Although these little devices help us and somewhat make our lives easier (depends who you are talking to), they do have an effect on the world we live in. 

Come Again?!

Yes they have an effect in the world you and I both live in. E-waste has become an issue that could get out of control if we don’t get a handle on it. With companies not properly recycling the electronic devices, it’s leading to issues that will soon have an effect on how we live in the future.

What effects am I talking about?

I came across this infographic created by Vangel Inc. using figures form 2013 titled “The State of E-Scrap”. Here are some topics this infographic covers:

• What percentage of electronics is actually being recycled
• Minerals that can be recovered by recycling cell phones
• Countries that are shipped recycled electronics

This infographic grabbed my attention, to know that only 25% of households electronics are recycled. That is crazy. Not to mention the average American replaces their cell phones at least every 22 months.

If you want to learn more about this topic view the infographic below and I hope this can help shine some light on how e-waste could become a problem if we don’t come up with a solution.

Comment on the issue or even how you think things could improve.

by taraurso.

Enter Class 1 Dielectric MLCC

Class 1 dielectric MLCCs are comprised of a different type of dielectric chemistry that does not exhibit ferroelectric behavior.  They are generally termed linear dielectrics.  Class 1 is an Electronics Industry Association (EIA) designation and these dielectrics are typically based on magnesium titanate, or calcium titanate, or neodymium titanate, or barium neodymium titanate or strontium calcium zirconium titanate materials, or the like.  They are called “linear dielectrics” because their dipole response associated with changing electrical field is linear in character. These dielectrics are highly stable with respect to numerous environmental factors.  They exhibit properties (primarily K and df) that do not change appreciably with changing temperature or voltage or pressure, or frequency, etc.  Additionally, they do not age (i.e., loose capacitance over time), and they do not “buzz” or convert vibration to output signal noise.  The most common designation within Class 1 dielectrics is the C0G.  There are numerous other designations for Class 1 dielectrics as well, such as C0H, etc.  More specifics about these designations may be found via the following link.  C0G is the most common and the most stable EIA Class 1 dielectric designation.  Many people (usually us “old timers”) still call it NPO, even though the two designations really shouldn’t be used interchangeably.

A Stable Ally

If you need a highly stable capacitor of value ~0.22 µF or less for your 100V or lower rated application, you should consider C0G MLCC (high voltage versions are available as well).  These capacitors are very stable with respect to temperature (i.e., capacitance varies +/- <=30 ppm/C from -55C to +125C), they typically have dissipation factors (df) well less than 0.1% and they do not experience capacitance aging.  They also have very low dielectric absorption and they do not exhibit significant piezoelectric or micro-phonic effects.  Class 1 C0G MLCCs also typically have low ESR and relatively low ESL and are typically available in sizes from 2225 (EIA) down to 01005 (EIA).  You will give up about 100 fold capacitance per unit volume with respect to Class 2 MLCC or tantalum capacitors, but Class 1 MLCC can have volumetric efficiencies that are equal to or better than film capacitors.  C0G MLCCs are also highly reliable and can be quite robust mechanically, if the dielectric used is zirconate based (SCZT or the like). 

Recent Developments

Just as with Class 2 dielectric MLCCs, Class 1 MLCCs have advanced over the years as well.  C0G MLCCs are now available with base metal internal electrodes (BME) and with relatively thin layers (~4µm dielectric thickness or less) and with very high layer counts (over 300 layers in some cases).  This has enabled a strong increase in capacitance per unit volume in C0G MLCCs, similar to the volumetric efficiency advances with Class 2 dielectric MLCCs discussed in previous blog posts.  However, the dielectric constants are still relatively low (ranging from ~10 to ~100 in most cases) as compared to Class 2 dielectrics (which typically exhibit dielectric constants on the order of 3,000 or higher), so even though C0G MLCCs have advanced greatly, it is still about 100 fold less than Class 2 MLCC with regard to capacitance per unit volume. 

Additionally, new SCZT (strontium calcium zirconium titanate) based dielectrics with either precious metal internal electrodes (PME) or base metal internal electrodes (BME) enable relatively high rated voltage per unit dielectric thickness.  This has enabled highly robust C0G MLCCs such as an EIA 1206 (3216 metric) 50V rated 0.1 µF, for example, that is basically “bulletproof.”  These dielectrics are robust with respect to temperature stability, df, and reliability.  Finally, the advent of low K dielectrics combined with copper BME internal electrodes in a Class 1 dielectric MLCCs has enabled very high quality factor (Q) capacitors that are excellent for high frequency applications.  These advancements have enabled the development of C0G MLCCs that are suitable for most needs at or below 0.22 µF.

