How can horizontal pulse plating improve PCB gold finger abrasion resistance? Three core parameters in detail

In the manufacturing of gold fingers for 5G communication equipment, traditional DC plating is prone to dendrites and porosity exceeding 15%, resulting in wear and tear after 500 times of plugging and unplugging. Weideng Electronics' technical team innovated the horizontal pulse plating process to achieve micron-level uniform gold plating by precisely regulating three core parameters:

1. Pulse Duty Cycle Optimisation to 30

Energise for 3ms and de-energise for 7ms within a 10ms cycle (as shown in Fig. 1), so that the metal ion concentration at the cathode interface can be restored in time to eliminate the concentration polarisation. Experiments show that when the duty cycle is reduced from 60% to 30%, the porosity of the plated layer is reduced from 12.4% to 2.1%, and the life of the salt spray test is extended to 96 hours.

2. Peak current density increased to 6ASD

The instantaneous high current causes the nucleation rate to be greater than the growth rate (Fig. 2), generating nanocrystalline structures. Electron microscope scanning shows that the grain size of gold plating layer under 6ASD condition is 35nm (120nm in conventional process), the microhardness is increased from 120HV to 200HV, and the wear resistance is increased by 300%.

3. Liquid turbulence control technology

The multi-directional turbulence generator (Patent No. ZL202310XXXXXXXX.X) patented by Weiden makes the bath liquid flow rate stable at 2.5m/s, avoiding hydrogen bubble stagnation. In a customer case, the defective rate of gold finger pinhole was reduced from 8.7% to 0.3%, and the annual cost of gold consumables was saved 1.2 million yuan.

Synergistic control is required in actual production:

Plating solution temperature: 28 ± 0.5 ℃ (temperature sensor real-time feedback)

Gold salt concentration: 6.8±0.2g/L (automatic titration replenishment system)

pH value: 4.2±0.1 (phosphate buffer system)

The process has been applied to Huawei's 5G base station connector mass production, after 1000 times of insertion and removal test, the contact resistance is still <10mΩ. Widener engineers remind: pulse power supply needs to be matched with constant voltage mode to avoid parameter drift due to line impedance. Relevant technical details can be found in Wieden's feature article in Plating & Finishing, Issue 5, 2024.