About the difference between various surface treatment processes of circuit boards

捷配pcb打样工厂

About the difference between various surface treatment processes of circuit boards [Copy link]

The main factor that directly determines the quality and positioning of a board is the surface treatment process. For example, OSP tin-spraying, gold plating, and immersion gold. Relatively speaking, immersion gold is for high-end boards. Due to its good quality, immersion gold is also relatively high in cost. Therefore, many customers choose the most commonly used tin-spraying process. Tin-spraying is divided into leaded tin-spraying (i.e. hot air leveling) and lead-free tin-spraying. You can see the difference between each process below;

After making circuit boards for a long time, you will always encounter various problems. For example, some end users require lead-free sample boards. When they are welded, processed and debugged, manual welding always feels that it is not as easy to tin as lead-free. At this time, it is not sure whether it is the problem of the circuit board factory or the problem of welding itself.

In fact, when manually soldering samples, it is easier to tin with lead. The wettability of lead is much better than that of lead-free because lead will increase the activity of tin wire during the soldering process. However, lead is toxic, and lead-free tin has a high melting point, so the soldering point is much stronger.

Leaded and unleaded tin can also be distinguished visually: leaded tin is brighter, and lead-free tin (SAC) is darker.

Lead-free process: A basic concept of lead-free electronic assembly is that in the soldering process, whether it is manual soldering, dip soldering, wave soldering or reflow soldering, the solder used is lead-free solder (pb-feer soder). Lead-free solder does not mean that the solder is 100% lead-free. In lead solder, lead exists as a basic element. In lead-free solder, the basic element does not contain lead.

[attach] 51)]

(Lead-free and leaded: from top to bottom)

Lead process: In the traditional soft soldering process of printed circuit board assembly, tin-lead (Sn-Pb) solder is generally used, in which lead exists and plays a role as a basic element of the solder alloy. Lead solder alloy has a low melting point, low welding temperature, and less thermal damage to electronic products; lead solder alloy has a small wetting angle, good solderability, and the possibility of "false soldering" of product solder joints is small; the solder alloy has good toughness, and the formed solder joints have better vibration resistance than lead-free solder joints.

Compared with the three surface treatments of .osp lead-free tin spraying and immersion gold process. Although they are all relatively environmentally friendly,

but most ordinary conventional boards are more used for the first two. Because the cost is relatively low. (The picture shows the OSP process)

OSP is suitable for fine lines and fine SMT spacing. The operating temperature is low, there is no damage to the board, and it is easy to rework and repair.

However, the boards made by the OSP process are not acid-resistant, and the high humidity environment will affect its welding performance. It is necessary to complete the welding in the shortest possible time. Although both immersion gold and gold plating are relatively wear-resistant, there are still differences between the two: in the case of gold plating, gold is only plated on the surface, and there is only copper-nickel on the side, which is easy to oxidize over time. This is a defect of the gold plating process and cannot be used in high-demand occasions.

(Pictures of gold plating and immersion gold: from top to bottom)

If you do immersion gold, the entire pad, including the side, can be plated with nickel gold. It is currently the most stable and can be used in various occasions. However, immersion nickel gold has a more headache and more difficult to find problem, that is, the adhesion is not as good as gold plating, and it is easy to fall off after a period of use.

After reading the comparison of these processes, I believe you have a new understanding of the process selection of the board. Welcome to find me to learn about proofing knowledge!

shakencity

The surface process directly affects the performance and quality of the circuit board. It is worth studying to make high-quality products.