PCB terminal principle, specification size, type, how to use the terminal block?
1. PCB terminal principle
When you open the universal computer keyboard, you can see a soft film (flexible insulating substrate) with a silvery-white (silver paste) conductive map and a position map. Because the universal screen is leaked
method to get this pattern, so we call this printed circuit board flexible silver paste printed circuit board. We went to Computer City to see various computer motherboards. Graphics. Network card. Modem. Sound cards are different from printed circuit boards on home appliances.
The substrate is made of paper-based (often used on one side) or glass cloth-based (commonly used on both sides and multiple layers), phenolic or epoxy prepreg, copper plates pasted on one or both sides of the surface, and then laminated and cured.
This circuit board is covered with a copper plate, which we call a rigid board. Then the printed circuit board is made, which we call a rigid printed circuit board. There is a printed circuit diagram on one side, we call it a single-sided printed circuit board, and there is a printed circuit diagram on both sides, and then the double-sided connection is made by the metallization of holes, which is called double-sided.
If both sides are inner layers. Two single-sided outer layers or two double-sided inner layers. The two sides serve as the outer printed circuit board, which is alternately connected by a positioning system and insulation bonding material, and the conductive pattern is connected into four layers according to the design requirements. Six-layer printed circuit boards, also known as multilayer printed circuit boards, have more than 100 layers of practical printed circuit boards.
2. PCB terminal size: 3.50mm.3.81mm.5.00mm.5.08mm.7.50mm.7.62mm.
3. PCB terminal type: plug and unplug terminal block. Screw terminal blocks. Spring terminal blocks. Fence terminals.
1) Plug and unplug the terminal block
The pitch is 220.127.116.11.5.0.5.08.18.104.22.168 poles, 2-24 wires are available with screwed sockets for matching and seismic connections. The plug uses side connection technology, i.e. the screw direction is perpendicular to the wire entry direction.
2) Screw terminals
Circuit board terminals have always played a very important role in the electronics industry and have become an important part of printed circuit boards. Its structure and design have the advantages of convenient wiring, firm screw connection, compact structure, reliable connection and advantages; The principle of sandwich lifting is adopted to ensure reliable wiring and large wiring capacity; The welding foot and the sandwich layer are divided into two parts to ensure that the distance of the tightening screw will not be transmitted to the solder joint, damaging the solder joint; The housing is robust and reliable, with accurate needle pitch.
3) Spring printed circuit board terminals
Spring printed circuit board terminals provide 2.54mm, 3.50mm, 5.00mm, 7.50mm, 7.62mm equidistance; The single-core wire can be inserted directly without the assistance of the handle, but the smaller wire can be clamped with the handle to open the clamp; There is no button specification, and the height can be greatly reduced. When retracting, the wire can be easily removed by simply pressing a starting point; large wires; Most springs are combined together; The wiring method is very suitable for communication systems. Lighting system. use of monitoring systems and building wiring; Various wiring directions facilitate assembly in tight spaces, and the number of wiring can be arbitrarily combined. Easy to operate, suitable for high-density wiring requirements.
4) Fence terminals
The fence model code is LW; The middle pin code is C; The pin code next to it is B; The fixed code is M; The bent needle code is R; The bond wire code is Q; LW fence products have simple structure, and the plate crimping line is intuitive and firm; Wire diameter range: 0.5m㎡-6m㎡.
4. How to use terminal blocks?
1) Identification method
a. The actual or relative position of the device terminal or specific wire terminal is determined and identified by the marking system of the relevant product.
b. Use the marking system of the relevant product to determine and identify the color marking of the device terminal and the specific wire terminal.
c. Use the graphic symbols specified in GB5465. If auxiliary symbols are required, they should match the GB graphics in 4728.
d. Use the alphanumeric symbols specified in GB5465.
2) Connection method
a. Screw connection
The screw connection adopts the connection method of screw terminal block, pay attention to the Z large, Z small section and Z large tightening torque allowed by different specifications of screws.
Soldering Z is common soldering. Solder Soldering Connection Z is important for the metal continuity between the solder and the solder surface. Therefore, welding is very important for cold pressing terminals. Tin alloy is a common coating for the terminal ring end soldered end Z. Silver and gold. Common solder ends have spring contact solder lug type. Punched and notched solder lugs: Pinhole contact has drilled arc notches for common weld ends.
Crimping is a technique of compressing and displacing metal within specified limits and connecting wires to the opposite side of the contact. A good crimp connection can produce a flow of metal melting to each other, so that the wire and contact deform the material symmetrically. The connection is similar to a cold-welded connection with good mechanical strength and electrical continuity to withstand harsher environmental conditions. It is generally believed that correct crimping is better than soldering, especially in high-current applications. Special crimping pliers or automatic crimping must be used. Semi-automatic crimping machine. According to the wire section of the cold-pressed end head, correctly select the conductor barrel that contacts the pair. It is important to note that the crimp connection is a permanent connection and can only be used once.
Winding is the winding column that winds the wire directly on an angular contactor. When winding, when the tension is controlled, the wire is wound, pressed and fixed at the corners of the contactor winding column to form a gas-tight contact. There are several requirements for winding wires: the nominal value of the wire diameter is within the range of 0.25mm~1.0mm; The wire diameter is not more than 0.5mm, the elongation of the conductor material is not less than 15%, and the wire diameter is greater than 0.5mm, and the winding tools include winding guns and fixed winding machines.
e. Puncture succession
Piercing connection, also known as insulation displacement connection, is a new high-reliability technology invented in the United States in the 60s of the 20th century. Low cost. Widely used in various printed board terminals, cold-pressed terminals, ring terminals and other characteristics. Suitable for connection of ribbon cables. There is no need to peel off the insulation layer of the cable when connecting, relying on the tip of the terminal "U" shaped contact spring to be pierced into the insulation layer, so that the cable conductor slides into the groove of the contact spring, clamps the copyright ownership of the control engineering network, and makes the cable conductor and the terminal spring tightly connected. It only requires simple tools, but the prescribed cable must be selected.