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Aluminum tape

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#39704

Aluminum tape | 15 February, 2006

Can anyone tell me where I can get aluminum tape for holding down thermo couples on PCB's ?

Thanks

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#39706

Aluminum tape | 15 February, 2006

Se�or Tech

Search the fine SMTnet Archives. For instance: http://www.smtnet.com/forums/Index.cfm?CFApp=1&Message_ID=25210

Roger Saunders, President, Saunders Technology summarized the pros and cons of taping thermocouples as [He's taking about Kapton tape, but many points are valid.]: PRO: * In most situations tape is quick and easy to use. * Thermocouples may be taped to any type of surface. CON: * Tape's adhesive grip weakens with increasing temperature. Consequently, at reflow temperature it relaxes the preload on the thermocouple, which can allow the thermocouple to lose contact with the surface being monitored, and read ambient temperature instead of surface temperature. * It can be difficult or impossible to tape a thermocouple down reliably in tight places, such as between components.

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#39709

Aluminum tape | 15 February, 2006

In order of effectiveness / accurate reading:

1. Hi-Temp Soldering 2. ECD's Temprobe or new Flexiprobe http://www.ecd.com

3. Glue, such as SMT adhesive 4. Aluminum tape

Capton tape should not be used as it expands at reflow temps.

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aj

#39710

Aluminum tape | 15 February, 2006

radionics

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#39715

Aluminum tape | 15 February, 2006

Robert McKeown Company makes thermally conduct Al tape.

KIC did a study on which method (Kapton Tape, Aluminum Tape, Hi-Temp Solder) is the most repeatable. The study can be found in their website: http://www.kicthermal.com

Al Tape placed 2nd, and there's no substitute for hi-temp solder (1st place)! The trick is in the preparation. You gotta get the Al tape to 'form' to the T/C bead, and use Kapton tape over the Al tape to re-inforce the bond. Nice results on the profile (non-wavy lines) when done correctly.

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#39718

Aluminum tape | 15 February, 2006

Is this Al tape you guys are talking about insulated? If not, and if it jumps the tc wires, it'll effect your values.

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RDR

#39720

Aluminum tape | 15 February, 2006

Put this one out a little early! I just looked at the data in the Kic site and also at the other place, it is interesting how the results are different except for the high temp solder which we should have all expected.

Now for my question

Do we really need to worry about 3 deg C variation from the different attachment methods? Reflow windows are usually around 20 Deg C variance!?

It appears to me that all of the "tape" type attachements are at the mercy of the person taping them down.

what is the temp at the board really? A large solder ball is going to affect the temp and ramp, as will most anything else used to attach

Just wondering if it really matters as long as you keep the T/C down on the board and the junction exposed

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#39725

Aluminum tape | 15 February, 2006

My understanding is that you get a reading that's the average of all of the jumped points if you jump tc wires with conductive tape.

If you're doing multiple parts on a board with varying masses and don't control the attachment method (i.e., how much tape you have touching the wires), you end up with a bunch of invalid delta T info.. if you then inturn use a profile that puts puts your max. near a component's upper limit or your min. near a component's minimum solderable temp. you're flirting with disaster.

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#39726

Aluminum tape | 15 February, 2006

I don't understand the issue with Kapton as long as you put a slight load on the tc so it can't lift. It takes a little more tape but it seems to work. Not as well as HT solder but much more convenient.

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#39736

Aluminum tape | 16 February, 2006

Good afternoon,

Readings from thermocouple fixed by kapton tape only are inaccurate. This is the fact. At least you need to fix thermocouple with aluminum tape covered by kapton tape. Pete C is right. High temperature solder connection is a preferred method but also it is a destructive one.

BR, Pavel

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#39743

Aluminum tape | 16 February, 2006

"Readings from thermocouple fixed by kapton tape only are inaccurate."

I keep hearing this, but I haven't heard why, exactly. Why would they be any less accurate than with Al tape, which by nature of it's conductivity can provide an inaccurate measurement regardless of how well it keeps the thermocouple held down?

I believe (because I've never heard otherwise, so feel free to clue me in) that the inaccuracies attributed to the use of polymid tape are due to it's tendency to lose adhesion and or stretch, allowing the thermocouple to lose contact with the board. If you can avoid this problem then it shouldn't make any difference, right? As far as using bad data, it's pretty obvious when a tc loses contact with the board from the profile.

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RDR

#39749

Aluminum tape | 16 February, 2006

I am in agreement with Steve. I take great pains to ensure that my tape jobs do not come undone. As someone else noted I also preload the tip to the board so it stays in contact. I still need to ask why do we need to care about this tiny differences? I understand being close to the limit but other than that does it matter if you are a couple of degrees off? I would really like to know.

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Tom Winchell

#39755

Aluminum tape | 16 February, 2006

Assuming the AL tape shorts the wires for the thermocouple, you effectively have three junctions at the business end of the wire: wire 1 to AL, wire 2 to AL, and wire 1 to wire 2. If the temperature of the junctions wire 1 to AL and wire 2 to AL are the same (same piece of AL), they drop out and the measured results will just reflect the increased thermal mass of the AL tape.

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