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[China Aluminum Industry Network] Aluminum and its alloys exist in aluminum alloys in several different forms due to the addition of different alloying elements. For example, a character that enters aluminum in the form of a solid solution; it occurs in the form of a microscopic dot of the element itself or an intermetallic compound particle consisting of aluminum or other alloying elements. Therefore, it is very difficult for different aluminum alloys to find a general pre-treatment and pre-plating process, and the forks have the same satisfactory results. In the brush plating process, we borrowed from the iron and steel repair brush plating process. which is:
Cathode Electrolytic Degreasing → Washing → Anode Activation → Washing → Pre-plating Copper → Washing → Tin Plating
Activation can only remove the thin oxide film produced by the process, and the thick, strong oxide film should be removed by a machine tool.
Aluminum is an active metal. It is easily oxidized in the air. The interval between coating processes should be as short as possible. Keep it moist and do not form dry spots. Once the dry spot has formed, it indicates that the surface of the workpiece has been oxidized again, reducing the strength of the coating layer. The surface of the activated workpiece should be flushed and replenished as soon as possible to prevent the surface of the workpiece from being re-oxidized during the process.
Although the above process is performed during the brush plating process, it is ideal for industrial pure aluminum and aluminum-manganese forging of Taiwanese gold, but gold is still produced in the production of aluminum-magnesium, aluminum-magnesium silicon, and aluminum-zinc-magnesium. It is difficult to batch-repair and increase the loop resistance. After multiple attack tests, we improved the composition of the activating solution. In the activation, dilute sulfuric acid was used instead of dilute hydrochloric acid. The best value was selected to improve the brushing and plating force of Al-Mg2 gold.
For the high-silicon ancient casting Taiwanese gold, the amount of fork was added to HF, although the amount was very small, but the effect was very obvious.
At the same time, after the phase detection of the tin-plated tin layer, we believe that the reasons for the high loop resistance and peeling in the production process are closely related to the thickness of the pre-plated copper and the current eagle. This also includes the current density of the brush plating. Alkaline copper plating solution is used for the transition layer of the brush, and it is often too thick to be plated. This can cause large stress on the coating and cause peeling. When the current density is too high, the brushed copper layer and the germanium layer are large, and the grains and grains are cross-linked together. The ring-shaped network structure of the transition layer microscopically reveals that the looseness is not dense and the strength of the substrate is poor. Causes foaming after brush tin plating or blistering after hot bake, which intensifies corrosion in the area when corrosion gas intrudes. As a result, the loop resistance increases and the tin plating layer peels off.
After many trial tests, we used the following brush tin plating process:
(1) Carefully polish the surface of the brush with water sandpaper and remove the oxide scale.
(2) Cathodic electrolytic degreasing, 12 to 15 V for 5 to 15 s, to the surface of the workpiece without hanging water, washed clean.
(3) Anode activation, regardless of material selection of the corresponding activation solution, voltage l5V, 8 ~ 12s, to the surface of dark gray, washed, with alkaline copper electroless plating surface wipe.
(4) brush plating copper plating voltage of about 10V, l ~ 2min, washed clean.
(5) brush tin, 8 ~ 12V, time calculated by power consumption.
According to the above process operation. In order to check the strength of the junction, according to GB5270 thermal shock test. Heat the part man oven to 150±10. C. The time is 2h. After the removal, the parts are placed in the water tank and cooled rapidly. It is found that the plating layer and the substrate are in good condition. No blistering or peeling. The loop resistance is tested by the assembly factory type test group. The T type of the electrical connector is used. Contact resistances such as L-type seats are maintained at l5 ~ 25m'~, and the electrical performance standards for the electrical contact elements at the desk.
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