A medium-frequency transformer can be made to occupy only one-tenth the volume of a conventional transformer. Its heat output does not decrease accordingly; it must be dissipated through that layer of thermal compound. Anyone who has worked on power supplies understands this principle. Yet over the past two months, I have read more than a dozen articles by SST, and not a single one has given serious consideration to this layer of compound. NVIDIA included it in its power-supply white paper; Eaton obtained TÜV South certification; State Grid officially announced the commissioning of its first demonstration station; and even CCTV began reporting that “copper usage has dropped by up to 80%.” Everyone has taken chips, magnetic materials, topologies, and control systems apart and explained them in detail; the more impressive the parameters reported, the fuller the slides on a press conference become. That layer of compound has never appeared on any list. Today, let us focus on it.
Let’s first work out a calculation that is easily miscomputed.
The component that accounts for the bulk of the cost in SST is not SiC. Solid-state transformers consist of three stages: the rectification stage, the isolation stage, and the inversion stage. The component that drives the cost is the core device in the intermediate stage: the medium-frequency transformer. According to publicly available company statements, it accounts for 60%–70% of the total system cost and represents the most technically challenging aspect of the design. What makes it difficult? The same power must be transformed within a volume that is less than one-tenth that of a conventional transformer. The magnetic core material has essentially entered a completely new technological track: 50 Hz silicon steel sheets are discarded in favor of nanocrystalline materials or ferrites, raising the operating frequency to 10 kHz–100 kHz. As the frequency increases, the core cross-sectional area and number of turns can be reduced by two orders of magnitude, thereby reducing volume and weight; the trade-off is that iron loss, copper loss, and proximity effect loss all increase, while the available space for heat dissipation becomes even smaller.
Heat is the first thing to hit a wall.
Those who have built prototypes of this type share a common observation: heat arrives faster than one might expect. On the test bench, the epoxy odor often leaves a deeper impression than the data do. In a 1 MW-class high-frequency transformer, the heat flux density can reach around 15 W/cm³. At this level of density, air cooling has long since become obsolete, and liquid cooling is required. However, heat must be removed from inside the magnetic core and windings; the final pathway for dissipation is still the potting compound that encases them. Conventional epoxy potting compounds have a thermal conductivity of less than 0.5 W/(m·K). This figure was more than adequate a decade ago; today, it represents the ceiling.
| Rectifier Stage • AC/DC | Isolation Stage • DC/DC (Core) | Inverter Stage • DC/AC |
|---|---|---|
| ✅ SiC / IGBT Power Module S | ✅ Medium Frequency Transformer MFT S | ✅ SiC Power Module S |
| Filter Inductor A | Resonant Inductor / Capacitor S | Output Filter Inductor A |
| Driver Board (Isolated) A | Primary / Secondary H-Bridge S | Busbar / High-Voltage Connector A |
| Auxiliary Power Supply B | DC-Link Capacitor A | Complete Electronic Compartment B |
| Layered Busbar A | ||
| Isolation Sensor B |
The insulation phase is even trickier.
As the frequency increases, the electric field becomes more concentrated, causing the inception voltage for partial discharge to drop by approximately 30%. What does this mean? It means that a design that previously passed acceptance may no longer pass it now. On the 10 kV side, the lightning impulse must still withstand a voltage of 95 kV. If even a single air bubble remains in the cast layer, no matter how well the external shielding is constructed, it will be completely ineffective. Before applying the potting compound, vacuum degassing must be performed; this is not merely a matter of procedural rigor, because once a bubble is present, it becomes a breakdown path.
There is also one thing that is mentioned even less often.
Stress. Nanocrystalline magnetic cores are susceptible to mechanical stress; once subjected to compression, their performance deteriorates. The edges of the tape are also extremely sharp and can pierce through the insulation. The common engineering practice is to encase the core in a 0.2 mm layer of polyimide and then secure it with silicone. Even more problematic are thermal cycling. The linear expansion coefficients of copper, the magnetic core, and the potting compound can differ by more than tenfold. When subjected to repeated temperature swings from −40 °C to +180 °C, the first failures are often not in the chip itself, but in cracking of the casting layer and interfacial delamination. Three challenges: thermal conductivity, insulation, and resistance to thermal shock—all must be addressed simultaneously.
Where does the material route currently stand?
