Passive Components Get Better

When you want to talk about cool new components, you are probably thinking about chips or, these days, even modules. Passive components like resistors, capacitors, and inductors are a solved problem, right? [Darshill Patel] begs to differ. There is still innovation happening in the passive market, and he highlights some of the recent advances.

There are thick-film resistors that don’t need lead, for example. There are also supercapacitor modules with very low ESR. For inductors, at least one manufacturer is moving away from traditional wire loops and using flat wire windings instead. These have a larger cross-section, which reduces unwanted resistance. In addition, it offers more cooling area for heat dissipation.

Of course, passive components have never been as simple as people think. Picking a capacitor’s value is only half the battle. You also need to consider the material to optimize how it works in your design. Wirewound resistors are also inductors unless you get special non-inductive ones that use special wiring techniques to cancel much of the parasitic inductance.

It shows that you can never stop learning about even the simplest components. We are still waiting to figure out what we want to do with a memristor. While tiny surface mount components are good for some assembly reasons, they also have helped reduce unwanted component effects.

38 thoughts on “Passive Components Get Better

    1. I haven’t had to buy any lately but there were at least two different ways that it could be done and that’s one of them. There also have been some that were wound in a back and forth direction. I don’t know what the technical name is for it, but it’s one single winding. It’s just the way the coils are arranged. I’m not sure there’s not other ways to do it too.

      1. If what you mean is that criss-cross way, that one is to minimize parasitic capacitance of a coil.

        The bifilar trick is to minimize inductance.

        Because everything is an inductor and a resistor and a capacitor mixed into one icky brew and the higher the frequencies we deal with the thinner the carpet we can sweep the unwanted two of the three (or all three if it is just the wire) under.

  1. Not exactly new anymore, but aluminum-polymer capacitors have gotten cheap. Thanks to their lower ESR you can often accomplish the same with smaller / less capacitors than traditional aluminum electrolytics.

    1. Back in the 80s at RMIT, engineer students had to design and build an intermittent windscreen wiper circuit.
      A basic astable circuit, but variable timing meant the students had to pick an appropriate value trimpot – and capacitor.
      Some students would try for a long delay, use a large capacitor – and discover the charging current “bleeding off” (circuit never triggered).

      If modern components don’t give the same experience, I’m not sure that’s a good thing.

      1. And why exactly is that an issue?

        Lead comes from the ground in the first place, and metallic lead is not very water soluble so it pretty much stays there. It’s only an issue if you’ve sited your landfill on top of the aquifer where you draw your drinking water from, but then you’ve got much bigger chemical hazards than lead.

      2. If you wanted to make a better point, you’d talk about e-waste ending up in Africa and the difficulty or recycling it – but the difficulty there too is that you’re not supposed to burn your e-waste in an open pit fire to get at the metals.

        1. But people do exactly that. The great thing about tech is that it can compensate for problems elsewhere. It’s like saying you’re not supposed to stick your hand in the saw. It’s true, but if you do accidentally , SawStop can make it not get chopped off.

          Tech is one of the industries we have the most control over. Why not build solutions into products as much as we can, rather than pushing off problems into layers we don’t have control over? It’s not a substitute for stopping open pit fire recycling, but it’s better than nothing.

          1. And then you get trapped into “we must do something” mindset, and mitigate something that’s not even a rounding error in the greater context, at significant cost for everybody involved and no significant benefit for everybody else.

            No, I won’t give up my lead-tin solder.

          2. In fact they burn it specifically to get at the precious metals inside the e waste in some places of the world. The places where our e waste gets sent, because they pay for it, then uses children to pick through the ashes to find the metal bits by hand and collect them for recycling. It’s almost better to put electronics in the trash so as to not contribute to this horrorshow. Don’t get me wrong, I’m a lefty blue nut job, who apparently wants to turn all children trans and make it so we own nothing and are happy im told, but in this case e waste recycling is absolutely horrific for the people who do it and their lands.

      3. Nothing should end up in a landfill, so there’s your problem. Trash should be recycled or incinerated, not buried and forgotten about. That said, I’m more worried about plastics than lead. Lead in the ground turns into inert/insoluble compounds almost instantaneously and is relatively immobile thereafter. Plastics decompose for centuries into god knows what.

