Brief History of PCB Development (2)

3. In order to meet the requirements of environmental protection, how will the PCB manufacturing technology change?

1) Reduce Lead Content

The method of making pattern electroplating by electroplating lead and tin is tending to be rapidly abolished. In the future, it will be more converted to the whole board plating (Panel Plating) process. In the case of using the pattern plating method, electroplating tin will also become the mainstream. In the case of using solder, the solder will be converted to a lead-free material, and there will be more progress in this area in the future. It is expected that this change will have little impact on the entire PCB manufacturing process.

2) Reduce The Amount of Formaldehyde Used

Formaldehyde is used as a reducing agent for electroless copper plating in PCB production. At present, from the perspective of environmental protection, there will be stricter restrictions on its use in the future. In the future, it will be the future development trend to reduce or no longer use formaldehyde materials through changes in the electroplating process. Direct electroplating will become a widely used electroplating method. The re-understanding of the significance of adopting this electroplating method and the further improvement of this process method are important tasks to be carried out in the future.

3) Progress of MID

Thermoplastic resin is a polymer material that can be easily recycled. In order to meet the requirements of environmental protection and maintenance of the ecological environment in the future, more thermoplastic resins will be used in circuit parts in the future. It is called: Molded Interconnect Device (MID for short), which will replace part of the PCB of traditional manufacturing technology. MID will become a potential “new army” in PCB.

4) Other Materials

Materials that are compatible with environmental protection, such as solder resist materials, printed circuit board substrate materials (flame-retardant non-halogen-containing substrates), will receive more and faster development. This also makes the main materials used in the PCB manufacturing process change greatly. For this reason, in PCB manufacturing, those original process technologies will be subject to a lot of impact.

4. High-Speed Circuit

It is generally believed that if the frequency of a digital logic circuit reaches or exceeds 45MHZ~50MHZ, and the circuit operating above this frequency has already accounted for a certain amount of the entire electronic system (for example, 1/3), it is called a high-speed circuit.

In fact, the harmonic frequency of the signal edge is higher than the frequency of the signal, which is the unexpected result of signal transmission caused by the rapidly changing rising and falling edges of the signal (or signal transition). Therefore, it is generally agreed that if the line propagation delay is greater than 1/2 the rise time of the driving end of the digital signal, such a signal is considered to be a high-speed signal and produces transmission line effects. The delivery of a signal occurs at the instant the signal state changes, such as rise or fall time. The signal passes a fixed period of time from the driver to the receiver. If the transit time is less than 1/2 the rise or fall time, the reflected signal from the receiver will reach the driver before the signal changes state. Conversely, the reflected signal will arrive at the driver after the signal changes state. If the reflected signal is strong, the superimposed waveform has the potential to change the logic state.

5. V_CUT

One way to form a circuit board is to cut a straight line at the same position on the upper and lower sides of the board but not cut it, so that it can be broken manually or using a jig to form a V-shaped groove from the side of the board, so called V_CUT.

6. Gold Finger

Refers to some circuit boards, such as network cards, the gold-plated wires on the edge of the upper panel are called gold fingers because their shape is similar to fingers.