Non Destructive BGA Profiling Test #1

I am currently investigating a non destructive method of BGA profiling that is reliable.  Here are the results of my first test.

Set Up:

Four thermocouples are attached to the same BGA (TOP, SIDE, INSIDE and BOTTOM surface), as pictured below.  Conductive aluminium double sided tape is used along with Kapton.  A KIC Explorer is the profiler.

To see more on Thermocouple attachment visit my post:  http://profilingguru.com/tcs/thermocouple-attachment/

A hole was drilled out to attach the INSIDE TC.

pic1

pic2

Results:

Two tests were run, the first was running the board on the belt followed by running the same board on the chain/tab conveyor.

sample1

As you can see the delta for ramp and peak is the greatest, while soak is minimal.  The inside TC runs the hottest and the underside bottom TC follows fairly closely the behavior of the inside TC.

sample2

This second profile was run on the belt with the same board but for a different BGA.   Again we see similar behavior, where the INSIDE and BOTTOM TCs exhibit similar behavior.

sample3

This third profile was running the same board and same BGA as in the second example but this time on the chain/tab.   Interestingly, all TCs were a good predictor of the INSIDE TC except when getting to the cooling zone.  The BOTTOM TC was only a good predictor of the INSIDE TC.

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Comments

  1. Tan,

    The method for attachment for flip chips is similar to that of BGAs. If you want to be absolutely certain of your joint reflow temperature you need to physically make contact thus drilling a hole. Currently RIT is conducting a very extensive study on “in-direct” methods of attachment, where one can use an off-set for example from thermocouples attached externally to the component. I’ve seen some of the preliminary data and it looks very promising, thought the study is focusing specifically on BGAs. The benefit of course is this is non destructive. This study should be completed by year end at which time I will be sure to post on this website as well.

    Brian

    Brian

  2. Do you have any information on where to attach thermocouples on Flip chip packages bonded on substrate? From various website, the answer is to drill a hole through the substrate which is a challenge. Any other solution eg attaching the thermocouple on the die surface, substrate surface and etc would be a closer option?

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