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localization of the temperature sensors on the pcb

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#57881

localization of the temperature sensors on the pcb | 26 January, 2009

Hi there, where can I find some hints about placing the temperature sensors on the pcb when determining the reflow profile? I'm interested especially in the case of a pcb having BGA's. Thanks for your answers ! gheorghe

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#57883

localization of the temperature sensors on the pcb | 26 January, 2009

Hello,

usually you will place your themocouples on the most critical parts on your board. I would say, very big parts, very sensetive to the temperature parts, heavy parts, parts with big heat-sink.... The easiest way is to solder your thermocouple with high temp solder on the pads you want. In your case solder to the BGA and all mantioned above parts.

Regards, Emil

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RLM

#57884

localization of the temperature sensors on the pcb | 26 January, 2009

IPC 7530 - Guidelines for Temperature Profiling for Mass Soldering Processes (Reflow & Wave)

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#57886

localization of the temperature sensors on the pcb | 26 January, 2009

Check Daan Terstegge's excellent jump site for articles on profiling http://www.smtinfo.net/Db/_Thermal%20Profiling.html

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#57890

localization of the temperature sensors on the pcb | 28 January, 2009

Don't know the specifics from the IPC spec. However our standard internal spec dictates - highest thermal mass, lowest thermal, most critical component, and center of PCB on the laminate surface. Our profilers have 6 inputs, so the other 2 are determined by the product team.

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#57893

localization of the temperature sensors on the pcb | 28 January, 2009

thanks for all your answers.

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#57911

localization of the temperature sensors on the pcb | 30 January, 2009

Hope your problem is resolved. Else I could provide some details if wanted. Pl. confirm.

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#57957

localization of the temperature sensors on the pcb | 3 February, 2009

Hi,

There is one thing missing still, you must put a TC from the bottom side of the BGA by making a hold on the test board at the TC can measure the temperature at exactly the middle of the BGA. You should be able to the dual time and peak temperature of this point to understand if the soldering is taken place correctly under the BGA.

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#57971

localization of the temperature sensors on the pcb | 3 February, 2009

I would agree if you have a board to setup the process. But sometimes this doesn't work...

If for some reason if the customers AVL has a Lead Free BGA and I am running Leaded paste (yes this really happens!), you will need to run hotter to get your BGA to pop. This has at times been the bane of my existance!

You will be running at the top of the reflow window with a particular paste, but the BGAs will not reflow properly.

In these cases, we adjust the profile until the BGA reflows (usually around 229/degC.) We can only do this visually, capture the profile and make sure we arent damaging any sensitive components.

Any suggestions on another way to verify???

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