In the shop -- measuring PCB temperatures in the cooker

You can be penalized for early delivery in some contracts. This sometimes gets to be a sales rep's job - holding product in their office and delivering in person. Anything to get the business.

I've seen suppliers renting warehouse space down the road from the client, just to meet their expectations. Just another cost built into the business - but only really paying off at larger scales.

RL

Two decades of Celsius from 1 deg. C, , not of Kelvin.

I've used diodes, Well specifically diode connected transistors (c-b shorted) to ~130 C (400K) but the voltage is getting kinda small up there. A regular diode might be a bit better.. the voltage vs. temperature has less slope. But they all needed at least one calibration point, variation at room temperature was +/- 3-4 mV (a few degrees C)

George H.

JIT only works if you run a modern operation with excellent scheduling

- MRP, ERP, SPC, and the works. It doesn't add costs if it's done right -- in fact, the whole point is to save money throughout the supply chain.

The idea is a Japanese import. It works pretty well in a country where the suppliers are an average of 10 - 20 miles from the OEM. It doesn't work nearly as well in big industries in the U.S.

My sister-in-law was a purchasing agent for Caterpillar in Aurora, IL. After a couple of years working with JIT, where they had castings coming in from halfway across the country and regular winter snowstorms, they renamed JIT to OSWO -- "Oh Shit, We're Out."

d8-)

Conversely I've seen highly reputable organisations deliver faulty/missing equipment early because the client requested it.

Deliver early, meet clients requirement for spending money in a certain financial year (use it or lose it). "Reject" it and have the correct equipment delivered in the next financial year.

Supplier happy. Client happy. Beancounters didn't care, even if they knew.

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

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

we occasionally use one of the those lab heating magnetic stirrer (with the magnet removed!)

-Lasse

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