Fault cause and elimination in PCB nickel plating process

1 Hemp pit (pinhole)

Pitting is the result of organic matter pollution. Large pits usually indicate oil contamination. If you don't stir well, you can't dislodge the air bubbles, which leads to pitting. Wetting agent can be used to reduce its impact, we usually call the small pitting spot pinhole, poor pre-treatment, metal impurities, boric acid content is too little, bath temperature is too low will produce pinhole, so bath maintenance and strict control process is the key.

2 Rough (Burr)

Rough means dirty solution, after adequate filtration can be corrected; Too high PH is easy to form hydroxide precipitation should be controlled; Current density is too high, anode mud and water is not pure into impurities, serious will produce rough (burr).

3. Low binding ability

If the copper coating is not activated to remove the oxide layer, the adhesion between copper and nickel is poor, and the coating will flake. If the current is interrupted, it may cause the nickel coating itself spalling; The temperature is too low, can also produce the phenomenon of spalling.

4. Coating brittleness and poor weldability

When the coating is bent or subjected to some degree of wear, brittleness of the coating is usually revealed, indicating the presence of organic or heavy metal contamination. Excessive additives, so that the coating endocked organic matter and decomposition products increase, is the main source of organic pollution, can be treated with activated carbon; Heavy metal impurities can be removed by electrolysis and other methods.

Coating darkening and uneven color

Coating dark and uneven color, indicating metal pollution. Since the copper plating is generally followed by nickel plating, the copper solution brought in is the main source of pollution. It is important to minimize the amount of copper in the hanging gear. In order to remove the metal contamination in the tank, the corrugated steel plate was used as the cathode, and the current density of 0.12 ~ 0.50A/d㎡ was electrolyzed. Poor pretreatment, poor bottom coating, too small current density, too low concentration of main salt, bad conductive contact will affect the color of the coating.

6 Coating burn

Possible causes of coating burns: insufficient boric acid, low concentration of metal salts, low working temperature, high current density, high PH value or insufficient agitation.

7 Low deposition rate

Low PH or current density will result in low deposition rate.

8 Coating foaming or peeling

Poor treatment before plating, prolonged power failure in the middle, organic impurity pollution, current density is too high, temperature is too low, PH value is too high or too low, serious influence of impurities will produce foaming or peeling phenomenon.

9 anode passivation

Anode activator is insufficient, anode area is too small, current density is too high.

Wiring rules for high speed PCB boards with four or more layers

PCB version is divided into many layers, which high four layers of wiring skills, the following for you to introduce, I hope to help you.

1, 3 points above the line, try to make the line through each point, easy to test, line length as short as possible, as shown below (according to the former) :

2. Try not to lay out wires between pins, especially between and around integrated circuit pins.

3. The lines between different layers should not be parallel to avoid the formation of actual capacitance.

4, wiring is as straight as possible, or 45 degrees broken line, to avoid electromagnetic radiation.

5, ground wire, power cord at least 10-15mil above (for logic circuit).

6, as far as possible to pave the polysemy line connected together, increase the ground area. Line to line as neatly as possible.

7. Pay attention to uniform component emission, so as to facilitate installation, plug-in and welding operation. Text emission in the current character layer, reasonable position, pay attention to the orientation, avoid being blocked, easy to produce.

8. The structure of component emission should be considered. Positive and negative electrodes of patch components should be marked in packaging and at the end to avoid space conflicts.

9, at present, the printed board can be used for 4-5mil wiring, but usually for 6mil line width, 8mil line distance, 12/20mil pad. Wiring should consider the influence of filling current, etc.

10, function block components as far as possible together, zebra strip and other LCD components can not be too close.

11, the hole should be coated with green oil (set to negative one times the value).

12. It is best not to place PAD or over empty under the battery holder. Pad and VIL are of reasonable size.

13. After wiring is complete, carefully check that each connection (including NETLABLE) is really connected (use the lighting method).

14. The oscillating circuit element should be as close to IC as possible, and the oscillating circuit should be as far away from the antenna and other areas prone to interference as possible. Ground pad should be placed under crystal vibration.

15, more consideration of reinforcement, hollowed out elements and other ways to avoid excessive radiation sources.