Silicon Carbide Foam Filter

Silicon Carbide Foam Filter

Porosity: 80%-90%

With competitive price and timely delivery, HEBEI CANGCHEN sincerely hope to be your supplier and partner.

Cell Size: 7-45 PPI

• Custom sizes and standard sizes in stock
• Quick Lead Time
• Competitive Price

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Silicon Carbide Foam Filter is a high-performance filtration material with excellent high-temperature resistance (up to ℃), chemical corrosion resistance, and high mechanical strength. It is widely used in metal casting, chemical, and environmental fields. As a leading supplier and manufacturer of premium silicon carbide products, we can supply high-quality silicon carbide foam filters with various specifications and competitive prices, offering customized solutions to meet specific requirements.

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Silicon Carbide Foam Filter Data Sheet

Silicon Carbide Foam Filter Description

Silicon Carbide Foam Filter is an effective molten metal filter with a unique porous structure, effectively removing impurities and gases from molten metal and improving the casting quality. It offers excellent high-temperature resistance (up to ℃), chemical resistance, and high mechanical strength, making it ideal for filtering aluminum, copper, iron, etc. The common porosities are 10 PPI, 20 PPI, 30 PPI, and 40 PPI. Advanced Ceramics Hub supports customized solutions in sizes, thicknesses, and pore sizes for diverse industry and research applications.

Silicon Carbide Foam Filter Specifications

How to Choose the Right Size of the Silicon Carbide Foam Filter?

• Calculate the required effective surface area of the filter (area through which molten metal flows) using the formula S=G/R, where G is the total molten metal to be filtered, and R is the filter’s filtration capacity per unit area.
• Verify the effective area against the flow restriction area of the pouring system. The recommended ratio is 1:3 for ductile iron, and 1:2 for gray iron and nodular cast iron.
• Add the support edge area (typically 5-15 mm) to determine the total filter area needed, then choose the filter size and quantity based on the total area and model specifications.
• Alternatively, filter size and quantity can be determined by considering the molten metal weight, the number of inner runners, the filtration capacity, and the filter specifications.
• Thicker filters offer better strength and efficiency, but at a higher cost. For optimal performance, recommended thicknesses are: 15-22 mm for 40-75 mm size, 22-25 mm for 75-120 mm size, 25-30 mm for 120-150 mm size, and 30-40 mm for sizes above 150 mm.

How to Choose a Suitable Pore Size of the Silicon Carbide Foam Filter?

The selection of the silicon carbide foam filter’s pore size mainly depends on the material of the molten metal, pouring temperature, casting size, and the purity of the molten metal. Since different molten metal materials have varying flow characteristics, the choice of pore size can differ significantly.

• Ductile iron castings typically use 10 PPI or 15 PPI products.
• Gray iron and cast copper generally use 15 PPI or 20 PPI products.
• Aluminum alloy castings commonly use 20 PPI or 30 PPI products.
• Nodular cast iron typically uses 30 PPI products.

Silicon Carbide Foam Filter Filtration Capacity

Silicon Carbide Foam Filter Features

• High Thermal Stability: Can withstand high temperatures (up to ℃), making them suitable for molten metal filtration.
• High Strength: Offers excellent mechanical strength, ensuring durability during metal pouring.
• Good Filtration Efficiency: Effectively filters out impurities, improving metal quality.
• Low Pressure Drop: Ensures smooth molten metal flow while minimizing pressure loss.
• Corrosion Resistance: Resistant to corrosion from molten metals, extending filter life.
• Lightweight and Easy Handling: Despite their strength, they are lightweight and easy to handle.
• Porosity Control: Can be manufactured with controlled porosity for specific filtration needs.

