cooper aperture on the PAD should be more than 6mil(0.153mm) ! This is the one tip that we never brought.

The soldermask from the pad cooper must more than 4mil(0.1mm). This is the anther point that we never brought before.

4. Character

The width of one character should more than 6mil(0.153mm), the height of a character should more than 32mil(0.811mm), it’s better that the ratio of a character be 5 (e.g. width 0.2mm, height 1mm).

5. Non-metallic based slot.

The minimum hole spacing for a non-metallic based slot is 1.6mm. The slot less than 1.6mm will not be cut and open.

As we recheck the gerber file of Dave’s MatrixDuino, the spacing form soldermask edge to pad cooper edge just 2mil, and it’s less than the 4mil. So maybe they change the soldermaske layer again – I have not get the assured response that if the operator modify the gerber but they promise to investigate and give me the reply.

We found that  the pad specifications challenge to the minimum limit, so the factory technology level may not reach this design. We are sorry that we cannot made this board with our prototyping service which at such low cost.

We will contract Dave and follow-up with this issue.