Potting compounds for electronics: epoxy, silicone, or PU?
Electronic assemblies must be reliably protected against moisture, mechanical stress, and temperature fluctuations. Encapsulants offer this protection—but which material is the right one? This technical article compares epoxy, silicone, and polyurethane encapsulants and shows when you should use which system.
What are casting compounds?
Potting compounds are liquid or paste-like materials that completely encase electronic assemblies and provide lasting protection after curing. Unlike coatings, which only form a thin protective layer, potting compounds fill the entire cavity around the electronics.
Main functions of casting compounds
- Moisture protection: Prevents corrosion and leakage currents on printed circuit boards
- Mechanical protection: Absorbs vibrations and shocks, secures components
- Electrical insulation: High dielectric strength prevents flashovers
- Thermal management: Thermally conductive variants dissipate heat loss
- Chemical protection: Resistance to oils, fuels, cleaning agents
Choosing the right potting compound depends on numerous factors: operating temperature, mechanical stress, chemical exposure, repairability, and, of course, cost. The three most important types of potting compounds—epoxy, silicone, and polyurethane—differ fundamentally in their properties.
Epoxy casting compounds
Epoxy resins consist of two components (resin and hardener) that undergo an irreversible chemical reaction when mixed. After curing, thermosetting plastics with excellent mechanical and electrical properties are formed.
Properties of epoxy casting compounds
- High mechanical strength: Shore D 70-85, very hard and stable
- Excellent adhesion: Adheres excellently to metals, printed circuit boards, ceramics
- High dielectric strength: Up to 25 kV/mm, ideal for high-voltage applications
- Chemical resistance: Resistant to acids, alkalis, solvents
- Temperature resistance: Standard -40°C to +130°C, special systems up to +180°C
- Low moisture absorption: Less than 0.5% water absorption
benefits
Epoxy potting compounds offer the best mechanical protection of all three systems. They are ideal for applications with high mechanical loads or when the assembly must be fixed in a completely rigid manner. Their excellent adhesion ensures that no cavities form in which moisture could collect.
Epoxy resins are often the first choice for high-voltage applications such as transformers, ignition coils, or power supplies. Their high dielectric strength and low creepage current ensure reliable insulation even under extreme conditions.
disadvantages
The high final strength is also the biggest disadvantage: epoxy-encapsulated assemblies are practically impossible to repair. Components can only be removed by mechanically destroying the encapsulation, which damages the circuit board. This can be problematic for prototypes or small series.
Epoxy resins are brittle and can crack when subjected to thermal cycling or mechanical shocks. The different thermal expansion coefficients of epoxy, printed circuit boards, and components lead to mechanical stresses that can damage sensitive components.
Typical applications
- High-voltage power supplies and transformers
- Ignition electronics in automotive applications
- Sensors in harsh environments
- Underwater electronics and marine applications
- Safety-related controls (tamper protection)
Product example: Permabond offers specialized epoxy potting compounds for electronics applications, including thermally conductive and flexible variants for different requirements.
Silicone casting compounds
Silicones (polysiloxanes) are a class of materials with unique properties. RTV silicones (room temperature vulcanizing) cure at room temperature and form elastic, temperature-resistant casting compounds.
Properties of silicone potting compounds
- High elasticity: Shore A 15-60, remains flexible even after curing
- Extreme temperature resistance: -140°F to 392°F (briefly up to 482°F)
- UV and weather resistance: No yellowing, no embrittlement outdoors
- Low mechanical stress: Minimal strain on sensitive components
- Good dielectric properties: 15-25 kV/mm dielectric strength
- Repairability: Can be removed mechanically without damaging the circuit board
benefits
The elasticity of silicone potting compounds is their greatest advantage. They absorb vibrations excellently and compensate for different thermal expansions between components and the circuit board. This makes them ideal for applications with extreme temperature fluctuations or mechanical stresses.
Silicone potting compounds retain their properties over an extremely wide temperature range. While epoxy and PU systems become brittle at low temperatures, silicone remains flexible down to -60°C. At high temperatures, they significantly outperform both alternatives.
Silicones are often the best choice for LED applications. Special optical silicones are transparent, do not yellow, and have a suitable refractive index. They protect the LED chips without reducing light output.
disadvantages
The low mechanical strength means less protection against direct mechanical impact. Sharp objects can easily penetrate silicone castings. Adhesion to some surfaces is weaker than with epoxies, which is why primers are often necessary.
