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©2011 ECA (Electronics Components, Assemblies & Materials Association), Arlington, VA CARTS Europe 2011 Proceedings, October 10-13, Nice, France

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KEMET Power Solutions for Automotive HID Applications

Evangelista Boni, Davide Montanari, Luca Caliari, Francesco Bergamaschi

KEMET Electronics Italy, via San Lorenzo 19, 40037 Sasso Marconi (Bologna), Italy Tel: +39 51 939 910, Fax: +39 51 939 324, e-mail: [email protected]

Reggie Phillips, John Bultitude, Mark Laps, Bill Sloka

KEMET Electronics Corporation, 2835 KEMET Way, Simpsonville, SC 29681, USA

Tel: +01-864-228-4052, Fax: +01-965-582-4707, e-mail: [email protected]

ABSTRACT Trends toward large-scale manufacturing of advanced lighting systems in the automotive market are challenging the capabilities of capacitors and other electronic components. One growing application for capacitors is to provide ignition and boost to increase voltages and currents to create ignition on High Intensity Discharge (HID) Xenon headlamps. In comparison to conventional halogen headlamps, the Xenon system provides 200% more lighting, illuminating the road ahead and the curb side more effectively and brightly. The lighting on the road is similar to the daylight and is, therefore, close to the natural viewing conditions of the human eye. As a result, the driving becomes more relaxing and safe. Xenon lamps need about 33% less power than halogen, and they last nearly as long as the vehicle itself.

At the capacitor component level, required features are: small dimensions, high reliability, low inductance, high dv/dt withstanding capability, good stability with time and humidity, long life expectancy, and high peak withstanding voltage. In addition, due to recent and upcoming legislation, lead-free materials of construction are mandatory1.

Two main circuits make Xenon lamps work: the igniter, whose task is the increasing of voltage and current in order to turn the lamp on, and the ballast, that provides the right power and energy to maintain the lamps operation after the initial ignition. Regarding the igniter circuit, the working temperature can even presently go up to 170 °C and the dv/dt level range is up to 8.500 V/µs.

Regarding the ballast circuit, the current working temperature for the capacitor is 125 °C, but new development of lower wattage (25 W) HID systems where the igniter and ballast circuits may be integrated may result in the boost capacitor’s working temperature of 150°C in some designs.

KEMET has recently launched dedicated film capacitor series using PEN to address the needs of the two above mentioned circuits present in Automotive HID applications, in particular regarding the working temperatures2.

Additionally, KEMET has recently launched a lead-free stacked MLCC (multi-layer ceramic capacitor) automotive product line, KEMET POWER SOLUTIONS (KPS) to meet higher temperature requirements in some automotive lighting circuits. Two dielectric types have been developed, a higher capacitance X7R option and an ultra-stable NPO/C0G option. Since MLCC capacitors lack the self-healing properties of film capacitors, long term reliability must be designed in. The ability of MLCC to withstand thermal shock when mounted on circuits with a large coefficient of thermal expansion (CTE) mismatch is of concern. The KPS stack lead frame technology improves thermal shock resistance by isolating the ceramic capacitors from the circuit board. The NPO/C0G MLCC has higher break strength than the X7R increasing thermal shock robustness. Thermal shock data on FR4 and Insulated Aluminum Substrates (IAS) is presented and the relationships between factors contributing to performance are analyzed.

This paper will cover technological advances in film capacitor technology to address Xenon HID lamp needs and will compare and contrast the basic electrical properties of the film and ceramic capacitors for automotive lighting as well as other performance characteristics such as dv/dt withstanding, time-to-failure (TTF), and thermal shock resistance. Capacitance vs. temperature and voltage will be compared for the different capacitor solutions.

INTRODUCTION This section will describe the igniter and boost circuits in detail and shall outline what solutions have been implemented in each of them at a capacitor level, where film capacitors have been designed until now in all the main Automotive lighting manufacturers.

Presently a 35 W version is used in the automotive market. In many countries it is required by law to have an automatic leveling and washing system, in order to prevent other road users from being dazzled, to ensure lenses are clean and

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have a good light distribution. These two integrated systems give a relevant contribution to the relatively high cost of the total Xenon headlamps light machines.

