2421-1e

Polymer Multi-Layer Capacitors (PMLCAP)TECHNICAL NOTES

Table of contents
1. Introduction ......................................................................................................................... 2
2. What is PMLCAP? ................................................................................................................ 3
3. Manufacturing Technology .................................................................................................... 3
4. PMLCAP structure ............................................................................................................... 4
5. Comparison between PMLCAP and other multi-layer capacitors ........................................... 4
6. PMLCAP characteristics and features .................................................................................. 5«Impedance/ESR characteristics» ........................................................................................ 5«DC bias characteristics»..................................................................................................... 6«Temperature characteristics» ............................................................................................. 7«Beat sound characteristics» ............................................................................................... 7«Harmonic distortion ratio» .................................................................................................. 8«Influence of vibration on C/N ratio» .................................................................................... 8«Dielectric absorption characteristics» ................................................................................. 9«Leakage current characteristics» ...................................................................................... 10«Solder heat resistance» .................................................................................................... 11«Self recovery» .................................................................................................................. 12«Deflection durability» ........................................................................................................ 13«Humidity resistance» ........................................................................................................ 13
7. Typical applications ............................................................................................................ 14«Audio equipment» ............................................................................................................. 14«LED backlight driver»........................................................................................................ 15«PLL synthesizer loop filter» .............................................................................................. 15«Energy harvesting» ........................................................................................................... 16p. 1
https://www.rubycon.co.jp/en2421-1e

Polymer Multi-Layer Capacitors (PMLCAP)TECHNICAL NOTES

1. Introduction
Along with the miniaturization and high performance of electronic equipment, miniaturization, high performanceand high reliability are required at all times for electronic parts used in the electric circuits. Rubycon responds
to its market requirements and offers a new type of multi-layer film capacitor PMLCAP which greatly miniaturizes
conventional multi-layer film capacitors.
PMLCAP has great features such as small size, light weight, high capacitance, excellent frequency / bias
characteristics, low dielectric absorption, low leakage current, high heat resistance, etc., and it can contributeto creating high-value added of various applications such as audio & visual equipment, communication equipment,wearable equipment, environmental power generation, etc.

p. 2
https://www.rubycon.co.jp/en2421-1ePolymer Multi-Layer Capacitors (PMLCAP)TECHNICAL NOTES

2. What is PMLCAP?

PMLCAP is the abbreviation for Polymer Multi-Layer Capacitor, asurface-mount capacitor made up of multiple polymer layers. The
conventional film capacitor also has a surface mount type, but thepoint where PMLCAP differs greatly is in the type of dielectric, andfurthermore on its manufacturing method.
The dielectric thickness of PMLCAP is 1 μm or less, which is difficult
to manufacture with biaxially stretched film used for conventional film

Photo.1 PMLCAP appearance

capacitors.
Rubycon succeeded in manufacturing a revolutionary high capacity and small film capacitor by establishing thetechnology to form this thin film dielectric layer. In addition, the dielectric resin used in PMLCAP is athermosetting resin with high heat resistance, and it has better heat resistance than conventional film capacitor
using thermoplastic resin.

3. Manufacturing Technology
Conventional film capacitors are manufactured aslead wire type, cylindrical type, box type, chip typeby winding or stacking a metallized film on which
metal is vapor-deposited on films such as PP, PET,PPS, PEN, etc. (metallized type)., or a set of eitherof these films and metal foil (foil type).
However, with such a manufacturing method, since

Photo. 2 Size comparison example with film capacitor

it uses a commercially available film, there is（10μF item）

inherent limitation in pursuing its miniaturization (thinner film thickness). Therefore, Rubycon began developing
the manufacturing technology to form a thin dielectric layer that leads to miniaturization of film capacitors andsucceeded in mass-producing PMLCAP in 2006.
PMLCAP employs electron beam curing resin as the dielectricmaterial and vacuum deposition polymerization technology as
manufacturing method. Specifically, a vacuum chamber is used topolymerize the dielectric layer, onto which the inner electrode layers(aluminum) are formed in patterns. These processes are continuously
alternated to build up the layered structure that will be used as theelement for capacitors. This element is cut to the requisite productsize, and the electrode layer is formed to complete the product. Usingthe vapor deposition polymerization method allows the dielectric layer
to remain pinhole free and evenly layered, even at sub-micron

Photo. 3 Stacking structurer
Dielectric layer thickness 0.4μm（Electron microscope photo : x5,000）

thickness. The number of layers is also high, ranging from several thousand to more than 10,000 layers.

p. 3
https://www.rubycon.co.jp/en2421-1e

Polymer Multi-Layer Capacitors (PMLCAP)TECHNICAL NOTES

4. PMLCAP structure
The element part (internal structure) of PMLCAP is composed only of dielectric and internal electrode, andacrylic polymer is adopted as dielectric material. The external electrode is made of multiple metal layers andconsists of tin plating, copper plating, and brass metal spray (metallicon) from the outside. Metallicon is
responsible for connection with the element part. By adopting a material with high heat resistance for thedielectric, we guarantee two times lead free reflow soldering at 260℃ peak.
Failure mode is “open” because of having a self-healing effect like the conventional film capacitor. In addition,
it does not contain environmental burden substances and complies with RoHS regulations.