The mainstream approach remains the epoxy vacuum casting system. It offers Class H temperature resistance, is compatible with SiC operating conditions ranging from 20 to 150 kHz, provides good mechanical strength, and keeps costs manageable. Its drawback is high rigidity; because its coefficient of linear expansion does not match that of copper or magnetic cores, the formulation must include toughening agents; otherwise, cracking will inevitably occur during thermal cycling. Silicone-based materials follow a different approach: they have lower modulus and stronger heat-shock resistance, making them suitable for internal module protection as well as for magnetic cores that are sensitive to stress. The trade-off is that their baseline thermal conductivity is relatively low; thermal conductivity is enhanced by increasing the filler content. Nano-silica typically has a thermal conductivity of around 0.35 W/(m·K), alumina is around 0.55, and boron nitride can exceed 0.6 W/(m·K); this also raises the breakdown electric field strength, which, according to publicly available research, can reach 21–26 kV/mm. In terms of component selection, several key performance indicators are unavoidable: thermal conductivity must be at least 1.0, with the mainstream range falling between 1.2 and 2.0 W/(m·K); Class H temperature resistance of 180 °C; a breakdown electric field strength starting at 20 kV/mm; a CTI exceeding 600; low partial discharge capability; and UL94 V-0 certification with halogen-free requirements.
I’d also like to clarify something that is often confused.
Potting compound is not the same as thermal interface material. The thermal pad or thermal gel between a module and a heat sink serves to fill gaps and dissipate heat. Potting compound, by contrast, serves a different purpose: it encapsulates the entire internal structure, conducts heat from the inside out, and simultaneously provides both insulation and mechanical fixation. In SST products, these two functions coexist. When a solution combines both, it essentially indicates that the project has not been developed. The industry moves rapidly. Eaton, TGOOD, Envision, Sungrow Power Supply, Jinpan Technology, Sifang Co., Igor, Weiguang Energy, and Xinte Electric have all already brought their MW-level products to market, with applications concentrated in AI data centers, ultra-fast charging stations, and flexible distribution networks. Some institutions predict that this market will grow from a scale of tens of billions by 2026 to one trillion by 2035. Once product forms converge, the key differentiator will no longer be who launches first, but who can achieve mass production and sustain performance for a decade. One thing is certain now: by the time everyone realizes the importance of monitoring this layer of compound, the window for adjusting formulations will have already closed.
Verified JOME Engineering Grades & Specification Cross-Reference
To qualify an industrial-grade adhesive, potting compound, or thermal interface material for this application, compare verified Shanghai Jome Industrial Co., Ltd. (JOME) formulations below or explore our primary category hubs: Potting & Encapsulating Compounds and Waterproof & Conformal Coatings.
| JOME Grade / SKU | Polymer Chemistry & Cure | Key Verified Specification | Primary Industrial Application |
|---|---|---|---|
| JOMS 5715A/B | 2K Optically Clear Self-Healing Silicone Gel | Dielectric >18 kV/mm | Soft shock-absorbing gel | Zero stress | IGBT modules, SiC power devices, automotive sensors & MEMS |
| JOME 3113A/B | 2K Thermally Conductive Epoxy Potting Compound | 1.2 W/(m·K) | Shore D 80–85 | High voltage insulation | Medium-frequency transformers, solid-state transformers, coils |
| JOME 3108A/B / JOME 8222 | 2K Thin-Layer Clear Epoxy & 1K SMT Red Epoxy | Low viscosity capillary flow (3108) / Thixotropic dot (8222) | PCB encapsulation, semiconductor underfill & SMT wave solder |
| JOMS 521 / JOMP 410 | 1K Silicone Conformal Coating & Non-Yellowing PU | Solvent-free moisture/salt-spray barrier | -55°C to +200°C | PCBA conformal coating, smart utility meters, outdoor LED drivers |
Interactive Engineering Tools: Master Substrate & Thermal Cross-Reference Chart · Potting Volume, Mix Ratio & ΔT Calculator · Industrial Adhesive Manufacturer Comparison
Need Technical Data Sheets (TDS) or Trial Samples for Line Qualification?
Share your substrate pair, operating temperature, or target cycle time—only Email and Application / Part Code are required. Our R&D engineers reply within 24 hours.
Request free sample
-Speak with our material engineer
WhatsApp +86 18918756805
Matched JOME Industrial Formulations: For production bonding, potting, and sealing qualification in this application, evaluate 2-Part Thermal Conductive potting Silicone Gel （2.0W/mK）, Thermal Conductive Polyurethane Potting Compound（0.82W）, Thermal Conductive potting Silicone Compound(0.75W), and Thermally Conductive Epoxy Potting Compound（1.2W） (ISO 9001:2015 and CTI RoHS 2.0 verified; free engineering samples shipped via UPS freight collect).
Frequently Asked Engineering Questions
Q: Which JOME adhesive or potting grades are recommended for the importance of potting compound in sst solid-state transformer?
Depending on substrate pair, continuous operating temperature, and curing line constraints, Shanghai Jome Industrial Co., Ltd. (JOME) recommends evaluating JOMS 5715A/B, JOME 3113A/B, and JOME 3108A/B / JOME 8222. Review our full specification table on this page or request a customized formulation sample.
Q: Can JOME customize viscosity, cure speed, or thermal conductivity for our automated production line?