In the future a power reduction to 25W is foreseen, lower than the minimum limit to have a mandatory automatic leveling and a washing system in many countries. This will reduce the cost of the light machine, possibly increasing the diffusion of this technology in lower-priced car segments than the ones presently using Xenon lamps.

LED lamps, an alternative new technology, are already available in the market, but their mass production is foreseen in no less than 10 years due to the current additional technical features needed and the cost implied. A controlled bi-directional air flow system, including fans, is in fact needed in order to keep the right environment temperature and to have a good efficiency. This has a severe implication on the system reliability and on its cost.

Here is a brief explanation, how Xenon lamps work:

In order to have the ignition of the Xenon gas on the lamp, two main circuits are used:

the igniter, whose task is the increasing of voltage and current in order to create arc inside the Xenon gas and turn the lamp on

the ballast, that provides the right power and energy to the igniter circuit for the ignition (also in case of low battery level and cold temperature conditions)

In the schematic circuit below, C1 and C2 are the boost capacitors (also referred to as ballast capacitors) while C3 is the igniter capacitor. In the market there are also layouts including one boost capacitor only:

Figure 1: Schematic of the ballast and igniter circuits on high intensity discharge - (HID) - Xenon headlamps

EXPERIMENTAL METHODS The instruments, tools and methods used to measure the performance of the SMD and leaded film capacitors are described below together with the specific measured parameters.

Agilent E4980, HP4284A Precision LCR meter and HP4192A Impedance Analyzer (1 kHz and 1 Vrms): Capacitance (C), dissipation factor (tan δ), Equivalent Series Resistance (ESR).

Charge/discharge equipment (Figure 2): δv/δt withstanding. The capacitor is charged with a DC supply (Vo) up to the spark gap (FS) discharge voltage level, which is lower than Vo. The discharge current flows through the capacitor. The below schematic permits, thanks to very low parasitic resistance, to maximize the current value. R2 and L1 are parasitic values.


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Figure 2: Charge/discharge circuit with spark gap (FS)

Kikusui TOS9201: First Breakdown Voltage - FBDV - test equipment.

The test is carried out applying the following voltage ramp (Figure 3) on the capacitor:

Figure 3: Voltage ramp-up used in the FBDV test

Weiss VT180 and Heraeus HC2020 humidity chambers: Damp heat tests.

The following equipment was used to measure SMD ceramic capacitors and for comparative film capacitor measurements with respect to the Boost application.

An HP4284A Precision LCR meter (1 kHz and 1 Vrms) was used to determine Capacitance (C) and Dissipation Factor (tan δ). Equivalent Series Resistance (ESR) was measured with an HP 4294 Impedance Analyzer. Dielectric breakdown measurements were made with a Quadtech Guardian 12kV HiPot Tester. A Saunders and Associates 4220A tester was used to determine TCC/VCC/IR. HALT testing was done using a MicroInstruments CE9051 Chamber. Pulse Testing was performed using a solid state switching circuit to charge and discharge the capacitors through separate resistors. The values of the resistors were selected to control the dV/dT rates stated. The modulus of rupture (MOR) and break strength data was obtained through testing in accordance with AEC-Q200 Rev. E Method - 003 "Passive Component Surface Mounted Ceramic Capacitors Beam Load (Break Strength) Test"

SMD and LEADED FILM CAPACITORS IN IGNITER AND BOOST CIRCUITS 1 - Igniter application: Design and performances of new naked stacked SMD PEN film capacitors A dedicated Naked Stacked SMD film capacitors range, for this special application, has been developed:

Figure 4: HID stacked naked SMD PEN capacitors

The capacitance range in the application is presently between 70 and 120 nF at 1.000 Vdc. In the Table 1 below the main igniter capacitor characteristics are listed:


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Igniter capacitor electrical characteristics Capacitance value 70 nF – 80 nF – 120 nF