Fig. 1 External electrode structure

5. Comparison between PMLCAP and other multi-layer capacitors
The electrical characteristics of PMLCAP are almost equivalent to polyester film capacitor.
Since one layer thickness of PMLCAP is thinner compared with general multi-layer film capacitors, it achieves
small in size at the same voltage and capacity and line-up large capacity (Max. 22 μF).
Compared with a high dielectric constant type multi-layer ceramic capacitors (MLCC) with piezoelectric effect,
PMLCAP has great feature such as less beat sound and no capacity reduction by applying DC bias, small
dielectric absorption, etc.

p. 4
https://www.rubycon.co.jp/en2421-1e

Polymer Multi-Layer Capacitors (PMLCAP)TECHNICAL NOTES

Table 1 Capacitor characteristics comparison
Capacitor

PMLCAP

Multi-layer film capacitors

MLCC

DielectricElectron beam curable resin（Acryl）

Resin film
（PEN，PPS）

High permittivity ceramic（BaTiO3）

Dielectric thickness<1μm/layer≧3μm/layer<1μm/layer

Dielectric constantApprox. 3Approx. 32,000～5,000Internal electrodeDeposited aluminum

Deposited aluminum

Nickel paste

Rated voltage

16Vdc to 200Vdc

16Vdc to 630Vdc

2Vdc to 3,150Vdc

Capacitance

0.0001μF to 22μF

0.0001μF to 1μF

51pF to 470μF

Temperature range-55℃ to +125℃-55℃ to +125℃-55℃ to +150℃(X8R)

SizeMiddle

Large

SmallFeatures

Poor DC bias characteristics
Less beat sound and excellent DC Less beat sound and excellent DC because of no piezoelectric effect.
bias characteristic because of no bias characteristic because of no Temperature compensation typepiezoelectric effect.
piezoelectric effect.
has good DC bias characteristic
but with large size.

6. PMLCAP characteristics and features
Noteworthy characteristics of the PMLCAP include "no capacitance change due to DC bias application", "littlecapacitance change due to temperature change", " small beat sound or small harmonic distortion caused by theextremely low piezoelectric effect "," small dielectric absorption "," low leakage current in high temperature
region ", and so on.. And PMLCAP structure also has resistant against applied instantaneous pulse overcurrent.
These characteristics make the PMLCAP suited for diverse uses such as those for equipment requiring soundquality improvement and silent design in the audio field, shortening the lockup time of the PLL loop filter due tolow dielectric absorption characteristics, and for energy harvesting where low leakage current is required. Inaddition, it is attracting attention as parts for automotive equipment. We offer to replace multilayer ceramic
capacitors (MLCC) or tantalum capacitors.
The characteristics and features of PMLCAP will be mainly explained by comparison with the high dielectric
constant type multi-layer ceramic capacitor (MLCC)., as follows.
«Impedance/ESR characteristics»
As an example, the frequency characteristics of impedance and equivalent series resistance (ESR) of 35 V 10
μF (5750 size) is shown. PMLCAP has excellent frequency characteristics of low ESR and equivalent series
inductance (ESL).

p. 5
https://www.rubycon.co.jp/en2421-1e

Polymer Multi-Layer Capacitors (PMLCAP)TECHNICAL NOTES

Fig.2 Impedance and ESR characteristic«DC bias characteristics»
PMLCAP is a capacitor with excellent characteristic stability without decreasing electrostatic capacity due topiezoelectric effect as seen in high dielectric constant type MLCC even when DC bias is applied.

Fig. 3 Capacitance change at DC bias application
In addition, PMLCAP does not change the impedance characteristics when applying DC bias, while on the other
hand high dielectric constant type MLCC shifts impedance curve due to DC bias application and may appear
flexion point on its impedance characteristics.

Fig. 4 Impedance characteristics when applying DC biasp. 6
https://www.rubycon.co.jp/en2421-1e

Polymer Multi-Layer Capacitors (PMLCAP)TECHNICAL NOTES«Temperature characteristics»
The temperature coefficient at -55℃ to + 125℃ of PMLCAP is about + 520 ppm /℃.