Yes. JOME's Shanghai RandD laboratory customizes A/B mix viscosity, thixotropic index, pot life, Shore hardness, and thermal filler loading (0.75 to 25.0 W/m·K) to match your dispensing equipment and environmental test standards.
Industrial Adhesive Categories, Matched Grades and Engineering Guides
Product and Application Categories: Thermal Conductive Bonding Adhesive · Thermal Conductive Grease · Epoxy Potting Compound · UV Potting Compound · Polyurethane (PU) Structural Adhesive · SMP Hybrid Structural Adhesive (MS Adhesive) · Sealant · SMP Hybrid Sealants (Silane Modified Polyether) · UV Curing Sealant · UV Cationic Epoxy Adhesive · Optical Clear UV Adhesive · Pre-coated threadlocker adhesive · Cylindrical retaining adhesive · Silicone · Polyurethane (PU) · Special · Fluorosilicone Sealant · Industry News Guides · Photovoltaic + Energy Storage Integration Guides · Hardware Accessories, Tools, Fasteners Guides · Semiconductor precision packaging Guides
Matched Industrial Adhesives: Silicone surface treatment agent primer coating agent · Single-component solvent-free elastic silicone rubber conformal coating · Thermally Conductive Epoxy Potting Compound（1.2W） · Single-component RTV silicone sealant (black, white, gray, red)-OEM · Clear long-term yellowing-resistant polyurethane encapsulation coating compound · Customized Thermal Conductive Pads with Various Thermal Conductivity Values(1.0-25.0 W/m·K) · High-strength 2-part epoxy structural adhesive · One-part highly elastic SMP Hybrid Structural Adhesive (MS Adhesive) · UV light-curing rapid fixation structural adhesive · 2K polyurethane structural adhesive · 2 – Part fluorosilicone sealant can effectively resist solvents, lubricants and gasoline · 638 Cylindrical metal bearing adhesive for fixation · Thermal insulation polyurethane structural bonding adhesive（2.0W） · Two-component high thermal conductivity filling sealant (8.0 W/mK) · Epoxy group microcapsule pre-coated threaded locking agent meets automotive industry standards. · Vehicle-grade transparent self-healing encapsulated silicone gel · 2K High-Temperature Resistant Epoxy Structural Adhesive · Clear shadowless UV glue is used for bonding glass and accessories · 2-Part Thermal Conductive potting Silicone Gel （2.0W/mK）
Technical Application Guides: Comparison Table of Core Characteristics of Three Types of Sealing Gels: Epoxy Gels, Silicone Gels, and Polyurethane Gels · Top Industrial Adhesive, Potting Compound & Thermal Interface Material Manufacturers: Engineering Comparison & OEM Sourcing Guide · Common issues with automotive power supply potting compounds: high viscosity, reduced strength, and poor heat dissipation · Requirements and Applications of Medical-Grade Adhesives (Endoscopic Capsules) · The gap between the copper tubing and the aluminum plate determines the upper limit of heat dissipation for the liquid-cooled plate · Adhesive Manufacturer & Supplier for Construction & Building · MS Polymer Adhesive and Sealant: Silane-Modified Hybrid Selection Guide · Silicone Potting Glue: Selection and Application Guide · Anaerobic Adhesive, Thread Adhesive Selection Guide: Instant Adhesive for Assembly and Maintenance · Advanced Adhesive Solutions for Smart Utility Meters (Electricity, Gas, & Water) · Advanced Thermal Interface Materials (TIM) Application Solutions: Telecom, Home Appliances, Automotive, and Mobile Devices · Introduction to Adhesives: Do You Really Understand Them All? — Adhesives Knowledge (Part 2) · A Comprehensive Guide to Structural Adhesives · Do you truly understand adhesives? An In-depth Guide to Adhesives Knowledge · What adhesive should be used for PE coating? · What adhesive should be used for PI-coated copper foil? · Which adhesive should be used to bond metal film materials? · Which adhesives are suitable for forming a film? · Adhesive for optical communications: specialty resin · Technical Analysis: Synthesis Principles and Key Applications of UV-High-Refractive-Index Resin and Monomers · A Brief Analysis of Dual-Curing UV Resins: Types and Applications · Adhesive Solutions for Public Transportation · Introduction to Adhesive Solutions for the Aerospace Industry · Introduction to adhesive and lubricant solutions for bearings and gears · The adhesive solution used in the bonding process (Die Attach adhesive) · Adhesive solution for electronic equipment control systems of new energy vehicles · Introduction to the Glue Solution for PCB Boards · New Energy Drive Motor Stator Winding Encapsulation Process · Five key applications of adhesives in the photovoltaic industry · Application solutions for adhesives used in aviation and ships · Adhesive Application Solution for Solar PV & Energy Storage System · Semiconductor packaging adhesive solution