Silicon Carbide Foam Filter Applications

• Metallurgy: Used in foundries to filter molten metals like iron, steel, and non-ferrous alloys, improving metal purity and casting quality.
• Casting: Used to refine the quality of castings, reduce defects like porosity, and enhance surface finish.
• Steel Industry: Helps in manufacturing high-quality steel by filtering molten steel before casting.
• Aluminum Casting: Widely used in aluminum and its alloys to remove impurities and improve casting integrity.
• Automotive Industry: Used in producing components such as engine blocks and other vehicles’ cast parts

Silicon Carbide Material Grades

• Reaction Bonded Silicon Carbide
• Pressureless Sintered Silicon Carbide
• Hot-Pressed Silicon Carbide
• Recrystallized silicon carbide
• Hot Isostatic Pressing Sintering Silicon Carbide
• Spark Plasma Sintering Silicon Carbide

Reaction bonded silicon carbide (RBSiC) is made by mixing SiC, carbon, and binder, then infiltrating with silicon at high temperature. The vapor-phase method reduces free silicon to under 10%, improving performance. The result is a silicon-silicon carbide composite (SiSiC), not pure SiC.

SiC powder + C powder + binder mixed → forming → drying → protective atmosphere for degassing → high-temperature silicon infiltration → post-processing.

Reaction Bonded SiC Advantages:

• Low sintering temperature
• Low production cost
• High material densification
• Carbon and silicon carbide framework can be pre-machined into any shape
• Shrinkage during sintering is within 3%, aiding dimension control
• Significant reduction in the need for finishing, ideal for large, complex components

Reaction Bonded SiC Disadvantages:

• Residual free silicon in the sintered body after processing
• Reduced strength compared to products from other processes
• Decreased wear resistance
• Free silicon is not resistant to corrosion from alkaline substances and strong acids (e.g., hydrofluoric acid)
• Limited usage due to corrosion susceptibility
• High-temperature strength is impacted by free silicon
• Typical usage temperature is limited to below -°C

Pressureless sintered silicon carbide refers to the densification sintering of samples with varying shapes and sizes at –°C without applying external pressure and using an inert gas atmosphere, by incorporating suitable sintering additives. The sintering process can be categorized into solid-phase sintering (SSiC) and liquid-phase sintering (LSiC).

Solid-Phase Sintering SiC (SSiC) Properties:

• High Sintering Temperature: Requires a high sintering temperature (>°C).
• High Purity Requirement: The raw materials must be of high purity.
• Low Fracture Toughness: The sintered body has lower fracture toughness and tends to undergo transgranular fracture.
• Clean Grain Boundaries: There is essentially no liquid phase, and the grain boundaries are relatively “clean.”
• Stable High-Temperature Strength: High-temperature strength remains stable up to °C without significant changes.
• Grain Growth: At high temperatures, grain growth is easy, leading to poor grain uniformity.
• High Crack Sensitivity: The material is highly sensitive to crack strength.

Liquid-Phase Sintering SiC (LSiC) Properties:

• Lower Sintering Temperature: Compared to solid-state sintering, the sintering temperature is lower.
• Smaller Grain Size: The grain size is smaller, with better uniformity of grains.
• Improved Fracture Toughness: Due to the introduction of a liquid phase at the grain boundaries, the fracture mode shifts to intergranular fracture, significantly improving fracture toughness.
• Additive Influence: Uses multi-component eutectic oxides (e.g., Y2O3-Al2O3) as sintering additives, promoting densification.
• Reduced Crack Sensitivity: Liquid-phase sintering reduces the material’s sensitivity to crack strength.
• Weakened Interface Bonding: The introduction of the liquid phase weakens the bonding strength at the grain boundaries.

Pressureless sintered boron carbide combines high purity and the excellent mechanical properties of boron carbide for use in both ballistic armor and semiconductor manufacturing.

Hot-Pressed SiC Advantages:

• Enables sintering at lower temperatures and shorter times, resulting in fine grains, high relative density, and good mechanical properties.
• The simultaneous heating and pressing facilitate particle contact diffusion and mass transfer.
• Suitable for producing silicon carbide ceramics with good mechanical performance.

Hot-Pressed SiC Disadvantages:

• The equipment and process are complex.
• High demands on mold material.
• Limited to producing simple-shaped parts.
• Low production efficiency.
• High production costs.

Recrystallized Silicon Carbide (RSiC) is a pure silicon carbide ceramic made via high-temperature evaporation-condensation, with a porous, high-strength structure, offering excellent heat, corrosion, and thermal shock resistance, used in kiln furniture, nozzles, and chemical components.

