Recently I started writing a regular column for Gearphoria magazine called Workbench Confidential, covering subjects related to electronics in the music industry. Gearphoria is a ground breaking quarterly online magazine that’s attracting a lot of Music Industry attention, so I’m excited to be contributing. I’ll be posting past issues of Workbench Confidential here at effectsblog.com, but you’ll need to go to Gearphoria to read the latest issues.
If you build electronics products for a living, often the difference between making a living and not, is the speed and reliability with which you can assemble and test your products. The lower the selling price of your product, the more efficient you need to be at assembling it. If you are the manufacturer of a $50,000 luxury Swiss watch, then a lot of the value of your product is in the days or weeks its takes the expert craftspeople to create it. For a $100 effects pedal, you are going to have to be quicker off the mark if you hope to pay the bills at the end of the month. Even at the snootiest end of the boutique pedal market, you are soon going to be in pretty deep doo-doo if it takes you days to build something that sells for even $500.
So how do we do it? We use machines, of course. Assembling circuit boards is one of the most time consuming stages of manufacture, and there are several mechanized techniques to accomplish this. The most efficient, and the way most consumer electronic products are assembled today, employs a Surface Mount Device, or SMD production line. The line comprises a number of machines interconnected by a conveyor. The first machine deposits solder paste onto the surface of the PCB through a stencil. Usually several PCBs are bundled together onto a large board called a panel. The panel is sawn apart, or ‘de-panelized’ into individual PCBs later in the process.
After paste is applied, the panel passes into a pick and place machine that feeds in components from reels similar to a film reel. A robot arm picks up the parts and drops them into place on the panel. Multi-head machines can place hundreds of components per second. After the parts have been placed, the conveyor carries the panel through a heating tunnel that melts or ‘reflows’ the paste, and solders the components to the board. The finished boards come out at the end where they can be cleaned and de-panelized into individual PCBs. Search ‘SMD Production Line’ on You Tube for some videos of the process.
The majority of the work is in programming the machines, and loading the reels of components. After that, the machine can be largely left to do its’ thing. The cost per board goes down when we can leverage the upfront programming and loading, and let the machines build more boards.
Another type of component is called ‘through hole’. These have leads that push through holes in the PCB and are the type that we often see in hand built boutique pedals. Some fans believe that hand soldered vintage style capacitors and resistors impart a special pedal mojo. If anyone can actually hear the difference in a circuit between through hole and SMD passives in a double blind test, I’ll eat my hat. In some circuits especially digital ones, components such as microcontrollers and flash memory may only be available in SMD anyway.
SMD has mechanical limits though, and larger components such as electrolytic capacitors, coils, connectors and controls may still be through hole. These can be added to SMD boards using a wave or selective solder machine, which uses a wave of molten solder to attach the component legs to the pads on the board. Running single panels through both SMD and through hole processes, costs more than just one process, so you have to plan for this when designing your product for manufacture.
Due to the high cost of these machines and the infrastructure to run them, many manufacturers send their board assembly out to specialty facilities. The populated PCBs can then be assembled in house into the final product. For final assembly and other work, such as small run and prototyping, there are machines too. Here are a few we use around our shop on a daily basis.
Automatic Wire Cutter and Stripper.
Feeds reels of hook up wire in one end, and precisely cut and stripped wires in specific lengths come out the other. The machine processes hundreds of wires per minute. Not only is it a massive time saver, but it also improves product quality and reduces the risk of repetitive strain injury. No one ever uses it without recalling doing this by hand and quietly whispering to themselves: “I so love this machine”.
Cuts plastic components, makes decals and labels, etches logos onto metal enclosures, creates templates, the list goes on. The Laser is THE general purpose small fabricating tool around the shop. Countless times a week a find myself instructing: “Just put in in the laser”.
The best way to remove flux and other residue from small run and re-worked PCBs. Drop in the assembly, and watch the magic bubbles. You can also clean your tools with it afterwards.
Using crimp terminals from a reel attached to the side of the machine, the operator feeds in the stripped cable end from the wire stripping machine and presses a footswitch, the machine takes care of the rest. 3 tons of force is applied making for a precise crimp. Correct wire termination is essential for compliance with safety standards if you are making AC powered products.