Mixed Assembly Placement
PCB circuit assemblies using both types of components, SMD and PTH, require special handling because they each use different soldering techniques.
Surface Mount Technology (SMT) Soldering
SMDs can be attach to the PCB using reflow soldering, or they can be wave soldered.
In the reflow process, solder paste is apply to the solder pads of the PCB using a stencil, and the SMDs are place with their leads on top of the solder paste. Both the SMDs and the PCB are heat, reflowing (melting) the solder, connecting the leads of the components to the solder pads on the PCB.
Functions of Assembly Capabilities
To wave solder, when connecting the SMDs to the PCB-Assembly, instead of reflowing the solder paste, a wave of solder can be used. However, after the components are place on the board, the board has to be turned over. To keep the components from falling off the PCB as it’s turned over for wave soldering, and having the wave of solder wash off any remaining SMDs, the SMDs first have to be glued in place onto the PCB.
Mixed Component Assembly Soldering
When both SMT and pin-through-the-hole devices are use on the same assembly, several steps are needed for soldering
- On the “component side” of the PCB, the SMDs are place and reflow solder.
- The board is turn over and on the “solder side,”without soldering them; the SMDs are then glue in place.
- The board turn over again, passing their leads through holes in PCB from “component side”, PTH components are machine insert.
- At this time, special-handling components are insert into the PCB by hand.
- The “solder side” of PCB is wave solder, SMDs glue to “solder side”of PCB,leads of special handling components, all in one step.
- The board is test.
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.
Rush PCB has both experience and expertise in all three types of assembly SMD, PTH, and mixture of both SMD and PTH.
Let our engineers at RUSH PCB work with you on the engineering and design of your mixed component assemblies.
For more information, contact us at [email protected], or call us at 1 408-496-6013.