In the shop -- measuring PCB temperatures in the cooker

Ok, you mean from 274K to 27400K? ;-)

The problem is that the invoice comes with the material. Time is money.

Jeez, everybody's a critic. My old scientific thermometer, which I broke years ago when I left it in my freezer and mistakenly threw a frying chicken on top of it, ran from something like -30C to 250C, or thereabouts.

My analog electronic tire thermometer was calibrated in deg. F, from

90 deg F to 220 F, but I tested it down to 32 F.

A variation on that tune; ship empty cases to get revenue into this year/quarter. I've been on both ends of that one (at IBM and Intel).

Sometimes. In the Intel case, they didn't tell us so the fit hit the shan when parts started failing incoming inspection. It's a good thing we had incoming inspection, at the time.

I was making a funny--note the smiley. There are two competing uses of 'decade', as in "the Seventies", i.e. 10 of something, as in "decade box", i.e. powers of 10.

Cheers

Phil Hobbs

Wow, if you went down to 0.001 C, you could have five decades.

Cheers

Phil Hobbs

You could have lots of things -- except common sense. d8-)

In the automotive business they want to fob off the job of warehousing parts (where the production process makes that more efficient) onto the suppliers so they may not even have the space allocated to store stuff if it arrives early. The power balance between automotive manufacturers and suppliers is highly weighted in favor of the former so they can tell them exactly how high to jump. Small guys don't have that power. I'm sure Ed Huntress could say a lot more on this subject.

If you have that kind of purchasing power I imagine terms could be imposed that dealt with overly early shipments.

The business of delivering stuff that's not quite done in order to meet accounting deadlines may be a bit dodgy. CRA says that the item must be in place and ready to use (or words to that effect) in order to take the capital cost allowance (depreciation) for that period so if it's not at least somewhat functional you could get an issue. The IRS, I believe, is similar with their "placed-in-service" date. Placed on the floor in big boxes doesn't count.

--sp

Is this the part where the physicist who wandered into the wrong coffee shop gets roughed up?

--sp

It feels that way...

In my little batch oven a lot of the heat comes from IR during the rapid positive slew portion of the programmed profile so high emisssivity parts are going to run a lot hotter than the shiny bits.

There's really not much to go wrong with a thermocouple if you use it 'reasonably' (make sure the leads are not sucking too much heat from the junction- put at least 1" of the leads into contact with the pcb for a typical AWG 30 bead thermocouple. You can tape it down to a tooling strip (you did include tooling strips right?) using polyimide (eg. Kapton) tape with silicone adhesive. If you feel like experimenting, bury a bead thermocouple into a suitable hole surrounding it with solder and observe the profile from that vantage point (again, keep the leads in contact with the board for 1" or so using tape.

The best way to measure surface temperature for this kind of application is a very fine ribbon thermocouple but they're not so cheap (I think

Sure... Automotive is not friendly to small business.

It all costs, in the end.

The IRS is a different issue than the execs making their annual goals.

I got a thermocouple temp controller for mine, and first tries with the thermocouple suspended in air. Two black boards later, it ocurred to me to poke the thermocouple into a plated through hole in the board. Worked GREAT! This allows the controller to control the ACTUAL temperature of the board, and gets quite repeatable results. I have a pretty fancy ramp and soak controller, so it can do the whole ramp up to 180 C, hold for one minute, ramp up to (your favorite temp here) hold for one minute, then cool down.

I've done thousands of boards with this rig, and the only problem is occasionally a board in the corner doesn't fully reflow. I often do 6 smaller boards per cycle.

One trick is you must let the board cool below about 100C to make sure you don't knock back side components off when moving the boards.

Jon

Every coffee shop I've ever been in has mostly college-age women all hours of the day. I think you mean maybe he was at the wrong bar?

I would suggest an IR thermometer, but I got one at Micocenter and it is fine around room temperature, but sucks when it is cold outside. Other thermometers say it is about freezing and the IR says it is 25 or even

22F, even when I point it right at the other thermometer.

If it works the way I think it does the sensing element is a thermopile or a bolometer which measures the difference in temperature between the target and the sensor. If it's REALLY cheap someone may have just taken a circuit that works in the lab and used it, or taken a circuit that's supposed to have a thermometer or a temperature controller and pulled the "extra stuff" off for cost savings.

During the ebola panic, there were security people with cheap chinese IR temp sensors shooting at people in line to board a plane, from like

10 feet away, looking for fevers. A cheap IR sensor is wildly inaccurate and has a huge field of view. The built-in laser pointers are a joke.

Emissivity matters, too. A brass lamp can burn your hand but indicate room temp on an IR thermometer.