      4. The big concern is that lead in the landfills will get into the groundwater.  Once a year, our water bill comes with a water quality report, which I started watching particularly for lead content since all of this stuff about RoHS (“row-hoss,” Europe’s Restriction of Hazardous Substances) started up.  There’s a landfill five miles from us, with three-quarters of a century of electronics trash in it.  The water quality report has continually said that the lead level is one-eighth of the action level; IOW, if it got eight times as high, they’d have to do something about it.  It has not been increasing.  However, it also says that the landfill is not one of the suspected sources, but erosion of natural deposits is.  Meanwhile, the car-battery industry is using 75% of the lead produced, and the electronics industry never used more than a very small percentage, maybe 2% but I don’t remember for sure; and there’s no restriction on lead for car batteries.

        Without lead, solder tends to crack more easily.  Consumer PC accessory boards I’ve gotten that were RoHS quickly got cracks in the solder connections that had to handle some stress, like an SD-card socket.  Re-soldering with leaded solder fixed them, and kept them working.  At work, we got a batch of boards from an assembler in the Orient a year or two ago who neglected to read our instructions and assembled the boards with no-lead solder, and some of the taller parts (tiny SMT electrolytic capacitors) got knocked off in the shipping before they even reached us.  The solder had broken.

        Without lead, solder also tends to grow tiny tin “whiskers” which short to neighboring pins.

        These are the reasons why, last I read, military and medical electronics are still not allowed to use no-lead solder.  I have not kept up with the latest, but I think there has been progress in the tin-whisker area, by adjusting the content of various metals in the solder.  Still, our company has told the European market that they’re not worth it.  If someone in Europe wants to buy our products, they can, but the quantities won’t be high enough for authorities to raise an eyebrow and want some investigation or certification, or if they did, the importer, not us, will have to deal with it.  So we still specify and use leaded solder.

        Leaded solder always need a higher temperature to melt it, which can be less friendly to components.  However, this has been taken into account in manufacturing the components, and in the temperature profiles used in automated soldering equipment, so I don’t think the higher temperatures are actually damaging any components.

        When fishing, my dad always used to crimp the lead weights onto the line by biting them, meaning he was undoubtedly getting lead on his teeth and subsequently swallowing it.  He’s 87, and if there’s any decline in mental sharpness, it’s undoubtedly from other dietary habits.  I spent years in a boarding school in another country where our water came to us in lead pipes.  A high percentage of those kids went on to become doctors and engineers; so I’d say the lead didn’t have any negative impact on our brains.

        1. The microUSB connectors on the tiny charger boards routinely fall off. Lead-resoldering is a good default preventive measure.

          The new euroedict with USB-C connectors for everything has its dark side – they did not solve the charging problem, they moved it between the connector and the board; instead of bigger robust connectors for laptops we got a flimsy one with lots of tiny pins and brittle solder. And instead of visible differences, we got chargers that look exactly the same and just support different USB-PD voltages so the compatibility is still hit or miss, just not seen upfront.

          For hand-soldering there is also the flux issue; every ten degrees C doubles the reaction rate, doubles the speed of flux degradation. The health risk of flux vapors is higher, the risk from lead is negligible. Unless you eat the solder, then there may be a measurable impact – if your instrumentation is sensitive enough.

          The leadless abominations make reworks and repairs more difficult. Everything has to be heated more. A risk of lifting a trace goes exponentially up.

          All for some do-gooders to feel good about themselves.

      5. You need to look into the telephone company wires buried en masse all over the planet. Encased in lead. To this day, they run air pumps in substation boxes all over the place to keep positive pressure in the lead sheath to keep groundwater out. Lead in a sealed landfill envelope is the least of our concerns compared to something like these underground wires. Anyway, we have these wonderful crustaceans like pillbugs and sowbugs who love to eat those heavy metals, they crystallize it in their gut. These little guys are very good at keeping these simple metals from leeching into groundwater. I will therefore take simple heavy metal pollution over more toxic “lead free!” compounds any day of the week. I’ve been exposed to so much lead in my life you can probably see it in my bones, and I’m just fine. Don’t let the exponentially decreasing “declared safe level of lead” coming from the corporate letter agencies deceive you. Their efforts are not to protect the people, but to justify increased spending on corporate entities who promise to “solve” the “problem”. They actually care nothing for us.

