You can find two sorts of construction employed in PCB assembly, through-hole structure and surface-mount construction. Both techniques have their own advantages and disadvantages and are both integral to this practice.
Through-hole construction involves the leads of components getting pushed through holes in the PCB fabrication and soldered to pads on the opposite side. This can either be done manually or with the usage of mounting machines.
Surface-mount construction involves components getting attached directly to the face of a PCB. Surface-mount components could be a lot more compact than there through-hole equivalents as they’ve substantially smaller leads and even none in any respect. They some times use hooks, horizontal contacts or solder balls rather than an alternate to directs.
Surface-mount components have many benefits over the older style through-hole components. As mentioned above they may be much smaller but they can also have a lot more connections. They also permit even faster and more easy assembly and components can be placed on both sides of the board. Additionally, they are also less costly than through-hole components as a general rule.
It is absolutely reasonable to state surface-mount components are preferred in modern PCB assemblies but both kinds are still used generally. There are nevertheless a few components that are only available at 1 type or one other and through-hole construction provides a few additional strength to this text that may sometimes be required. Due to the complex nature of minding surface-mount components, amateurs hobbyists are considerably more likely to use through-hole components.
Components are attached to both PCBs with numerous different soldering techniques. Large scale production is usually completed with machine positioning & most probably reflow ovens. Very little components could be attached by highly skilled professionals with the help of a microscope and accuracy tools.
Once assembly is complete the circuit is usually analyzed by visual inspection to inspect the quality of the building, analog signature analysis whilst the power is off, in circuit testing to inspect frequency and voltage while the ability is still around and finally a operational evaluation to guarantee that the circuit works in the way it was meant to.