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Thermo-couple attachment

#24428

Thermo-couple attachment | 7 May, 2003

I was wondering if anyone has done a study on thermo couple attachment with light cure adhesive.I have read all the papers and articles about aluminum tape, Kapton, and high temp solder.I have yet to hear anything regarding the accuracy of light cure adhesive. I am using a unit called a Dymax.

Thanks

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#24431

Thermo-couple attachment | 7 May, 2003

We use uV Dymax glue for thermocouple attach sometimes, but don't like the remainder [anal] and loosing attach, sometimes.

Roger Saunders, President Saunders Technology, Inc; said: PRO: � These products are easier to use than high temperature solder. � Accelerator and UV activated products set quickly, to speed installation. � High temperature, two part epoxies will withstand reflow temperatures for many cycles. � Both products can attach thermocouples to unsolderable surfaces such as plastic or ceramic components or FR4 board. CON: (Accelerator or UV activated adhesives) � Their low temperature rating makes them prone to popping off during reflow, where peak temperatures are around 210�C. � Their relatively poor thermal conduction makes it essential that the thermocouple junction be held securely against the surface to be measured while the adhesive is activated. � They are usually easy to remove by "popping " them off with a knife. However, they do leave a film-like residue that is noticeable on FR4 and dark components, and can be difficult to remove. The most effective solvents, like acetone, also dissolve plastics, and can therefore damage circuit boards. CON: (Epoxies) � High temperature epoxy requires an oven cure of several hours. This is inconvenient, especially for quick trouble shooting. � It also requires careful fixturing to insure that the thermocouple junction stays in contact with the surface to be measured, throughout the oven cure cycle. � It is difficult to remove this material cleanly, without damaging the board or component. � Quick curing epoxies like "5 minute" epoxy are rated in the range of 130�C, so they often pop off during reflow.

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#24432

Thermo-couple attachment | 7 May, 2003

Thanks for the response Dave.

FYI: In my experience using the light cure adhesive, I have found that the newer the adhesive is the less prone it is to popping off during a reflow cycle. Also I have found that it only takes a very small amount to secure the probe.It seems the more you put on the more likely it is to pop off during reflow.A small piece of Kapton ontop your dot helps too.

What glue are you using? We are using Dymax 3073. I don't have any residue problems after I pop probes off.The area where the dot was appears to be clean as a whistle after I pop it off.

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#24433

Thermo-couple attachment | 7 May, 2003

We use Dymax �Ultra Light-Weld�.

We use an ADAC Technologies handheld for uV cure. What do you use?

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#24434

Thermo-couple attachment | 7 May, 2003

Well Dave,

Check the number that is on your adhesive tube. They make several different types of adhesives for use on different substrates. The rep from Dymax recommended the 3073 for bonding to FR4. We use a Dymax HHL400 handheld curing light. Click the link below to look at different light cure adhesives and their respective applications.

http://www.dymax.com/products/glass/ultrafast_glass.asp

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