In sports, there is a well-known correlation between strength and speed. Basically, strength or capacity for power is a determinant in how fast you can move. However, there is a point where this positive correlation between strength (which is closely tied to muscle size) and speed no longer holds and adding size and strength actually slows you down. Similarly, in the not-too-distant past, productivity and efficiency had a comparable relationship in manufacturing.
Today, the most advanced manufacturing facilities are highly automated. This reduction in reliance on the human repetitive capability has increased efficiency and productivity and aligned both of these metrics more closely with process speed. This is certainly true in optimal printed circuit board assembly (PCBA) where equipment capacity and process techniques define productivity and efficiency. Ensuring the boards are well designed and following good design for assembly (DFA) guidelines can minimize the need for human intervention. Let’s review the process to help identify design focus areas to maximize PCBA speed.
The Printed Circuit Board Assembly (PCBA) Process
Transforming your design into the completed physical structure requires three steps: 1) fabrication, 2) component procurement and 3) assembly. Printed circuit board assembly or PCBA is one of the two PCB manufacturing processes. The other stage, fabrication, is performed first. During fabrication, your board design is constructed and prepared for assembly, where the components are securely attached to the board. Although PCBA may be comprised of ten or more steps, the process can be divided into the following major tasks:
Before placing surface mount technology (SMT) components, an initial layer of solder paste is applied to the board’s pads. This is done to promote good flow during soldering and minimize assembly defects. The application method may be manual or automated using a stencil or jet printing.
- Component Placement
For SMT components, accurate placement of components on pads is crucial. Misalignment can lead to bad solder joints or tombstoning, where one side of the component is not attached to the board. Through-hole technology (THT) components are more flexible; however, it is usually advisable to have the component body as close to the board surface as possible.
The most common method for securing SMT components is reflow. For THT components, wave soldering is the preferred method. If both types of components are used, the SMT components are usually placed and soldered first. Only then are the THT components are placed and soldered, which extends the soldering task. Soldering is further extended for two-sided boards, as components are mounted on both the top and bottom surfaces. After the soldering step for each component type, the connections are inspected and if any issues are discovered, then rework is performed to correct them.
Cleaning is performed to remove any excess debris from the board’s surface(s). Alcohol or deionized water is effective at removing most contaminants.
Depanelization, which is the separation of the multi-board panel into individual units or PCBs, is the final major task and should not be overlooked. Inefficient panelization or panel design can result in significant waste and additional cost.
The above tasks are performed by your contract manufacturer (CM) and the quality of the manufacturing process depends on your selection of fabrication and assembly services. However, certain design tactics can be employed to optimize PCBA, especially for speed.
Designing Your Boards to Optimize PCBA Speed
Any design decisions made with the objective of improving PCBA can and should be a part of your DFA guidelines. These include options intended to increase the efficiency, quality or speed of the process. In particular, for speed, we can define a checklist of specific tasks that, if performed during design, can optimize the process.
PCB Assembly Speed Optimization Checklist
Prioritize speed when selecting a CM and assembly services.
Select components that are and will be available throughout development.
Make sure that your component footprints exactly match the BOM.
Clearly mark component and connector orientations.
Use your CM’s default materials, solder mask and silkscreen colors and surface finish.
|Tempo‘s Custom PCB Manufacturing Service
Tempo Automation is the industry leader in producing high-quality boards fast. We employ a software-driven turnkey manufacturing service that is designed to fabricate your boards, procure components and perform PCBA as quickly as possible, even for complex designs or critical systems.
And to help you get started on the best path, we furnish information for your DFM and enable you to easily view and download DRC files. If you’re an Altium user, you can simply add these files to your PCB design software.
If you are ready to have your design manufactured, try our quote tool to upload your CAD and BOM files. If you want more information on the printed circuit board assembly (PCBA) process or how to design for its optimization, contact us.