Recrystallized SiC Properties & Applications:

• The sintering process, based on evaporation-condensation, doesn’t cause shrinkage, preventing deformation or cracking.
• RSiC can be shaped through methods like casting, extrusion, and pressing, and its shrinkage-free firing allows for precise dimensions.
• After firing, recrystallized RSiC contains 10%-20% residual porosity, primarily influenced by the green body’s porosity, providing a foundation for porosity control.
• The sintering mechanism creates interconnected pores, making RSiC suitable for applications in exhaust and air filtration.
• RSiC has clean grain boundaries, free from glass and metal impurities, ensuring high purity and retaining SiC’s superior properties for demanding high-performance applications.

Hot Isostatic Pressed Silicon Carbide (HIPSiC) is a high-performance ceramic produced via hot isostatic pressing. Under high temperature (around ℃) and uniform high-pressure gas (typically argon), silicon carbide powder is densified into a nearly pore-free structure.

Hot Isostatic Pressed SiC Advantages:

• Uniform mictrostructure and fine grain size
• Low sintering temperature and time
• High density
• High purity and component control

Hot Isostatic Pressed SiC Disadvantages:

• Difficult packaging technology
• High initial investment and operational costs
• Limited for large or complex shapes

Spark Plasma Sintering Silicon Carbide is a high-performance ceramic produced using spark plasma sintering technology. This process employs pulsed current and pressure to rapidly density silicon carbide powder at relatively low temperatures (around - ℃) in a short time.

Spark Plasma Sintering SiC Properties:

• Faster heating rate
• Lower sintering temperature
• Shorter sintering time
• Fine and uniform grains
• High density
• Appliable for small and precision parts

Silicon Carbide Ceramic Machining

Silicon Carbide (SiC) is a highly durable ceramic material with extreme hardness (9.5 Mohs), thermal stability (up to ℃), and resistance to wear, corrosion, and high temperatures. However, machining silicon carbide presents challenges due to its extreme hardness and brittleness. Specialized techniques and tools are required to achieve precise cuts and shapes. The common machining methods include:

• Diamond Grinding: Diamond tools are used to achieve smooth surfaces and precise shapes.
• Laser Cutting: Suitable for cutting thin SiC materials. Laser cutting offers high precision and minimal material waste.
• Ultrasonic Machining: This method uses high-frequency vibrations to cut and shape brittle materials like SiC without causing cracks.
• Electrical Discharge Machining (EDM): A non-traditional method that uses electrical sparks to remove material, effective for hard ceramics like SiC.
• Grinding With CBN Tools: Cubic boron nitride (CBN) tools can be used for grinding SiC, providing an alternative to diamond grinding for certain applications.
• Water Jet Cutting: Using a high-pressure jet of water, sometimes with abrasive particles, to cut through SiC. This method is useful for cutting complex shapes.

Silicon Carbide Ceramic Packaging

Silicon Carbide ceramic products are typically packaged in vacuum-sealed bags to prevent moisture or contamination and wrapped with foam to cushion vibrations and impacts during transport, ensuring the quality of products in their original condition.

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To customize your silicon carbide foam filter, please provide the following details:

• Dimensions: Specify the length, width, thickness, or diameter.
• Shapes: Rectangular, square, round, or customized.
• Cell Size: Choose the right cell size base on the application (e.g., 10 PPI, 15 PPI, 20 PPI, 30 PPI, etc.)
• Molten Metal Type: Specify the molten metal (e.g., iron, steel, aluminum, copper, etc.)
• Pouring Temperature: Indicate the pouring temperature of the molten metal.
• Filtration Efficiency: Indicate the level of the filtration efficiency required.
• Quantity of the products you need
• Alternatively, you can provide a drawing with your specifications.

Once we have these details, we can provide you with a quote within 24 hours.

We carry a wide variety of silicon carbide ceramic products in stock, and for these, there is generally no minimum order requirement. However, for custom orders, we typically set a minimum order value of $200. The lead time for stock items is usually 1-2 weeks, while custom orders usually take 3-4 weeks, depending on the specifics of the order.

Primarily used for molten metal filtration (Al/Cu/Zn alloys) to remove impurities and gases, improving casting quality.

Standard: 10 PPI, 20 PPI, 30 PPI (customizable 7-45 PPI).

≥95% removal for impurities >20μm (varies by pore size).

