Dec 13, 2017 | by Grace Hand
Five Steps to Successful PCB Assembly
As technology has advanced, PC boards have progressed with it. PCBs have become both more compact and complex, enabling electronics and electrical manufacturers to power machines that can do more and more.
To understand how to build the best possible prototypes and products, you’ll need to know how to successfully assemble today’s advanced PCBs. This article will walk you through five steps to develop boards that will fully serve your purposes.
1. Design: Create an Assembly Diagram
Your board’s design diagram is your roadmap. Without a well-thought-out design, you won’t end up with a quality product. This diagram will show you where each component should be placed on the board and how components will connect to one another.
You’ll need to determine what components you’ll need, how they’ll be arranged, and how they’ll worth together, within the space constraints that you have. Companies with in-house teams typically design their own schematics. Other companies outsource the design to a firm that specializes in design for manufacturing.
2. Stenciling: Apply Solder Paste
Before you can actually begin assembly, you must apply solder paste to the board. This process uses stencils to ensure the paste is placed where it should be.
3. Component Assembly: Surface Mount or Through-Hole
There are two different types of mounting processes, each of which has pros and cons. Through-hole mounting runs component leads through the board, creating extremely strong connections. It’s recommended for applications that require high reliability, such as military and aerospace products that experience severe environmental stress. It’s also used for prototyping because it allows for manual adjustments, and parts are easy to switch out. And since through-hole mounting has been used the longest, components are widely available.
The disadvantages of through-hole mounting are what brought about the invention of surface mounting. Through-hole requires drilling holes, which takes time and expense. The routing area is also limited with through-hole mounting, and you’ll need to solder both sides of the board.
Surface mounting doesn’t require any holes to be drilled through the PCB, so the process is faster and cheaper. The components are smaller, and they can be mounted to both sides of the board — you can fit a lot more components on a single PCB. Perhaps the biggest advantage of surface mounting is that it allows a conductive connection between the different layers of a PCB. Another plus of surface mounting is that it performs better in shake and vibration conditions. On the downside, products using surface mounting don’t stand up to significant stress over time.
4. Board Reflow and Inspection: Pass the PCB Through the Oven
After the components are mounted, the board must be passed through a reflow oven to bond the components with the circuit board. Then the board is inspected to make sure that the connections are placed at the right locations.
5. Cleaning and Testing: Remove Contaminants and Ensure Performance
You’ll need to remove the leftover solder paste and other contaminants from the PCB. You have the option of using a variety of different cleaning solutions, which vary from organic detergents to harsh chemicals.
You’ll also want to test your prototype to ensure it performs like you think it will before starting production. If something isn’t working like it should, you’ll need to make adjustments and continue the process.
Precision and attention to detail are essential for assembling quality PCBs. Each step in the process is important, due to the complex nature of today’s PCBs.
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