The most Misused and Misunderstood terms in Electronics.

Having just seen an article from a major EDA company that should know better, I figured we could amuse ourselves by identifying the most misused, misunderstood and misguided terms used in electronics.

Being equal opportunity, feel free to chip in with terms from around the technology industry.

The one above. FR-4. Good old PCB material, usually Epoxy and resin mix, but it doesn't have to be. The only thing FR-4 actually means is that the material is flame retardant (usually to UL94V-0 - self extinguishing). The generic term FR-4 has no meaning at all for any other parameter.

If you take a look at this datasheet (which meets FR-4) and this one (which also meets FR-4) you will notice significant differences between them, such as the variation of permittivity (very tightly controlled in the second item for great high speed performance) and moisture resistance to name but two items.

They are both FR-4, but the electrical and mechanical performance is completely different.

Even specifying material to IPC4101/xxx doesn't mean anything for electrical properties of PCBs.

Baud Rate.

Quite possibly the all time contender for the title.

This one started out in the days of analog modems (you remember them, right?). Baud rate is a measure of the number of symbols per second in a transmission medium (and only equal to the bit rate if we are using 1 bit per symbol). It was (and still is) used when it should not be (the data rate in bits per second is not always equal to the baud rate).

The highest actual baud (symbol) rate in those old modems was 1200; a 2400 bps modem had a 600 symbols per second baud rate (using QAM16 encoding) I once had to explain to a somewhat incredulous experimenter that a non-linear (i.e. cheap) 2-wire to 4-wire conversion (necessary on a POTS telephone line) was simply not going to work for 2400 bps communications because it added horrible phase artifacts to the signal rendering it pretty much useless.

It is not unusual to see QAM64 and even QAM256 (a bit difficult in practice) used for everyday stuff amongst other multi-bit encoding schemes.

Bit rate and baud rate are often the same, but the definitions are different and therefore they are not necessarily the same. Any technical teachers out there? Hammer this into your students hard.

Glass Transition Temperature (Tg)

Particularly for PCB material, but for other items as well.

Tg is not a step function; many materials have a significantly higher CTE above Tg, but the temperature specified for Tg is usually in the middle of the change of CTE. Due to manufacturing variation, it is usually specified as typical or minimum (see the laminate datasheets above).

This can be a major issue for PCB assemblers (particularly in lead free processes) as the longer the board is above Tg, the more it expands (particularly in the Z axis). I have seen boards that come straight off the production line with cracked vias because a very cheap material (with Tg of perhaps 105C) has been used. With a peak reflow temperature of up to 260C, a low Tg material has more susceptibility to problems in reflow.

As I mentioned in the curious case of the charred capacitor, this is also the underling cause of components being destroyed simply by putting them through a standard process.

Amperage and Wattage.

Distinctly bush league and has the same effect as dragging nails across a blackboard.

We might refer to the current capacity of something or the current rating, but never amperage (well, not if we don't want to appear uneducated). Likewise for wattage; we would refer to the power handling capacity or perhaps the power rating of a device, but again, never wattage.

This is but a small list of things (there are others, such as RS/EIA232 which many believe is a protocol and it is nothing of the sort - it specifies the electrical levels only). Feel free to add others you may know in the comments.