1
\$\begingroup\$

I recently designed a board around the D12F200A buck converter; I use it to convert from 5V down to 1.4V. Earlier today, I increased the load on the converter beyond what I had ever done (still well below its limits), and a trace blew almost instantly. However, the trace that blew was a signal trace-not a power delivery one.

I have attached photos showing where the trace blew and the current path. The trace is 20mil and the board was manufactured using 1oz copper. Could a crack in the trace or a manufacturing defect have caused this? I have used this board for a total of ~20 hours across the past few weeks.

Schematic showing where trace blew PCB layout showing where the trace blew Photo of blown trace

\$\endgroup\$
10
  • \$\begingroup\$ Clearly, it wasn't low-current for at least a few moments! \$\endgroup\$
    – Hearth
    Aug 8, 2020 at 2:44
  • \$\begingroup\$ You say it's a low current, but I have my doubts. What makes you call it that? The D12F200A is 40A output converter. Running at its limit, 40A of current could have been in that tiny 0.5mm trace. What were you powering with this thing? \$\endgroup\$
    – DKNguyen
    Aug 8, 2020 at 3:13
  • \$\begingroup\$ @DKNguyen You’re right, the converter is NOT low current, however the trace that blew is limited by a 270+ ohm resistor and doesn’t carry the power to or from the D12F200A. Given that the input voltage is 5v and the output is 1.4v, it’s hard to imagine more than 20ma of current passing through the trace without something else interfering. \$\endgroup\$
    – Thoughtyness
    Aug 8, 2020 at 3:15
  • \$\begingroup\$ No ideas here, but you could clean up the blown trace, use a fiberglass burnishing brush to scrape off some solder mask and glue a small fuse to bridge the trace, then try again. \$\endgroup\$
    – DKNguyen
    Aug 8, 2020 at 3:22
  • \$\begingroup\$ @DKNguyen Thank you. I went ahead and placed the metal lead off of a resistor parallel to the trace and then used some flux to solder everything together. It seems to be working now, though I haven’t used as much power. \$\endgroup\$
    – Thoughtyness
    Aug 8, 2020 at 3:26

1 Answer 1

Reset to default
0
\$\begingroup\$

if the board layout is the same as the schematic layout then current to C! flows through that trace. if there's a lot of ripple that could be a high current. Also current from P1 flows through that trace.

\$\endgroup\$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.