• Higher mechanical strength
• Better thermal shock resistance
• Reusable 3-5 times.

Advanced Ceramic Hub, established in in Colorado, USA, is a specialized supplier and manufacturer of silicon carbide ceramic (SiC). With extensive expertise in supply and export, we offer competitive pricing and customized solutions tailored to specific requirements, ensuring outstanding quality and customer satisfaction. As a professional provider of ceramics, refractory metals, specialty alloys, spherical powders, and various advanced materials, we serve the research, development, and large-scale industrial production needs of the scientific and industrial sectors.

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类似文章

Over the past decade, the incorporation of Silicon Carbide (SiC) in power, LED, and RF devices has steadily increased, allowing for this technology to progressively mature in all aspects. This is due to the many desirable qualities this wide-bandgap substrate has relative to its silicon (Si)-based counterparts — the ability to achieve much higher power per given die size, at much faster switching speeds, and with excellent thermal performance.

Contrary to popular opinion, all of these characteristics actually lead to the employment of fewer power devices, magnetics, and respective gate drivers, actually yielding a lower system cost when compared with Si-based high-power designs (e.g., OBCs, string inverters). From growing the boules to the fabrication and device packaging, the stringent qualification process for SiC devices has been thoroughly developed. Moreover, with over 30 years of legacy in SiC, Wolfspeed power devices have experienced over 6 trillion field hours — reaching a point at which data on long-term reliability can be adequately ascertained.

This article dives into the qualification process of SiC components and how this yields high extrinsic device reliability while looking into the accumulated data on long-term wear-out for SiC. There is an additional discussion regarding industry capacity and continuity of supply to support the ever-growing demand for SiC-based devices.

Why Silicon Carbide?

The SiC power device has steadily infiltrated a number of industry verticals for power devices from solar power conversion, power grid systems, industrial motor conversion, and on-board charging for EVs. The proliferation of SiC-based MOSFETs and diodes are for a good reason — when compared with standard Si-based power devices (e.g., IGBTs, SJ MOSFETs), SiC devices offer half the losses, at a third of the size, and with 20% lower system costs. The higher power conversion per die size is due to the fact that SiC has nearly 3× the bandgap, 10× the breakdown electric field, over 2× the thermal conductivity, and 5× the power density when compared with Si.

Further reading:
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As more and more designers are currently, or have in the past, designed with SiC, several fundamental long-term effectiveness questions based on SiC quality, reliability, and supply crop up. Some frequently asked questions include:

• What qualifications do you apply to SiC?
• How do I know if SiC is reliable?
• What capacity will the SiC market need and will it have enough?
• How do you predict long-term wearout with SiC?

These are critical questions for vendors to ask in order to position themselves strongly within the power device market long term. The Si substrate has a familiarity within the industry from its fabrication to packaging and device-level completion — the technology has been able to mature over 60 years in the fab and the field. However, this does not outweigh SiC in the power device market. Wolfspeed has over 30 years of legacy with SiC, from delivering the world’s first SiC MOSFET in to being the only vertically integrated SiC manufacturer from growing the SiC boules to packaging die — all while steadily driving up voltage and current ratings, increasing wafer diameters to bring down cost per unit, and meeting stringent industry and automotive qualifications. The massive benefit of this focused effort over three decades? The collection of relevant data to perform in-depth reliability analysis comparable with that of Si.

A basic glance at quality and reliability: The bathtub curve

Reliability engineers are familiar with the basic bathtub curve to understand the varying regions of device failures (Figure 1). The first region (Region I) of the bathtub curve includes wear-in failures, or “infant mortality,” and is often dependent on rigorous device qualification. Region II of the bathtub curve relates to the steady state, or field failure rate with constant (random) failures such as external stressors that lead to failures. Finally, Region III of the curve relates to long-term wear-out of the device with accumulation of damage over time. Each of these regions of the bathtub curve correlate to different types of deterioration modeling. In other words, the three areas that the market cares about involve the following:

1. Extrinsic failures in the early life of the device
2. Observed failures during the steady-state field life of the device
3. Intrinsic failures that occur as the device ages

For the power device, the first region relies on qualification testing. The second region relies on device hours (e.g., 1,000 hours, 10,000 hours, 1 million hours) in the field to accumulate sufficient data to acquire a failure in time (FIT) rate. The third region relies on lifetime prediction models and mean time to failure (MTTF) calculations.

