Electronic Assembly UK

Capabilities: Mixed Assembly Placement


The Surface Mount Devices (SMDs) and the solder pads are attached to the same side of the Printed Circuit Board, the pads can be on both sides of the PCB.

Pin-Through-Hole devices (PTH) are placed on the top side of the PCB, have their leads inserted through holes in the PCB, and are soldered from the bottom usually through a wave soldering process.

PCB circuit assemblies that use both types of components, SMD and PTH, require special handling because they each use different soldering techniques.

Surface Mount Technology (SMT) Soldering

Surface Mount Devices uses reflow or wave soldering to be attached to the Printed Circuit Board.

Reflow Process

  • Solder Paste is applied to the Solder Pads to the PCB with a stencil
  • The SMDs are applied with their leads on top of the Solder Paste
  • The Surface Mount Device and Printed Circuit Board are heated
  • Reflowing (melting) the solder, connects the leads of the components to the solder pads


Wave Process

  • The components are place and glued on the PCB
  • The Printed Circuit Board is turned over

Pin Through Hole Soldering

Pin-Through-Hole devices, or Plated Through-hole Devices (PTH) must be wave soldered

After the PTH components are inserted into the holes of the PCB, and without turning the board over, the PCB is passed over the wave of solder, connecting the component leads to the printed circuit board.

Mixed Component Assembly Soldering

When both SMT and pin-through-the-hole devices are used on the same assembly, several steps are needed for soldering:

  • On the “component side” of the PCB, the SMDs are placed and reflow soldered;
  • The board is turned over and on the “solder side,without soldering them; the SMDs are then glued in place;
  • The board is turned over again, and passing their leads through the holes in the PCB from the “component side”, PTH components are machine inserted;
  • Now, special-handling components are inserted into the PCB by hand;
  • The “solder side” of the PCB is wave soldered, soldering the SMDs glued to the “solder side”of the PCB, the leads of the PTH components, and the leads of the special handling components, all in one step
  • The board is tested.

Mixed Component Assembly Issues

Before submitting the PCB for manufacturing, some design issues are of special concern and need attention:

  • To allow maneuvering of the insertion machines, PTH devices require extra room on the PCB;
  • When making decisions about assembly using lead-free techniques, the thermal profile issues affecting the soldering process should be addressed.

Mixed Component Assembly

Rush PCB UK has both experience and expertise in all three types of assembly SMD, PTH, and mixture of both SMD and PTH.  Regardless of your Printed Circuit Board needs our engineers will be able to make your project a reality.

Let our engineers at RUSH PCB work with you on the engineering and design of your mixed component assemblies, your project is too important to trust it to anyone else.

For more information, contact us at sales@rushpcb.uk, or call us at 0203 750 0201