Size 50.40 - 45.43 - p10 - p15 Max temperature of the reflow 245°C Operating temperature (3000h) -40 °C to +155 °C Operating temperature (300h) +155 °C to +170 °C

dv/dt up to 8.500 V/μs Max allowed voltage during ignition 1.250 Vdc

Number of ignitions 200.000 Damp heat 60 °C – 95 % R.H. 500h Max ΔC = ± 7 %

Table 1: Main requirements of the igniter capacitor Igniter capacitor needs to withstand high voltages, very high peak current (8.500 V/µs), high working temperature, a LF (Lead Free) reflow process1 and critical humidity environment. Especially due to the very high peak current requirement, stacked technology has been chosen instead of wound technology. This for two main reasons:

a stacked capacitor is built of several hundred independent layers (small capacitors) all put in parallel. If one layer disconnects because of high electric stress, the capacitance is slightly reduced, but the remaining layers’ connections are safe. In a wound capacitor on the contrary, in case a layer disconnects, the capacitance value does not change, increasing the current through the remaining contacts (avalanche process) leading at the end to an open capacitor.

thanks to the capacitance decrease in case total / partial disconnection of a layer in a stacked capacitor, it is quite easy to detect potentially weak capacitors during the electrical testing included in the manufacturing process or during the assembling / final testing in Customer’s process.

Considering the requirement of the working temperature up to 170 °C, PEN has been chosen as dielectric.

In the following picture both voltage and current waveforms applied on the igniter capacitors during the ignition are shown:

Figure 5: Voltage and current on igniter capacitor during the ignition of the Xenon lamp

The above graph demonstrates the great difference in terms of electrical stress between the ignition phase and steady working phase, after the lamp has been turned on. For this reason, the reliability of this capacitor is not measured in hours, but in ignition cycles. The typical requirement from the market is 100.000 to 200.000 cycles.

In the following graphs performance under high peak current stress is showed. It is important to underline that the current flows on a single metalized film capacitor instead of a double metalized one. This design choice has decreased the dimensions of the igniter capacitor:

Figure 6: single and double metalized technologies


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In order not to decrease the efficiency of the igniter circuit, high capacitance stability is required. In Figure 7 the distribution of capacitance deviation is showed after 200k cycles with a voltage of 1.000 V and a peak current equivalent to 8.500V/µs (600 A with a capacitance value of 70 nF):

Figure 7: Distribution of the capacitance deviation after a charge/discharge test at 1000 V and 8.500 V/µs

In order to check the trend of the capacitance deviation in relation to the number of ignition cycles, the following charge-discharge test has been performed with the same current value as in the preceding test (600 A on a capacitance value of 70 nF). According to Figure 8 the capacitance trend is quite linear in a semi-logarithm graph:

Figure 8: Trend of the capacitance value during the ignition cycles

Considering the harsh automotive environment (especially inside headlamps), several tests in severe humidity conditions have been carried out:

Figure 9 and 10: Humidity performances of the igniter capacitor (named HNS) in terms of capacitance and dissipation factor The above graphs show an increase of the capacitance value within 56 days. Humidity, with its high εr value and penetrating inside the capacitor, increases the capacitance value. A capacitance drop would be due to a de-metallization process causing a decrease of the active area inside the capacitor (not reversible process). The fact that no meaningful


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capacitance reduction vs. the starting value has been observed, underlines the optimum results obtained with this naked capacitor design.

The humidity withstanding has been improved increasing the capacitors’ compactness through the dedicated thermal treatment during the manufacturing process.

A critical parameter for the igniter capacitor is the voltage withstanding, especially after the LF reflow process. In order to monitor the igniter capacitor performance from this point of view, a voltage value is recorded to indicate the first°Ccurrence of partial discharges when a constant voltage ramp-up is applied on the capacitor (this procedure is referred to as First Breakdown Voltage - FBDV - test). What is measured in this way is not the real “break-down” of the dielectric, but only a partial discharge that, in some cases, can create only very small and brief current flow.

