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Looking for a fast way to produce prototype PC boards? This device lets you make your own quicker than it takes to get a courier delivery from a prototyping bureau. Quick Circuit 5000 It mills away the copper for fast PC board prototypes By PETER SMITH Traditionally, printed circuit board manufacture involves both photographic and chemical processes. The equipment and labour costs in these processes mean that companies that design PC boards rarely produce them in-house. Instead, the designs are shipped off to speciality manufacturers in electronic format. How long it takes to get your design back as a PC board depends on how much you want to pay. And even if you pay the top rate, chances are you’ll still wait for 24 to 48 hours. Even if that’s fast enough for your needs, a number of other outstanding features make this system worth a look. Manufactured by the US company 4  Silicon Chip T-Tech, Quick Circuit is a radically different, although not entirely new system for circuit board prototyping. Quick Circuit bypasses the usual manufacturing processes by engraving designs directly onto PC board copper. In other words, it’s a purely mechanical process that does not require chemical etching. Quick Circuit is controlled via the serial port of most Windows-based PCs. It is supplied with software that will read the output from any PC board design package, and includes a num­ ber of handy “last minute” checking and editing features. Starting with blank PC board material on an X-Y table, a high-speed spindle motor is fitted with various drilling, milling and routing bits to remove the required amount of copper, drill all the holes and finally “cut out” the finished product. Quick Circuit can handle single and double-sided designs up to 25cm x 28cm and a variety of options are available if you need plated-through holes. Minimum track width and spacing is 0.100mm (0.004"), which means it can handle both surface-mount and through-hole designs. RF and microwave engineers will be especially interested in Quick Circuit’s precision milling capabilities; imagine being able to fine-tune your designs right without too much difficulty. The experts at SATCAM are happy to provide advice if needed, too. Generating the engraving pattern The complete Quick Circuit 5000 system. The black box in the middle drives the table’s motors and solenoid under command of a PC running Windows-based software. on the desktop! Odd-shaped boards, irregular internal cutouts and large hole sizes are all handled with ease using Quick Circuits profile routing feature. As a bonus, plastic, aluminium and other soft metal panels can be drilled, milled and routed for a super-professional finish. In all my years in this business, I’ve never managed to get a “D” connector cutout exactly right – could this be the answer? Another day at the office? Once the word got out that I would be test driving the Quick Circuit machine, a whole pile of future Silicon Chip prototype designs appeared on my desk with an assurance that they would “really test” the machine! I waited expectantly for it to arrive. Rob Leslie from SATCAM set up the machine and provided about half a day of hands-on training. Anyone with a reasonable amount of technical/mechanical know-how should be able to drive the machine Before a design can be transferred to the Quick Circuit machine, it must first be manipulated by a stand-alone software package called IsoPro. IsoPro reads the standard Gerber and Excell­ on files generated by all popular PC board design packages (we use Protel 99). As the name suggests, IsoPro allows you to define the isolation (clearance) that you would like between tracks, pads, etc on the finished board. Isolations are generally performed in a series of passes with progressively larger mill sizes. For example, if a design has minimum clearances of 0.012", then isolations at 0.012", 0.020" and 0.040" would probably be performed. Note that although a single isolation at 0.012" would provide a perfectly valid result in this case (all nets are electrically isolated), the board would be difficult to populate without generating lots of solder bridges. With this in mind, about 0.030" to 0.040" final clearance is recommended. Once isolation is complete, there will usually be some “dead” (unconnected) copper remaining on the board. Leaving this copper in place greatly speeds completion time but if your design calls for it, a final “rubout” pass can be performed to remove it. To save time, IsoPro allows you to selectively define areas to be cleared on the rubout pass. Importing the drilling info As mentioned above, IsoPro also reads the drill (Excellon) file output from your design software. Once loaded, the next step is to ensure that the drill layer is correctly registered with the copper layers. If it’s not, IsoPro provides an excellent function that snaps them into perfect alignment with a couple of mouse clicks. If you’re