First Class all the Way!

Class 1 dielectric MLCCs have advanced in a manner that is similar to Class 2 MLCCs.  In the same vein as “A Farad on the Head of a Pin for Free,” you can now get more capacitance in a smaller package, for less $, all with higher voltage rating and better reliability.  So when you need a stable, robust capacitor in the 0.22 µF or less range, always look for the C0G MLCC solution first, because Class 1 dielectrics are definitely First Class.  TTFN!

You Don’t Get Something for Nothing

You see, stuffing all of that capacitance into a tiny little package requires the use of dielectric materials that have a very high dielectric constant (K), which is basically a unitless measure of the charge density of active dipoles in a given volume as compared to an equivalent volume of vacuum.   All other things being constant, capacitance per unit volume increases linearly as K increases.  Because of this, most Class 2 MLCC are made with high K (i.e., K = 2500+) ceramic materials, that are almost all based on the “magical” crystal chemistry of barium titanate (BaTiO₃) or BT.  But BT also has a “bad side.”

God’s Gift to Ceramics

Barium titanate is an amazing material.  It is not found in nature and was originally developed in the early 1900s for use in radar systems for its ferroelectric properties.  These properties are discussed in Venkel’s White Paper: Testing and Measurement Practices of High Capacitance Ceramic Capacitors and those properties are profound...so much so that one of my professors at Alfred University deemed it “God’s Gift to Ceramics.” 

While these ferroelectric properties enable dielectrics with extremely high K, they also result in movement of the internal crystal structure (i.e., piezoelectric effect and to a lesser extent, electrostriction) when an electric field is applied, and they also result in a build-up of charge (electric field) when an external mechanical stimulus is applied.  This movement of the internal structure can translate to the exterior of the material and can be quite significant.  Because of this, BT can be used to make buzzers, speakers and other devices requiring mechanical displacement, as well as devices that convert mechanical stimulus into electrical charge, such as igniters. That mechanical displacement can make noise, and that noise can add up if multiple MLCCs “see” a similar and significant electronic signal in the audible range resulting in a “choir of singing MLCCs.”  This effect can be further “amplified” if the MLCCs are rigidly coupled to the circuit board in a manner that results in amplification of the resulting pressure waves, causing a makeshift speaker of sorts.  This effect becomes more prominent if the board is relatively large.

It should be noted that the above piezoelectric and electrostrictive effects also “work in reverse,” meaning that mechanical displacement of Class 2 MLCCs from the exterior of the MLCC device (i.e., noise, vibration or the like) may resulted in added electrical noise to your signals.  This is called “microphonic effect” and has the same scientific bases of operation.

Trade-Off Time

So here is the conundrum.  How do you take advantage of BT’s high K for your high capacitance density MLCC needs, while minimizing piezoelectric and/or electrostrictive side effects that accompany ferroelectric behavior and that result in an annoying buzzing when a signal of significant field, in the audible frequency band is applied (or half the audible band, in the case of electrostriction, due to its frequency doubling effect)?  The answer lies in the trade-offs that you are willing to take in your design. 

You can avoid signals in the audible frequency range.  You can also reduce the amplitude of the signal such as by reducing ripple in a circuit or the like.  You can also change the waveform, for example to a relatively gentle sinusoid from a sharper digital waveform.

You can also use a device that will effectively “see” a smaller signal field.  That can be accomplished using an MLCC with a higher voltage rating than is needed (i.e., one with a thicker dielectric, and thus reduced signal field).  You can also use lower capacitance values (in parallel if necessary).  This can be especially effective at reducing noise if you use a mutual cancellation approach, such as populating the board on both sides and feeding the same signal to two MLCCs that are directly opposite to each other.  Additionally, you can swap the MLCC with one having a lower dielectric constant, as this effect (e.g., d₃₃) tends to increase with increasing K (e.g., swap an X5R for a Y5V, or an X7R for and X5R, or a C0G (Class 1) for any of these).  This will likely come at the expense of board real estate however.  If a C0G MLCC cannot be used, you may want to consider using a tantalum capacitor in place of the “singing capacitors” if the signal is appropriate so as to avoid imposing reverse polarity to the Ta caps.