In the graphs in Figures 11 and 12, FBDV results have been recorded after reflow process with two different peak temperatures (233 °C and 245 °C). Considering that in the application the discharge voltage level of the spark gap is 800 Vdc with a tolerance of ± 20 %, the lower specification limit (LSL) inserted in the graph below, to evaluate the PPM performance, is 960 V. One of the most excellent successes of this design consists in the negligible differences, in terms of FBDV test performances, after the reflow process with different peak temperatures:

Figure 11 and 12: FBDV test on the igniter capacitor after a LF reflow with different peak temperatures (233 °C and 245 °C) 2 - Boost application: Design and performances of new naked wound SMD PEN film capacitors

For the Ballast application, another dedicated naked SMD PEN film capacitor family has been developed, focused on withstanding high voltage peaks during the ignition phase of the lamp. This capacitor family has rated voltage lower than peak voltage in the application. Therefore it offers smaller dimensions with respect to the standard general purpose stacked naked SMD PEN capacitors family.

The size aspect was the biggest challenge for a successful design as the available space on the board is very limited due to the continuous miniaturization activities running on automotive appliances.

Figure 13: SMD wound naked capacitors in PEN


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In the Table 2 below the main boost capacitor characteristics are listed:

Boost capacitor electrical characteristics

Capacitance value 270 nF - 1.200 nF Size 50.40 - 60.40 - 60.54

Max temperature of the reflow 245 °C Operating temperature range -55 °C to 125 °C

Max allowed voltage during ignition (60 ms) 480 Vdc Number of ignitions Up to 500.000

Damp heat 60 °C – 95 % R.H. 500h Max ΔC = ± 7 % Table 2: Main requirements of the boost capacitor

The main requirements are small dimensions, withstanding of voltage peaks, critical humidity environmental conditions, rapid change of temperature and LF reflow process1.

Wound technology was chosen on this application for its intrinsically good performances in withstanding voltage peaks. This intrinsic property is mainly explained by the fact that wound capacitors do not have a cutting surface as stacked capacitors. In this case the peak current is not critical, and so the risk described in the igniter section is extremely limited (overloading of current on not detached layers in wound capacitors). See Figure 14 here below where the V/I waveforms on the boost capacitors during the ignition cycle are plotted:

Figure 14: Voltage and current in the boost capacitor during the ignition of the Xenon lamp

Since the withstanding of voltage peaks and the dimensions were the main application requirements, R&D efforts have been focused on these characteristics, with the final result of reducing the film thickness by about 33% vs. the one used in the general purpose SMD naked stacked PEN capacitor family. This reduces therefore dramatically the volume of the capacitor. This result has been obtained with R&D design activities in pre-treatment of film material, and in winding, pressing and thermal treatment manufacturing phases.

The simultaneous reduction of the volume shown in Figures 15 and 16 is highlighting the design improvements:

Figure 15: Increasing of the capacitance range in 60.54 size Figure 16: Volume comparison between stacked and wound


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In order to increase safety vs. voltage withstanding, FBDV tests have been carried out, as was done for the igniter capacitor:

Figure 17 and 18: FBDV test on general purpose stacked PEN SMD version compared to the new wound PEN SMD version The above comparison was made using the same film thickness (4µm) and therefore the same rated voltage (250 Vdc). According to Table 2, the peak voltage is up to 480 V. Therefore, from the graphs in Figures 17 and 18 it is evident that the general purpose naked stacked SMD version, rated 250 Vdc, is not able to work in this application while the new wound release is.

The importance to have stable FBDV test performances, before and after a LF reflow process, amplifies the correctness of the choice of PEN dielectric.

As in the case of the igniter capacitor, the capability to work in critical humidity conditions is extremely important for the boost capacitor design:

Figure 19: Humidity performance of the new naked wound SMD version (named SWN)

The boost capacitor’s working temperature is currently up to 125°C, but with the upcoming new 25 W version, the integration between the igniter and the ballast circuits might be an option. For this reason, the boost capacitor’s working temperature can rise up to 150°C, validating even more the choice to use the PEN dielectric3.

