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Profiling LQFP-144 with ground plane

Profiling LQFP-144 with ground plane

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I have a pcb with an ENIG finish that is using a 144 pin LQF... - Feb 24, 2022 by Josh S

Could you include some info about how the thermocouples were... - Feb 24, 2022 by dontfeedphils

The thermocouples were attached with a square of aluminum ta... - Feb 24, 2022 by Josh S

Looks like a decent profile. Only recommendation I have wou... - Feb 24, 2022 by dontfeedphils

Also, do you have a pic of a "bad" joint so we can... - Feb 24, 2022 by dontfeedphils

Here are some images of the joints. ... - Feb 24, 2022 by Josh S

They don't look that bad, especially for SN100. There is evi... - Feb 24, 2022 by DWL

there is evidence of wetting on the heel. This is the first... - Feb 24, 2022 by Josh S

Couple notes here: 1. Try to shoot for 250C peak temperature... - Feb 28, 2022 by Evtimov

Thank you for the information. One thing i forgot to state... - Feb 28, 2022 by Josh S

Josh S

#87658

Profiling LQFP-144 with ground plane | 24 February, 2022

I have a pcb with an ENIG finish that is using a 144 pin LQFP and being soldered withSN100C/NC258 T4 paste. I used a oven profiler where the probes are taped down to the joint and the profiling software adjusts the program for the best profile for the board after several passes. I ran my first batch of pcb's with my profile and notice that the solder joints on the LQFP are not the best. I can see where the lead is pressed down into the solder and a minimal joint is made but the solder does not flow up the sides of the leg. This pcb does have a large ground plane layer covering the majority of the board. Could this cause the pcb to not heat adequately for good joints? If this is a factor any suggestions on how to compensate for the ground plane but still allow the profiler to adjust the program without making manual adjustments?

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dontfeedphils

#87659

Profiling LQFP-144 with ground plane | 24 February, 2022

Could you include some info about how the thermocouples were attached (pic) and the resulting profile?

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Josh S

#87660

Profiling LQFP-144 with ground plane | 24 February, 2022

The thermocouples were attached with a square of aluminum tape holding the probe to the part joint. Kapton tape was used to secure the aluminum tape to the board surrounding but not covering the probe. We are using a X5 KIC profiler with the 2G software. Attached is the oven profile we used.

Attachments:

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dontfeedphils

#87661

Profiling LQFP-144 with ground plane | 24 February, 2022

Looks like a decent profile. Only recommendation I have would be to possibly try and high-temp solder the thermocouples rather than the aluminum tape/kapton, only because you can get air-gaps and inaccurate readings using the tape method on assembled PCBAs.

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dontfeedphils

#87662

Profiling LQFP-144 with ground plane | 24 February, 2022

Also, do you have a pic of a "bad" joint so we can confirm if it really is?

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Josh S

#87663

Profiling LQFP-144 with ground plane | 24 February, 2022

Here are some images of the joints.

Attachments:

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DWL

#87664

Profiling LQFP-144 with ground plane | 24 February, 2022

They don't look that bad, especially for SN100. There is evidence of wetting on the toe and the paste on the pad seems to have reflowed properly. What does the heal look like? That's the more critical part of the solder joint for Gull leaded parts.

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Josh S

#87665

Profiling LQFP-144 with ground plane | 24 February, 2022

there is evidence of wetting on the heel. This is the first time I have had this type of joint using SC100C on a leaded part. Usually there is at least some wetting on the sides instead of just looking like it is pressed in and sitting on top of the solder.

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Evtimov

#87673

Profiling LQFP-144 with ground plane | 28 February, 2022

Couple notes here: 1. Try to shoot for 250C peak temperature. 2. Use all your 10 zones in profiling for more accurate profile. You should not reach your highest temp in zone8. Try to reach it in zone 10. 3. Go quicker. Your profile might be too long.

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Josh S

#87674

Profiling LQFP-144 with ground plane | 28 February, 2022

Thank you for the information. One thing i forgot to state is that we are using the long ramp-soak profile.

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