an old hand at PCB design, you’ll appreciate the ability to edit both the drill and aperture tables. If you don’t know what these are, don’t worry; there’s a full explanation in the Users Manual. Creating notches and cutouts One of the great features of this product is the ease with which you can create notches and cutouts. Outlines can either be imported from the mechanical layers of your design or drawn directly on a new layer in IsoPro. Once you have the outline, a simple procedure generates the necessary information for use with Quick Circuit’s profile routing tools. All designs have at least one cutout that needs to be defined – the board outline! Final inspection In addition to these “special” features, IsoPro is also a general purpose Gerber editor. In short, this means that you can examine the final output from your PC board design software and make last minute changes if required. Clearances can be checked, hole sizes changed, pads and tracks edited, text added, etc. Finally, IsoPro provides a graphical representation of Quick Circuit’s X-Y table, allowing easy and accurate placement of the design within the board material workspace. It also provides a means of keeping track of which areas you’ve already used when making a number of smaller boards from a larger section of material. Exporting your work The last step is to export all the isolation, drilling and routing information referred to above ready for input to the Quick Circuit table control software, QuickCAM. If you hadn’t already guessed, IsoPro does not need to be run on the PC controlling the Quick Circuit machine. This means that designs can be prepared in advance, perhaps while another is on the table. Note, however, that IsoPro is licensed per PC – you need a hardware “dongle” plugged into the parallel port to enable all its features. If all that sounds tedious and time-consuming, it’s not! After a few practice runs, I was able to get a medium-sized double-sided design in and out of IsoPro in less than 10 minutes. Installing the Quick Circuit table Setting up the Quick Circuit table for the first time is quite straightforward. Access to a vacuum source is required, as Quick Circuit uses this to clear swarf off the board during all machining operations. If you don’t November 2000  5 This assortment of completed boards shows that no matter how odd the shape or small the size, Quick Circuit can handle it. Note the waveguides on the long PC board. already have a vacuum source, many industrial vacuum cleaners are suitable for the task; SATCAM can help with recommendations here. Noise levels will be an important consideration for some businesses. In practice, we found that the old office vacuum cleaner made a lot more noise than the milling and routing! You need a PC running Windows 95, 98 or NT4 to control the table. The PC is set up right next to the table and hooked up via a spare serial port. All the Quick Circuit table electronics are housed in a small “black box” which can also provide switched power to the vacuum source. With the PC hooked up, the next step is to load the table control software, QuickCAM. Using the information exported from IsoPro, this software sends the actual direction and speed data to the table’s “black box”, where it is converted to high power drive signals to move the table’s various motors and solenoid. Securing the board material Quick Circuit uses standard 12 x 18" fibreglass (FR4) board material, although it is also perfectly capable of producing designs on more exotic base materials such as PTFE and ceramics. Two tooling pins anchor the board material to the table, so all you have to do is drill a hole in either side, drop in the pins and you’re ready to go. Oops – I almost forgot to mention that you also need a piece of backing material underneath so that you don’t drill into the bed! OK, so we’ve installed the machinery and mounted the blank board. Now we can begin the most satisfying part – exposing the masterpiece! Crunch time Fig.1: IsoPro accepts the standard output from PCB design software and calculates the paths (also called “isolations”) that will need to be milled to create the desired pattern in the copper. This shot shows a design with .010" (orange), .020" (yellow) and .040" (pink) milling paths. 