SMD CERAMIC CAPACITORS FOR BOOST CIRCUITS The integration of igniter and ballast in newer designs has limited the space available for the boost capacitor. This has increased the times and temperatures that capacitors will be exposed to as well as requiring circuit designs to dissipate heat. Stacked multilayer ceramic capacitors (KEMET Power Solutions) have been developed to address these needs. Stacking 2 MLCCs allows the capacitance to be doubled for a given pad space and the leads add significant mechanical robustness with respect to board flexure cracks as reviewed previously4. The performance of stacks made with 2 types of dielectric, X7R and NP0/C0G will be compared and contrasted to PEN film capacitors for these boost capacitor applications. The basic electrical properties, dimensions and breakdown voltage versus rating for the 3 capacitor types are shown in Table 3.


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Table 3: Basic electrical properties, ratings and dimensions for the capacitors evaluated

Both types of ceramic capacitor have higher capacitance density at 25°C compared to the film capacitor. The X7R has 5.93µF/cc compared to 1.07µF/cc for NP0/C0G and 0.689µF/cc for PEN. The breakdown voltage of the film capacitor is higher than the stacked ceramics. The rated voltages of the ceramic capacitors are based on reliability testing with continuous dc voltage higher than the rating (≥ 1.2X) applied at an elevated temperature of 125°C.

In this application the boost capacitor reaches a peak voltage typically < 450V at 0.16V/µsec followed by a rapid drop at 4.5V/µsec to a steady state voltage around 20% of this peak voltage. To test the capability of these capacitors it was therefore necessary to develop a test based on this application. Samples of 25 capacitors of each type of ceramic were exposed to 90.000 pulses to a peak voltage of 430 V at 25°C and 150°C respectively. In all cases no failures ocurred during this pulse testing indicating that all these capacitors tested can potentially perform in this application. However, the temperature may exceed 125°C and reach up to 150°C for a few hundred hours and this is a concern with respect to how these capacitors will perform particularly with DC voltage applied. The effect higher temperatures to 150oC and dc voltage on characteristic properties of these capacitors such as capacitance, insulation resistance (IR) and electrical series resistance (ESR) were therefore evaluated.

The temperature coefficient of capacitance (TCC) for the 3 capacitor types measured at a nominal voltage of 1 Vrms, 1 kHz is shown in Figure 20.

Figure 20: TCC of the different capacitor types

The X7R capacitance is reduced by 33% at 150°C, the NP0/C0G exhibits no significant change and the PEN increases by about 5% compared to 25oC. To determine the effect of voltage these capacitors were re-measured with 200 Vdc applied. This temperature coefficient and voltage coefficient (TCVC) of capacitance are shown in Figure 21.


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Figure 21: TCVC at 200 Vdc of the different capacitor types The X7R capacitance loss increases to 55% of capacitance at 150oC with 200 Vdc applied whereas the NP0/C0G and PEN capacitance show no significant changes with respect to the values at 25oC. The voltage coefficient of capacitance at 25oC (VCC) was also measured at higher voltages of 250 V and 430 V as shown in Figure 22.

Figure 22: VCC of the different capacitor types Applying dc voltage has virtually no effect on the capacitance of the PEN or NP0/C0G but for the X7R capacitance is reduced by 77% at 430V. For this reason the nominal capacitance of the X7R has to be far higher than the NP0/C0G or PEN for any given boost capacitor application. The insulation resistance at different temperatures up to 150°C was measured for all 3 capacitor types and is shown in Figure 23.

Figure 23: IR vs. Temperature of the different capacitor types


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The average insulation resistance of the PEN and X7R measured at rated voltage for 60 seconds is lowered to 0.17 GΩ and 0.29 GΩ at 150°C respectively. After reaching a minimum of 4.88 GΩ at 125oC the NP0/C0G recovers to 12.28 GΩ at 150oC. At this temperature the C0G/NPO is over 40X lower leakage than the X7R and over 70X less than the PEN.

The ESR of the capacitors was measured over the range 40 Hz to 10 MHz at a temperature of 25°C as shown in Figure 24.

