Electronics Forum: ground (Page 1 of 78)

Treading on dangerous ground

Electronics Forum | Wed Jul 22 13:50:49 EDT 1998 | Justin Medernach

My firm has just begun it's first PCB that will use BGA packaging. I have been reading up on the processes involved with BGAs and was wondering if you need to apply solder paste to the pads prior to applying heat and mounting the part to the board

Profiling LQFP-144 with ground plane

Electronics Forum | Thu Feb 24 16:34:54 EST 2022 | joshsvoboda

Here are some images of the joints.

Profiling LQFP-144 with ground plane

Electronics Forum | Thu Feb 24 00:37:08 EST 2022 | joshsvoboda

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

Profiling LQFP-144 with ground plane

Electronics Forum | Thu Feb 24 13:02:19 EST 2022 | dontfeedphils

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

Profiling LQFP-144 with ground plane

Electronics Forum | Thu Feb 24 15:14:48 EST 2022 | joshsvoboda

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 sof

Profiling LQFP-144 with ground plane

Electronics Forum | Thu Feb 24 15:36:34 EST 2022 | dontfeedphils

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 assemble

Profiling LQFP-144 with ground plane

Electronics Forum | Thu Feb 24 15:37:53 EST 2022 | dontfeedphils

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

Profiling LQFP-144 with ground plane

Electronics Forum | Thu Feb 24 20:13:22 EST 2022 | dwl

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.

Profiling LQFP-144 with ground plane

Electronics Forum | Thu Feb 24 20:39:05 EST 2022 | joshsvoboda

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

Profiling LQFP-144 with ground plane

Electronics Forum | Mon Feb 28 21:38:08 EST 2022 | joshsvoboda

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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