0
\$\begingroup\$

I am new to this forum. I am building a prototype board which uses a 48 pin LQFP 0.5mm pitch IC including other components. Included on the board I have 1206 SMT components and SOIC components.

All components reflow well however the 48 pin LQFP keeps shorting during the reflow.

My board is professionally made but it does not include silkscreen and solder mask (bare proto board). I am also using a stencil. I have read that this type of board could cause shorting of pins with fine pitch components during reflow.

I am using a DIY home-made toaster oven following the general temperature curve for solder reflow.

I have tried applying various amounts of solder paste with no luck.

Any suggestions how to successfully solder such a component to the board?

\$\endgroup\$
  • 1
    \$\begingroup\$ A lack of mask will complicate your life here. \$\endgroup\$ – Scott Seidman Mar 8 '16 at 12:04
  • \$\begingroup\$ After contacting the board manufacturer I have tried a higher reflow temperature (peak at 235 deg.c) to meet the paste specification however this also did not show any improvement. Yet again the only component that bridges is the 48LQFP. My current stencil thickness is 130um. I believe a thinner stencil (100um) will also ensure less paste is applied, thereby reducing the risk of bridging. When I order some more boards I will try the thinner stencil and include the soldermask. \$\endgroup\$ – Darmesh Nana Mar 8 '16 at 20:47
2
\$\begingroup\$

You could hand solder it. It's just one component, and it's actually probably one of the easier components to solder, once you get the hang of drag soldering. Also, if it's not drifting in the oven and you simply have solder bridge issues, do a pass with solder wick after the oven to clean up bridges.

Also, soldermask may improve the situation. It's rare for soldermask to cost extra, may I ask why you've not got it?

\$\endgroup\$
  • \$\begingroup\$ I am new to PCB design and I understand that a bare board without the mask gives the possibility to easily probe and adjust during initial prototype phase. The idea is that you can easily cut and bridge connections during hardware debugging. \$\endgroup\$ – Darmesh Nana Mar 8 '16 at 7:45
  • 1
    \$\begingroup\$ You can still do that with soldermask, you just need to scrape away small bits of mask or solder to existing pads. I think you'll find that the advantages of silkscreen and soldermask are significant. (Debugging a complex board without silkscreen would be awful.) \$\endgroup\$ – uint128_t Mar 8 '16 at 7:47

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

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