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PCB Blog - Reasons for Blackening of Electroplated Gold Layer on PCB board

PCB Blog

PCB Blog - Reasons for Blackening of Electroplated Gold Layer on PCB board

Reasons for Blackening of Electroplated Gold Layer on PCB board

2022-11-16
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Author:iPCB

With regard to the causes and solutions of the problem of blackening of the gold plating layer on the PCB board, it is very common for the PCB board to blacken the gold layer when it is copied. However, due to the different production lines, equipment and liquid medicine systems used in various actual factories, we will analyze it from the following three aspects:



1. Nickel coating thickness control

Everyone must say that blackening of the gold coating is a problem. How do we talk about the thickness of the electroplated nickel layer. In fact, the gold plating layer of PCB is usually very thin, which is reflected on the gold plating surface. Many problems are caused by poor nickel plating performance. In general, thin nickel plating will cause the product appearance to turn white and black. Therefore, this is the first item checked by factory engineers and technicians. Generally, the thickness of nickel layer needs to be electroplated to about 5um.

PCB board

2. Solution of nickel plating cylinder

Still talking about nickel cylinders. If the nickel cylinder solution is not well maintained for a long time and the carbon treatment is not timely, the nickel coating is easy to produce lamellar crystals, which increases the hardness and brittleness of the coating. Serious blackening coating problems can occur. This is the control focus that many people often neglect. This is often an important cause of problems. Therefore, please carefully check the liquid state of your production line, conduct comparative analysis, and conduct thorough carbon treatment in time to restore the activity of the liquid and clean the electroplating solution.


3. Gold bottle control

Now we are talking about the gold column control. Generally speaking, as long as good liquid medicine filtration and supplement are maintained, the pollution degree and stability of gold bottle will be better than that of nickel bottle. However, it is necessary to check whether the following aspects are good:

1) Is the gold can supplement sufficient and excessive?

2) How to control the pH value of liquid medicine?

3) Conductive salt?

If there is no problem in the inspection result, use the AA machine to analyze the impurity content in the solution. The state of safely storing the liquid medicine in the tank. Finally, don't forget to check whether the gold canister filter cotton core has not been replaced for a long time.

Layers and their order are also important basic aspects of PCB design. For multilayer surface mount device (SMD) packaging, determine the optimal sequence of layers, stack PCB board, and define the construction method of circuit boards and the functions of printed circuits. There are many factors that affect your choice of stacking. The questions that must be answered include how many signal layers are needed, how many ground layers are needed, the thickness of the layers, and what materials should be used. In order to optimize the PCB layer and its layout of the circuit board, you need to fully understand the type and characteristics of the PCB board layer.


4. PCB board layer type

Number of PCB layers PCB structure refers to the number of different layers or layers that will carry signals. The layer type represents the type of signal that will propagate along the layer. Each signal layer or PCB board layer is composed of a dielectric material with a copper surface. Most layers are etched. However, the copper surface can also be a solid plane for grounding or energizing. Generally speaking, signal types can be divided into high frequency, low frequency, power supply or grounding. Dielectric and copper may have different design requirements depending on the type of signal.


5. PCB board layer type design requirements

The main materials of PCB layer are dielectric and copper. Dielectric materials provide isolation between different signal types on adjacent layers. This is also the main factor determining the resistivity of the circuit board. The surface copper of this layer defines the tracking current capacity, resistance and loss. The weight or thickness of copper is used to ensure sufficient current. Closely related to the weight of copper is the tracking width and length, which are used to specify the physical space of each signal path. For high-frequency PCB AC signals, trace matching (length and width) is very important for signal integrity, while for power and ground signals, minimizing losses (corresponding to shorter traces) is very important. The following table summarizes the design requirements that should be considered when designing PCB layers.


6. How to optimize the PCB board layer

In order to create the best PCB layout for your design, it is necessary to optimize it, which is made and operated by your cm. This can only be achieved through the optimal selection of the stack and the PCB board layer it consists of. Following these tips will help you achieve these goals.


7. PCB board layer stacking skills

1) Determine your motherboard signal type

The type of signal that appears on the board and on the board is the most important factor in selecting stacks and layers. For special and multi signal processing, you are likely to need more layers due to isolation and different reasons.

2) Determine the number and type of vias

Another factor that determines stacking requirements is through choice. For example, if you choose to bury vias, additional internal layers may be required.

3) Determine the number of signal layers required

After determining the signal type and vias, you can design the stack by defining the required number of layers and their types.

4) Determine the number of aircraft required

Select your power and ground planes so they can be used to shield the signal layer and reduce EMI.


8. PCB board layers tips of selecting

1) Define layers according to signal type

In order to determine the best parameters or material properties, each layer needs to be classified according to its function or the type of signal it will carry.

2) Select layer dielectric and copper according to signal requirements

After classifying the layers, you can select their dielectric constant and copper value. These choices will seriously affect the mechanical, electrical, thermal and chemical properties of each layer. However, other material properties should also be considered to optimize your selection based on their importance to the PCB layer type. Only by following good examples to make the best material selection and working with the CM that can achieve your selection can you optimize the PCB layer of the PCB board.