You can also reduce the stiffness of the mechanical coupling of the MLCC to the board using compliant lead devices and by not using epoxy or other rigid materials to attach the MLCC to the circuit board in areas other than the terminals (typically used for wave solder attach).  Additionally, you can orient the internal electrode plates of the MLCC orthogonal to the plane of the board, which will reduce mechanical coupling to the circuit board on the Z-axis.  Further, you can populate the MLCCs toward the periphery of the circuit board as opposed to the middle of the board, but be sure to consider design rules regarding flex cracks if you do this, and to remember that local grouping of multiple MLCCs that “see” this type of signal should be avoided as the volume of the noise increases significantly when MLCCs “seeing” that type of signal are grouped. 

Seen and Not Heard

So please remember that the Class 2 MLCC in your design can produce noise (and can add noise to your signals) in certain designs.  If your design or your application needs to be quiet, you will need to select devices appropriately as well as to design your circuit so that it “speaks no evil” and “hears no evil.”  Prudent device selection and circuit design can minimize or eliminate these effects so that your capacitors can be “seen and not heard.”  I wish you well with your designs.  Until next time, TTFN!

(This post is part of a series. See Part 1 to get caught up.)

Hello fellow engineers, task masters, and problem solvers.  Hope all is going well and productive in your world. Well, it looks like Test machines and LCR meters have been at it again – not supplying the correct and adequate test voltage to a high value ceramic capacitor when undergoing testing to determine if their capacitance is within specification for these little multi-layer ceramic devices (components)]. 

 Because the current required to drive a 1KHz signal across a 10μF DUT (device under test) capacitor at either 0.5VAC or 1.0VAC may exceed the AC current capability of a typical LCR meter, it may not be best (in order to obtain an accurate reading) to measure capacitance values of 10μF or above at 1KHz, as this may cause the test voltage at the DUT to be reduced significantly below the set value, leading to erroneously low measured capacitance. This is certainly the case for values from 22uF to 220uF but the 10uF seems to be a special case as all manufacturers call for the 10uF to be tested at 1V  RMS and 1KHz.  I know you have heard the phrase “ if all else fails – read the directions – we’ll, in this case it would be the owner’s manual of your capacitance meter.  Reading it will help you understand the current capability of its power supply. If the current capability of the power supply of your meter exceeds approximately 70 mARMS, it may be suitable to use it to measure capacitance of 10μF capacitors at 1 KHz. Otherwise, it may not be suitable to test at  1KHz, and may be necessary to measure capacitance at 120Hz in order to obtain the actual capacitance value (or at least get close to it).  I will go into the 10uF case at another time but for now, here is some data that will help set this all up and hopefully provide some insight into this issue (or maybe it’s better termed as an “on-going challenge”).

The impedance values at two common measurement frequencies (120Hz and 1000Hz) for the same capacitance values is indicated in Table 1 below:

   Table 1.  Impedance of a MLCC at 120Hz & 1KHz

Figure 1. Z vs. frequency for MLCC’s for a large range of capacitance values

So what does this all mean?  How can it help me understand my test set-up and results? What should I do to get better and more accurate results?  Questions that we will discuss and go into further detail next time. For now, keep solving those problems and remember, there is no “failure”, only feedback.  It may be bad or good feedback, but it’s still feedback.

Until next time.

Greetings designers!  So, you just finished your latest circuit design and you are amazed that you were able to find MLCCs that were smaller than the ones recommended by your power supply vendor.  Your circuit footprint is now smaller and the total components cost is less.  Congratulations! Give yourself a “high five” for your accomplishment!

No High Five for You!

The next week your design “crashes” during evaluation, due to excessive voltage drop, or to out of spec. ripple, or to…  You ask yourself, “What happened?”  You used the same capacitor values with the same “dielectric” that the power supply vendor recommended (“X5R”…whatever that is).  Heck, you even used the same voltage rating that they recommended.  What could have happened?  Does size really matter that much?

Well, while you thought that the power supply specification was just old, and not up to date with the latest miniaturized capacitor offerings, it may be that the power supply vendor actually was current and was looking out for you, having tested their design recommendations (and perhaps others that didn’t work as well) prior to publication.    

