Commonly used fasteners for PCB are screws, nuts, washers, pressure plates and wire clips
1. Screws
Most of the currently used screw structures are slotted and cross-recessed. Because the cross recess has the advantages of good neutrality and the screwdriver is not easy to slip out, it is currently widely used. Type of screw
According to the structure of the head, the commonly used screw types include: non-protruding screws, spherical non-protruding screws, knurled high head screws, semi-round head screws, flat head screws, cylindrical head screws, hexagon socket screws, tapered end locking screws, flat end Tighten the screws, etc.
In addition, there are countersunk head screws, tap screws (self-tapping screws) and other types.
screw selection
(1) In most cases, when there is no special requirement for the mechanical connection surface, cylindrical head or round head screws can be used. Among them, the cylindrical head screw, especially the spherical cylindrical head screw, has a deep notch, and it is generally not easy to damage the notch when the screwdriver is tightened hard, so it is more suitable for parts that require greater tightening force than the half round head screw.
(2) When the surface to be connected is relatively flat, countersunk screws should be used. When the countersunk hole of the panel is adapted to the countersunk screw, the height of the screw and the panel can be kept very consistent, and the connecting piece can be positioned more accurately and the surface is more beautiful. It should be noted that this kind of screw generally cannot withstand large fastening force because of its shallow notch. Therefore, in electronic equipment, they are often used on the second layer panel of the whole machine (the first layer panel is often called a false panel in the industry), that is, the appearance panel.
(3) Tap screws are used on metal plates or wood boards and other similar materials. Because they can self-tapping threads, they can also be called self-tapping screws.

2. Nut
There are many types of nuts, and the more commonly used nuts are: wing nuts, round nuts, hexagonal nuts, square nuts, cap nuts, etc. All types of nuts serve specific purposes.
The common feature of the nut structure is that it can be turned by hand or wrench. Nuts apply pressure to the screw or bolt head and the object being fixed. When tightening the nut with a wrench, be careful not to use force, round the corners of the nut or peel off the threads.

3. Gasket
Common flat washers include flat type, external type, built-in type, spring cone, spring lock washer, fiber washer and so on. The flat washer can prevent the flat surface from being affected by the turning nut or screw, and the spring lock washer can protect the flat surface, but when tightening, the spring tension must be maintained to keep the nut from loosening. When metal to metal contact, the toothed combination can be used lock washers.

4. Pressure plate and wire clamp
Clamps and clamps are used to hold individual wires, harnesses, components and devices in defined positions. They provide a mechanical connection to reduce movement and strain on electrical connections. Clamps and wire clamps come in a variety of shapes and sizes, but apart from size and basic construction, the main difference lies in the covering being fastened. Sometimes it is necessary to pad plastic material or rubber material on the fastener to protect the covered surface, and at the same time provide protection or ease the covered object from vibration impact.