          1. Lmao, two different people jump in with “citation needed” when the well-proven point is made that simple elemental metals are not as harmful as man-made compounds…. So, which corporation or “environmental agency” do you work for? I’m going to guess one of the corps who make one of the countless “forever chemical” compounds? You know, the ones that take eons to break down in landfills and the environment and cause all manner of cancer and illness, meanwhile those pesky elemental metals get gobbled up by crustaceans with ease and continue to not be the threat that the corporate-owned environmental agencies keep claiming that they are? You ask for a “scientific, primary source” while rejecting the presented empirical evidence… I think what you meant was a “corporate sponsored source” LOL

  2. Unless I’m missing something, I’m not seeing the “news” on this one… other companies had lead-free thick-film resistors out years ago (Yageo, for example, has a line… others exist). And flat wire being used in inductors? That’s a (many) decades-old option.

    Darshil’s article was just announcing new product lines… not innovations or advancements. To couch it as anything other is a stretch, at best.

    1. I’d be less harsh on them.

      An innovation becomes more relevant to us down in the trenches when it rolls out of the labs and into production and onto markets and becomes (hopefully cheap) off the shelf.

      Until then we can just watch and drool and want.

  3. First appearing as a two part article in a 1980 issue of Audio magazine, the Walter Jung/Richard Marsh article “Picking Capacitors” is a real eye-opener on how much cap construction can impact measurable and audible distortion and apparent sound quality.

  4. Because Bosch bought Fein and stoppen selling replacement parts, i have struggle to find replacementparts for a really overengineered 40 year old Tool. Finding a replacement Capacitor or Resistor isn’t easy.

  5. I’m late to reply to that 2017 post about “what is a passive component”, but I feel like EE types could save some time with my caveman take on the question.

    I just assumed “passive” meant “components you can make using only wire”. Or to put it another way, “components that can appear in your circuit without you putting them there”.

    (you never hear people worrying about “parasitic 80386ance” in their designs)

  6. This reminds me about stories I read about mining in Death Valley (and in the American west in general). Gold and silver mining are the “glamour” commodities — but the big money makers were non-metallics like good old borax.

    1. Similar in shipwreck salvage.

      The glamor is in finding couple kilograms of gold in a Spanish galleon.

      The money are in that thousands tons of copper ingots in some nameless freighter.

  7. Ceramic capacitors are an area of continual innovation as well, and shouldn’t be overlooked. Capacitance per volume is probably the primary metric everyone oohs and ahs over, but the highest values are often encumbered by dielectric limitations that result in poor DC bias or piezoelectric performance. As technology progresses, the capacitance per volume of actually useful devices is also improving.

  8. We are speaking of the lead, that base element that is a critical part of leaded solder. Surely you must be aware of how corporations continue to replace more basic compounds used for everything from pesticides to fertilizers to mold release compounds. And as these compounds become more complex they also become more environmentally persistent. Pill bugs won’t eat those exotic metal compounds until they eventually decompose into their base elements, but they readily eat arsenic, mercury, lead, etc – All elements which occur naturally in the environment – Where do you think they came from in the first place??? Do I really need to “cite” where we get these base elements from? Is this not common knowledge?

    1. Landfill leeching into ground water and lead being aerosolised when people burn trash (like some places burn ewaste to extract metals) leads to the lead getting inside people. This makes for stupid people.

      If you look at a map of IQ, you’ll notice it is lower around regional airports, where they still use leaded gasoline in the small aircraft that operate there. 

      1. That would be interesting to see, since such airports have so little traffic, and people are generally nowhere near as smart today as they were back when all cars were using leaded gasoline.  But as I wrote above, once a year, our water bill comes with a water quality report, which I started watching particularly for lead content.  There’s a landfill five miles from us, with three-quarters of a century of electronics trash in it.  Our water comes from local wells.  The water quality report has continually said that the lead level is one-eighth of the action level; IOW, if it got eight times as high, they’d have to do something about it.  It has not been increasing.  However, it also says that the landfill is _not_ one of the suspected sources, but erosion of natural deposits _is_.

  9. The surprising part is that most commonly used surface-mount resistors still rely on lead. Although not a top source of pollution, one would have thought technology has long progressed to the point of relying more on higher precision instead of special materials. After all, the job is to make poor conductors in a controlled manner. Unlike making capacitors, where the challenge is more obvious.
    How is lead used here anyway? Probably not to make solder joints inside. Does it make the resistor value more stable over temperature ranges? Not very likely, current-sensing shunts usually use commonplace metals like copper, nickel, manganese, and are expected to have dependable values. Is it still hard to shape resistive elements accurately?

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