Fig. 5 Capacitance change with temperature«Beat sound characteristics»
PMLCAP does not have electrostrictive effect. This makes it possible to suppress beat sound drastically and toachieve silence of equipment. In contrast, high dielectric constant type MLCC has electrostrictive effect, so ina circuit with a large amplitude pulse signal, the capacitor vibrates and can cause beat sound.

Fig. 6 Beat sound comparison
Fig. 7 shows a result of beat sound-frequency characteristic when capacitor is mounted to a LCD backlight
circuit. Noise of high dielectric constant type MLCC increases in the middle frequency range over 1kHz due topiezoelectric effect. Thus PML CAP is superior to MLCC, because noise in the range between 1kHz and 10kHz
is audible to humans so that capacitors with less noise in this range are preferable.

p. 7
https://www.rubycon.co.jp/en2421-1e

Polymer Multi-Layer Capacitors (PMLCAP)TECHNICAL NOTES

Fig. 7 Beat sound-frequency characteristic on LCD backlight circuit«Harmonic distortion ratio»
In audio equipment, distortion characteristics can be a hindering factor in playback of the original sound, so low
distortion PMLCAP is increasingly adopted, especially for high quality audio equipment that prioritizes soundquality.
In contrast to PMLCAP, high dielectric constant type MLCC tends to have higher harmonic distortion rate due
to voltage dependent impedance change.
PMLCAP is effective in improving sound quality since it has a structure with a very high interlayer adhesion bya laminate production technique by continuous vapor deposition of a dielectric layer and an internal electrodelayer in a vacuum, and furthermore, it is made up of the external electrode excluding the magnetic material.

Fig. 8 Comparison in harmonic distortion ratio«Influence of vibration on C/N ratio»
Fig. 9 shows a comparison example of VCO C/N ratio of PLL synthesizer when vibration is added to the circuit.
Since PMLCAP does not have a piezoelectric effect, deterioration of C/N ratio is not observed. But deteriorationof C/N ratio is seen in high dielectric constant type MLCC due to piezoelectric effect and this causes
deterioration of wireless communication quality.

p. 8
https://www.rubycon.co.jp/en2421-1e

Polymer Multi-Layer Capacitors (PMLCAP)TECHNICAL NOTES

Fig. 9 Influence of vibration on C/N ratio«Dielectric absorption characteristics»
Dielectric absorption happens due to delayed polarization of dielectric.
PMLCAP has small dielectric absorption (almost equal to that of polyester film capacitors), and it is much better
than high dielectric constant type MLCC. Therefore it is effective for shortening the lockup time of PLL
synthesizer and so on.

Fig. 10 Comparison of dielectric absorption
Fig. 11 shows a comparison of lockup time when frequency is switched from 1.4 GHz to 1.5 GHz by PLL
synthesizer. Although PMLCAP converges to 1.5 GHz in a short time, MLCC does not converge to 1.5 GHz.

p. 9
https://www.rubycon.co.jp/en2421-1e

Polymer Multi-Layer Capacitors (PMLCAP)TECHNICAL NOTES

Fig. 11 Comparison of lockup time in PLL synthesizer«Leakage current characteristics»Compared with MLCC, aluminum electrolytic capacitors and tantalum electrolytic capacitors, PMLCAP has low
leakage current characteristics due to its high insulation resistance even in high temperature range. Therefore,
it can be said that PMLCAP is an excellent energy storage device for energy harvest handling small electricpower.

Fig. 12 Temperature characteristics comparison of leakage current
Figure 13 compares the output voltage of environmental power generation when applying pulse current (0 to 10V,1 kHz, duty 50%) at 25℃ and 85℃.
PMLCAP, shows no change in the output voltage (8V) regardless of the temperature, whereas in the case ofMLCC, an output voltage drop of about 1 V is observed with the increase in the leakage current at hightemperature (85℃).

p. 10
https://www.rubycon.co.jp/en2421-1e

Polymer Multi-Layer Capacitors (PMLCAP)TECHNICAL NOTES

Fig. 13 Comparison of output voltage when pulse current is applied«Solder heat resistance»
With the thermally hardened polymer (decomposition temperature of about 400 ℃ ) as dielectric material,
PMLCAP has very high heat resistance as compared to general surface-mount multi-layer film capacitors. Whena soldering iron is brought into contact with the product body for 5 seconds, a usual multi-layer film capacitor
will cause short-circuit failure due to dissolution of the contact portion, but PMLCAP retains its characteristics.
In addition, it can deal with various mounting methods such as reflow, flow and hand soldering, contributing toimprovement of flexibility in designs with such power supply boards and miniaturization of devices.

p. 11
https://www.rubycon.co.jp/en2421-1ePolymer Multi-Layer Capacitors (PMLCAP)TECHNICAL NOTES

