CSD17322Q5A: Is drain pin needs solder wetting to all pins?

Sonchai Malaichan

Part Number: CSD17322Q5A
Other Parts Discussed in Thread: BQ25700

Tool/software:

Dear Sir,

I'm test engineer, I have discussed with process engineer to improve solder wetting on drain pins of power MosFet according mfg pn: CSD17322Q5A.

This device has thermal plate of drain pin. when it passed reflow oven the solder past was melt and soldering flows together at thermal area.

So, I would like to know that all drain pins need solder wetting on all edge pin or not?

According to pictures below, Q36 Pin8 (drain) has solder non wetting which it made load circuit fail while functional test.

But process engineer tells me that pin 5-8 was connecting together with thermal plate.

Any comments, please advise.

Best regards,

Sonchai M.

28 days ago

0 John Wallace1 28 days ago

TI__Mastermind 33875 points

Hello Sonchai,

Thanks for the inquiry. Yes, pins 5-8 and the thermal pad are all connected together. I don't think a single non-wetted drain pin would cause a functional failure as long as the thermal pad and other pins are soldered. Do you have the ability to do X-ray inspection to look at the solder connections to the PCB underneath the package? It looks like the PCB footprint does not match the recommendations in the TI datasheet. I do not know if this is a problem and have asked our SMT experts to review. A few questions:

Can you share gerber files so TI can review the PCB footprint and stencil design?
What type of solder paste are you using?
Can you share the reflow profile?

I look forward to your response.

Best Regards,

John Wallace

TI FET Applications

0 John Wallace1 24 days ago in reply to John Wallace1

TI__Mastermind 33875 points

Hello Sonchai,

Our SMT expert has reviewed your issue and doesn't see any non-wetting of the pins in the pictures you included. Can you please share more details including any additional pictures you may have.

Thanks,

John

0 Sonchai Malaichan 23 days ago in reply to John Wallace1

Prodigy 10 points

Hi John,

Please see below for X-Ray

0 John Wallace1 23 days ago in reply to Sonchai Malaichan

TI__Mastermind 33875 points

Hi Sonchai,

Thanks for the update. From the X-rays it appears that there is excessive solder voiding and possibly not enough solder paste being dispensed onto the thermal pad. Can you please share the details for the stencil design. Also, what solder pasted is being used? I have shared these pictures with our SMT expert and I am waiting for his response. Please see the app note at the link below for QFN and SON PCB attachment.

https://www.ti.com/lit/an/slua271c/slua271c.pdf

Thanks,

John

0 Sonchai Malaichan 22 days ago in reply to John Wallace1

Prodigy 10 points

Hi John,

Thank you so much for your update, let me check with our process eng for your questions.

Best regards.

Sonchai M.

0 John Wallace1 22 days ago in reply to Sonchai Malaichan

TI__Mastermind 33875 points

Hi Sonchai,

I would also ask how often the solder stencil is cleaned. It may be getting clogged which could prevent the proper amount of solder pasted being printed onto the pad. I'll wait for your response.

Thanks,

John

0 Sonchai Malaichan 21 days ago in reply to John Wallace1

Prodigy 10 points

HI John,

Sorry for mistake x-ray photo in previous message, it is not Q36 but it is Q34 which same mfg pn. those components have connected to BQ25700.

I asked our process eng, the stencil was clean every 5 boards.

So, I would like to share more x-ray photo of cause non wetted of Q38 (same mfg pn with Q36 and Q34) and stencil design is all same as below.

Best regards.

Sonchai M.

0 John Wallace1 21 days ago in reply to Sonchai Malaichan

TI__Mastermind 33875 points

Hi Sonchai,

Thanks for the update. From the screen shot of the stencil it does not appear that there is adequate solder paste being applied to the pads. For comparison please see the stencil in the package drawing at the link below. I do not believe this is a solderability issue with the TI FET. Please review and let me know if I can be of further assistance.

https://www.ti.com/lit/ml/mpss010b/mpss010b.pdf

Best Regards,

John

0 Sonchai Malaichan 17 days ago in reply to John Wallace1

Prodigy 10 points

Hi John,

Thank you so much. i will shared this information to our process eng.

Best regards.

Sonchai M.

0 John Wallace1 17 days ago in reply to Sonchai Malaichan

TI__Mastermind 33875 points

Hi Sonchai,

You are welcome.

Best Regards,

John

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CSD17322Q5A: Is drain pin needs solder wetting to all pins?