Why are these Advanced DFM Checks Necessary?
Most PCB CAD systems display your PCB design perfectly on the screen and your DRC passes with 'flying colors'. However the most common problem many CAD systems make is they don't offer a "perfect" representation of your design when outputted to Gerber & NC (plane layers especially). How can it be outputted perfectly? The Gerber Format is just unintelligent X,Y coordinate data with apertures. It's the actual Gerber/NC files which are used to manufacturer your boards, so it doesn't matter what your CAD system says... it's the gerber files that determine the quality of your boards. Here's a more detailed article about these potential pitfalls: Don't blindly trust your Gerbers
While it's great to view your Gerber/NC files, and perform basic DFM Checks on your files (such as minimum trace & space) before sending out for manufacturing; It's even better to make sure you also verify these critical Advanced DFM Checks?
Silkscreen over Solder Mask - Locate if there are any locations where the silkscreen overlaps with openings in the solder mask layers. Elevated Risk: May cause contamination of the pads and make electrical testing plus SMT soldering more difficult.
Non-Functional Internal Pads - Essentially these are unconnected internal pads typically found on plane layers. Elevated Risk: May break loose and cause potential drilling problems, risk of shorts, and more.
Isolated Connections - One of the most common problems is to determine whether your PCB CAD system has properly outputted good plane connections to the copper plane. Critical: A board will fail if any plane connections is not properly connect the copper plane.
Mask Slivers - Areas in the solder mask where the resist is so narrow that it may cause small pieces of the resist to flake off and present soldering problems later. Critical: A board can fail if the resist falls in an area that needs to be soldered later on.
Power/Ground Shorts - Determine any potential shorts between Power and Ground planes. Critical: A board will fail if there is a short between the power and ground planes.
Copper Slivers - Narrow areas in the copper where the potential for over-etching is great. This typically happens when trace angles are 30 degrees (or less), when composites are used, and on plane layers. Critical: A board can fail if certain copper area are over-etched. Resulting in shorts and decrease in board yield.
Solder Bridges - Typically when the mask layers, contain openings which are too large, and may expose other adjacent conductive areas. Critical: During fabrication, copper may get too close and form a bridge to other adjacent conductive areas.
Negative Plane Thermal Conflicts - Determine if any via or plated hole is connected to more than one negative plane together. Elevated Risk: May result in poor board performance.
Thermals - Check whether a thermal connection to the copper plane has been constricted by overlapping or adjacent data that is way too close. Critical: May result in poor board performance, short, or other undesired effect.
FInd Acid Traps - Due to the surface tension during the etching process, larger deposits of acid may get trapped into certain areas - resulting in over-etching. Critical: Over-etching will directly effect your board yields.
Antennas / Dangling Traces - Search for Non-terminating traces which may behave as an antenna. Elevated Risk: May result in poor board performance, short, or other undesired effect.