Not Your Father’s Capacitor

You see, not all X5R dielectrics and MLCC designs are the same.  The X5R specification simply indicates an “envelope” that the dielectric will stay within throughout the temperature range between -55C to +85C (i.e., ≤+/-15% deviation in capacitance (typically measured at 1 VAC@1 KHz and 0VDC), relative to the “room temperature” capacitance (typically measured at either 20C or 25C)).  It also indicates that it meets some type of reliability specification (which varies from manufacturer to manufacturer and with voltage rating) at 85C temperature and at rated voltage (or a multiple of rated voltage).  Unfortunately, the specification does not cover allowable variation in capacitance with applied DC voltage, which can be quite considerable, and can vary greatly depending upon the chemical composition of the dielectric as well as the MLCC design.  The reasons for this are based primarily in the chemistry of the ferroelectric dielectric materials used in the Type 2 MLCC, as well as in the MLCC design (primarily dielectric thickness) of the capacitor.  Venkel recently published an excellent technical paper (link) that discusses the detail behind these reasons.

With progress in MLCC development (more capacitance in a smaller package), MLCC manufacturers have moved the boundaries of performance in order to meet the specifications that they have to meet (e.g., primarily X5R or other temperature characteristic, as well as specified reliability).  In some cases, that has resulted in compromise of other factors (e.g., sensitivity of capacitance to voltage in this case).  Small “tweaks” in dielectric chemistry or MLCC design, introduced with each new generation of MLCC, can have significant influence on these other factors (such as capacitance sensitivity to voltage).  Not wanting to “air their dirty laundry” some manufacturers have been reluctant to publish these data, in some cases, to the detriment of their customers.

This Could Happen to You

As a result some circuit designers have been “blindsided” when selecting MLCCs for their designs.  For example, capacitance can decrease as much as 80% or 90% when rated voltage (DC) is applied as compared to the 0VDC applied voltage in the manufacturer’s specification.  Imagine purchasing a 10µF 0402 MLCC and finding that it is really a 1µF capacitor at rated voltage, and ask yourself can your designs withstand that much change in capacitance?  If so, fine.  If not, you should choose a different capacitor. 

In order to make an informed decision, look at the voltage sensitivity curve for the device you are interested in (link for examples).  If you cannot accept the variation indicated in your design, look at the voltage sensitivity of other capacitors (higher voltage rating, larger case size, or less sensitive dielectric, or higher capacitance value, or the like) until you find a suitable solution to your design needs.  Whatever you do don’t assume that Type 2 MLCCs have stable capacitance with respect to applied voltage, because typically, they don’t.

Parting Shots

So go forth and prosper using the best and most economical capacitor solution that you can find to meet the needs of your designs.  Just be sure to “read the fine print” with regard to the performance aspects that are important to you.  If the data that you need aren’t available, be sure to ask for it (http://www.venkel.com/technical/electrical-characteristics-data).  The last thing that you want is to have your circuit fail in performance testing because of your improper selection of a sub-penny component.  Now redesign that circuit, test it and give yourself that “high five!

Set-up, measurement, accuracy, test method, result; Words that test engineers know and live by.  We all want accurate results and if you ask 10 test engineers, you might get 10 different answers on how to get there.   When you tell a test engineer that his or her results are incorrect, they may take offense and push back and say they’re ones that are correct and its your products that are out of specification. 

 This is what we find when encountering measurement or correlation issues when endeavoring to measure high value (typically considered to be > 1uF) Multi-Layer Capacitors or MLCC’s.  The inability to accurately measure high value MLCC’s has been an issue in our industry for years with the advent of high value MLCC’s, the issue does not appear to be going away anytime soon. This is due to the fact that many capacitance testers and LCR meters used throughout the industry are not designed to, nor have the capability to correctly measure capacitance of high capacitance (Hi-Cap) MLCCs. This is the case whether we are measuring capacitors at 1 VAC and 1 KHz or 0.5 VAC and 120 Hz. The inability to correctly measure high capacitance MLCCs is due to two reasons. First, many LCR meters do not have the capability of supplying enough current to the capacitor being tested at 1KHz and 1 VAC, resulting in a reduced measurement voltage which results in an artificially reduced capacitance reading. Second, Hi-Cap MLCCs typically utilize Class 2 dielectrics (e.g. X5R, X6S, X7R, X7S, etc.) that are sensitive to test voltage in the sense that changing test voltage results in change in capacitance. Since Class 2 dielectrics are typically made with ferroelectric dielectric materials that are non-linear in behavior with respect to test voltage, this change in capacitance will occur. These two reasons plus the ageing phenomenon (discussed in an upcoming Blog) exacerbates the issue and explains why it is essential to ensure that you apply the correct test voltage to the MLCC when measuring or testing a capacitor and trying to obtain its actual capacitance value. Incorporating the right bridge and applying the correct parameters is essential in obtaining an accurate capacitance measurement.