Photo 4 Comparison of soldering heat resistance
Table 2 Soldering conditions for PMLCAP MU series
Reflow

Peak 260℃, 2 times

Flow

Peak 260℃, 2 times

Hand soldering

Iron head temperature 350℃

«Self recovery»
One of the technologies of the PMLCAP for ensuring reliability is self-healing ability. When a momentary
excessive voltage or large current is applied to a capacitor, dielectric material and surrounding electrode material
are eliminated at a defective or weak part due to Joule heat, restoring insulation properties. Also, even if a
microscopic dielectric breakdown occurs there, no short circuit occurs and a certain level of resistance ismaintained to prevent the circuit from breaking down completely.
Fig. 14 shows monitored waveform of the instantaneous applied voltage (186V) which far exceeds the rated
voltage (35V) of the capacitor and the voltage between terminals of the PMLCAP when the voltage is applied tothe PMLCAP via the resistor of 2Ω.
At the moment the voltage is applied, the voltage between terminals of the PMLCAP decreases (insulation drop)
once, but the voltage recovers instantaneously to the original level (self recovery).

p. 12
https://www.rubycon.co.jp/en2421-1e

Polymer Multi-Layer Capacitors (PMLCAP)TECHNICAL NOTES

Fig. 14 Self recovery in applied overvoltage«Deflection durability»
PMLCAP has high stress resistance against deflection due to the physical properties of the dielectric material
and the external electrode structure. On the other hand, general multilayer ceramic capacitors do not havestress resistance due to low bendability of the dielectric, therefore short circuit may occur by cracking.

Fig. 15 Comparison of deflection durability«Humidity resistance»
PMLCAP standard MU series are increasingly adopted in the market as compact and high heat resistant chipp. 13
https://www.rubycon.co.jp/en2421-1e

Polymer Multi-Layer Capacitors (PMLCAP)TECHNICAL NOTES

film capacitors. However, since humidity resistance guarantee conditions are 40 ° C and 95% RH, improvementof moisture resistance performance has been desired. In response to this requirement, MS series of new
dielectric materials with high moisture resistance have newly released.
Moisture resistance guarantee of the MS series is 85℃ 85% RH / 1,000 hours, and it has achieved significant
improvement in moisture resistance compared with conventional products. As a result, it is expected thatPMLCAP adoption will be expanded in automotive, communications and industrial equipment applications wherehigh environmental resistance performance is required.

Fig. 16 Life test applied rated voltage under 85℃85%RH condition （PMLCAP MS series）

7. Typical applications
Typical applications of PML CAP include audio equipment making use of high sound quality, passing capacitor
for power supply making use of less beat sound and loop filter for PLL (Phase Lock Loop) making use of lessdielectric absorption and storage capacitor for Energy Harvesting making use of low leakage current.
«Audio equipment»
PMLCAP is good for coupling capacitors for direct current cutting of amplifiers and output filters of class D
amplifiers. As the sound quality, the transparency of the middle-high range will increases. Use of PMLCAP tooutput filter reduces distortion and the sound quality improves, because of no capacitance fluctuation (no voltagedependence).

p. 14
https://www.rubycon.co.jp/en2421-1e

Polymer Multi-Layer Capacitors (PMLCAP)TECHNICAL NOTES

Fig. 17 Application for class D amplifier«LED backlight driver»Thin film as the dielectric of PML CAP has no piezoelectric effect so that beat sound is much less than MLCC.
This property is ideal for passing capacitor in power supply handling large ripple current. In LED backlight using
PWM (Pulse Width Modulation) in audible frequency range, use of MLCC may causes large beat sound. In following
figure, PML CAP is used as passing capacitor for input and output of a boosting converter circuit, but in voltage
reducing converter, PMLCAP`can be used to input passing capacitor.

Fig. 18 Application for LED backlight driver«PLL synthesizer loop filter»
When used as PLL synthesizer loop filter, since the dielectric absorption is smaller than that of high dielectric
constant MLCC, switching time called the lock-up time can be greatly shortened. In addition, PMLCAP has nopiezoelectric effect, so degradation of C/N ratio due to vibration is reduced.

p. 15
https://www.rubycon.co.jp/en2421-1e

Polymer Multi-Layer Capacitors (PMLCAP)TECHNICAL NOTES

Fig. 19 Application for PLL synthesizer loop filter«Energy harvesting»Since PMLCAP forms dielectric layer with thin film, it has very small leakage current and is smaller size andlarger capacity than conventional film capacitors. Therefore, it is suitable for energy harvesting «environmental
power generation» storage capacitor to collect and save tiny amount of electric power.

Fig. 20 Energy harvesting↑Page topp. 16
https://www.rubycon.co.jp/en