Silicones have higher gas permeability than epoxy or PU. This can be problematic in very humid environments or with aggressive gases. Silicones are also generally more expensive than the two alternatives.
An often underestimated problem: Low-molecular siloxanes can outgas and contaminate sensitive contacts. Only low-bleeding silicones should be used for high-reliability applications.
Typical applications
- LED modules for outdoor lighting and automotive applications
- Temperature sensors and thermocouples
- Automotive control units with high temperature requirements
- Outdoor electronics (solar inverters, outdoor sensors)
- Medical electronics (biocompatible variants)
- Aerospace (extreme temperatures)
Product example: The Bluesil series offers RTV-2 silicone potting compounds with different Shore hardnesses and viscosities. Special thermally conductive variants achieve over 3 W/m·K for efficient thermal management.
Polyurethane casting compounds
Polyurethane casting compounds (PU) are positioned between epoxy and silicone. They combine good mechanical properties with sufficient flexibility and are often the most economical solution.
Properties of polyurethane casting compounds
- Medium hardness: Shore A 60-95, semi-flexible to hard
- Good abrasion resistance: Better than silicone, robust surface
- Moderate temperature resistance: -40°C to +120°C
- Excellent adhesion: Adheres to most substrates without primer
- Good electrical insulation: 16-22 kV/mm dielectric strength
- Economical: The most affordable of the three systems
benefits
Polyurethane casting compounds offer a balanced range of properties at an attractive price. They are perfectly adequate for many standard applications in electronics. Processing is straightforward, and the pot life is longer than with many epoxy systems.
The semi-flexible consistency of many PU casting compounds offers good vibration damping while providing sufficient mechanical stability. They are more flexible than epoxies but more stable than soft silicones—ideal for control devices in harsh industrial environments.
PU casting compounds can be partially repaired if necessary. Areas can be exposed using suitable solvents or mechanical means without destroying the entire assembly. This is particularly valuable during the development phase.
disadvantages
Moisture sensitivity is the main disadvantage of polyurethane systems. PU is hygroscopic and absorbs moisture, which can impair its electrical properties. Epoxy or silicone are better suited for continuous operation in humid environments.
UV light causes yellowing and embrittlement in many PU casting compounds. For outdoor applications or transparent castings, UV-stabilized variants should be selected or silicone should be used instead.
Temperature resistance is limited. Many PU systems begin to soften above 100-120°C. They are not suitable for high-temperature applications in the automotive or industrial sectors.
Typical applications
- Industrial controllers and PLC modules
- Switching power supplies for indoor applications
- Consumer electronics (protected environment)
- Measuring devices and sensors (moderate temperatures)
- E-mobility: Chargers, BMS modules
- Building automation and smart home devices
Comparison table: Epoxy vs. silicone vs. polyurethane
| property | epoxy | silicone | polyurethane |
|---|---|---|---|
| temperature range | -40°C to +130°C (+180°C special) |
-60°C to +200°C ( , +250°C for short periods) |
-40°C to +120°C |
| Shore hardness | Shore D 70-85 (very hard) |
Shore A 15-60 (soft to medium) |
Shore A 60-95 (medium to hard) |
| Dielectric strength | 20-25 kV/mm (excellent) |
15-25 kV/mm (very good) |
16-22 kV/mm (good) |
| thermal conductivity | 0.2-3 W/m·K (filled up to 5 W/m·K) |
0.2-3 W/m·K (standard to filled) |
0.2-1.5 W/m·K (limited) |
| chemical resistance | Excellent (acids, alkalis, oils) |
Very good (limited in the case of solvents) |
e (sensitive to strong acids) |
| UV resistance | Good (may yellow) |
Excellent |
Moderate (yellowing, brittleness) |
| moisture absorption | < 0.5% (sehr niedrig) |
< 0.2% (niedrig) |
1-3% (hygroscopic) |
| repairability | Very difficult (destructive) |
(mechanically removable) |
Possible (partially solvable) |
| price level | Medium to high | High | Low to medium |
| Pot life (typical) | 10-60 min. | 30-120 min. | 20-90 min. |
Decision matrix: Which casting compound for which application?
