Capacitor manufacturers are aware of the challenges that supply shortages bring and can help designers with alternative options — selecting different values, evaluating other technologies, and redesigns

By Richard Quinnell, Editor, Technical Special Projects

A confluence of
rising demand and capacity limitations is creating shortages in interconnect,
passive, and electromechanical (IP&E) component supplies. And the situation
is likely to persist for perhaps years because vendors have delayed investing
in additional manufacturing capacity, fearing a repeat of the dot-com boom/bust
cycle. While many might consider supply shortages a manufacturing or
procurement problem, though, designers are in an ideal position to help find a
long-term solution.

The current IP&E
shortage
is a cause for serious concern. Demand has so
outstripped production that common components such as multilayer ceramic chip
capacitors (MLCCs), chip resistors, and the like are now seeing lead times of
40 to 60 weeks. That’s enough to exhaust any reasonable inventory reserve that
a manufacturer might have and result in a shutdown of a production line and
corresponding loss of revenue and even market share. These shortages, then,
become a company-wide concern, not just a manufacturing or procurement worry.

A typical bill of
materials (BOM) and component specification control drawings for a design may
identify drop-in alternatives for such components, but in current market
conditions, that may not be enough to help purchasing acquire the needed parts.
Other companies have similar choices, after all, so the competition for alternatives
may be nearly as great as for the preferred parts.

What
manufacturing needs are alternatives to using unavailable parts that are not simple
cookie-cutter replacements but, instead, use different component types or
values. Identifying and validating such alternatives are best done by the
design team.

Consider, for
instance, trying to find substitutes for the MLCCs that have become popular
because of their small size, low cost, and low equivalent series resistance
(ESR). Such devices have lead times approaching a year, and the shortages are
not expected to begin easing before 2020, so identifying an alternative is
essential.

If a slight board
redesign is a viable option, and the capacitance is not critical (such as a
bypass application), it might be possible to simply use a greater capacitance
in a larger, less popular, and, thus, more available package size. Another
alternative might be to use two lower-value capacitors in parallel to achieve
the desired capacitance.

But in many
cases, altering the printed circuit board (PCB) to make room for a larger
footprint alternative may not be possible. In such cases, another alternative
might be to use a different capacitor technology type to replace the MLCC, such
as tantalum or aluminum polymer. In these situations, developers will need to
dig deeper and explore parameters like voltage rating, ESR, resonance
frequency, and leakage current in addition to size and capacitance when
choosing an alternative.

Fig. 1: Capacitor technologies have different responses to factors
such as bias voltage, one of several factors that needs to be accounted for
when choosing an alternative. (Image: Murata)

There may be some
pleasant surprises in store. Tantalum or aluminum polymer capacitors can
achieve a greater capacitance in a given size and volume than MLCCs, so it may
well be that a single polymer capacitor can replace two MLCC devices being used
in parallel. This substitution can thus yield a reduction in parts count and a possible
increase in reliability.

But making such
evaluations requires a depth of understanding about capacitor types that many
engineers lack. Fortunately, there is help available. The manufacturers of chip
capacitors and resistors or other IP&E components are acutely aware of the
challenges that supply shortages can raise for their customers.

So they have
begun providing help. In the MLCC market, for instance, Panasonic has created a
guide, “How
to Survive the MLCC Shortage
,” comparing and
contrasting the attributes of MLCC devices against their solid polymer aluminum
families. Similarly, Kemet has produced a whitepaper — “MLCC Shortage:
When You Can’t Find the Cap You Need
.”

Trade
organizations are also offering advice. The European Passive Component
Institute (EPCI) has a fairly detailed “first
aid
” guideline for switching between tantalum and
MLCC capacitor types.

Another source of
information on possible substitutes for short-supply components is electronics
distributors. Most major distributors have engineering staff on hand to help customers
address many types of design challenges, including identifying substitutes for
parts in short supply.

The best time for
identifying and validating alternatives to parts in short supply is before the
production inventory runs out, and the earlier, the better. This timing
requires that there be cooperation and communication between procurement and
design, going well beyond the typical “over-the-transom” approach of simply
sending the BOM to parts buyers when a design is complete.

Being
prepared to weather a parts shortage before it happens can help ensure that
production is able to continue with minimal or no interruption. It also means
that there is time to thoroughly engineer a solution to the problem rather than
make decisions in a rush to prevent, or at least minimize, a manufacturing
shutdown.