Introduction To The PCB Etching

A large number of quality problems related to the etching surface are focused on the etched part of the upper surface, and these problems come from the impact of the etching agent produced by the colloidal laminate. It is important to know this because the colloidal laminates accumulate on the surface of the copper. On the one hand, it will affect the injection force, on the other hand, it will block the supplement of fresh etching solution so that the etching speed is reduced. Because of the formation and accumulation of colloid like laminate, the etching degree of the upper and lower graphics of the substrate is different. The substrate entered first is not yet formed because of the accumulation, and the etching speed is fast, so it is easy to be thoroughly etched or caused by corrosion. Then the substrate entered because of the formation of the accumulation and slowed down the etching speed.

PCB etching process should pay attention to what problems

Maintenance of etching equipment

The most critical factor in maintaining etching equipment is to ensure high cleanliness and no blocking of the nozzle so that the nozzle can spray smoothly. Blocking material or slagging can cause pressure action during injection and impact the plate surface. And the nozzle is not clean, it will cause uneven etching and the whole circuit board scrap.

Obviously, the maintenance of the equipment is to replace the damaged parts and wear parts, because the nozzle also exists the problem of wear, so the replacement should include the nozzle. In addition, the more critical problem is to keep the etching machine without slagging, because many times too much slagging accumulation will affect the chemical balance of the etching solution. Similarly, if there is a chemical imbalance in the etching solution, slagging will become more severe. When a large number of slagging occurs suddenly in the etching solution, it is usually a signal that there is a problem with the balance of the solution. At this time, a strong hydrochloric acid should be used for appropriate cleaning or supplement of the solution.

Reduce side erosion and edge burst, improve etching coefficient

Side erosion can produce a burst edge. Usually the longer the printed board in the etching solution, the more serious the side erosion. Side erosion will seriously affect the precision of printed wire, and serious side erosion will make it impossible to make fine wire. When the side etching and abrupt edge decrease, the etching coefficient will increase, high etching coefficient means the ability to maintain thin wire, so that the etched wire can be close to the original size.

Whether it is tin-lead alloy, tin, tin-nickel alloy, or nickel plating etching agent, the conductor will be short-circuited when the edge is excessive. Because the protrusion is easy to tear down, the electrical disconnection is formed between the two points of the wire.

There are many factors affecting lateral erosion, and the following points are summarized:

Etching mode:

Soak and bubble etching will cause greater side erosion, splash and spray etching side erosion is small, especially the best effect of spray etching.

Types of etching solution:

Different etching solution, its chemical composition is not the same, etching rate is not the same, etching coefficient is not the same.

For example, the etching coefficient of the acidic copper chloride etching solution is usually 3, while the etching coefficient of alkaline copper chloride can reach 4.

Etching rate:

A slow etching rate will result in severe side etching.

There is a great relationship between improving the etching quality and accelerating the etching rate. The faster the etching speed, the shorter the time the substrate stays in the etching, the smaller the side etching amount will be, and the etched figure will be clearer and tidy.

The pH value of etching solution:

When the pH value of the alkaline etching solution is higher, the side erosion will increase.

In order to reduce side erosion, the pH value should generally be controlled below 8.5.

The density of etching solution:

The low density of alkaline etching solution will aggravate the side erosion, and the choice of the high copper concentration etching solution is very beneficial to reduce the side erosion.