 To ensure that capacitance is correctly measured, each capacitor must be tested under the correct conditions. The correct conditions for measurement depend upon the capability of the measurement equipment as well as the nominal capacitance to be measured. Since Capacitance measurements are typically performed in the low range of the frequency scale around 120Hz-1KHz, the capacitive reactance (X_C) typically dominates the impedance equation, and Z may be estimated from the relationship:

From this relationship, it is clear that the impedance of a capacitor is dependent upon frequency and capacitance value. So why does the electronic industry make a standard to measure a 10uF MLCC at 1KHz but a 15uF at 120Hz?

In my next post I will discuss this in more detail and demonstrate how that works in the form of a graph and some additional data.  Then,  I will continue with providing information and data to support the theory that MLCC’s with the value of 10uF should also be tested at 120Hz and not 1kHz. This should “stir the pot” a bit as I have encountered numerous instances where this is the case when older test equipment is used throughout the industry.  Some customers have re-evaluated their test frequencies based on cap value and the type of test equipment they have and have done so with good success.

 Hope to see you next month and as you know – “Engineers make the world go around! ”^TM

The Conflict Minerals issue has been around for a few years now, but only recently has it become something that more people are taking notice of. The ambitious Dodd-Frank Wall Street Reform and Consumer Protection Act was signed into law in 2010 and brought considerable attention to this sensitive subject. For those who may want an overview of the issue, Venkel Ltd. has developed an infographic that illustrates the Conflict Minerals issue.

This infographic briefly defines what a conflict mineral is and follows up with a map that shows worldwide production of each mineral. We have also included a graphical representation of the estimated amount of funds that are going to the armed conflict within the Democratic Republic of the Congo (DRC). Below this is a list of the major players involved in the trade of these minerals. We closed out the infographic with several human rights groups that have more information on the subject. We hope that you find this an informative resource. Please feel free to contact us with any questions or suggestions related to this infographic.

Conflict Minerals continue to be a topic of discussion leaving us wanting to learn more. Not to mention, the laws that are now in effect for the electronics industry.

Which brings me to the question; do you really know the affects these minerals have on The Democratic Republic of the Congo?

In our newly redesigned infographic we show you these details in a creative format.

Let’s Rewind  

In 2011 Venkel released our "Conflict Minerals 3TG" infographic. You may have seen this in numerous places on the web or even in a training session or webinar on the topic.

The infographic is based on information from 2009 data made available by the USGS. Since then much has changed. Not just the amount of money funding the war in the DRC but also the top 5 producers of conflict minerals Tin, Tungsten, Tantalum and Gold also known as 3TG.

Fast Forward to the Present

Venkel recently released a 2014 refresh of the infographic, using 2011 USGS data.

Although some parts may look similar to the 2011 infographic, the data has changed in many ways. We will take a look at changes you would see from the 2011 vs 2014 infographic.

As you can see in the table above, the amount being mined in the DRC for Tungsten and Tin has decreased. However, Tantalum and Gold have steadily increased over time. Whether production has decreased or increased, money is still helping fund the war in the DRC. You will see in the next section just how much money is funding the war.  

The most shocking result is the amount of money Gold is funding. Gold is a big and significant part of the funds for the war in the DRC. From 2011 to 2014 the Gold funding the war has dramatically increased over 2 times the amount in 2011.  Though Tin and Tungsten have decreased over time, with Gold still being an issue it is the number 1 mineral helping fund the war as you can see.

Our new infographic can be used as a training tool helping others see the importance of this topic and the severity of trying to get a handle on the supply chains of the manufacturers of products that use either of these minerals. With the increase in demand of electronic components/devices this has made it harder to trace the actual source of these minerals. It is very important that you get with your manufactures and request smelter information to help ensure that products being sold to you are conflict-free so that together we can help slow down this epidemic.

View the updated 3TG Conflict Minerals Infographic and don't forget to sign up for email alerts that will notify you when we release updated conflict minerals content.

Please see our Conflict Minerals compliance page for information on Conflict Minerals and our products.

Hey circuit designers!  Have you ever wondered why a circuit that you designed just didn’t act like you thought it should?  Well, that could be due to many reasons; several of which may be related to the capacitors that you selected for your circuit.  In this case you could be a victim of “deviant behavior”…behavior that differs from a norm or from accepted standards.  In this case, the standards of interest would be those set by the mythical “perfect capacitor”…the Unicorn of passive electronics. 

