What is a PCB counterbore?
What is a PCB counterbore?
The countersunk hole is a blind hole processed from the surface of an object to the inside of the object, and is often used to install bolts or other connecting parts.
Countersunk holes are drilled on the board with a round-tip drill or a gong knife, but they cannot be drilled through (that is, half-buried holes). The part of the connection between the surface layer at the outermost/larger diameter and the surface layer at the smallest round hole is Parallel to the surface of the PCB, part of the connection hole is a plane, not a slope.
Buried holes, to put it bluntly, are translucent and all-through, and can be made according to the size of the hole or the liquid hole. The effect is:
a, for connection, can be made into external thread buried hole.
b, as the cylinder of the piston engine.
c. It is used to transport liquid, gas, smoke and dust with the help of pumps, etc.
d. In daily life, the clothes and jeans that people wear are also examples of the use of buried holes.
The general crimping hole is a software hole with electroplated copper.
Due to the special design of the component feet, after being inserted into the hole, it can be tightly connected to the hole by relying on its own structural support.
The advantage is to reduce the wave soldering required to solder these components; if these holes are not soldered in the end, it will be easier to replace parts. Of course, changing it multiple times will affect the stability of the hole.
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Component feet that specify a crimping hole generally have a swelling effect instead of an external thread effect.
Some will be welded together later when other components are welded by xx welding, while others are only welded.
Before the implementation of the GB-1984 standard, the counterbore was divided into three names:
1. The top of the head of the standard part is completely sunk into the step hole of the part, which is called countersunk hole
2. The top of the head of the standard part is not completely sunk into the step hole of the part, which is called the lower hole
3. The head of the standard part basically does not sink to the part, and only the surface of the part is spot-faced. The hole is called a fisheye lens pit
The distinction between the lower hole and the countersunk hole depends on the drilling above the anchor bolt hole: the countersunk hole is a straight cylindrical structure; the lower head hole is a 45-degree structure, which is more stable than the countersunk hole.
Drilling holes above the anchor bolt holes can accommodate the top of the anchor bolt head, so that the top of the screw head is not lower than the surrounding surface. Bottom hole and countersunk hole are just two different names.
Generally, the countersunk head is used in places where the surface is smooth and not raised after the connection is required, because the countersunk head can be screwed into the parts. The round mouth can also be screwed into the part. The tightening force of the square head can be larger, but the specification is very large. In addition, in order to better meet the needs of tightening after installation, there are holes in the top of the head and holes in the stem. These holes can prevent the anchor bolts from loosening when they are vibrated. Some branches without external threads need to be thinner, which are called thin-waisted bolts. This type of anchor bolt is good for connections subject to variable forces. There are special high-strength bolts on the steel frame structure, the top of the head will be bigger, and the size will also change.
In addition, there are special uses: TV-shaped groove anchor bolts are placed more on the chuck of the machine tool, and the shape is unique, and both sides of the top of the head must be cut off. Anchor screws are used to fix equipment and ground connections, and there are many shapes. U-bolts, as previously described. These. There are also special-purpose nuts for electric welding. One end has an external thread and the other end does not, which can be welded on the part, and the nut is directly screwed on the other side.