Figure 24: ESR of capacitors at 25°C

It is important to have a low ESR in order to reduce heat on applying current since the power dissipated Pw = I2R. The ESR of the NP0/C0G is considerably lower than the other capacitor types at 25°C over a broad frequency range.

No failures occurred in any of these capacitor types following exposure of 10 samples of each through a 248°C Pb-free solder reflow profile or when 40 samples of each were tested through 85% relative humidity at 85°C for 250 hours with 200 Vdc applied.

As mentioned earlier the boost capacitor circuit assembly has to be designed to effectively dissipate heat. One way of addressing this is to use an insulated metal substrate to allow heat to be more effectively conducted away from the assembly. However, this presents some technical challenges for the ceramic capacitors related to thermal shock cracking due to coefficient of thermal expansion (CTE) mismatch. This is because insulated aluminum substrates (IAS) have CTE ~ 23PPM/oC that compares to ~15 PPM/oC for FR4 and ~10 PPM/oC or less for MLCC1. Although the leads add additional compliancy to the ceramic capacitors it is important to test their thermal shock performance when mounted on substrates with high CTE. For this reason 30 capacitors of the 2 ceramic dielectric types were mounted on IAS and tested through 500 cycles of thermal shock from -55 to +150°C with a 40°C/min transition between these temperatures. The results of IR testing before and after this thermal shock are shown for the X7R and NP0/C0G in Figures 25 and 26 respectively.

Figure 25: Results of 500 cycle thermal shock testing for X7R


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Figure 26: Results of 500 cycle thermal shock testing for NP0/C0G

The X7R had several low IR shorts after thermal shock testing whereas the NP0/C0G had no failures. The X7R shorts were confirmed to be due to thermal shock cracks across active electrodes of opposed polarity by post test destructive physical analysis. The much higher break strengths and modulus of rupture (MOR) for the NP0/C0G MLCC compared to X7R (Figure 27) are believed to contribute to this robust thermal shock performance.

Figure 27: Comparison of Break strength and MOR of NP0/C0G and X7R MLCC The NP0/C0G has more stable capacitance compared to the X7R with respect to temperature and voltage as well as being more resistant to thermal shock failure on insulated aluminum substrates. The characteristic performance of the NP0/C0G capacitor is more similar to the PEN film capacitor in many respects. However, unlike the PEN film capacitors the ceramic capacitors do not exhibit any self healing. Although all 3 capacitor types performed well in pulse testing, their ability to sustain excessive continuous dc voltage at 150°C was evaluated by highly accelerated life testing (HALT). Samples of 20pcs from each type of capacitor were HALT tested to failure at 300Vdc and 500Vdc for 92 hours as shown in Figures 28 and 29 respectively. It should be noted that this is a highly accelerated test compared to the steady state voltage of around 100 Vdc that the parts are typically subject to after the initial ignition pulse.


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Figure 28: HALT Test at 300Vdc, 150°C

Figure 29: HALT Test at 500Vdc, 150°C

At 300 Vdc there were no failures detected in any of the capacitor types. At 500 Vdc the film capacitor showed some failures but this is due to the nature of the test that registers a failure when the current exceeds 500 µA. Since the film has a self healing mechanism if current had continued to be applied, the failures should heal with no detriment to the performance of the capacitor. However, although most of the ceramic capacitors completed HALT testing at 500 Vdc with no failures there were some failures recorded in both the X7R (2/20) and NP0/C0G (2/20). To determine if these failures represent a potential reliability issue the following analysis was performed. The first failure was recorded at 1.477 minutes (24.6 hours) for the NP0/C0G. Although we did not reach a mean time to failure (MTTF) for the ceramics in this testing we can use the Prokopowitz Vaskas equation to calculate some failure rates at 150°C at lower voltages by making the following assumptions. Since there is no change of temperature the mean time to failure at the lower voltage, t1 = (V2/V1)n x t2 where V2 is high voltage with mean time to failure of t2 and V1 is the lower voltage. If we set these values so t2 = 24.6 hours, V2 = 500V, t1 can then be calculated at V1 = 100V, that approximates to the steady state voltage, for various values of n. In recently published work5 we determined n = 9 for similar types of C0G MLCC. Using this value of n gives a t1 = 4.8 million hours. Using a far lower voltage acceleration factor, n = 3 gives a t1 = 3075 hours that is 10 X longer than the part will be exposed to at this temperature and continuous voltage.

