Growing up, I sometimes felt like a spoiled brat. My father was in the Air Force, not the Army, and we only moved a couple of times. However, every PCB Manufacturing we relocated to a new city, I had to face the same problems. Basically trying to fit in a new environment with new people.
From that perspective, trying to learn about PCB fabrication and assembly and what role certain processes play can be similar. It is to the advantage of our design and development to apply good design for manufacturing (DFM) practices to ensure that our boards can be manufactured and are reliable. Therefore, it is important to know where and how the manufacturing process may be affected.
Although these are clearly defined steps for PCB manufacturing, there are alternative techniques and materials that can and are applied by different manufacturers. The welding method used to secure your components is one of these processes. The best known and most widely used over the years has been wave soldering, which has certain advantages and disadvantages. Let’s take a look at PCB manufacturing and assembly processes and how you can design your board so that wave soldering can easily fit in.
PCB Manufacturing Process
The goal of PCB fabrication is to turn your software design into a usable device, the PCB, containing the components you’ve defined and the connectivity you’ve defined. Manufacturing is the first process here. During this process, the board is prepared for your components to connect to. Each step builds on the previous one, resulting in a PCB containing all traces, holes, component pads, and any additional images such as logos or text.
The first step in the CAMTECH PCB manufacturing process is to design an image of the layout. This image must be exactly like the one you have created in the software and can be printed on the plate or on an image overlay. The next step is the engraving of the inner layer. During this step, excess copper is removed from the inner layers of the board so that only trace amounts of copper remain.
The next step is to add all the layers that will make up the board, which is called stacking. At this point, the PCB has been built, including all internal layers. The next step is drilling the holes, which includes vias and mounting holes. Once this is done, the outer layer is etched leaving traces of copper on the surface layer. With the holes drilled, the cladding can be done by way.
Solder masking is done next, covering all areas of the board where solder should not be applied. The screen printing step is where symbols, pin 1 indicators, logos, and other images are added. Finally, the plate is cleaned and the remains are removed. A protective layer is also added. This is the final step of the pcb manufacturing process. Now, the base with which your components will be joined, by soldering, is complete.
PCB Assembly Process
Once manufactured, your board is ready to mount components. Every step during the assembly process supports the security of your components on the PCB. The actual method of securing components is by welding. This is true whether the components are surface-mount devices (SMD) or through-hole.
The soldering method used for through holes and SMD is usually different. Depending on the components of your design, the assembly may vary slightly; however, the overall process can often be defined by a specific set of steps. The first thing that is done to the manufactured board is to apply an initial layer of solder. If your design includes them, the SMDs are placed so that they are connected to the appropriate pads. To secure SMDs, solder reflow is done when the solder is heated in an oven to form connections.
In this case, the connections are checked to ensure a good connection. If necessary, repeat the work, which may include manual welding or replacement components. If your design includes them, perforated components will be installed. One type of wave welding can be used to supply perforated components, which is its most useful application.
This can be full plate wave soldering if your design has all through-hole components and they are properly spaced or selective wave soldering where a directed jet is used to apply the solder. Again, an inspection of the component connections is performed. Any excess residue or potential contaminants are washed away and the boards are separated into individual units.
Where Wave Soldering Fits
Wave soldering was the first automated method of securing components to PCBs. Over the years, the method has been adapted to keep up with the changes in component types and sizes that have occurred. Today, wave soldering competes with other methods that have emerged primarily to improve accuracy in the soldering application. Depending on your component choices in your design and on the board, wave soldering may be the best technique for your PCB assembly .