LED modules and lighting
Recommendation: Silicone – LED modules generate heat and often require transparent encapsulation. Silicone offers the best temperature resistance, does not yellow, and has excellent optical properties. Thermally conductive silicone variants efficiently dissipate heat loss.
For indoor LED applications with moderate temperatures, clear polyurethane can also be a cost-effective alternative. However, yellowing must be expected after a few years.
Automotive electronics (engine compartment)
Recommendation: Silicone or epoxy – The engine compartment poses extreme challenges: temperatures up to +150°C, vibrations, oils, and fuels. Silicone is ideal for sensors and control units exposed to high temperatures. Epoxy offers better dielectric strength for high-voltage ignition modules.
Modern electric vehicles have cooler drives, which means that high-quality polyurethane can also be used for BMS modules and chargers.
medical technology
Recommendation: Silicone (biocompatible) – Medical devices require biocompatible materials in accordance with ISO 10993. Special medical silicones meet these requirements and can be sterilized. They are skin-friendly and do not cause allergic reactions.
Only tested medical silicones may be used for implantable electronics.
Industrial controls and PLCs
Recommendation: Polyurethane – Industrial control systems usually operate in protected control cabinets at moderate temperatures. The mechanical stress is manageable. Polyurethane offers the best price-performance ratio with sufficient protection.
For environments subject to high levels of vibration (machines, systems), flexible silicone may be the better choice.
Outdoor electronics and solar
Recommendation: Silicone – UV radiation, temperature cycles from -30°C to +80°C, and humidity make outdoor applications challenging. Silicone is UV-stable, temperature-resistant, and does not age. Solar inverters and junction boxes are encapsulated with silicone as standard.
High-voltage power supplies
Recommendation: Epoxy – Dielectric strength is crucial for transformers and high-voltage circuits. Epoxy resins offer the highest creepage current resistance and prevent partial discharges. Mechanical fixation prevents vibrations in the magnetic field.
Processing instructions
Mixing ratio and dosage
All three types of casting compounds are usually two-component systems. The correct mixing ratio is critical for the final properties. Deviations of more than ±5% lead to incomplete curing, a sticky surface, or reduced mechanical strength.
For small batches, mixing by hand with a precise scale is sufficient. For medium quantities and above, dosing systems with volumetric or gravimetric dosing are worthwhile. Modern 2K cartridges with static mixers ensure reproducible quality.
Ventilation and vacuum casting
Air bubbles in the encapsulation significantly reduce dielectric strength. Even small air pockets can lead to partial discharges and premature failure. Vacuum deaeration is essential for high-quality encapsulation.
Typical process: Mix the material, vent for 5-10 minutes at 10-50 mbar, pour under vacuum. Alternatively, you can evacuate again after pouring. Low-viscosity systems are easier to vent than high-viscosity ones.
Pot life and curing
The pot life describes how long the mixed material remains workable. It is highly dependent on temperature: at a temperature 10°C higher, the pot life is often halved. For complex castings, the pot life should be at least 30 minutes.
Curing can be accelerated by temperature. Typical cycles: 2 hours at 60°C or 1 hour at 80°C. But be careful: heating too quickly leads to stress cracks due to uneven heating. A heating rate of max. 2-3°C/min is recommended.
Important: Post-curing
Even though the casting is touch-dry after 24 hours at room temperature, it only reaches its full mechanical and electrical properties after 7 days. This period should be taken into account for functional tests. Tempering at 60-80°C for 2-4 hours accelerates the post-curing process.
Common processing errors
- Incorrect mixing ratio: Leads to incomplete curing and a sticky surface
- Insufficient mixing: streaks in the material, inhomogeneous properties
- Moisture-sensitive components: Polyurethane hardener reacts with air humidity; always seal containers.
- Contamination: Silicones are sensitive to sulfur, amines, and tin catalysts (inhibition).
- Excessive casting temperature: Thermal shock can damage components
- No primer: Primers are necessary for difficult substrates (PP, PE, PTFE).
Frequently asked questions (FAQ)
Advice on casting compounds for your electronics application
Are you unsure which casting compound is best suited to your application? Our technical team will assist you in selecting the right material and advise you on processing, testing methods, and quality assurance.
SILITECH AG
Worbstrasse 173, 3073 Gümligen
Phone: +41 31 398 50 70
Email: info@silitech.ch
To the SILITECH websitePotting compounds for electronics: epoxy, silicone, or PU?