The NP0/C0G capacitors show similar performance characteristics to PEN film capacitors accept they have lower ESR. The X7R capacitors have higher capacitance at 25°C but this is significantly lowered when higher temperatures and DC voltage is applied. The X7R capacitors are more prone to thermal shock cracking when placed on high CTE insulated metal substrates compared to NP0/C0G. Both types of ceramic capacitor have higher capacitance density than the PEN film capacitor so allow the size required for the boost capacitor to be reduced. Unlike film capacitors neither type of ceramic capacitor exhibit self healing but pulse and HALT testing indicate they will have sufficient reliability in the boost capacitor application.

No Failures @ 92 hours


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SUMMARY HID technology in automotive lighting systems requires extremely high performance and reliability, at a component level in particular. KEMET is currently serving this demanding market, for igniter and boost applications, with naked SMD and leaded film capacitors, a technology that has proven to be in line with the automotive reliability needs through the last 10 years.

Evolutions and new trends in automotive market might anyway, in the medium-term future, require new strong miniaturization steps of the circuits present in HID applications. This might come due to the constantly increasing electronics density in automobiles and/or from price pressure from the market.

KEMET is therefore moving ahead not only in the development of the current technology offered (SMD and leaded film capacitors), but is getting prepared to offer automotive HID lamps producers a different technology (MLCCs) as an option. The data outlined in this paper proves that MLCCs developments are very promising, showing interesting advances from the electrical and environmental perspectives.

Here below a table showing the main advantages of each state-of-the-art technology for HID applications described in this paper:

Technology Main advantages

Naked SMD and leaded film capacitors

• 10-year field proven reliability • working temperature for the igniter

capacitor up to 170 °C • Robustness Vs. vibrations • Robustness Vs. thermal shocks • Self-healing • High dV/dt

KPS stacked ceramic capacitors (NP0/C0G)

• Small dimensions with improved volumetric efficiency

• Reliable at high temperatures to 150°C • Lower ESR • Higher IR @ 150°C • Lead frame mitigates risk of flex, thermal

shock & vibration failures

BIBLIOGRAPHY 1. “Advances in Class-I C0G MLCC and SMD Film Capacitors”, Xilin Xu, Matti Niskala, Abhijit Gurav, Mark Laps, Kimmo

Saarinen, Aziz Tajuddin, Davide Montanari, Francesco Bergamaschi, and Evangelista Boni, Proceedings CARTS 2008, March 2008, Newport Beach, CA, page 5-6

2. “SMD naked film capacitor technologies for severe application environments and circuit functions”, Evangelista Boni, Davide Montanari, Luca Caliari, Fabio Bregoli, Luigi Barbieri, Francesco Bergamaschi, Proceedings CARTS 2011, March 2011, Jacksonville, FL.

3. “SMD naked film capacitor technologies for severe application environments and circuit functions”, Evangelista Boni, Davide Montanari, Luca Caliari, Fabio Bregoli, Luigi Barbieri, Francesco Bergamaschi, Proceedings CARTS 2011, March 2011, Jacksonville, FL, page 4, Table 3.

4. “High Capacitance Stacked Multi-Layer Ceramic Capacitors with Robust Performance”, Travis Ashburn, Tim Hollander, John Bultitude, John McConnell, Mark Laps, Abhijit Gurav, Lonnie Jones, John Prymak and Reggie Phillips, Proceedings CARTS Europe 2010, November 10-11, 2010, Munich, Germany, p 189-209

5. “Ceramic Capacitors and Stacks for High Temperature Applications”, Abhijit Gurav, Xilin Xu, Jim Magee, John Bultitude, and Travis Ashburn, Proceedings High Temperature Electronics Network (IMAPS), St. Catherines College, Oxford, UK, p30-38

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