1、 Characteristics of PCB ink
1. Viscosity and thixotropy
in the manufacturing process of printed circuit boards, screen printing is one of the indispensable and important processes. In order to obtain the fidelity of image reproduction, the ink must have good viscosity and appropriate thixotropy.
the pigments and mineral fillers of PCB inks are generally solid. After fine grinding, their particle size does not exceed 4/5 microns, and form a homogeneous flow state in solid form.
2、 Types of PCB inks
PCB inks are mainly divided into three types: circuit, solder mask and character inks.
1. The circuit ink is used as a barrier layer to prevent corrosion of the circuit. It protects the circuit during etching. It is generally liquid photosensitive; There are acid corrosion resistance and alkali corrosion resistance.
2. The solder resist ink is applied to the circuit after the circuit is completed to protect the circuit. There are liquid photosensitive, heat curing and UV hardening types. The bonding pad is reserved on the board to facilitate the welding of components and play the role of insulation and anti-oxidation.
3. Character ink is used to mark the surface of the board. For example, it is usually white.
in addition, there are other inks, such as strippable adhesive ink, silver paste ink, etc.
The application of PCB is familiar to everyone. It can be seen in almost all electronic products. There are many types of PCB in the market. Different manufacturers produce the same type of PCB, which is also different. It is difficult for users to distinguish the quality when purchasing. In this regard, the technician organized and introduced the methods to distinguish the quality of PCB circuit board:
First、 Judging from the appearance:
1. Weld appearance.
Due to the large number of PCB parts, if the welding is not good, the PCB parts are easy to fall off, which seriously affects the welding quality and appearance of the PCB. It is very important to identify carefully and make the interface stronger.
2. Standard rules for size and thickness.
Because the thickness of standard PCB is different from that of PCB, users can measure and check according to the thickness and specification of their own products.
3. Light and color.
Generally, the external circuit board is covered with ink, which can play an insulating role. If the color of the board is not bright, less ink indicates that the insulation board itself is not good.
Second、 Judging from the plate:
1. Ordinary HB paperboard and 22F are cheap and easy to deform and break. They can only be used as a single panel. The color of the component surface is dark yellow with an irritating smell. The copper coating is rough and thin.
2. The price of single-sided 94v0 and CEM-1 boards is relatively higher than that of paperboard. The color of the component surface is light yellow. It is mainly used for industrial boards and power boards with fire rating requirements.
3. Fiberglass board, with high cost, good strength and green on both sides, is basically used for most double-sided and multi-layer hard boards. Copper coating can be very precise and fine, but the unit board is relatively heavy.
No matter what color of ink printed on the Printed Circuit Board, it shall be smooth and flat. There shall be no false line exposed copper, blistering, easy falling off and other phenomena. The characters shall be clear, and the oil on the through hole cover shall not have a sharp edge.