Appendix – PCB DFM 14

Extracted from the Seeed Fusion Design for Manufacture (DFM) publication, this tid-bit of information is often missed when describing electronic devices. Are my boards double sided or single sided? Is it through-hole or surface mounted? Can you have through hole and surface mount components on the same board? This entry clears up any misunderstanding.

14.1 PCBA Constructions

Single Sided (SMT) Mounting

Surface mounted components only on one side of the boards, or component side. Since there are no through hole components, these boards don’t need drill holes and the copper pads and solder mask are only needed on one side. The latter point is the same with single sided through hole (TH) boards, except the pads are needed on the opposite side of the board, also referred to as the solder side.

Single Sided Mixed (SMT and THT) Mounting

Both through hole and surface mount component bodies on the component side. Although, called single sided, the PCB board itself needs to be double sided since the through-hole pads need to be on the solder side, the opposite side to the component bodies.

Double Sided (SMT) Mounting

Simple and compact, double sided SMT boards utilise both sides to make the most of the available area and enable strict form factors to be met. No plated drill holes needed here.

Wave-Soldered Double Sided Mixed (SMT and THT) Mounting

THT and SMT on both sides. This construction is similar to single sided mixed mounting except the spaces between the long component leads on the solder side are also utilized to maximise SMT real estate. For mass production, wave soldering is required to solder both SMD and THT components.

Hopefully, that was useful and helped clear up a few misconceptions. But there is much more where this came from, check out the chapters below for more valuable PCB design tips and guidelines.

More Chapters:
1. Brief Introduction
2. Seeed Fusion PCB Specification
3. Panelization and Bridge Design
4. Component Layout Considerations
5. PCB Hole design
6. Solder Mask Design
7. Copper Trace Design
8. Silkscreen Design
9. PCB Lamination Structure
10. PCB Dimensions Specification
11. Fiducial Mark Design
12. Surface Treatment
13. Files for Manufacture Requirements

About Author