Electronic assemblies must be reliably protected against moisture, mechanical stress, and temperature fluctuations. Encapsulants offer this protection—but which material is the right one? This technical article compares epoxy, silicone, and polyurethane encapsulants and shows when you should use which system.
What are casting compounds?
Potting compounds are liquid or paste-like materials that completely encase electronic assemblies and provide lasting protection after curing. Unlike coatings, which only form a thin protective layer, potting compounds fill the entire cavity around the electronics.
Main functions of casting compounds
- Moisture protection: Prevents corrosion and leakage currents on printed circuit boards
- Mechanical protection: Absorbs vibrations and shocks, secures components
- Electrical insulation: High dielectric strength prevents flashovers
- Thermal management: Thermally conductive variants dissipate heat loss
- Chemical protection: Resistance to oils, fuels, cleaning agents
Choosing the right potting compound depends on numerous factors: operating temperature, mechanical stress, chemical exposure, repairability, and, of course, cost. The three most important types of potting compounds—epoxy, silicone, and polyurethane—differ fundamentally in their properties.
Epoxy casting compounds
Epoxy resins consist of two components (resin and hardener) that undergo an irreversible chemical reaction when mixed. After curing, thermosetting plastics with excellent mechanical and electrical properties are formed.
Properties of epoxy casting compounds
- High mechanical strength: Shore D 70-85, very hard and stable
- Excellent adhesion: Adheres excellently to metals, printed circuit boards, ceramics
- High dielectric strength: Up to 25 kV/mm, ideal for high-voltage applications
- Chemical resistance: Resistant to acids, alkalis, solvents
- Temperature resistance: Standard -40°C to +130°C, special systems up to +180°C
- Low moisture absorption: Less than 0.5% water absorption
benefits
Epoxy potting compounds offer the best mechanical protection of all three systems. They are ideal for applications with high mechanical loads or when the assembly must be fixed in a completely rigid manner. Their excellent adhesion ensures that no cavities form in which moisture could collect.
Epoxy resins are often the first choice for high-voltage applications such as transformers, ignition coils, or power supplies. Their high dielectric strength and low creepage current ensure reliable insulation even under extreme conditions.
disadvantages
The high final strength is also the biggest disadvantage: epoxy-encapsulated assemblies are practically impossible to repair. Components can only be removed by mechanically destroying the encapsulation, which damages the circuit board. This can be problematic for prototypes or small series.
Epoxy resins are brittle and can crack when subjected to thermal cycling or mechanical shocks. The different thermal expansion coefficients of epoxy, printed circuit boards, and components lead to mechanical stresses that can damage sensitive components.
Typical applications
- High-voltage power supplies and transformers
- Ignition electronics in automotive applications
- Sensors in harsh environments
- Underwater electronics and marine applications
- Safety-related controls (tamper protection)
Product example: Permabond offers specialized epoxy potting compounds for electronics applications, including thermally conductive and flexible variants for different requirements.
Silicone casting compounds
Silicones (polysiloxanes) are a class of materials with unique properties. RTV silicones (room temperature vulcanizing) cure at room temperature and form elastic, temperature-resistant casting compounds.
Properties of silicone potting compounds
- High elasticity: Shore A 15-60, remains flexible even after curing
- Extreme temperature resistance: -140°F to 392°F (briefly up to 482°F)
- UV and weather resistance: No yellowing, no embrittlement outdoors
- Low mechanical stress: Minimal strain on sensitive components
- Good dielectric properties: 15-25 kV/mm dielectric strength
- Repairability: Can be removed mechanically without damaging the circuit board
benefits
The elasticity of silicone potting compounds is their greatest advantage. They absorb vibrations excellently and compensate for different thermal expansions between components and the circuit board. This makes them ideal for applications with extreme temperature fluctuations or mechanical stresses.
Silicone potting compounds retain their properties over an extremely wide temperature range. While epoxy and PU systems become brittle at low temperatures, silicone remains flexible down to -60°C. At high temperatures, they significantly outperform both alternatives.
Silicones are often the best choice for LED applications. Special optical silicones are transparent, do not yellow, and have a suitable refractive index. They protect the LED chips without reducing light output.
disadvantages
The low mechanical strength means less protection against direct mechanical impact. Sharp objects can easily penetrate silicone castings. Adhesion to some surfaces is weaker than with epoxies, which is why primers are often necessary.
