Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Thermocouple

Daniele

#27629

Thermocouple | 11 March, 2004

Hi I have a question about proper installing thermocopule to PCB. I have thermocouple which consist of two wires and they are conected at the end by solder bead. I would like to use adhesive tape to connetct it to the PCB. Should i remove solder bead? or only place the thermocouple on the component lead and fix it by adhesive tape? should i twine the wires at the end? or is it ban?

Daniel

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#27630

Thermocouple | 12 March, 2004

Don't detach the bead and don't twist the wires! The bead should be what makes contact with where you want to measure temperature. Tape is not the ideal method to attached thermocouples for reflow soldering but is OK when using for wave solder preheat.

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#27631

Thermocouple | 12 March, 2004

The solder bead IS the thermocouple. A thermocouple is two different metal welded together. The junction generates voltage. You can use tape, glue, paper clip, whatever works on your particular situation. Just make sure the thermocouple does not move and stays in contact with the object you wish to measure the temp.

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#27721

Thermocouple | 24 March, 2004

Daniele

The other repsonses have it right. The junction of the wires measures the temperature.

If your poduct needs to be re-used I would suggest either kapton tape or aluminim tape(the better of the two). If this is your "golden board" I would suggest a high temp solder (prefered) or adhesive to attach. Check with your data logger supplier for suggestions on where and how to attach. thanks marc

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#27727

Thermocouple | 24 March, 2004

KIC Thermal Profiling did a DOE [Nepcon West 1999] [you probably can find it posted on their site] on thermocouple attach. Comparing the reliability and repeatability of thermocouple attachment methods: * High temperature solder was found to be the most reliable and repeatable method of attaching thermocouples to PCB. * Aluminum tape provides a reliable alternative to high temperature solder, though it is slightly less repeatable. * Kapton Tape is not reliable or repeatable. * Conductive Epoxy is reliable for a single profiling run, but offers poor repeatability. Its thermal conductivity is very inconsistent, and the results of these profiles do not seem accurate or reliable.

As I recall, Roger Saunders [President, Saunders Technology, Inc] wrote a paper that compares various [eg, mechanical, solder, adhesive, etc] approaches to thermocouple attach. You can probably find it on their site.

The other responders are justifiably alarmed at the thought of you cutting the junction from your thermocouple. Here's a overview of how thermocouples work: http://www.picotech.com/applications/thermocouple.html

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Ren�

#27744

Thermocouple | 25 March, 2004

Hi Daniele: In a design of experiments with four methods for attaching thermocouples : High Temperature Solder, Aluminum Tape (Chomerics T405), Kapton Tape and Conductive Epoxy (Loctite Tak Pak 382. The most reliable method is high temperature solder & Aluminium Tape ( Using Kapton also) .

For more Details to how attach & results in the DOE please consult the next page : http://www.kicthermal.com/library/nw99-ts19.html It will give you a great help to learn about thermocouples .

Saludos Ren�

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#27783

Thermocouple | 29 March, 2004

ECD has a product called the Temprobe that is an alternative to hi-temp solder, tapes and glues for thermocouple attachedment. The cool thing about the Temprobe is that you can use it on a pasted board too.

http://www.saunderstech.com/

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Frank Zomber

#27925

Thermocouple | 5 April, 2004

What type of aluminium tape should be used? I tried one, but it wouldn't stick to the board at reflow temperatures.

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#27926

Thermocouple | 5 April, 2004

Frank Zomber

Ren� advised "Chomerics T405" above in this thread http://www.smtnet.com/Forums/Index.cfm?CFApp=1&Message_ID=27744

Searching the fine SMTnet Archives will give contacts, like: http://www.smtnet.com//forums/index.cfm?fuseaction=view_thread&CFApp=1&Thread_ID=6308&#Message25211

Whose tape have you tried and had bad luck with?

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#28483

Thermocouple | 8 May, 2004

We have just been audited by our customer. One of the major finding was the thermocouple attachment. They insist that we use conductive epoxy to attach the thermocouple to the IC body and PCB surface. Any suggestion on what brand/model of conductive epoxy we can use? Thanks

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#28489

Thermocouple | 8 May, 2004

Your customer doesn't know what he / she is talking about. Read the papers on the links provided by Ren� and Pete C above in this thread.

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Ken

#28491

Thermocouple | 8 May, 2004

If this is a requrement from your customer then:

They should supply the name/brand of the material, AND they must supply solder samples because their requiremnt is a destructive profiling technique. You should charge them more dollars for setup and profiling.

I assume your a CM? Ask your customer if they profile with fully populated boards? IF no, ask them why they go through the trouble and expense of using conductive epoxies (presumably for "some performance benefit") and then don't use a representative model for the thermal process.

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