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PCB Design Tips  


 
  General Information




This section is devoted to giving a manufacturer’s view of PCB design (design for manufacturability). Our goal is to produce the circuit boards on time, at lowest cost, and which meet all your requirements. You can help us in this objective by observing the following guide lines.

PCB Design Tips
 
     
 
  To avoid delay please submit following information with your order:
  Gerber Files that can go straight to production avoiding costly delays.

We can use Gerber files in either 274D or 274X format for all layers, including silkscreens and soldermasks.

If using 274D format, we require a seperate aperture list/report File, this will tell us the pad and line sizes you used to design the board.

Tool file/chart, telling us which tool is what size and how many of each tool is used

Fabrication drawing or Manufacturing Requirements

NC Drill file in ASCII format

Example:
               %
               T01
               X035Y0075
               X03525Y01225
               M30

Readme file. It is a good idea to include a readme file with information such as; contact person’ name, phone/fax number and other information about your board requirements, this would aid in quickly moving your job from pre-engineering to production floor. This file can be in either ASCII (*.TXT) or Microsoft Word (*.DOC) format

 
     
 
  Design Tips:
Hole Size and Pad Size:
For power and ground layers, make the pad size 0.045 in larger than the hole size. For component, solder and inner layers make the pad size 0.017 in larger than the hole size. It allows more room for drilling and decreases the chances for shorts. Soldermask pads should be 0.005 in. larger than the soldering pad

Draws and Flashes:
When designing a board, try to limit the amount of draws you use. Draws use a lot of memory and slows the programming time. Ex.: Use a flash for pads instead of draws. If for some reason we need to increase or decrease that pad size, it can easily be done by changing the D-code, if they are done with draws it could be a nightmare.

Silkscreen rules:
Keep silkscreen at least 0.006 in away from pads (except vias). The minimum line thickness is 0.008 in and the minimum letter height is 0.100 in. Ensure that no silkscreen falls on any pads this could effect the soldering process. Avoid printing component outlines, aspecially if you are using automatic assembly.

Routing:
To speed programming - add a borderline to one of your files, this will give us a route reference for routing the PCB to size

 
 

 

 
 
  Cost Cutting Tips:
Order in Larger Quantities:
Price per board is significantly lower when ordered in higher quantity. We offer a split delivery option that allows you to get a lower per board price without the extra cost on your part for maintaining an inventory.

Quick Delivery time:
Most companies charge a premium for quicker than two weeks turn around, therefore allow as much time as possible.

Avoid paying Tooling charges twice:
Avoid paying tooling charges twice by selecting a single vendor who is competitive for quick turn prototype as well as production run.

Hole sizes:
Hole sizes smaller than 0.020, especially in boards thicker than .062 boards, limits the number of panels which can be drilled at the same time, therefore, adding cost to the drilling operation and high aspect ratios which makes plating difficult. Also, limit the number of different hole sizes. Review your design to see what flexibility you have with the hole sizes.

Annular ring:
Try to provide at least a 10 mil annular ring. A smaller annular ring creates manufacturing difficulties which result in lower yield and higher cost.

Line width and spacing:
Manufacturing cost increases significantly when line width and spacing drop below 10 mil, so you should avoid them if your application does not require such fine line and space.

Blind and Buried Vias:
The use of blind and buried vias can increase the unit cost by up to 50 %, therefore, use them only if you have compelling reasons.

Layer Stackup:
If you have flexibility in your layup specification, discuss with your vendor, he may have some cost effective suggestion using his standard materials.

Panel Layout:
If you can be flexible with your panelized PCB panel size, consult your PCB vendor to discuss the size. This will allow the manufacturer to arrange the maximum number of boards on their standard panel size. This may have a major impact on cost especially in production quantities. Many manufacturing costs are the same for small or large panel size.

Electrical Testing:
The complexity involved in making the test fixture depends on factors such as; type of board (Thru hole or SMT one side or SMT both side), number of test points, spacing between pads (pitch), therefore, the cost of test fixture can vary from $200 to over $1000. Also, testing would add 1-2 days to manufacturing cycle. So consider the cost and time factors when deciding if you want Electrical Testing or not.
 
 
     
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