Extrinsic reliability: SiC-specific potential failure mechanisms for infant mortality

SiC MOSFETs involve several salient features that, when optimized, offer high quality and more reliability. These include:

• The SiC epitaxial layer (e.g., defects, thickness, doping)
• MOS channel (e.g., inversion-layer mobility, gate dielectric)
• Edge terminations
• Implantation/doping
• Ohmic contacts

The two potential failure modes of a SiC device are related to blocking voltage and gate voltage. Figure 2 shows the common failure mechanisms in SiC devices as well as some industry reliability tests to ensure proper operation of the MOSFET.

Gate oxide breakdown

Gate oxide breakdown can occur in SiC MOSFETs due to the smaller thickness of the gate oxide layer combined with the application of a higher electric field relative to Si-based devices. This can cause the threshold voltage to increase over long periods of time. However, this problem is sidestepped when MOSFET gate voltage is regularly switched between on and off states as the threshold voltage reverses during the switch.

Edge termination breakdown

In planar structures, breakdown voltages at planar junctions can limit the potential reverse-bias blocking capability of SiC MOSFETs due to an electric field crowding effect. With this effect, the electric field becomes spatially non-uniform and causes crowding at the device periphery. Effective edge termination structures can mitigate this effect and increase device reliability. In most devices, the blocking voltage does not reach the ideal breakdown value for one of two reasons: defects in the active area or the electric field crowding effect. There is, however, a balancing act between edge termination length (termination area) and material cost. It is therefore optimal to strike a balance between the two.

Intermetal dielectric leakage/breakdown

The electrical and thermal performance of the interconnect in power devices become more challenging as device dimensions become smaller. The intermetal dielectric (IMD) breakdown relates to the IMD leakage current that occurs in the event of dielectric breakdown due to a high voltage pulse or continuous power. This is typically tested with the time-dependent dielectric breakdown (TDDB) test in order to screen out defect-related breakdowns that can lead to infant mortality.

Steady-state field reliability: Silicon Carbide-specific potential random failure mechanisms

Neutron collisions

More often than not, the random failure mechanism for an already-qualified SiC device would be due to cosmic radiation. Terrestrial neutron irradiation occurs when neutrons collide with lattice atoms in the power device; this causes atoms to recoil and protons and/or neutrons to be emitted. Charges spike along these trajectories, leaving ionization trails that are not negligible — on the order of micrometers, which is comparable with epilayer thickness. The current transients that are induced by the neutron collision can cause failures in both bipolar and MOSFET-type SiC devices. In the bipolar NPN, bipolar turn-on can occur, causing burnout. In the MOSFET, charge accumulation can occur, causing a gate oxide failure.

The SiC device has an intrinsically higher reliability when compared with Si counterparts (e.g., IGBTs) due to the relatively smaller die size — there is far less physical area to get hit with a neutron bomb. As demonstrated by the graph in Figure 3, the failure rates increase proportionally with device area while the failure rates also decrease as voltage rating increases. This is the main failure mechanism at steady-state, particularly for high-altitude applications such as aerospace, high-altitude power installations, or even an EV driving around a mountain.

The first third of the bathtub curve: How are Silicon Carbide devices qualified?

With these common failure mechanisms in mind, Wolfspeed utilizes proven industry-standard testing to ensure the SiC devices are of the utmost quality prior to releasing them (Figure 2). This includes the qualification testing across large samples sizes in different lots to ensure a 90% confidence, or <1% failure rate. The product qualification that the SiC devices undergo ensures a high extrinsic reliability.

Wolfspeed leverages industrial (JEDEC) and automotive standards (AEC-Q101) that were constructed around silicon. The AEC-Q101 standard is generally more stringent than the JEDEC: The automotive standard requires 77 samples to be tested across three separate lots, while the JEDEC industrial standards require 25 samples across three lots. The AEC standards require the high levels of electrical and optical screening available and also monitor drift and shift within the lots under test. The major industry consortia including JEDEC, IEC, AEC, and JEITA are all actively developing SiC-specific standards to meet the needs for SiC technology and customer base. Wolfspeed is integrally involved in this process, working with subcommittees and task groups on SiC reliability and qualification testing.

