How to design a printed circuit board ?


       To eliminate PCB defects, it is best to work with an EMS provider who offers design, fabrication, and assembly services. Defects arise in most instances due to incorrect or incomplete designs and poorly executed fabrication and assembly. The key to successfully produced PCBs is experience and know how to curtain even the slightest possibility of a defect. Here is a sampling of many suggestions for assuring your PCB project has zero defects.



  • Make sure the designer has carefully detailed fabrication and assembly drawings with all aspects of your PCB design.
  • If RF circuitry is involved, ask about the shielding and where it’ll be placed to avoid crosstalk and subsequent defects.

  • Ask questions about machine limitations, board spacing, and properly designed in tolerances. If doubts arise, so will defects.

  • Understand complex PCB requirements and assembly processes because if details aren’t provided, such defects as tomb stoning, component skewing, and flux inactivation with solder paste will result.

  • Know the limitations of the EMS provider’s fabrication and assembly process machines. Any minor deviation in these machines, especially with complex PCBs, will lead to defects.

  • Using incorrect PCB surface finishes, especially if lead-free PCBs are involved, guarantees certain defects and large headaches.

 

Improper design, fabrication, and assembly cuts an extremely wide path of defects, unless careful and experienced attention is given at the design stage. PCB defects run the gamut. For example, as stated above, deteriorated RF signals can result from poor shielding. Also, incorrectly structured boards are produced due to sketchy or ambiguous fabrication notes. At assembly, miscalculated thermal profiles are the basis for BGA, CSP, and/or QFN-based solder defects.


SAMPLE DRC FILE


If you want defect free PCB want defect free pcb


                  The most effective way to avoid having your order go on CAM hold is to take advantage of FREE DRC CHECK. You will get the following benefits: Please e-mail us the files to use this free service.

Free Drc for PCB

  • Free PCB design file check for manufacturability

  • We check to make sure we have the files and data necessary to build your job

  • Results e-mailed to you in minutes

  • You get a graphical report, showing any potential issues with detail as to their nature 

  • Reduces possibility of CAM Hold issues after order placement

  • Most important your PCB will not get rejected due to minor problems.


Creating Gerber files that accurately reflect what you want manufactured is a challenge no matter how long you have been a PCB designer. However, by learning from others and avoiding the most common mistakes, you can speed up the turnaround time, reduce the chance of orders placed on hold, and complete your projects faster. The following list reviews the top seven most common mistakes made with Gerber files and how you can avoid them.



 

Aperture List

 

 

274X FROMAT


 274D FROMAT

 

Aperture is a list of D-codes. D-code defines the shape and size of trace and pad. Some old PCB design software is providing a separate aperture along with 274D Format. Old Circuit maker which is still use in India, outputs separate aperture list (with ‘.TXT’ extension) for each layer gerber files. This software outputs high quality Postscript file but the accuracy is an issue for these Postscripts. Old Protel PCB design (version 1.27) software is also still in use India. This Software creates single aperture list for all gerber file (with ‘.APT’ extension).

 

You have to providing a unique D-code list with your gerber file or the simplest resolution is provide 274X format files which don not required separate aperture list.  

Excellon Drill File


excellon drill


Excellon drill files along with drill report files are used for the location of holes and drill size. It also report file contain information whether the drill is plated or non-plated. All PCB Design software outputs Excellon drill file.


 There are many excellon formats are used by PCB manufacturers but the most popular and accurate one is 2.4 Trailing Zero suppression, English.

Annular Ring


Annular_ring

    

An annular ring is the extra space or boundary which remains after drilling the holes on copper layer please see above fig. for more details. This is very important thing as it related to component solderability. Some PCB designer ignore this which tend towards cam hold or defective PCB manufacturing.


Minimum annular ring should be at least 0.008“ per side for component holes. For via it should be minimum 0.005”

Insufficient Copper Trace Spacing


minimum spacing

  

Minimum air gap between Pad to trace, trace to trace and Pad to Pad should be 0.006” to avoid increase in cost of your PCB. Also it ensures you that your PCB will be produce with no defect of shorts and opens.


Keep the minimum gap 0.006” default, keep your online DRC ON during routing the nets which solves most of the problem.
  • Missing D-code List

  • Missing Drill file

  • Insufficient Annular Ring

  • Insufficient Spacing

             

                QUALITY PCB 

                                                                                                                                 

IPC Tools

The following TOOLS are from IPC and  COPYRIGHTS are belongs to IPC only. We have just placed links to help our Clients.

 

 

 

 



The engineers at ExpressPCB have assembled a few general rules-of-thumb that can help beginners design their first circuit board. These tips are not specific to using our CAD software, but instead provide an overview to help explain how to position the components on the board and how to wire them together.

http://www.expresspcb.com/ExpressPCBHtm/Tips.htm