PCBA manufacturer PCB printed circuit board component lead formation
There are two pretreatment steps: lead forming and component assembly before welding Pcba components to printed circuit boards.
The lead of a plug-in component must be bent to fit the PCB installation before it is welded to the PCB, known as lead forming.
1. The purpose of lead forming
Printed circuit boards welding wire, instrumentation components will lead forming processing, for the axial lead components lead out from both sides into a glyph (components), in order to make its instrumentation on the printed circuit board, to the same direction vertical bending, two lead to and two leads to parallel with the plane of the horizon, not only can alleviate the immersion tin lead thermal shock, Protection components and circuit board, installation convenient and reliable, and can make components for the lead in the same direction of components (such as transistors, etc.), in order to increase the distance of the heat conduction, to improve the thermal resistance, ease during welding due to the electric heating temperature change caused by thermal expansion, shrinkage stress and so on, also want to lead forming processing, Lead forming should pay attention to bending at a certain distance from the lead root, can not apply any stress to the root, because this kind of components in the production and processing process due to heat treatment and brittle, easy to break.
2. Wire forming and welding
Wire in the printed circuit board as a connecting line, can be seen as a plug-in, so before welding wire also need to be shaped. Cut the wire to an appropriate length according to the connection requirements. The cut wire must be straight and not twisted. Strip the tin on the wire and clamp it 20mm away from the end of the search wire with a needle-nose pliers. Be aware that holding the wire down with your thumb may cause it to become contaminated, so use tweezers or another pair of needle-nose pliers to work together to bend the wire.
Determine the welding pad hole to be connected, insert one end of the bent wire into the side jack, test the length of the two holes to be welded, take out the wire, and square the other end of the wire into a right Angle; The conductor can not be inserted into the manhole, but the method of bending the insertion part vertically upward towards the jack, and the other end is aligned with the welding hole on the other side, and the conductor is directly bent into a right Angle.
After the wire is formed, insert the wire into the welding pad hole. When inserting the wire, the lead should be vertical. If the wire is too short or too long, the welding of the wire will be unqualified, as shown in Figure 4-28.
Wire insert need to be done at the other side of the circuit board welding after work, if turn directly to the circuit board welding, wire can fall from the welding plate hole, so you need to take a certain method, can be inserted in the wire to wire bending processing, after keep wire sticktite, pay attention to keep long nose pliers and parallel to the circuit board when bending, bending wire and circuit board into 30 °, Bend the other side of the wire in the same way, following the direction of the circuit board copper foil, but not beyond its edge. In addition, insulating small board can also be used. When the connecting wire lead is inserted, the insulating small board is covered on the connecting surface, and then the insulating small board and printed circuit board are welded. This method has obvious advantages in disassembly and welding.
After welding the connecting wires, cut off the excess wires with diagonal pliers. The reserved length of the wires should not exceed the radius of the pad and be flush with the top of the solder joint as far as possible.
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