Silicones have higher gas permeability than epoxy or PU. This can be problematic in very humid environments or with aggressive gases. Silicones are also generally more expensive than the two alternatives.
An often underestimated problem: Low-molecular siloxanes can outgas and contaminate sensitive contacts. Only low-bleeding silicones should be used for high-reliability applications.
Typical applications
- LED modules for outdoor lighting and automotive applications
- Temperature sensors and thermocouples
- Automotive control units with high temperature requirements
- Outdoor electronics (solar inverters, outdoor sensors)
- Medical electronics (biocompatible variants)
- Aerospace (extreme temperatures)
Product example: The Bluesil series offers RTV-2 silicone potting compounds with different Shore hardnesses and viscosities. Special thermally conductive variants achieve over 3 W/m·K for efficient thermal management.
Polyurethane casting compounds
Polyurethane casting compounds (PU) are positioned between epoxy and silicone. They combine good mechanical properties with sufficient flexibility and are often the most economical solution.
Properties of polyurethane casting compounds
- Medium hardness: Shore A 60-95, semi-flexible to hard
- Good abrasion resistance: Better than silicone, robust surface
- Moderate temperature resistance: -40°C to +120°C
- Excellent adhesion: Adheres to most substrates without primer
- Good electrical insulation: 16-22 kV/mm dielectric strength
- Economical: The most affordable of the three systems
benefits
Polyurethane casting compounds offer a balanced range of properties at an attractive price. They are perfectly adequate for many standard applications in electronics. Processing is straightforward, and the pot life is longer than with many epoxy systems.
The semi-flexible consistency of many PU casting compounds offers good vibration damping while providing sufficient mechanical stability. They are more flexible than epoxies but more stable than soft silicones—ideal for control devices in harsh industrial environments.
PU casting compounds can be partially repaired if necessary. Areas can be exposed using suitable solvents or mechanical means without destroying the entire assembly. This is particularly valuable during the development phase.
disadvantages
Moisture sensitivity is the main disadvantage of polyurethane systems. PU is hygroscopic and absorbs moisture, which can impair its electrical properties. Epoxy or silicone are better suited for continuous operation in humid environments.
UV light causes yellowing and embrittlement in many PU casting compounds. For outdoor applications or transparent castings, UV-stabilized variants should be selected or silicone should be used instead.
Temperature resistance is limited. Many PU systems begin to soften above 100-120°C. They are not suitable for high-temperature applications in the automotive or industrial sectors.
Typical applications
- Industrial controllers and PLC modules
- Switching power supplies for indoor applications
- Consumer electronics (protected environment)
- Measuring devices and sensors (moderate temperatures)
- E-mobility: Chargers, BMS modules
- Building automation and smart home devices
Comparison table: Epoxy vs. silicone vs. polyurethane
| property | epoxy | silicone | polyurethane |
|---|---|---|---|
| temperature range | -40°C to +130°C (+180°C special) |
-60°C to +200°C ( , +250°C for short periods) |
-40°C to +120°C |
| Shore hardness | Shore D 70-85 (very hard) |
Shore A 15-60 (soft to medium) |
Shore A 60-95 (medium to hard) |
| Dielectric strength | 20-25 kV/mm (excellent) |
15-25 kV/mm (very good) |
16-22 kV/mm (good) |
| thermal conductivity | 0.2-3 W/m·K (filled up to 5 W/m·K) |
0.2-3 W/m·K (standard to filled) |
0.2-1.5 W/m·K (limited) |
| chemical resistance | Excellent (acids, alkalis, oils) |
Very good (limited in the case of solvents) |
e (sensitive to strong acids) |
| UV resistance | Good (may yellow) |
Excellent |
Moderate (yellowing, brittleness) |
| moisture absorption | < 0.5% (sehr niedrig) |
< 0.2% (niedrig) |
1-3% (hygroscopic) |
| repairability | Very difficult (destructive) |
(mechanically removable) |
Possible (partially solvable) |
| price level | Medium to high | High | Low to medium |
| Pot life (typical) | 10-60 min. | 30-120 min. | 20-90 min. |
Decision matrix: Which casting compound for which application?
