SMT surface mount technology (namely
, is the electronic group
A, 1, the layout of the components when circuit board into the reflow soldering furnace of conveyor belt, the axis of the components should be and equipment of vertical transmission direction, so that we can to prevent the occurrence of components on the board in the welding process drift or monuments, 'vertical' phenomenon.
2, on the PCB components to uniform distribution, especially to the high power devices spread out, to avoid local overheating on PCB circuit work stress, and influence the reliability of solder joints.
3, double SMT components, on both sides of bulky device to stagger the installation position, or in the welding process will influence welding effect because of the local thermal capacity increase.
4, and cannot be placed on the surface of the wave soldering PLCC/QFP device has pin.
5, installed in a large SMT components on the surface of the wave crest welding and solder wave, its long axis to flow direction is parallel, thus reducing the solder bridge between the electrodes.
6, large and small on the surface of the wave soldering SMT components cannot be arranged in a straight line, to stagger position, so as to protect the welding with the solder wave 'shadow' effect of virtual welding and leakage caused by the welding.
2, 1, wave soldering of SMT solder SMT components, its larger components of welding on the surface of the disc (
Such as transistors, socket, etc. )
To add more, such as SOT23 bonding pad can lengthen 0.
1 mm, so that you can avoid because of the element 'shadow effect' and the empty welding.
2, the size of the welding plate, welding plate should be determined according to the size of the components is equal to or slightly greater than the width of the width of the components of the electrode, the welding effect is best.
3, between the two connected components, to avoid big welding using a single disk, because big welding plate solder will take two components to the middle, the right thing to do is to separate two components of bonding pad, between two bonding pad with a finer wire connection, if required wires through the larger current can cover several parallel wire, wire green oil.
4, SMT components of welding plate or in the vicinity can't have a hole, or in the REFLOW process, welding plate after the solder melts flow along the hole, can produce a virtual welding, little tin, is also likely to cause a short circuit flow to the other side of the board.
SMT characteristics of high density assembly, electronic products, small volume, light weight, the volume and weight of the SMT components only about 1/10 of the traditional instrumentation component, generally USES the SMT, electronic products smaller 40% ~ 60%, 60% ~ 80% reduction in weight.
High reliability, anti-seismic ability.
Solder joint defect rate is low.
Good high frequency characteristics.
Reducing the electromagnetic and radio frequency interference.
Easy to realize automation, improve production efficiency.
Reduce the cost of
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