# Tag Info

66

I can give you an answer because I had been one of those who either wrote or verified the specs of semiconductor ICs. Legally and ethically speaking, I could only sign off on the parameters within which we have verified the IC/processor would work. And then my boss, and her/his boss, and everyone else would see the evidence of the tests, and they too would ...

63

The maximum temperature the silicon experiences can be much more than ambient. 50 °C ambient certainly happens. That's only 122 °F. I've personally experienced that in the Kofa Wildlife refuge north of Yuma Arizona. You need to design to worst case, not wishful case. So let's say ambient can be 60 °C (140 °F). That by itself isn't much ...

53

I once designed an amplifier that would oscillate at -10°C. I fixed it by changing the design to add more phase margin. In this case, the oscillation did not cause any damage, but the circuit did not work well in this condition, and it caused errors. These errors went away at higher temperatures. Some plastics crack when they freeze. Dry ice is -78.5°C, and ...

52

First of all, military equipment is expensive. You can afford to actually test things for high temperatures only if your customer is willing to pay. Military customers tend to have budgets that normal people can only dream of. Then, obviously, if you put an IC into a missile, you might not want that thing to fail if your missile gets hot from its burning ...

42

2nd Edit! Modified my answer about semi-conductors based on jk's answer below, read the history if you want to see the wrong bits I modified! Everything gets weird within certain limits. I mean, sure, the resistance improves in conductors but it increases in semi-conductors, and that change effects how the IC works. Remember that the way that transistors ...

36

There are two effects going on. The heat sinking effect of the connections and the temperature coefficient on the wire. Initially the wire is all at the same temperature. You turn the power on and it starts to heat up. The heating is determined by the electrical power dissipation in the wire, for any given section of the wire Power = Current * Voltage. ...

21

Realistically it's very difficult to measure to that system level of accuracy. The particular sensor you show is DIN class A tolerance, meaning that the maximum error of the sensor alone is 150mK + 2mK*|T| (with T in degrees C). So at 100 degrees C, the maximum sensor error alone (not counting self heating) is 350mK, 35 times what you say you want. This type ...

20

Other than maybe batteries and maybe the LCD components generally don't get damaged directly, even by extreme cold temperatures. If temperatures are changed to extremes, especially rapidly, there can be physical damage due to mismatched contraction with temperature or temperature gradients. However, operation at cold temperatures may not be possible- ...

20

In the relevant part of the infrared spectrum for this application$^1$, air has a high transmittance: (taken from here licensed under Creative Commons Attribution-Noncommercial-Share Alike 3.0 United States License) So wherever you point an IR temperature sensor, the output will be dominated by the surface you are pointing at and not the air in between. ...

20

Whoever said it probably did so in person, and the odds that any of us met the true first person are low. This is the sort of engineering observation that could have been invented by several different people back in 1940, for all we know. Elecia White's 2011 Making Embedded Systems quotes this anonymously, so the latest possibility is 2010. Her PowerPoint ...

19

The temperature on the X axis is the temperature difference between the two thermocouple junctions. That's not the absolute temperature. If both junctions are at 0oC, the thermocouple voltage would be 0V. If both junctions are at 100oC, the thermocouple voltage would be 0V still.

18

I have powered the board for days at a time. The code that was running was very simple, but there was absolutely no damage. It is worth it to note that it was being powered by a pre-regulated 5v source so the on-board regulators were not burning up. I doubt that with anything lower than 9v there could be any sort of hardware damage, but with larger ...

17

Thermocouples: wide range of temperature sensing (Type T = -200-350°C; Type J = 95-760°C; Type K = 95-1260°C; other types go to even higher temperatures) can be very accurate sensing parameter = voltage generated by junctions at different temperatures thermocouple voltage is relatively low (4.3mV for Type T thermocouple with one end at 0 C, other at 100 C, ...

17

Military (and aerospace in general) equipment is often: In an unpresserised bay which means cooling the equipment is by conduction. Convection cooling loses meaning at 30,000 feet as there are very few air molecules to transfer heat by convection. It is much more difficult to effectively transfer heat by conduction only. In a glare zone (think just under ...

16

The bond wires are not soldered to the die. They are predominantly attached via a process called gold ball bonding. It uses gold bond wires, and welds them to a gold pad on the die using a combination of heat, pressure, and ultrasonic energy. Gold melts at a much higher temperature than any soldering process, making for a solid bond to the die.

