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 attached to the PCB using reflow soldering, or they can be wave soldered.
In the reflow process, soldered paste is applied to the soldered pads of the PCB using a stencil, and the SMDs are placed with their leads on top of the soldered paste. Both the SMDs and the PCB are heated, reflowing (melting) the solder, connecting the leads of the components to the soldered pads on the PCB.
Functions of Assembly Capabilities
Instead of reflowing solder paste, SMDs can also be wave soldered onto the PCB the SMDs to the PCB-Assembly, instead of reflowing the soldered paste, a wave of soldered can be used. However, after the components are placed on the board, the board has to be turned over. To keep the components from falling off the PCB as it is turned over for wave soldering, and having the wave of soldered wash off any remaining SMDs, the SMDs first have to be glued in placed 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 placed and reflow soldered.
- The board is turned over and on the “soldered side,” without soldering them; the SMDs are then glued in placed.
- The board turned over again, passing their leads through holes in PCB from “component side”, PTH components are machine inserted.
- At this time, special-handling components are inserted into the PCB by hand.
- The “soldered side” of PCB is wave soldered, SMDs glued to “soldered side” of PCB, leads of 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.
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.
