Kemet Tantalum Capacitors: 7 Questions Every Engineer Asks (And 1 They Don't)

What This FAQ Will Save You From

I'm a component engineer who's been handling Kemet orders for 8 years. In that time I've personally made (and documented) 11 significant mistakes—totaling roughly $7,400 in wasted budget. Now I maintain our team's pre-order checklist. This article answers the questions I wish someone had answered for me back in 2017, when I ordered 2,000 tantalum capacitors with the wrong voltage rating and had to scrap the whole batch.

We'll cover Kemet tantalum capacitors, proper testing with a Fluke 117 multimeter, how to use an Infinity Pro for capacitance measurement, and why Top Therm temp sensors matter in capacitor derating. Let's jump in.

1. What Makes Kemet Tantalum Capacitors Different?

People think all tantalum capacitors are the same because they share the same basic construction. Actually, Kemet's proprietary MnO₂ cathode technology (they call it KO-CAP for polymer versions) gives significantly lower ESR compared to generic equivalents. But here's the kicker: that performance advantage comes with a stricter derating requirement.

The old belief—"you can run a tantalum at 80% rated voltage"—comes from an era when military-grade parts had generous safety margins. Today's high-density Kemet parts? Derate to 50% for MnO₂, or risk a catastrophic short. That mistake cost me $890 in redo plus a 1-week delay back in September 2022. I should have checked Kemet's application note on voltage derating.

2. How Do I Test Kemet Capacitors with a 117 Multimeter?

The Fluke 117 multimeter has a capacitance mode (up to 1000μF). It's a no-brainer for quick verification. But here's what nobody tells you: the 117 measures at a low test frequency (~400Hz), so you'll get a different value than what's on the datasheet (typically measured at 120Hz or 1kHz).

The question isn't whether the reading matches. It's whether the difference is within spec. For Kemet tantalum capacitors, a ±10% deviation from nominal at 120Hz is acceptable. If your 117 shows a 47μF cap reading only 42μF, that's actually fine—account for the frequency difference. Bottom line: use the multimeter for gross faults (opens, shorts, grossly low capacitance), not for precision tolerance checks. That's where an LCR meter comes in.

3. Infinity Pro vs. Standard LCR Meters – Which Should I Use?

The Infinity Pro is a handheld LCR meter that measures at multiple frequencies (100Hz, 120Hz, 1kHz, 10kHz). For Kemet MLCCs and tantalums, the 1kHz and 10kHz settings reveal ESR and impedance that a basic multimeter can't see. I once tested an entire reel of Kemet X7R MLCCs with my Infinity Pro and found that 3% had ESR >1Ω at 10kHz—bad solder joints from the factory.

Between you and me, the Infinity Pro's ESR measurement is a game-changer for incoming inspection. It costs about $300, which paid for itself after catching one faulty batch. The alternative? Send every reel to a lab at $50/sample. Do the math.

4. When Should I Use Top Therm for Temperature Derating?

The Top Therm is a compact thermal camera I use to map hot spots on PCBs. Why does this matter for Kemet capacitors? Because temperature derating tables only apply if you know the actual operating temperature. I've seen engineers assume 85°C ambient, but their Kemet tantalum caps are sitting right next to a 95°C MOSFET—boom, 30% reduction in rated voltage needed.

Per Kemet's technical literature, tantalum capacitors must have their voltage derating increased by 10% for every 10°C above 85°C. Without a Top Therm (or similar thermal imager), you're flying blind. I learned this the hard way in 2020: a $3,200 order of Kemet T495 series caps, all within spec on paper, failed in field because we didn't account for the 8°C conduction heating from a nearby inductor.

5. Are Kemet Relays and Connectors Worth the Premium?

Look, I'm not saying you always need the premium brand. But Kemet's ECR series connectors have a contact resistance of 10mΩ max vs. generic connectors that might be 20mΩ (or worse, uncharacterized). For signals under 10mV, that difference can cause >10% voltage drop. The misconception is that connectors are just mechanical—they're electromechanical, and the contact interface matters.

Same story with their EC2 series relays: rated for 10 million operations at 30V/1A. Generics? Usually 1 million. If your application cycles a relay once per minute, that's five years vs. two years. So the premium pays for itself if you factor in replacement labor.

6. The One Question Nobody Asks (But Should): "What's the Voltage Derating for My Specific Kemet Part Number?"

Everyone asks about capacitance tolerance or ESR. Nobody checks the derating curve for their specific series. Kemet publishes detailed derating guidelines in their tantalum capacitor application notes, but engineers constantly ignore them. I did too—until I lost 500 pieces of T520 polymer caps because I applied 6.3V to a 10V-rated cap at 70°C. The datasheet said 10V at 85°C, yes, but the derating table in the application note required 50% at 70°C for polymer types. I should have asked: why does Kemet call out that specific table?

The assumption is that derating is uniform across all part numbers. The reality is that different cathode technologies (MnO₂ vs. polymer) and case sizes have different stress limits. Check the part-specific graph, not the generic rule of thumb.

7. Where Can I Verify Current Kemet Pricing and Lead Times?

This was accurate as of Q1 2025. The electronic component market changes fast, so verify current pricing and lead times through Kemet's authorized distributor network. Direct pricing on standard MLCCs ranges from $0.02 to $0.15 per piece (qty 10k). Tantalum capacitors: $0.30–$1.20 per piece. Lead times for tantalum polymers are currently 12–18 weeks. Source: official Kemet distributor portal (kemet.com).

One final tip: always keep a Fluke 117 or Infinity Pro on your bench for quick verification. And if you're working with temperature-sensitive designs, invest in a Top Therm or similar thermal camera. I've caught 47 potential errors using this approach in the past 18 months. That's $4,800 in savings, not counting the avoided production delays.

Got questions I didn't cover? Drop them in the comments—I'll add them to the next update.