Through Hole Technology
As a through-hole mounting (English through-hole technology, THT; pin -in- hole technology, PIH ) is called in the construction and connection technology, a way of mounting leaded electronic components. In contrast to surface mounting (English: surface- mounting technology, SMT) through-hole mounting is characterized in that the components have wire connections ( " wired components "). They are in the assembly is inserted through the contact holes in the circuit board and then connected by soldering (conventional hand soldering, wave soldering, or selective soldering ) with the conductor.
Technology
In the conventional PCB assembly dual -inline package be used with a pitch of 2.54 mm. The grid, or also known as pitch, is the center distance between two connection pins of the device. By using SMD technology can be dispensed with contact holes for the soldering of the components, but not completely to the holes in the printed circuit board, which is needed in the form of plated-through holes for electrical connection through a plurality of layers.
Thus, a much higher density of components on the printed board and achieves a reduction in manufacturing steps and hence the manufacturing cost. As part of this savings opportunity THT was attempted to be replaced.
Areas of application
Information Electronics
In the area of Information Electronics wired components were largely replaced by SMD components in the industrial sector. Simple and inexpensive products in the consumer sector but they remain partially or completely made with wired components.
Power Electronics
The situation is different in the field of power electronics. There default leaded components are used, among other things because of the required current carrying capacity of the devices themselves and the connection of current-carrying components in the different layers of the circuit board as before.
Some components with high mechanical stress (eg connectors, larger switches, larger electrolytic capacitors, power inductors and power semiconductors) must continue to be secured by means of through-hole mounting on the PCB, because often these components are not shown SMD types. For purely surface-mounted components is under high mechanical loads or high current load is a risk that the soldering or the interconnect is over-stretched or damaged. For this reason, circuit boards are often mixed stocked. Here, the disadvantage that the THT process is not continuous automated, thus causing additional costs.
Hand-made devices
Devices that are hand soldered by craftsmen or hobby electronics engineers are usually made with discrete components because they are easier to handle. So keep for example, even during the soldering process in the PCB, while SMD components need to be fixed. Because of their size, through hole components are less at risk of overheating and can also be soldered with conventional soldering iron sizes. Due to their size, their types can be well seen with the naked eye, and they can be processed well with bare hands.
Kits for electric devices are usually designed with discrete components. Since the soldering is performed here by the end user, the work of the industry to the etching of the PCB and the packaging of the components is limited. So there are no additional costs for the industry, but it is opened up, a larger customer base.
Chance, however, SMD components are used when it comes to small size or good high frequency characteristics in these areas.
THT Reflow Technology
In the age of SMD placement by automated placement machines and soldering it offered itself, therefore, such as connectors, which are not suitable really for this type of construction, nevertheless make the reflow soldering available. In this context, the through hole reflow technology ( THR) has been developed. Here, Through-hole components designed for automatic assembly and the high thermal load in the reflow oven. This allows the mounting cost of automatic PCB assembly lowered because some process steps of the normal THT assembly omitted.
"Pin in Paste" and PIHIR - - For THR Technology, the terms are used PiP " Pin in Hole Intrusive Reflow ".