The so-called tin spraying is to immerse the circuit board in molten tin and lead. When enough tin and lead is attached to the surface of the circuit board, hot air pressure is used to scrape off the excess tin and lead. After the tin-lead is cooled, the soldering area of the circuit board will be stained with a layer of tin-lead of appropriate thickness. This is the general procedure of the tin-spraying process.
The surface treatment technology of PCB, currently the most widely used is the spray tin process, also called hot air leveling technology, which sprays a layer of tin on the pad to enhance the conduction performance and solderability of the PCB pad.
As the most common form of surface coating for circuit board surface treatment, tin spraying SMOBC&HAL is widely used in the production of circuits. The quality of tin spraying will directly affect the quality of soldering and soldering during subsequent customer production. Solderability; therefore, the quality of spray tin has become a focus of quality control for circuit board manufacturers
For general double-sided boards, the tin spraying and OSP processes are the most used, while the rosin process is widely used on single-sided PCBs, and the gold-plating process is used on circuit boards that require bonding ICs. Immersion gold is used more on the plug-in board.
As shown in the figure below, this is a picture of a double-panel sprayed tin.
The main function of PCB tin spraying:
(1) Prevent oxidation of bare copper surface;
Copper is easily oxidized in the air, resulting in non-conduction of the PCB pads or reducing the soldering performance. By applying tin on the copper surface, the copper surface can be effectively isolated from the gas, and the continuity and solderability of the PCB can be maintained.
(2) Maintain solderability;
Other surface treatment methods include: hot melt, organic protective film OSP, chemical tin, chemical silver, chemical nickel gold, electroplated nickel gold, etc.; but the cost-effectiveness of the tin-sprayed board is the best
Process characteristics of spray tin PCB board
The spray tin plate includes two layers of copper and tin metal, which can adapt to poor environmental conditions and has better solder performance. It is more suitable in high temperature and corrosive environments. This type of board is commonly used in industrial control equipment communication products and military equipment products
Advantages of tinned PCB:
In the usual PCB surface treatment, the tin spraying process is called the best solderability, because there is tin on the pad, when soldering the tin, it is easier to compare with the gold-plated board or the rosin and the OSP process. . This is very easy for us to solder by hand, and soldering is very easy.
Manufacturing process of spray tin board PCB:
In PCB manufacturing, for double-sided and multi-layer boards, if mass production, the most commonly used is to make tin-sprayed craft boards. If bonding or immersion gold boards are not required, it is recommended that users use spray-sprayed boards in mass production. Tin craft