LED modules and lighting
Recommendation: Silicone – LED modules generate heat and often require transparent encapsulation. Silicone offers the best temperature resistance, does not yellow, and has excellent optical properties. Thermally conductive silicone variants efficiently dissipate heat loss.
For indoor LED applications with moderate temperatures, clear polyurethane can also be a cost-effective alternative. However, yellowing must be expected after a few years.
Automotive electronics (engine compartment)
Recommendation: Silicone or epoxy – The engine compartment poses extreme challenges: temperatures up to +150°C, vibrations, oils, and fuels. Silicone is ideal for sensors and control units exposed to high temperatures. Epoxy offers better dielectric strength for high-voltage ignition modules.
Modern electric vehicles have cooler drives, which means that high-quality polyurethane can also be used for BMS modules and chargers.
medical technology
Recommendation: Silicone (biocompatible) – Medical devices require biocompatible materials in accordance with ISO 10993. Special medical silicones meet these requirements and can be sterilized. They are skin-friendly and do not cause allergic reactions.
Only tested medical silicones may be used for implantable electronics.
Industrial controls and PLCs
Recommendation: Polyurethane – Industrial control systems usually operate in protected control cabinets at moderate temperatures. The mechanical stress is manageable. Polyurethane offers the best price-performance ratio with sufficient protection.
For environments subject to high levels of vibration (machines, systems), flexible silicone may be the better choice.
Outdoor electronics and solar
Recommendation: Silicone – UV radiation, temperature cycles from -30°C to +80°C, and humidity make outdoor applications challenging. Silicone is UV-stable, temperature-resistant, and does not age. Solar inverters and junction boxes are encapsulated with silicone as standard.
High-voltage power supplies
Recommendation: Epoxy – Dielectric strength is crucial for transformers and high-voltage circuits. Epoxy resins offer the highest creepage current resistance and prevent partial discharges. Mechanical fixation prevents vibrations in the magnetic field.
Processing instructions
Mixing ratio and dosage
All three types of casting compounds are usually two-component systems. The correct mixing ratio is critical for the final properties. Deviations of more than ±5% lead to incomplete curing, a sticky surface, or reduced mechanical strength.
For small batches, mixing by hand with a precise scale is sufficient. For medium quantities and above, dosing systems with volumetric or gravimetric dosing are worthwhile. Modern 2K cartridges with static mixers ensure reproducible quality.
Ventilation and vacuum casting
Air bubbles in the encapsulation significantly reduce dielectric strength. Even small air pockets can lead to partial discharges and premature failure. Vacuum deaeration is essential for high-quality encapsulation.
Typical process: Mix the material, vent for 5-10 minutes at 10-50 mbar, pour under vacuum. Alternatively, you can evacuate again after pouring. Low-viscosity systems are easier to vent than high-viscosity ones.
Pot life and curing
The pot life describes how long the mixed material remains workable. It is highly dependent on temperature: at a temperature 10°C higher, the pot life is often halved. For complex castings, the pot life should be at least 30 minutes.
Curing can be accelerated by temperature. Typical cycles: 2 hours at 60°C or 1 hour at 80°C. But be careful: heating too quickly leads to stress cracks due to uneven heating. A heating rate of max. 2-3°C/min is recommended.
Important: Post-curing
Even though the casting is touch-dry after 24 hours at room temperature, it only reaches its full mechanical and electrical properties after 7 days. This period should be taken into account for functional tests. Tempering at 60-80°C for 2-4 hours accelerates the post-curing process.
Common processing errors
- Incorrect mixing ratio: Leads to incomplete curing and a sticky surface
- Insufficient mixing: streaks in the material, inhomogeneous properties
- Moisture-sensitive components: Polyurethane hardener reacts with air humidity; always seal containers.
- Contamination: Silicones are sensitive to sulfur, amines, and tin catalysts (inhibition).
- Excessive casting temperature: Thermal shock can damage components
- No primer: Primers are necessary for difficult substrates (PP, PE, PTFE).
Frequently asked questions (FAQ)
Advice on casting compounds for your electronics application
Are you unsure which casting compound is best suited to your application? Our technical team will assist you in selecting the right material and advise you on processing, testing methods, and quality assurance.
SILITECH AG
Worbstrasse 173, 3073 Gümligen
Phone: +41 31 398 50 70
Email: info@silitech.ch
To the SILITECH website