WHAT IS AN ACTIVE DISCRETE?
Discrete components are electronic devices with just one circuit element rather than an integrated circuit.
The circuit element can be either a passive component (resistor, capacitor, inductor, or potentiometer for example) or an active component (MOSFET and IGBT transistors, diode, and LED). Active discrete commonly contain a wafer since we don’t use vacuum tubes much anymore. They are generally used for power regulation and switching, although LED are hybrid diodes which illuminate (optoelectronics). Both active and discrete components are used in almost every electronic circuit.
HOW ARE THEY PRODUCED?
As active discrete contain a die, their assembly is similar to other electronic components containing a wafer. They are generally in robust packages as their use in power regulation causes larger temperature swings in their regular use. Higher voltage or power devices require a metal heat sink to dispel the heat that occurs in high current and/or voltage applications. The package sizes follow standard industry conventions such as TO and SOT packages.
The bond wires have larger diameters than we commonly see in integrated circuits so they can withstand the higher loads, and are commonly made of aluminum or copper alloys while integrated circuits are frequently gold.
As their packages are designed to be robust, they tend not to be MSL sensitive.
HOW SHOULD THEY BE TESTED?
We have purchased many samples from Tier 1 and alternate manufacturers, whose specifications claim to be identical to the Tier 1. We have also found alternate devices with the same DC characteristics but in lower voltage and/or amperage models. We then conducted extensive testing and experimentation to identify the best ways to identify non-authentic product. While there are rarely traceable die markings on these devices, the structure of the die and bond wire lands can be telling.
Due to the risk of high-power devices being sold as high-power, they must be tested at the full test conditions for amps and voltage to check the most dangerous case of catastrophic application failure. Complete testing of all DC parameters, switching speed, and AC capacitance values will identify substandard product. A suite of inspection services should be utilized to ensure sourced product is not remarked and there is no deviation from manufacturer specifications, or deviations between samples from the same lot.
WHAT IS THE GENERAL RISK LEVEL?
Like their passive brethren, active discrete are not complicated devices and they use common package sizes. As such, there are many companies that produce similar products, so the availability of clones is significant. The devices from alternate manufacturers can even be purchased unmarked, making remarked counterfeit product difficult to detect with only visual inspection. While not as easy as simply swapping out the label on a box of MLCC, it is relatively easy
to make an alternative device look like the requested one.
The risk, of course, is that the sold product does not have the same specifications or lifecycle capabilities of the requested device. Particularly with the applications being high power, the danger is devices that cannot handle the loads to which they will be subjected. Ultimately the risks are complete system failure and even combustion.
HOW DO WE KNOW OUR RESULTS ARE ACCURATE?
Our standard profile for active discrete was updated following controlled experimentation, starting with the test conditions specified in CCAP-101. We analyzed the history of reported field failures and experimented with many common and enhanced inspection methods to compare measurements to manufacturer specifications and between authentic devices and their clones.
We use automated test equipment (ATE) that tests all DC characteristics simultaneously with a range of 2KV and 100A. The alternatives to ATE are multimeter, curve trace, or bench testing. These test methods test only selected characteristics but with a greatly limited range of coverage. Our test system is used by the most advanced active discrete manufacturers for their production testing. Note with the high-power devices in
shortage, this voltage and amperage range is extremely important.
Our equipment and fixtures were then put through GR&R studies and compared to measurements from the manufacturers on the same device (correlation testing).
The results were all consistently high and adequate for lab measurement usage.
WHY ARE THEY IN SHORTAGE?
These devices have been in shortage since Q3 of 2018 and are now projected to remain so through at least Q3 of 2019. It began with rising raw materials pricing and was exacerbated by under-forecast market demand which lead to a shortage of 8” wafers. The amount of metal used in the packages has a higher cost than in devices that do not carry as much current and, therefore, do not require heat-sinks or large-diameter bond wires. As the global price for metals, most notably copper, grew, many buyers projected
a component price increase, so purchased ahead of the price increase and built their own stocks, but in doing so they depleted stocks at distributors and manufacturers, thus creating a shortage for other buyers.
As with the passive discrete, and mostly MLCC, the growth in the automotive electronics market was far stronger than forecast. Automotive applications are high voltage and power, even more than common commercial applications. The number of
electronics in standard automobiles has increased and the emergence of purely electric vehicles pushed the demand for the components beyond where manufacturers could support. Lead-times are commonly seen at 36-50 weeks and are now projected to last through Q4 of 2019. The shift in demand and therefore productive capacity to automotive requirements has left devices for commercial applications in shortage.