Although Henry Ford didn’t actually invent the assembly line, his perfection of the technique used for building the Ford Model-T automobile revolutionized the world of manufacturing. Today, most products that are mass produced are built on an assembly line, which has been further revolutionized over the years through the use of automation.
Modern circuit board assembly plants also rely quite heavily on automation to handle the placement and soldering of electronic components onto printed circuit boards. Does that mean the need for skilled manual assembly technicians has passed? Not at all.
Even though automated assembly brings the consistency and speed needed to stay competitive in the market, there are still some circumstances in which components require manual assembly. This could be due to the uniqueness of a specific part or the need to manufacture a board according to a certain process. Either way, there will still be times where the assembly of a PCB will require the human touch. Here are some examples of how both the automated and manual assembly processes have importance in the manufacturing of your PCBA.
When it comes to manual vs. automated assembly, automated is preferred, but sometimes a human touch is needed.
Automation Preferred When Comparing Manual vs. Automated Assembly
As with any type of manufacturing process, automated assembly is the preferred method to reduce costs as well as increase speed. Manual assembly requires multiple skilled technicians to do what one automated assembly line can do at a faster rate. There is also the chance of human error with manual assembly, whereas an automated assembly system will do its job at the same consistent level of quality again and again. These justifications are universal no matter what kind of manufacturing is being done, but the assembly of PCBs have some other considerations as well.
Some electronic components are not compatible with manual assembly processes:
- Large, dense components with their pins underneath, such as ball grid arrays (BGAs), require automated solder reflow due to the difficulty in manually soldering the pins that are hidden underneath.
- Large quad flat packs (QFPs) with fine pitch pins are sensitive to coplanarity, where not all of the pins rest even on the surface of the board. This makes them difficult to solder manually, and the automated solder systems are preferred.
- On the other end of the size spectrum, small chip components, such as resistors and capacitors, in 0201 packages (or smaller) are too difficult for manual placement and soldering.
Component placement also is a factor in automated assembly. For boards that have their parts tightly placed, it is very difficult to do consistent manual assembly. There just isn’t the room for operators to place and solder the parts.
There are, however, other circumstances in which manual assembly of components on PCBs is preferred over automated assembly processes.
When Manual Assembly Techniques Are Required
As important as automated assembly lines are, there are times when it is more cost effective to rely on the skills of manual assembly technicians. Automated assembly processes require set-up for the boards they are going to be processing, and in the case of low-volume production runs, it can sometimes be faster and less expensive to do the assembly by hand.
Thru-hole components on low-volume runs are good candidates for manual assembly, as are custom parts and sub-assemblies that are attached to a board. Other examples include stand-offs and press-fit connectors, which are commonly used in low-volume PCBAs.
Prototype builds will also leverage manual assembly for unusual component placements and configurations, or last-minute components that took longer to be delivered than expected to the factory.
Another important use of manual assembly is in the cleanup of the automated assembly processes:
- Some components are not able to be adequately inspected by the automated optical inspection equipment and require a technician to verify their placement and touch-up any soldering problems.
- Some surface mount connectors may also require manual inspection and touch-up.
- Smaller components that may have “floated” during reflow or are prone to solder bridging also require manual cleanup by a technician.
Problems like these are fed back into engineering for design for manufacturing (DFM) optimization on the next assembly run, but the initial boards still need to be manually corrected.
The Benefits of a CM that Knows How to Expertly Blend Assembly Methods
Although automated assembly is preferred, there are times when the manufacturing of a circuit board will still need that human touch. The best contract manufacturers have the automated assembly equipment and skilled technicians to be able to do both, and they know how to combine the processes to build you the highest quality boards.
Your CM should also have the capability to bridge both processes with new technology, such as selective soldering. Using an automated soldering system, this technique provides manual-like soldering results to components that are manually placed.
At VSE, we are always reviewing our assembly processes and looking at next-generation equipment to further enhance our capabilities and the level of quality that we are able to provide. We also monitor every critical step in our processes, which results in real-time feedback for the optimization of our overall assembly operations.
In addition, we have one of the best manual assembly teams in the industry. Our manual assembly and touch-up technicians are extremely experienced, many with more than 10 years of experience working on complex PCBAs. We have built our business on the ability to know and understand your circuit board needs, and our automated and manual assembly processes are designed to give you the highest level of quality in your PCBA.
