Some assembly houses work well with either Surface-Mount-Devices (SMDs), or with
Pin-Through-Hole-devices (PTHs). However, Printed Circuit Boards (PCBs) that are
assembled with a mixture of both SMDs and PTHs, require special handling.
Does your PCB Assembly House work well with this mixed assembly?
SMDs and PTHs each use different soldering techniques.
The SMDs can be assembled onto the PCB using reflow soldering, or they can be wave
In the reflow process, a solder paste is applied to the solder pads of the PCB,
using a screen printing process, and the SMDs are placed on the solder paste. Then
the SMDs and PCB are both heated, reflowing, or melting, the solder, which connects
the leads of the component to the pads.
Instead of reflowing a solder paste, a wave of solder can be used to connect the
SMDs to the PCB. However, the SMDs have to be glued to the PCB first, or they may
fall off the PCB as it is turned over, and the wave of solder would wash off any
Pin-Through-Hole devices, after they are inserted into the holes, require wave soldering
to connect them to the PCB.
When a mixture of both surface-mount and through-the-hole-devices are used on the
same PCB, several steps are needed for soldering:
1. SMDs are reflow soldered on the "component-side" of the PCB.
2. On the "solder-side", the SMDs are then glued in place, without soldering.
3. PTH components are machine inserted, with their leads through the holes, from
4. Special handling components are inserted into the PCB at this time.
5. The solder-side of the PCB is wave soldered; soldering the SMDs glued on the
solder-side, the leads of the PTH components, and the special handling components,
all in one step.
6. The board is tested.
Issues that may need to be addressed before submitting the PCB for manufacturing:
o PTH devices need more room on the PCB, to allow maneuvering of the insertion machines.
o Thermal profile issues should be considered when lead free techniques are used
The expertise encountered at RUSH PCB Inc., with all three types of assembly, SMD,
PTH, and mixture of both SMD and PTH, makes Rush PCB a good choice for assembly.
Please call or email us at
with your questions, or to receive more information.