Pulse power supply gold plating superiority:
The superiority of pulse power supply plating can be better reflected especially on gold plating. Pulse power supply gold plating could obtain dense crystal electroplating layer coating, that not only significantly increased its finish degree, corrosion resistance, weldability, wear resistance, high temperature capability and have a greater degree of discoloration, but also greatly saved gold.
Someone think no need pulse power supply gold plating:
But there is a view: that barrel gold electro plating using pulse power supply of little significance to improve the density, which their reason is that the barrel plating machine tumbling action make the coarse crystals can not grow, therefore can get dense electroplating layer coating, bright, so no need use a pulse power supply. This view seems not unreasonable, but that is biased. Because barrel plating machine tumbling just a mechanical polishing action, its limited capacity and can not replace the role of fine-grained action generated large pulse current by electro chemical polarization. Therefore, if there is high quality requirements of gold plating, still need to use pulse rectifier gold plating, which this is the best control method outside the plating tank.
Vivid explain to tell you why need pulse power supply gold plating:
For example, now integrated lead frame, linear tube shell, connectors and other parts the pulse power supply barrel plating has been very common.
Also, there is gradually formed a consensus that gold plating bottom plating – nickel layer electroplating should also adopts pulse rectifier plating. The reason is pulse-plated nickel layer of stress, density, uniformity is far superior to the DC rectifier nickel plating, which undoubtedly will lay a solid foundation for gold electro plating, thus greatly improving the functional indicators of gold plating.
For example, one electronic products factory choosing pulse rectifier plating for products gold plating, and the thickness of the gold electro plating layer meet the requirements, which plating workpieces appearance is also good, but still can not meet the 380 ℃ ~ 450 ℃ temperature assessment test. Then they hire experts to help them to solve the problem. One of the measures is to use a pulse power supply nickel barrel plating instead of DC power supply, of course, there are other measures, such as strict operation, improved Pulse power supply gold plating liquid formulations and so on.
The parameters pulse power supply gold plating adopt can refer to the following:
Single pulse: 10% to 20% duty cycle (turn on: 0.1ms ~ 0.2ms, turn off: 0.8ms ~ 0.9ms), pulse frequency 900Hz ~ 1000Hz, the average current density equal to or slightly larger than the DC power source plating;
Reverse pulse: positive pulse duty cycle of 20% (turn on: 0.2ms, turn off: 0.8ms), working time 100ms, the average current density equal to or slightly larger than the DC rectifier plating;
Reverse pulse duty cycle of 10% (on 0.1 ms, off 0.9ms), working time 10ms, an average current density of the reverse peak current density of the positive peak current density of 1 to 2 times, obtained by calculating backwards.
But many people believe that when acidic gold plating, because the gold anode insolubility, reverse peeling double pulse does not work, so the use of the double pulse is superfluous. In fact, the double pulse reverse reeling gold plating only improve the uniformity small, but it can not say that is superfluous, or can not say there is no significance. There is a small experiment may indicate the presence or absence of other dual pulse gilded significance. In the same acidic gold plating solution, the same current density, respectively, DC power source, single pulse, double pulse at the same time each plating a test piece. Comparison of three test pieces, can see clearly that the plating coating brightness is incrementally from DC to single pulse and then to double pulse power supply gold plating.
This shows dual pulse reverse stripping gold plating for improving the crystallization is advantageous, otherwise adopting double pulse plating will not more bright than the single pulse. This should be due to that though reverse pulse not achieve anodic dissolution, but can play the role of electro-polishing, which facilitates the subsequent cathodic deposition coating pulse period is more detailed, bright.
Further, reverse pulse may also have the plating coating be more fully in the subsequent recrystallization cathode pulse period effect, and thus the plating layer coating will be finer grain.
But the reverse pulse work time shall not too long (less than 1/10 of the positive pulse time), otherwise the deposition rate is slow. Also, reverse pulse peak current density should not be less than the positive pulse, otherwise reverse electro-polishing effect is not obvious. Double pulse barre plating as well. Decorative gold plating barrel plating time is short, thin plating coating, good brightness Ni underlying coating nonfunctional requirements, so generally not suggest the use of pulse power supply plating, in order to save the cost of expensive pulse rectifier. But production practice shows that, use double pulse power supply gold plating, if select parameter properly, plating time can be shortened more than 1/3, so as to achieve the effect of the save gold.