System and method for detecting defective back-drills in printed circuit boards
A method for detecting failed back-drills in PCBs in the process of fabricating a PCB so that the failed back-drill can be screened out or repaired. short to ground connection is added for every back-drill via that will be cut when the back-drill removes the via stub. If the back-drill is bad or failed the short to ground will fail the subsequent electrical tests. The PCB can be repaired by re-drilling the hole or via. Failed back-drills may be detected in the manufacturing stage using standard equipment and test procedures. This process creates a simple pass-fail measurement that uses an existing common test process to catch failed back drills in the PCB fabrication facility. This allows for easy and cost-effective repair and guarantees back-drill failures do not pass into the field.
1. A printed circuit board (PCB) comprising:
a plurality of layers comprising conductive traces;
a plurality of vias configured to electrically couple said traces formed on different layers of said plurality of layers of said PCB; and
a shorting trace from a non-ground via to a ground plane of said PCB.
2. The printed circuit board (PCB) of claim 1 wherein the non-ground via is physically and electrically isolated from the ground plane due to back-drilling of the PCB.
3. The printed circuit board (PCB) of claim 1 wherein subsequent to back-drilling of the PCB, the non-ground via is electrically coupled to the ground plane.
4. The printed circuit board (PCB) of claim 1 wherein the shorting trace comprises a stub length of 10 mils plus or minus 5 mils.
5. The printed circuit board (PCB) of claim 1 wherein the shorting trace is disposed on a power or ground plane layer of the PCB.
6. The printed circuit board (PCB) of claim 1 wherein the shorting trace is disposed on a signal layer of the PCB.
7. The printed circuit board (PCB) of claim 1 comprising a plurality of said shorting traces on a plurality of layers of the PCB.
8. A printed circuit board (PCB) comprising:
a plurality of layers comprising conductive patterns;
a plurality of vias configured to electrically couple traces formed on different layers of said plurality of layers; and
a shorting trace from a non-power via to a power plane,
wherein said power plane is one of said plurality of layers, and
wherein the non-power via is physically and electrically isolated from the power plane due to back-drilling of the PCB.
9. The printed circuit board (PCB) of claim 8 wherein subsequent to back-drilling of the PCB, the non-power via is electrically coupled to a power plane.
10. The printed circuit board (PCB) of claim 8 wherein the shorting trace comprises a stub length of 10 mils plus or minus 5 mils.
11. The printed circuit board (PCB) of claim 8 wherein the shorting trace is disposed on a ground plane or power plane layer of the PCB.
12. The printed circuit board (PCB) of claim 8 wherein the shorting trace is disposed on a signal layer of the PCB.
13. The printed circuit board (PCB) of claim 8 comprising a plurality of said shorting traces on a plurality of layers of the PCB.