Common fasteners for PCB are screws, nuts, washers, pressure plates and wire clamps
First, the screw
Most of the screw structures currently used are in the form of a slot and a cross slot. Since the cross recess has the advantage of being neutral, the screwdriver does not easily slide out, so it is currently widely used.
1, the type of screw
According to the head structure classification, common types of screws include: no-out screws, spherical non-leaving screws, knurled high-head screws, semi-circular head screws, flat-head screws, cylindrical head screws, hexagon socket screws, taper end locking screws, flat ends Tightening screws, etc.
There are also types of countersunk screws, tap screws (self-tapping screws).
2, the choice of screws
(1) In most cases, cylindrical heads or semi-circular head screws are available when there are no special requirements for mechanical joint surfaces. Among them, the cylindrical head screw, especially the spherical cylindrical head screw, is deeper than the notch, and it is generally difficult to screw the notch when the screwdriver is firmly tightened, so it is more suitable for the part requiring larger fastening force than the semi-circular head screw.
(2) When the surface to be connected is relatively flat, the countersunk screw should be used. When the counterbore of the panel is fitted with the countersunk screw, the screw can be kept at a consistent height with the panel, and the connector has a relatively accurate positioning and a beautiful surface. It should be noted that such a screw generally cannot withstand a large fastening force because the slot is shallow. Therefore, in electronic devices, they are often used on the second layer of the whole machine (often referred to as a dummy panel in the first layer panel industry), that is, the appearance board.
(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.
Second, the nut
There are many types of nuts. The more commonly used nuts are: wing nut, round nut, hex nut, square nut, cap nut and so on. All types of nuts have specific uses.
The common feature of the nut structure is that it can be rotated by hand or by hand. The nut applies pressure to the screw or bolt head and to the object being fixed. When using the nut on the plate, you must be careful not to use the brute force. You cannot round the corners of the nut or peel off the thread.
Third, the gasket
Common flat washers are flat, external, built-in, spring-conical, spring-loaded washers, fiber washers, and more. The flat washer prevents the flat surface from being affected by the rotating nut or the screw. The spring lock washer can protect the plane. However, when tightening, the spring tension must be maintained to keep the nut from loosening. When the metal and the metal are in contact, the toothed joint can be used. Lock washer.
Fourth, the pressure plate and wire clamp
Platens and wire clamps are used to secure individual wires, harnesses, components, and components where they need to be defined. They provide a mechanical connection to reduce motion and tension at the electrical connections. The shape and size of the platen and wire clamp are varied, but apart from the size and basic structure, the main difference is the fastened cover. Sometimes it is necessary to place a plastic or rubber material on the fastener to protect the covered surface, while also providing protection or mitigating the covering from vibration shocks.