Double sided PCBs are gaining popularity due to several advantages that they offer. These PCBs are becoming regular part of mission critical applications such as industrial controls, power conversion equipment, HVAC, automotive dashboards, etc. Many PCB manufacturers agree that double sided PCB assembly is a complex and time consuming process due to repetition parts on both the sides of the PCB. These manufacturers involve various assembly techniques depending on customer requirements. This post discusses three such important techniques that are employed for placing components on both sides of the double sided PCBs.
Introduction to 3 Important Double Sided PCB Assembly Techniques
Before describing the techniques, let us give you a brief idea about a double sided PCB.
The circuit comprises the following layers:
- Solder Mask
- Circuit Copper Layer
- Dielectric Layer
- Circuit Copper Layer
- Solder Mask
These layers are assembled through the following technologies:
- Surface Mount Technology: This is the technology of mounting components directly on the circuit boards. Basically, a printed circuit board normally features a flat silver, tin-lead, and gold plated copper pad without holes. A solder paste is first applied on the pad using nickel or stainless steel stencils or an appropriate ink jetting machine. After applying the paste, the board is delivered to the production line, and then conveyed to the reflow soldering oven. Inside the oven, the temperature of board and components is gradually increased to a limit, where solder paste melts, and helps components bond easily. For double sided boards, this process of printing, component placement, and reflow is repeated using a glue. After soldering the boards are washed to remove flux residues. Finally, the board is inspected for missing components, misalignment, or improper soldering issues. If needed, rework is performed, and then boards are sent for in-circuit testing or functional testing. Surface Mounting Technology (SMT) allows placement of smaller components, enables higher density connections, and improves mechanical performance under vibrations.
- Through-hole Technology: This technology refers to the mounting scheme where components are inserted into holes that are drilled on the PCB, and soldered on the opposite side manually or automated assembly machines. This technology is applied for PCBs that require stronger connections between layers. Through-hole Mounted (THM) double sided PCB circuits having stronger bonds are employed for aerospace and military products due to their high stress endurance capability. This technology is also employed for creating double sided circuit boards for prototyping and testing applications.
- Mixed Technology (THT and SMT): As the name suggests, this technology involves the mix of surface mounted and through-hole technologies. Most manufacturers perform this task using complete automated technology equipment, selective wave soldering machines, fast and accurate placement machines, etc.
There are lots of PCB manufacturers who provide double sided PCB assembly, but there are a handful who can handle design complexities efficiently. Accelerated Assemblies is one such leading PCB assembly services in the US that can deliver double sided PCBs created using any of the three techniques. For more information, please click here.
