Artwork Spacing/Fine Line Technology
Whilst it may seem sheik to design a board with very fine lines, 8 thou and under, the production costs soar as the lines get thinner. To make a board with 5 thou tracks, 5 thou clearances and point 3mm drills when it's absolutely unnecessary is not being very smart. The golden rule in design is common sense. Make tracks and pads wherever possible as thick as possible.

The environment benefits when tracks and pads are made as large as possible. Whilst the copper etching process on one board may not seem much, the combined billions of boards produced over the years across the globe can produce tons of unnecessary waste. Co-operation is the name of the game, not conflict. Things run better and cost are reduced whenever there is a healthy relationship between designers and manufacturers. The other advantage of larger pads and tracks is that it easier to work with when repairing or reworks.

Buying CAD PCB Design Programs
There are low cost overseas packages appearing on the scene that are not fully supported by all PCB makers here. It would be wise to check with your supplier to see if they support that package which you are considering buying. If the package does not create a aperture file ready for loading into another program then the cost of your boards may skyrocket. Some of these packages just list the aperture data and these then have to be keyed into a Gerber reading package that manufacturers use. Acetronics recommends and uses Protel. CLICK HERE for your free shareware version.

Drilling Sizes
WYSIWYG applies without exception. The drill sizes you specify when pads are placed is what you will get. New chums tend to come up with pads something like this; .95mm and .9mm. The difference between .95 and 9 is nothing to write home about and hardly noticeable when it comes to inserting components. Sometimes it's better to err on the side of bigger rather than smaller. It's a lot easier to add an extra bit of solder rather than drill out a 100 or so holes on each board.

PCB drills are made of tungsten carbide and are very brittle. Circuit boards are drilled in stacks. The smaller the drill size, the less the stack, the more it costs you for your board. Most artwork is made with 3-4 drill sizes. Some artworks have 9 mind boggling drill changes on a single sided board. The more work you make your manufacturer do, the more it will cost you.

In the table is a list of most commonly used drill sizes in the industry. If you specify non standard drill sizes then your order may be delayed if drill size is not stocked by your manufacturer. Some manufacturers may even charge you extra for the drills as they may never be used by anyone else.

Duplicate Pads
Drill files are created directly off your artwork. The program reads the size you have stipulated for that pad and then the drilling machine does the rest. If you place pads on top of pads then this can cause havoc with drilling. If the pads are not lined up 101% then the drills will break.

Duplicate pads will also prolong the time it takes to do the drilling. You can check for duplications with Cad packages by creating a drill file. Use a text editor to read the drilling information sheet. Most packages will tell you that there are duplications.

Copper Up Side (CUS)
Many artworks are sent to manufacturers without any indication of which side is which. Whilst most people work from the component side on screen, some work the opposite way. The only way to ensure that your board is not made the wrong way round is to add some text to the bottom layer on single sided boards and on the top and bottom layers of all others. Developing smart artwork habits reduces the chances of errors. Avoid at all costs text that is the same no matter how one looks at it. eg: HOH. It's essential for shop floor staff to be able to identify which side is which from the negatives made for production. A part number like HOH may easily be placed upside down by a distracted employee.

Establishing Board Dimensions
Some CAD programs read the dimensions, not from the border you create but, from whatever is placed on screen. That means that if the heat sink of a component like a TO220 is outside your board border by 10 mm then you will be quoted on your board size plus 10mm. This may not mean much on a small runs, but on larger runs it can add many dollars onto your costs.

Final Trim/Cutting
When creating a circuit board use a continuous line border. The use of cross hairs or L shaped corner marks allows mistakes to happen. Tracks can end up outside your board. These will then be cut off or cut in half when the board is routed. WYSIWYG also applies to trimming. Most manufacturers will assume that trimming should be done on the inside edge of the border tracks. If you require otherwise, please specify clearly what your specific needs are on your artwork or on a job sheet print out.

Slots & Other Cut Outs
Use tracks on the bottom layer to indicate where the slot is. Modifying a pad and expecting someone to guess that it should be routed just does not seem to work. Please indicate to your supplier clearly that routing is required. Unless specified other wise, it will be assumed that cutting should be no greater than the outside edge of your routing track.

Prototyping
The accepted standard in the industry is to create a prototype. The advantages of PROTOTYPING before production is immense. The artwork is proved, the function is proved, the mechanical aspects is proved. If you have your manufacturer make your proto then that will also prove that the drilling is correct as well. On large runs this can be crucial.

Avoiding Confusion & Mistakes
Ideally the filename should be the same as the part number on your board. There is nothing worse than trying to find an artwork that has a different filename. Using revision numbers also helps to avoid confusion and mistakes, ie REV 1, REV 2 etc. Using revision numbers standardizes the system and is readily understood by most.

Current Capacity & Conductor Spacing
WYSIWYG is not always true with cad artwork. What you see depends entirely on the resolution of your monitor and printer. It can be deceptive and tracks and pads can seem very close together. Some CAD packages have a clearance check function. For standard production a minimum clearance of 12 thou be used. Clearances below 12 thou should be checked out with your manufacturer. Keep in mind that the tighter the tolerance the greater it costs to produce the boards. Very tight tolerances need a lot of extra diligence and the production failure rate is much greater. If your CAD package does not have a clearance check facility then use a 600DPI laser printer. In most cases that is near enough to what you will get as a finished product. Refer to Tables Below.

Some Useful Information...
 

Minimum Conductor Spacing      60% of the above clearances may be used      where a board is to be coated with a suitable spray.

Current Capacity of 1oz Copper Track