3. The technological conditions and preparation sodium phosphate as the reducing agent as a condition of electroless plating nickel plating solution is the most widely used process at home and abroad, divided into two categories: acidic solution and alkaline solution. Acidic electroless nickel plating solution composition and technological conditions, are shown in table 4-25:
Table 4-25 acid chemical nickel plating solution composition and technological conditions
Plating solution composition (g/l) 1, 2, 3, 4, 5 and the process conditions
Nickel sulfate 30 20 25 25 25 to 30
Sodium hypophosphite 20-25 15-25 24 20 to 24
Sodium acetate 5 15
Sodium citrate May 15
Succinic acid May 16
Lactic acid is 80% (25 25 ml/l)
Amino acetic acid 5-15
Malic acid 24
Boric acid 10
Sodium fluoride 1
(Pb2 +) (in the form of lead acetate to join) 0.001 0.003
PH 4-5 3.5 5.4 4.4 4.8 4.4 4.8 4.4-6
Temperature (鈩?, 80-90, 85-80, 90-94, 90-92. 90-93
Deposition rate (mu m/h) 10 10 to 13 15-22 48 12 to 15
Load (dm2 / L) 1 1 1 1 1
Phosphorus content in the coating (%) 8-10 7-11 8-9 8-9-11
No. 1 formula solution preparation method is as follows:
The container with 60 ~ 70 鈩?hot distilled water dissolved sodium citric acid and acetic acid, in another container with hot distilled water soluble nickel sulfate, dissolves into the solution under stirring constantly, filtering the mixture into the slot. During the chemical plating, first to dissolve well in advance and filtered sodium hypophosphite solution to join groove, stir well. Add distilled water to the desired volume, with 10% of dilute sulphuric acid or sodium hydroxide solution finally adjust pH value to the upper limit prescribed scope.
2, 3, 4, 5, the formula of solution can be prepared by reference to the above method.
But in the formula 3, 4, lactic acid solution with sodium bicarbonate solution in advance and to pH value of 4.6 or so, then can be mixed with other components.
Alkaline chemical nickel plating solution composition and technological conditions of 26 - see table 4.
Table 4-26 alkaline chemical nickel plating solution composition and technological conditions
Plating solution composition (g/l) 1, 2, 3, 4, 5 and the process conditions
Nickel sulfate 10-20 33 30 25 to 30
Sodium hypophosphite 5-15 15 25 25 to 30
Sodium citrate 30 to 60 50
Sodium pyrophosphate 60-70-50 to 60
Lactic acid 80% 1-5 (ml/l)
Triethanolamine, 100
PH 7.5 8.5 8 to 10-10.5-10-11
Temperature (鈩? 40-45, 90, 70-75, 65-75-30-35
Deposition rate (20-30 mu m/h) 15 October
Phosphorus content in the coating (%) 7-8 about 5 about 4
Formula 1, 5, suitable for plastics metallization layer, general plating 10 minutes can.
Formula 5 add triethanolamine, besides have complexation, also can adjust pH value, can make the plating solution at low temperature is still high deposition rate. When adding nickel salt, must first after the complexation of triethanolamine and add the plating tank, otherwise it will produce precipitation. Preparation, the ratio of nickel sulfate and sodium hypophosphite or sodium pyrophosphate should be roughly control in 1:2, so we can ensure that nickel complex state.
Formula applicable to chemical nickel plating on aluminium and aluminium alloy.
Formula 4 can work in a wider range of concentration, the pH value had better more than 10, otherwise pyrophosphate nickel complex decomposition will occur. Addition of nickel sulfate, also should be dissolved in ammonia and then join the plating tank.
4. The composition of electroless nickel plating solution and process conditions
< 1 > nickel salt concentration effect on the deposition rate
(1) in the fluid of the acidic electroless nickel plating nickel ion concentration increases, can increase the deposition rate of electroless nickel. Especially when the concentration of nickel salt under 10 g/L, the increase of nickel salt concentration, the nickel deposition rate was accelerated. For example, when the solution containing sodium hypophosphite in 20 g/L, 20 g/L sodium acetate, temperature is 82 ~ 84 鈩? pH = 5.5, nickel salt concentration from 5 g/L to 60 g/L change, effect on the deposition rate are shown in table 4-27:
Table 4-27 nickel salt effect on the deposition rate
Nickel sulfate (g/l) 5 10 20 30 to 40 50 to 60
Laminated speed (mu m/h) 12 19 24 21 20 20 20
When the nickel salt concentration up to 30 g/L, we will continue to increase concentration, the coating deposition rate is no longer increasing, and even fall. Nickel salt concentration is too high, to cause a decline in the stability of the plating solution, and is easy to appear rough coating.
(2) in the fluid of the alkaline chemical nickel plating, nickel salt concentration in 20 g/L, increase the speed of chemical deposition of nickel salt concentration significantly improved; But when the concentration of nickel salt is higher than 25 g/L, it is continue to improve the content of nickel salt, the deposition rate tends to be stable.
Figure 4-15 sodium hypophosphite concentration effect on the deposition rate < 2 > sodium hypophosphite concentration effect on the deposition rate
Increase the concentration of sodium hypophosphite, deposition rate can be improved, as shown in figure 4 to 15. But sodium hypophosphite concentration increased, and can't infinite to improve the deposition rate of electroless nickel, different concentration nah2po2 concentration in the bath.