China Report Hall News: Industrial-grade optocouplers are upgrading towards high isolation voltage, low leakage current, and high heat dissipation to meet the technical requirements for equipment stability in fields such as industrial automation and new energy. Bonding wires, as key components in the packaging process, directly determine the market competitiveness of optocoupler products based on their cost control and reliability levels.

1. Bonding wire technology bottlenecks and breakthrough solutions

01、Traditional 99.99% Gold Cost Issue

The "China Optocoupler Industry Market Research, Study and Investment Prospect Analysis Report 2025-2030" points out that 99.99% pure gold wire accounts for as much as 53.5% of the material cost in a thousand optocoupler packages,gold price fluctuations directly compress profits; and the high gold price has increased the material cost of a single optocoupler by more than 20%.

02、Reliability defects of low-k gold alloys

The experimental comparison shows that the use of low gold content (8% gold content): the weld ball push force is attenuated by 40% compared to pure gold, which can not meet the industrial photo coupler 85℃/85% RH 1000h aging test standard; in a high temperature and high humidity environment, it is easy to appear weld ball cracks, and the photo coupler failure rate reaches 6×10⁻⁵.

03、65% Au-Pd-Ag alloy wire technology verification

• The Au-Pd-Ag quaternary alloy has increased the bonding strength by 20% by precisely regulating the gold content, while reducing the cost of a thousand light coupling wires from 24.09 yuan to 16.15 yuan.

• Wire Breaking Force Test:

65% alloy wire 0.98N, 19.5% improvement over 0.82N gold wire; in terms of weld ball push force, 65% alloy wire 63cN, 21% improvement over 52cN gold wire. SEM observations revealed that its weld balls were full without pits, EDS element distribution was uniform, and the ratio of Au, Pd, Ag was stable, suppressing excessive growth of IMC and ensuring that the interface of the optocoupler remained dense under long-term high-temperature operation.

• Accelerated test at high temperature and high humidity at 85℃/85% RH for 1000h:

The ball push force retention rate of the 65% alloy wire is 92%, while that of the gold wire is only 85%; the corresponding failure rate of the optocoupler drops from 6×10⁻⁵ for the gold wire to 7×10⁻⁶, a decrease of more than an order of magnitude. After 1000 hours of high-temperature storage at 120℃ and a cold-hot cycle of -50~120℃, the break strength of the alloy wire degrades by less than 8%, significantly better than the more than 15% degradation of the low gold content formula.

• Electrical tests show:

The leakage current of the optocoupler encapsulated with 65% alloy wire is stable at the 10μA level, which is one order of magnitude lower than the gold wire, effectively reducing the risk of false triggering; the forward voltage is 1.78V, only 0.05V higher than the gold wire, with an impact on the LED luminous intensity of <3%, fully meeting the industrial optocoupler specifications with a transmission distance ≥10mm and an isolation voltage of 3750Vrms.

04、65% Au-Pd-Ag alloy wire preparation process parameters

The current analysis of the optocoupler industry points out that the preparation process of this alloy wire needs to follow the following key parameters:

1200℃ vacuum refining → 50mm/min continuous casting → 7mm billet → multi-mode drawing to 23μm → 400℃ annealing;

Under these conditions, the alloy wire has a breaking load of 0.98N, an elongation of 12%, an initial modulus of 78GPa, which maintains sufficient rigidity to prevent wire collapse, and also has excellent plasticity to adapt to the high-speed welding wire machine with a bonding cycle of 20ms, with a production yield greater than 99.5%.

2. Economic benefits and industry impact

01、Economic benefit calculation

Assuming an annual production capacity of 100 million opto couplers:

• Single material cost reduction of 0.08 yuan, annual direct material cost savings of 8 million yuan;
• The risk of gold price fluctuation superposition has decreased, the capital occupation of inventory has been reduced, and the comprehensive economic benefit has exceeded 10 million yuan.

02、Industry competition driving force

With the annual demand for industrial optocouplers expected to exceed 3 billion pieces by 2025, this alloy wire solution is expected to reduce the overall cost of domestic optocouplers by 8%, helping the domestic content rate to surge from 42% to 60%, and winning the initiative for the optocoupler industry in the dual competition of price and reliability.

Three, Key Issues Answered

Question 1:What is the core solution to break through the contradiction between the cost and reliability of bond wires in the optocoupler industry in 2025? What are the data for the improvement of its cost and reliability?

The core scheme is to adopt four-element alloy wire with 65% gold content, replacing traditional pure gold wire with 99.99% and low gold alloy wire:

1. Cost increase:The cost of raw materials for 1,000 pieces of optocoupler wire has dropped from 24.09 yuan to 16.15 yuan. With an annual production capacity of 100 million pieces, the annual direct material cost saves 8 million yuan, and the comprehensive benefits exceed 10 million yuan. The product price reduction space has increased by 8%;
2. Reliability Enhancement: The wire break force increased from 0.82N to 0.98N (+19.5%), the ball push force increased from 52cN to 63cN (+21%), the failure rate under high temperature and high humidity (85℃/85%RH) decreased from 6×10⁻⁵ to 7×10⁻⁶ (a decrease of more than one order of magnitude), and it can pass the 85℃/85%RH 1000h aging test, meeting the industrial grade requirements.

Question 2: What is the driving effect of the 65% Au-Pd-Ag alloy wire scheme on the domestic market competition and the domestic content target for optocouplers in 2025?

The program promotes the development of domestic optocouplers in three aspects:

1. Cost side:Helping to lower the overall cost of domestic optocouplers by 8%, enhancing price competitiveness;
2. Performance end:Leakage current (10μA magnitude), isolation voltage (3750Vrms), and other indicators meet the standards, solving the reliability shortcomings of traditional domestic optocouplers, and enhancing the ability to compete with international brands;
3. Market end: The annual demand for industrial optocouplers is expected to exceed 3 billion pieces by 2025, and this alloy wire solution is expected to reduce the overall cost of domestic optocouplers by 8%, helping the domestic content rate to surge from 42% to 60%, and winning the initiative for the optocoupler industry in the dual competition of price and reliability.