16

Thermal inertia is playing against you. Also take into account that lead-free solder needs temperatures in excess of 220°C to melt down (compared to 180°C for tin-lead solder), so the thermal gradient will be quite high to begin with. Because of this, I would recommend preheating the board to 120°C by using one of the following methods: A preheating plate, ...

15

I'd say NTC, yes. This one is the cheapest I could find at Digikey. About half a dollar, that's much cheaper than temperature sensor ICs, which have about the same precision. The advantage of an NTC is that it only needs a series resistor and an ADC input on your microcontroller, which most do have nowadays. The low price has also a disadvantage: NTCs are ...

15

Storing batteries/cells in a refrigerator slows down their rate of self-discharge, which is a good thing. See below some graphs of self-discharge rates as function of temperature for different battery chemistries. For SLA: For alkalines: alkalines http://www.digikey.com/en/articles/techzone/2011/dec/~/media/Images/Article%20Library/TechZone%20Articles/...

14

The specification says that the ACK consists of a low level after the 8th clock pulse, as shown by this diagram: The bus master will generate a 9th clock pulse to read the level. The specification doesn't talk about pulsing ACK, and the master will not take notice of it either. Follow the spec and take care of data setup and hold times (250ns and 5\\$\...

14

Kit's answer is dead right about components in space, but I thought I'd expand a bit on semiconductors vs conductors (very loosely without the maths). Conductors resistance decreases with a drop in temperature. This is loosely, because the resistance comes from the free flowing electrons being slowed down by vibrations in the crystal lattice they are ...

14

The basic problem is that the density of the "free" charge carriers in semiconductors is a strong function of temperature. When the temperature drops low enough, there just aren't enough available carriers to allow the transistors, etc. to function, and the effective series resistance of the bulk semiconductor rises as well. The overall gain of the circuit ...

14

The crude way you'd ensure you were not on the edge of operation would be to test it outside the range. For example, you might test the parts at -65°C at voltage at a higher clock speed and higher/lower voltage than normal. The manufacturer probably does not test at temperature extremes themselves, but they know how much margin is required under test ...

14

This is well beyond the ratings of most parts. You can expect outright failures, major departures from guaranteed specs, flaky (eg. partial) operation, huge leakage and so on. Unless you buy qualified parts, you are on your own, so you are looking at major costs, and it may not be possible to thoroughly test some parts without inside information. Downhole ...

14

BGA have a very good thermal contact with PCB- total cross section of all balls is a quite large figure. So before solder type, all PCB is sinking the heat from your BGA. So you have to preheat all of it to 150C, then power flow will become much lower (delta T is lower) and then you will not need more than 300-350C.

13

You can not guarantee more accuracy, but you can possibly get better signal to noise ratio. Imagine if all the sensors were off by the same amount as allowed in the specs. Averaging them would not yield better accuracy. If you had a reasonably large number of these sensors and they had a random error distribution within their allowed error band, then you ...

13

FR4 PCB is glass-reinforced epoxy laminate. Several research studies have been published of the effect of low temperatures on such material. A specific quote from the paper "Dynamic failure behavior of glass/epoxy composites under low temperature using Charpy impact test method" (Shokrieh et al): it is found that failure mechanism changes from matrix ...

13

Lets break your questions into sub-questions: Faster computer: The most common measure of computer's "speed" is its maximum clock frequency. This measure has never been an accurate one (Megahertz myth), but it became totally unimportant in recent years after multi-core processors became a standard. In today's computers, the top performance is determined by ...

13

I would be inclined to use traces on or in the PCB as a direct heater, as you suggest. Obviously, you'd start by insulating the board as much as possible to minimize the energy required to maintain temperature. Pay particular attention to external electrical connections, which can also be good conductors of heat. Extra lengths of wire buried in the ...

13

I've used FR4 at 4K and others have used it at much lower temperatures. The physical characteristics go somewhat downhill at low temperatures, but board failure such as delamination does not normally occur from mere exposure to cold temperatures. The Charpy tests referred to in your linked answer are a measure of strength of a notched specimen to shock (...

13

Several other comments and answers have mentioned that electronic circuits need to be in enclosures and their own heat production makes it hot in there. That has not been stressed enough. For industrial, commercial and automotive equipment, electronic circuits often need to be sealed up in tightly sealed enclosures to keep out all sorts of contaminants. In ...

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