6  Silicon Chip Drilling is usually performed as the first step. In QuickCAM, the drill file (exported from IsoPro) is loaded and with a couple of mouse clicks we’re under way. QuickCAM prompts for each drill size in turn and automatically positions the head off the front of the table for easy (manual) drill swaps. The only adjustment needed here is to the drilling depth; we need to make sure that holes are drilled right through the board and slightly into the backing material underneath. A nice feature allows large holes to be profile routed rather than drilled. This means that, say, the .062" routing tool can be used to “drill” all holes .070" and larger. This means that there is no need to stock large drill sizes. With the drilling done, we can begin the first (smallest) isolation pass. This is generally performed using a missile-shaped milling tool. Because of the tip shape, the depth of the cut determines the actual width of copper (or “milling path”) that is removed. The depth is set with the aid of feeler gauges and a knob on the head assembly. A fairly simple procedure detailed in the manual provides a means of checking the milling path to ensure that it’s exactly right. QuickCAM is then loaded with the relevant file (exported from IsoPro) and milling can begin. Subsequent (larger) isolation passes are performed with end mills. As the name suggests, these tools are flat on the end and their size relates directly to the milling path width. Once again, feeler gauges are used to set the cutting depth, which in this case will simply be the copper thickness. If it’s a double-sided design, the board is simply flipped over on the bed and the isolation processes repeated. Because of the way the material is pinned to the bed, layer registration is spot on every time. If you’ve ever hand-made double-sided boards yourself, you’ll know that this is one of the A design takes shape as the first milling pass is performed. hardest things to get right! Profile routing is the final step in the machining process. Any internal cutouts are routed first, followed by the board outline to “cut out” the board from the base material. A quick clean and coat of solder-through circuit board lacquer to keep oxidisation at bay completes the job. Note that as well as the bare copper type, solder-plated copper board material is also available. We suggest that even solder-plated boards be protected with lacquer, as milled edges will be bare copper. Double trouble? Three methods are available if your double-sided designs require through- hole connections. The simplest of the three, from Harwin, involves inserting “via” pins for each through-connection using a special handtool and then soldering them on both sides. This system is cheap and simple but does have one obvious drawback. Holes that must contain component leads as well as provide through-connections need to be soldered on both sides, and this is not always possible. The second method, called Copper­ set, overcomes this limitation by using copper tubes for the through-hole connections. These are provided in long lengths, pre-filled with solder for strength and scored at regular intervals so that they can be easily inserted and November 2000  7 Above: one of the boards we made during our review. The results appear similar to any high quality “conventional” manufacturing technique. Right: this demo PC board shows the results of each isolation pass, including the optional dead copper rubout. snapped off. They are then swaged over on the top and bottom with a special tool and the solder removed from the centre if necessary. This is an excellent method that produces results very similar to plated-through holes, although is a little time-consuming for complex designs. The final method involves actually plating the holes with a system called Quick Plate. Although we didn’t look at this system during our review, it seems to be quite easy to use and boasts very good results. Quick Plate uses the traditional method of electrolysis to perform the plating, which means that it involves the use of an electrolyte, copper anodes, plating tank and power supply. According to T-Tech, a 9 x 12" PC Fig.2: QuickCAM controls the machining table using the milling paths generated in IsoPro. This shot shows a “zoomed in” view of a design positioned on the table ready for the first isolation pass. 8  Silicon Chip board can be plated through in about 35 minutes. How quick is quick? It is to be expected, of course, that any prototyping system will be labour intensive, and Quick Circuit is no exception. Despite the preparation needed in IsoPro and the machine setup and manual tool changes, we were able to produce a 12cm x 12cm single-sided board in about one hour. And once you know what you’re doing, the machine can be left unattended during milling runs. The Quick Circuit system is unquestionably the quickest way of producing prototype printed circuit boards. Why doesn’t everyone have one? Well, the speed comes at a price… The Model 5000 reviewed here sells for $17,000, which includes all cables, software and 10 assorted tools. Also available is the Model 7000, which includes a larger table (12 x 18") and sells for $22,000. The Quick Plate 912 through-hole plating system for 9 x 12" panels sells for $8750. Note that these prices do not include GST and are subject to exchange rate fluctuations. Contact SATCAM on (02) 9807 7081 or email satcam<at>ozemail.com.au for more information. You can also find more information on these products on the web. For the Quick Circuit and Quick Plate systems, check out www.t-tech.com For the Copperset through-hole connection system, go SC to www.multicore.com