### Dielectric Absorption of Multilayer Organic (MLO™) Capacitors

```Dielectric Absorption of
Multilayer Organic (MLO™)
Capacitors
Edgardo Menendez
Field Applications Engineer, AVX, 1 AVX Blvd., Fountain Inn, SC 29644, USA
Tel: 864-967-2150, e-mail: [email protected]/* <![CDATA[ */!function(t,e,r,n,c,a,p){try{t=document.currentScript||function(){for(t=document.getElementsByTagName('script'),e=t.length;e--;)if(t[e].getAttribute('data-cfhash'))return t[e]}();if(t&&(c=t.previousSibling)){p=t.parentNode;if(a=c.getAttribute('data-cfemail')){for(e='',r='0x'+a.substr(0,2)|0,n=2;a.length-n;n+=2)e+='%'+('0'+('0x'+a.substr(n,2)^r).toString(16)).slice(-2);p.replaceChild(document.createTextNode(decodeURIComponent(e)),c)}p.removeChild(t)}}catch(u){}}()/* ]]> */
1
What is Dielectric Absorption and why is it Important?
Capacitors with Dielectric Absorption (DA) recover some of their charge even after the
capacitor has been fully discharged (see Figure 1). (Ref. 2) It is expressed in percentage and it is
based on the measured voltage after discharging and charge recovery divided by the maximum
voltage that was originally applied (see Equation 1).
=
2
∗ 100%
1
Equation 1: Dielectric Absorption Equation,
Where V1=Max Applied Voltage, V2=Voltage after Discharging
Figure 1: Dielectric Absorption
Source: Ref 2.
Dielectric absorption differs for a variety of dielectric materials. Generally, dielectrics with low
permittivity tend to have a lower DA than those with a higher permittivity constant.
Dielectric absorption poses a problem in sample/hold circuits. During the hold time of the S/H
circuit the voltage across the capacitor is assumed to be a specified predetermined number.
Because of dielectric absorption this may not be the case. Depending on the length of the hold
period, as the capacitor is left in open mode, it will recover some of its charge causing a voltage
error to appear at Vout of the S/H circuit. (Ref. 1) This is where capacitor selection should be
considered carefully as some capacitors will exhibit higher dielectric absorption than others
(see Table 1).
MLO™ capacitors have been shown to exhibit the lowest dielectric absorption with 0.0015%
versus other technologies like NP0 ceramics who’s DA can be as high as 0.6%.
Measurement Techniques – MIL-C 19778
Dielectric absorption measurements were performed on MLO capacitors under the test set up
shown in figure 1. The test was based on MIL- C 19778. The conditions for the test were as
follows: a 2”x2” laminate which serves as the core of the MLO device was charged for 1 hour
charging at 250V and discharged using a 5ohm resistor. The thickness of the dielectric core is
25um. The voltage across the capacitor was measured 15 minutes after discharging the
resistor.
2
Dc voltage source
(hi-pot tester)
2” dia 25LD-1/1oz
capacitor laminate
millivoltmeter
Figure 2: Source from http://www.wima.com/EN/absorption.htm
For a 5 ohm resistance we measure a dielectric absorption of 0.0015% for the MLO dielectric.
(Testing was performed by Oak-Mitsui.)
Comparison between MLO™, ceramic dielectric, and glass dielectric shows that MLO exhibits
the lowest dielectric absorption (see Table 1).
Dielectric Material
MLO ™
NP0 Ceramic
Stable
High K Ceramic
Ceramic Discs
Internal Barrier Layer
Reduced Titanates
Multi-Layer Glass
“T” Characteristic
“U” Characteristics
“V” Characteristics
Teflon
Mica
Polyester
Poly-Carbonate
Poly-Propylene
Polystyrene
Solid Tantalums
Aluminum Electrolytics
Dielectric Absorption (%)
0.0015%
0.6%
2.5%
N.A.
Same as Multilayers
N.A.
N.A.
0.05%
0.1%
0.1%
1.3%
<0.01%
0.3% - 0.7%
0.5%
0.35%
0.05%
0.05%
N.A.
N.A.
Table 1: Dielectric Absorption Comparison
Chart by Dielectric
3
The MLO™ Material System
MLO™ materials are thin, low loss, organic dielectrics with low permittivity that exhibit
exceptional high frequency characteristics. The MLO technology utilizes large area fabrication
techniques and unique lumped element design topologies to achieve high Q, low loss RF
components, including capacitors, inductors, diplexers, couplers and crossovers, among others.
A unique alternative to traditional fired components, such as LTCC and ceramics, the MLO
material system provides stable, low loss performance from DC well into microwave
frequencies.
In addition to low loss operation across a wide frequency range, MLO components have
numerous physical advantages. A non-fired technology, MLO materials provide several design,
example, MLO devices, which can be made as thin as 0.45mm, are typically thinner and lighter
than competing technologies. Additionally, due to its material performance and ability to
create heat pipes using a variety of via structures, MLO technology exhibits superior thermal
performance when compared with competing technologies, as well as features a coefficient of
thermal expansion that is matched to most FR4 circuit boards (CTE approximately 16 to 18
ppm/oC). Consisting of one or more RF dielectric layers embedded between layers of other
laminates, MLO components also shield internal electrodes and traces and provide routing and
bonding pads for SMT placement. Moreover MLO materials allow for only the most minimal
moisture uptake, typically <0.04%.
Summary
Capacitors with dielectric absorption recover their charge after being completely discharged.
Dielectric absorption can vary from 0.001% to more than 10%, with low K dielectrics exhibiting
the lowest DA. MLO™ capacitors have been shown to exhibit exceptionally low DA of about
0.0015%, making them highly suitable for sample and hold circuits, where DA can cause errors
at the output.
References:
1. Pease, R. A. “Understanding Capacitor Soakage to Optimize Analog Systems,” EDN,
October 13, 1982, p.125
2. Analog Circuits, “MT-090 Tutorial: Sample and Hold Amplifiers”,
http://www.analog.com/static/imported-files/tutorials/MT-090.pdf, p.10
4
```