Typically, a higher failure rate is seen at the extrinsic part of the bathtub curve, as this is the stage where faulty components are screened out. Table 1 lists the typical product qualification that a SiC device undergoes at Wolfspeed. Table 2 lists how these stress tests relate to performance for devices that require a high drain bias, high altitude, high humidity, high gate bias, or third-quadrant operation — each of these requirements relate to specific potential failure mechanisms. A high blocking voltage requires a high electrical field reliability, while a high gate oxide voltage needs a high gate oxide reliability. A high switching speed necessitates a high threshold voltage (VGS(th)) stability, high body diode is requisite for third-quadrant operation, and finally, there is a need for high terrestrial neutron reliability for high-altitude applications.

Table 1

Typical Product Qualification

Stress TestSample Size Per Lot# of LotsReference StandardRequirements/DescriptionAccept on # FailedHigh Temperature Reverse BiasHTRB773MIL-STD-750-1 M Method A hours at Vmax and Tcmax0High Temperature Gate BiasHTGB77 each
Vgs>0 and Vgs<03JESD22 A- hours at Vmax and Vgasmin and Tcmax0Temperature CyclingTC773JESD22 A- cycles Ta_max/Ta_min0Unbiased Highly Accelerated Stress TestUHAST773JESD22 A- hours at 130C and 85% RH0High Humidity High Temperature Reverse BiasH3TRB773JESD22 A- hours at 85C, 85% RH with device reverse biased to 100V0Intermittent Operational LifeIOL773MIL-STD-750 M cycles, 5 minutes on/5 minutes off, devices powered to ensure DTJ≥100C0Destructive Physical AnalysisDPA23AEC-Q101-004 Section 4Random sample of parts that have successfully completed H3TRB and TC0Time-dependent Dielectric BreakdownTDDB---Apply high gate voltage and test time to failure-Negative Bias Temperature InstabilityNBTI---Measure of threshold voltage shift with time-High Temperature StorageHTS--- hours Tstorage_max-Low Temperature StorageLTS--- hours Tstorage_min-Vibration----Sinusouidal sweep at nominal g (e.g., 5 g), # of hours per x, y, z axis-Mechanical Shock----Half sine pulse at high g (e.g., 30g), # of times in the x, y, z direction-

Table 2

Potential Failure Mechanisms and Corresponding Standard Tests

RequirementGate Oxide BreakdownSiC BreakdownBipolar NPNEdge Termination BreakdownThreshold Voltage DriftIncreased resistance and Reduced Current FlowHigh drain biasHTRB, ALT-HTRBHTRB, ALT-HTRBHTRB, ALT-HTRBHTRB, ALT-HTRBHigh altituden-irradiated HTRBn-irradiated HTRBn-irradiated HTRBHigh humidityTHBTHBHigh gate biasTDDB, HTGBNBTI, PBTI3rd quadrantBody diode HTOL

The middle of the bathtub curve: FIT rates

Observed failures

As stated earlier, Wolfspeed’s legacy in SiC has allowed the compilation of massive amounts of data — over 6 trillion field hours. From this data, FIT rate analysis has been performed on various Wolfspeed SiC devices, as shown in Table 3. While qualification is paramount to ensure basic field reliability, the failures that occur post-qualification truly dictate the viability of the supplier and the quality of the technology. The FIT rates are calculated according to industry standards, wherein the first three months of sale are discounted, the actual field hours are ascertained by factoring in when the device is not being used, and the failures due to cosmetic reasons (e.g., part returns) are discounted from the calculation for accuracy.

As seen in the table, the Wolfspeed FIT rates are typically below 5% ppb and decrease with an increase in field device hours. For this reason, the C6D diode appears to have the highest FIT rate, as it is at the tail end of the extrinsic part of the bathtub curve as a relatively new product.

Table 3

Wolfspeed SiC Power Device Field Reliability

TechnologyFielded Device Hours
(billions)FIT Rate
(valid field failures per billion device hours)C3Dxxx060 Diode.05C4Dxxx120 Diode.2C2M MOSFET.3C3M MOSFET512.3

The last third of the bathtub curve: How do I know if Silicon Carbide is reliable?