An Imperfect World

You see, like all electronic components, capacitors are not perfect.  The type of capacitor that you select will determine how far from perfection, or deviant the capacitor’s performance will be in your application.  Each real capacitor is a device that has not only a characteristic capacitance (C), but a characteristic resistance (R, typically termed equivalent series resistance or ESR) and an inductance (L, typically termed equivalent series inductance or ESL).  These “parasitics” can adversely affect circuit performance, but in certain situations may be used to your advantage. 

I remember how one of my sarcastic coworkers used to joke about “parasitics.”  He would say, “Shoot!  I don’t understand why our customers are so unhappy about parasitics; we ship them a free inductor and a free resistor with every capacitor!” J

Curves Ahead

Simply put, parasitics affect impedance (Z) as frequency is changed (i.e., the “Z curve”), which may affect circuit performance.  A perfect capacitor exhibits Z = 1/(2πfC) where f is frequency.  As C is increased, Z is reduced in a manner that is linear on a log-log scale (see left side of graphic above).  As f increases, Z of a perfect capacitor continues to decrease in this manner out to infinite frequency.  With a real capacitor, however, C “runs into” either R (typically ESR) or L (ESL) as f is increased, establishing either a “flat” or a minimum in the impedance curve.  If ESR is relatively low, L will largely determine this minimum and the Z curve will be V or gull wing shaped in the case of extremely low ESR.  If ESR is relatively high, R will establish a “floor” or “flat” in the Z curve over a relatively broad range of f.  At higher frequencies L dominates, as Z is ~2πfL, resulting in increasing Z as f is increased in a manner that is linear on a log-log scale (see right side of graphic above).   

You Got to Know When to Hold’em…and Know When to Fold’em

Prudent selection of capacitor type may be useful in achieving a desirable Z curve for your application.  For example, use of capacitors having moderate or high ESR, combined with low ESL, typically results in a relatively flat Z curve.  This may be useful for power delivery designs such as power delivery networks (PDNs), as a relatively “flat” impedance curve is often desirable.  Capacitors, such as controlled ESR reverse geometry or controlled ESR interdigitated capacitors (IDCs) or face down solid electrolyte tantalum (Ta) or low ESL solid electrolyte aluminum (Al) capacitors may be useful in these applications.  On the other hand, use of capacitors having very low ESR combined with low L, may be useful for inline high pass filter designs or for designs requiring high speed decoupling.  Discoidal ceramic capacitors are typically used for high pass filtering, and standard IDC or reverse geometry capacitors may be useful in filtering or high speed decoupling applications.   More recently the design community has favored use of numerous, small case size MLCC in parallel for high speed decoupling designs, as these MLCCs have moderate-to-low ESL (L), take up little space and can be used local to the decoupled device, and are relatively inexpensive.  Additionally, use of capacitors having very low ESR, combined with moderate-to-high L, may be useful in band pass filter designs. Standard MLCCs typically “fit the bill” here, and low loss (high Q), tight tolerance, type 1 dielectric capacitors such as C0G MLCC are typically used here for consistency in resonance frequency (the frequency at which C and L cross if R is 0 or is nearly 0).

A Little Help from Your Friends

Capacitor manufacturers spend significant development resources optimizing the above qualities for different applications.  With regard to parasitics, it’s all about the design, the dielectrics and the electrodes.  For example, in order to minimize ESR, MLCC developers will take advantage of high active layer counts and relatively thick electrodes.  To maximize ESR in an MLCC, special electrode designs may be used in IDC MLCC or resistors may be put in series with other MLCC using specialized termination materials or the like.   For low ESR, special low resistivity internal electrode materials, such as copper or specialized electrode designs may be used. 

Get Real

All combined, these materials and design factors may be used alone, or in combination, to optimize the C, R and L properties of a given capacitor design for one or more specific application(s) requiring a characteristic impedance (Z) curve, making it important for circuit designers to model their circuits with the real (C, R, L and Z) properties of the capacitors selected for their designs.  That way, you may be able to take advantage of that free resistor and inductor that is included with each capacitor! J (At the very least you will be able to compensate for their idiosyncraZies in your design).  Next time we will discuss part 2 of Deviant Behavior, but as Winnie the Pooh would say, “Ta ta for now!” (TTFN :-))