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LM5113: LM5113 DSBGA PCB solder mask issue.

Ryan Yu
Prodigy 95 points
Part Number: LM5113

Working in a University lab. Is using LM5113 DSBGA recently. Get the PCB and find the solder mask is not as good aligned as expected. Some pads are large while others are small.

I tin the pins and use hot air to solder (typically doing these in university lab). Check the pins connection and find some of them are not connected, try 10 times unluckily none working. Is there any suggestions that I can still use these PCB without getting a new layout. The boards are still under IPC class 2 tolerance.

Have some Questions:

Q1: Is that going to save the board If I order a laser cut stencils and use type 3 solder paste.  

Q2: Is LM5113 DSBGA has to use laser direct imaged solder mask? 

  • 0
    TI__Intellectual 2910 points

    Hi Ryan,

    Thanks for using the LM5113 driver in your design. I can see that the board fabricator didn't do you any favors with this PCB. Check and see if all the tolerances you requested were observed as you may be able to request then to re-do the fabs.

    One thing you can try is to not add any solder paste -- rather just add some flux on the PCB, align carefully the device to the copper (not the silkscreen) using a microscope, and then apply heat. Unfortunately it may take a few tries to get good contact on the solder bumps. If you have multiple boards, I recommend checking them all with a microscope first and use the ones that are better aligned first.

    Regarding your questions: (Q1) using  the stencil is worth a try, but I cannot tell for sure whether it will address your needs, and (Q2) Laser-cur solder mask is not required for the LM5113 DSBGA -- this application note provides information about the Die Size BGA (DSBGA) package and how to use it on PCBs, including footprint definitions: http://www.ti.com/lit/an/snva009ag/snva009ag.pdf

    Good luck!

    - Daniel

  • 0 in reply to Daniel Ruiz
    Prodigy 95 points
    Thank you for your reply. But the board is still under IPC class 2 tolerance. My actual design of using LM5113 is to drive synchronous rectifiers of 48V output LLC converter. The board is 12 layer so probably hard to redo. I will try your suggestions.