Blocking voltage and gate voltage long-term wear-out

The reliability testing of SiC devices and the various lifetime prediction models reveal the typical failure mechanism as the device ages. Wolfspeed employs common testing techniques for intrinsic wear-out by pushing the device to way over the maximum voltage rating or current rating for as long as possible and under the worst conditions possible. In Figure 4, a 1,200-V–rated Wolfspeed MOSFET is pushed up to 1,700 V and predicted hours of operation are obtained based upon this stress.

It should be noted that a 1,200-V–rated Si device generally rolls out at about 1,250 V; therefore, SiC devices generally have much more margin on their voltage ratings. Typically, a 1,200-V–rated SiC MOSFET is working on a 700- to 800-V bus — in this case, there are over 300 million hours of theoretical safe operation before the device fails from a failure mechanism due to blocking voltage. The very same process is applied to gate voltage with the TDDB method.

The TDDB method is another method of understanding the MTTF of power devices. This method subjects a population of MOSFETs to a constant bias at accelerated bias conditions as well as elevated temperatures. The failure time statistics are calculated and Weibull distributions are fit to the failure statistics to estimate lifetime. In Figure 4, a device with a gate voltage rating of 15 V is pushed to beyond 35 V and the probability of failure at the rated gate voltage becomes 50 million device hours. For the Gen3 650-V Wolfspeed MOSFETs, the MTTF stands at 70 million hours at 15-V continuous gate bias, showing a nearly identical gate reliability to the 1,200-V and 1,700-V MOSFETs.

Wolfspeed’s reliability bathtub curve calculator

In order to accurately assess all regions of the bathtub curve for their SiC devices, Wolfspeed developed a bathtub curve calculator that uses a mission profile as input. As shown in Figure 5, this profile is based upon field, qualification, and testing parameters such as VG, VD, TJ, altitude, and an hours histogram.

Power and packaging reliability

While much work is done to ensure the successful operation of a bare die SiC, the power and packaging is an unavoidable reliability issue for both Si and SiC alike. Typically, power packaging is the weakest link, especially at higher temperatures where the failures tend to be more intrinsic in nature (e.g., wire bonds and die attach rip off) The industrial power cycling test is the standard way to characterize the wire bond thermomechanical fatigue wear-out mechanism. It has been shown that the reliability performance is comparable between SiC and Si devices and that failures occur due to thermomechanical fatigue for both types of devices regardless of substrate material.

Understanding Silicon Carbide production capacity

Now that it is well established that SiC is both high-quality and high-reliability, with sufficient data to prove so, the question then pivots to the ability to supply these devices. Wolfspeed is fully invested in meeting present and future demand with a billion-dollar investment in the largest state-of-the-art dedicated SiC fabrication facility. This allows for 30× the original capacity of Wolfspeed, meeting the predicted world market growth of a tenfold increase in SiC semiconductors from to . This is a considerable growth in capacity when compared with other market suppliers of this semiconductor, wherein the closest supplier comes in to serve approximately $720 million of the $2.4 billion market estimate — meeting only a fraction of the capacity capability that Wolfspeed has (Figure 6).

Conclusion

SiC semiconductor applications are expanding greatly due to their excellent performance, power capacity, efficiency, die size, and relative cost-effectiveness. With over 30 years to compile past and present data, there is a large swath of information that allows for FIT rate analysis and extrinsic characterization, ensuring that SiC products are of high quality. This momentum is pushing standards committees to develop and evolve SiC-specific industrial standards, allowing for the continued maturity and utilization of SiC technology. Long-term wear-out and reliability analysis is continually being performed to better assess the failure mechanisms of these devices due to aging, and while it is not as established as Si devices that have had over 60 years of legacy, this data is maturing for more accuracy and dependability.

Wolfspeed is a leading vendor in SiC technology as the only vertically integrated SiC manufacturer with a significant investment in ensuring any and all SiC devices are robust prior to launch. This has also allowed for the continual progression of a strong support ecosystem with design software and tools to implement SiC.

With 6 trillion field hours of data to build upon, extended wear-out studies, and FIT rates in the single digits, Wolfspeed is leading the way on quality, long-term reliability, and safe use of SiC devices.

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