High-Performance Silicone Encapsulant DOWSIL™ 170 in Industrial 5G Communication Power Supply Modules​

With the rapid advancement of 5G technology, its infrastructure, particularly the power supply modules within communication base stations, faces unprecedented demands. These modules must operate reliably and continuously under harsh conditions involving extreme temperature fluctuations, high-frequency vibration, moisture, and dust, all while ensuring effective heat dissipation under high power density and long-term electrical insulation reliability. A renowned communications equipment manufacturer (hereinafter referred to as "the customer") encountered these severe challenges when designing their new generation of industrial-grade 5G base station power supply modules.

​​Challenges & Requirements:​​

The customer's power module integrated sensitive components such as high-frequency transformers, power inductors, MOSFETs, and precision control ICs. Initial testing with traditional epoxy resin encapsulants revealed significant issues: Firstly, the high hardness and high modulus of cured epoxy resin generated substantial internal stress during intense thermal cycling (-40°C to +85°C) due to the coefficient of thermal expansion (CTE) mismatch between the epoxy, components, PCB, and metal housing. This led to micro-cracks or fractures in multilayer ceramic capacitors (MLCCs) and solder joint fatigue failures. Secondly, internal hot spots emerged, and the insufficient thermal conductivity (approx. 0.2 W/mK) of the traditional encapsulant caused critical power devices to overheat, compromising overall lifespan and efficiency. They urgently needed a material that could simultaneously provide excellent stress absorption, good thermal conductivity, convenient repairability, and UL-certified flame retardancy.

​​Material Selection: DOWSIL™ 170 Silicone Elastomer​​

After extensive evaluation and rigorous testing, the customer ultimately selected Dow's DOWSIL™ 170 two-part silicone encapsulant as their solution. The decision was based on its outstanding comprehensive properties:

1. 1. 1.

      ​​Excellent Flexibility & Stress Relief:​​ DOWSIL™ 170 cures to a soft elastomer with a Shore A hardness of 47. Its low modulus effectively absorbs and dissipates thermal and mechanical stress, acting like a "protective cushion" for delicate components, completely eliminating failures caused by CTE mismatch.

   2. 2.

      ​​Good Thermal Conductivity:​​ With a thermal conductivity of 0.48 W/mK, significantly higher than common encapsulants, it efficiently transfers heat from power devices to the metal housing, reducing internal operating temperatures and enhancing power density and long-term reliability.

   3. 3.

      ​​Exceptional Electrical Insulation:​​ Its extremely high volume resistivity (>5.6×10¹⁷ Ω·cm) and dielectric strength of 472 V/mil (18 kV/mm) provide enduring and reliable insulation protection for high-voltage, high-density circuits, preventing leakage current or short circuits in humid environments.

   4. 4.

      ​​Convenient Processing & Repairability:​​ The 1:1 mix ratio greatly simplifies metering and mixing processes, reducing production complexity and waste. Its mixed viscosity of 2135cP offers good flowability, ensuring thorough penetration and filling of complex geometries and fine gaps. Crucially, if a module requires rework, the cured silicone can be precisely cut and peeled away. Components can be repaired and the area re-potted, significantly reducing after-sales costs—a clear advantage over rigid epoxies.

   5. 5.

      ​​Reliable Flame Retardancy & Certifications:​​ DOWSIL™ 170 is UL 94 V-0 certified and complies with the railway standard EN 45545-2 (HL3 level), meeting stringent safety requirements for industrial applications.

​​Application Process:​​

On the customer's automated production line, the process was as follows:

1. 1. 1.

      ​​Preparation & Mixing:​​ Components A and B were brought to room temperature from cold storage. They were then precisely metered and mixed at a 1:1 volume ratio using automated dispensing equipment.

   2. 2.

      ​​Potting:​​ The homogeneously mixed liquid was dispensed into the power module housing containing the assembled components. Thanks to its suitable flowability, the material readily filled all voids and encapsulated every sensitive component without the need for additional vacuum degassing (for this specific structure).

   3. 3.

      ​​Curing:​​ To enhance production efficiency, the modules were placed in a 70°C oven for 25 minutes for complete curing. Alternatively, curing could be achieved at 25°C for 24 hours, offering scheduling flexibility.

​​Results & Benefits:​​

After potting with DOWSIL™ 170, the performance of the customer's 5G power modules was significantly enhanced:

• • •

    ​​Greatly Enhanced Reliability:​​ The modules passed over 2000 cycles of stringent thermal cycling tests and extended damp heat tests with zero failures due to stress or insulation issues.

  • •

    ​​Optimized Thermal Management:​​ The peak operating temperature of power devices decreased by approximately 15°C, projected to more than double the product lifespan.

  • •

    ​​Production Efficiency & Cost Optimization:​​ The simplified mix ratio improved production yield, and the repairability drastically reduced after-sales service costs.

  • •

    ​​Increased Market Competitiveness:​​ High performance and reliability became core selling points, enabling the customer to successfully secure contracts for multiple major 5G infrastructure projects.

​​Conclusion:​​

In this application, DOWSIL™ 170 silicone encapsulant perfectly demonstrated its value as a high-performance packaging material. It is not merely a filler but a critical engineering material that enhances product reliability, power density, and long-term durability. Its unique combination of flexibility, good thermal conductivity, ease of processing, and repairability makes it an ideal choice for potting protection in high-end electronic equipment operating under harsh conditions, such as power and control units in 5G communications, industrial controls, new energy vehicles, and rail transportation.