From the perspective of circular economy, engineers from Yin Te Electronics view TVS recycling technology

Experimental data shows that the recovery rate of silicon material by this process is stable at over 85%. The TVS made from recycled silicon has no significant difference in breakdown voltage (VBR) consistency (± 3%) and surge withstand capacity (400W) compared to native material products

2. Reuse process of precious metal electrodes: the entire process from disassembly to purification

The electrode system of TVS (such as gold-plated pins and silver paste solder joints) contains precious metals such as gold (Au), silver (Ag), palladium (Pd), etc., and its recycling value accounts for more than 60% of the total recycling value of the device; Differentiated recycling processes are required for different packaging forms (such as SOD-123, DO-214):

Step 1: Precision disassembly stage: For surface mount packaged TVS, laser cutting (wavelength 1064nm, power 5W) is used to separate the pins from the housing along the packaging edge. The laser spot diameter is controlled below 50 μ m to avoid damaging the electrode coating. Plug in packaging uses a pyrolysis process (300 ℃ nitrogen atmosphere) to soften the joint between the pins and the plastic package, and then uses a robotic arm to remove the pins with a force of 0.1N, achieving a detachment rate of up to 99%.

Step 2: Separation and Enrichment Stage: Place the disassembled electrode material in a aqua regia solution (concentrated hydrochloric acid: concentrated nitric acid=3:1) and stir at 60 ℃ for 30 minutes. Precious metals such as gold and palladium will dissolve to form chloroauric acid (HAuCl ₄) and chloropalladic acid (H ₂ PdCl ₆), while base metals such as copper and nickel will be separated by adding sodium sulfite solution for precipitation (pH controlled at 2.0-2.5). For silver electrodes, the nitric acid dissolution sodium chloride precipitation method is used to generate silver chloride (AgCl) precipitate, which is then reduced with hydrazine to obtain metallic silver powder with a purity of up to 99.95%.

Step 3: High purity refining stage: The electrolytic refining method is used to improve the purity of precious metals. The recovered crude gold is used as the anode and pure gold flakes are used as the cathode. In a chloroauric acid solution with a concentration of 50g/L, the current density is controlled at 200A/m ². After 24 hours of electrolysis, the purity of the cathode gold can reach 99.99%. For the refining of palladium, a solution system of [Pd (NH ∝) ₂] Cl ₂ is used, and the purity of palladium can be increased to 99.995% by controlling the ammonia concentration (8mol/L)

The total recovery rate of precious metals in this process is 92% for gold, 95% for silver, and 88% for palladium. The TVS electrode made from recycled precious metals has conductivity (resistivity<2.0 × 10 ⁻⁸Ω· m) and welding performance (wetting time<2s) comparable to new precious metal materials, and can recover 350-500 grams of gold per ton of electronic waste, with significant economic benefits

3. "Design Production Recycling" closed-loop management mode: reducing the difficulty of recycling from the source

To build a closed-loop system throughout the entire lifecycle, it is necessary to incorporate the concept of recyclable design throughout the entire product process

3.1 Optimization of Recyclability in the Design Phase

Adopting a modular electrode design, the thickness of the precious metal coating is reduced from the traditional 2 μ m to 0.5 μ m (ensuring conductivity through nanocrystalline coating technology), and 0.5% fluorescent markers are added to the packaging material for automated sorting equipment to identify TVS devices. The connection between the pins and the chip uses biodegradable solder paste (containing 5% plant-based resin), which can be completely dissolved in 80 ℃ hot water, simplifying the disassembly process.

3.2 Green processes in the production stage

Introducing cyanide free electroplating technology (such as sulfite gold plating) to reduce toxic waste liquid in the recycling process; Using laser welding instead of traditional soldering to avoid interference from heavy metals such as lead and tin on precious metal recycling. Establish a material traceability system to record the material composition of each batch of TVS (such as silicon crystal orientation and precious metal purity), providing accurate data support for subsequent recycling

3.3 System construction during the recycling phase: Establish an Extended Producer Responsibility (EPR) system, where electronic device manufacturers are required to reserve dedicated recycling interfaces for TVS (such as QR codes indicating the location of TVS during PCB design) and bear 30% of the recycling processing costs. Establish a regional recycling network, adopt unmanned aerial vehicle inspection+Internet of Things traceability technology, and improve the collection efficiency of electronic waste (target coverage rate>80%).

This closed-loop mode can increase the material recycling rate of TVS from the current 30% to over 75%. Calculated based on an annual production capacity of 1 billion pieces, it can reduce silicon material consumption by 200 tons per year, recover precious metals worth over 200 million yuan, and reduce the landfill volume of electronic waste by 1500 tons, achieving a win-win situation of environmental and economic benefits.

Summary:

The TVS recycling technology from the perspective of circular economy is not only a breakthrough in the "end of pipe treatment" model, but also a reshaping of the resource flow logic of the electronics industry through the combination of material recycling technology and full lifecycle management. With the maturity of chemical exfoliation and optimization of precious metal recycling processes, TVS is expected to become one of the devices with the highest recycling rate and the greatest regeneration value in electronic waste, providing key support for the green transformation of the electronics industry

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