Setting up a production line - Part 1 - History
Thought I'd take a moment to describe some of the efforts that are taking place to get get a small production flow set up here at expat audio (namely, my garage... but I have eyes on more if you guys start buying!)
Since the dawn of the industrial revolution, engineers, scientists and anyone self employed have made efforts to streamline repetitive tasks associated with their product. By streamlining, we create greater efficiency and lower the time and effort required to create a product.
The next few pictures are credited to user "bluesky636" on the Fender Guitar Amplifiers forum.
Electronic circuits were originally assembled using a point to point topology. Components were carefully selected, and connected to each other carefully, and hand soldered together. This can still be seen in some very high-end boutique guitar amplifiers. Obviously, this is painstaking work, and in today's economy only reserved for the most expensive of products. It's also limited to larger discrete products. Fine pitch IC's need not apply.
Once developers realized the error of their ways, and looked for more automation and efficiency in building equipment, along came "turret board". Again, a similar technology to point to point, Turett board was designed for large discrete components (resistors, capacitors, large transistors etc) but rather than needing to know exactly what connects to what, a simpler layout is created, that can documented for re-use by trained manufacturing staff.
Again, this can be found in some boutique guitar amps again.
In the 1950's following world war two, Printed Circuit Boards started making their way in to modern consumer goods. (Thanks wikipedia!). Printed Circuit boards originally still required human beings to stuff all the parts, as almost everything require pushing the leads of components through specifically placed holes on the circuit board. It's this technology that many of the Pro Audio clones we make at groupdiy were originally assembled in. Assembly Operators (people who stuff the circuits) were now able to have minimum training to populate components into circuit boards.
In fact manual assembly is still quite popular for circuits that must use through hole (devices will leads) components. Most large connectors (such as XLR's or 1/4" jacks) are hand soldered to circuit boards, even if everythign else is machine assembled!
An honourable mention at this point needs to be made for a technique known as wire-wrapping. This is very similar to point-to-point, but small wire is used to make the connection between one device and another. Devices are normally held in place in a fine 0.1" array of holes. Wire wrapping actually created a very strong bond between the wire and the device being held. It is a manual process, but seeing as the devices are held in a specific place, documentation for assembly operators is possible. In fact, the Apollo Guidance Computer, used to take man to the moon, was entirely assembled using wire wrap technology.
Anyway, back to consumer goods and PCB's!
There are some really clever ways that factories trained their operators to know where to put the right components. In my travels in the semiconductor industry, I visited a factory where components were kept in automated component bins, that would pop out automatically, as the product was assembled. Then above the workstation, a specific light would shine on the PCB to show the operator where to position the component that was in the tray. (really wish I'd taken a picture now!). In short, only one component is available to the operator at any one time, and pre-programmed slideshow would shine down on the board to tell the operator where to place that part.
Through hole components on a printed circuit boards can either have their leads soldered manually by operators, or can be run through a solder wave.As the name hints, this is literlly a wave of molten solder that the circuit boards is run over, which solders the legs of through hole components to the circuit board. This process is still used regularly today.
By the 70's and 80's smart machines had been trained to pick up and place the thru hole components, but they still weren't perfect. In a quest for continued efficiency, much of the electronic design community moved to surface mount components or SMD. This more or less brings us up to date.
Today, surface mount devices compromise the lions share of consumer electronic products on the market. Without SMD components, small portable electronic products really wouldn't be possible, as the assembly machines can be much more accurate than a human being trying to assemble at speed. (yes, prototyping with SMD is possible, and manufacturing in small volume is possible - but VERY tedious!).
Surface mount boards typically go through 3 processes -
- Solder paste (rather than solder wire!) is applied to the pcb's through a stencil.
- The PCB is then put into a "Pick and Place" Machine -- a machine will all the components held in reels or tubes, that has an vacuum nozzle on an XY axis. The vacuum nozzle picks up the part from a reel, then moves to a preprogrammed location on the pcb, and drops the part (on to the solder paste)
- PCB's with solder paste and components in place now go through a process calls "reflow soldering", where the entire board is heated to the point where the solder paste liquifies and the tiny balls of solder in the paste turn into a liquid of their own. This solder connects the legs of devices to the pads on the PCB.
The next blog entry is going to talk about how we (at Expat Audio) will set up our own SMT production flow, to create a family of modules that can be used in your DIY systems!