Dear P.C. Board User:

Attached is a list of general guidelines that can assist during the design stages of your circuit boards for manufacturability. It covers several of the basic elements such as trace widths, spacing, pad sizes, solder mask clearances, etc.

The following general design guideline may be used as a tool to ensure a seamless transition from design to finished product.
 
                                                                        Standard                        Advanced 
Maximum layer Count

12 layers

up to 22 layers

Minimum trace width       
                                  ½ oz copper

.005”

.003”

                                  1 oz copper

.007”

.004”

                                  2 oz copper

.015”

.010”

Minimum space                                       
                                  ½ oz copper

.006”

.004”      

                                 1 oz copper

.007”

.006”

             2 oz copper

.010”

.008”

Minimum finished via hole size

.010”

.005”

Minimum finished via pad size

.025”

.018”

Maximum drill aspect ratio

8 to 1

10 to 1

Controlled impedance tolerance

+/-10%

+/-5%

Minimum thickness tolerance

+/-10% or .007”

+/-5% or .004”

Minimum finished boards thickness

.031”

.015”

Minimum Plated through hole tolerance

+/-.003”

+/-.002”

Minimum Non plated hole tolerance

+/-.002”

+/-.001”

Minimum routing tolerance

+/-.005”

+/-.003”

Minimum warpage tolerance

.010” / inch

.007”/ inch

Minimum solder mask clearance

.005”

.002”

Minimum internal clearance

.018”

 .015”      

Minimum dielectric spacing

.005”

.002”

Legend line width

.010”

.006"                 

Helpful fabrication notes: 
  • Part Number and revision level.
  • Artwork revision information if it differs from the drawing information.
  • Outside dimensions of the board including tolerance.
  • Finished thickness and tolerance.
  • A hole chart including symbols, specify plated or non plated, hole diameter and tolerance. The symbol for each hole size shall correspond to the symbol on the view of the board.
  • Layer sequence.
  • Dielectric spacing requirements.
  • Copper weight of each layer.
  • Type of laminate.
  • Type and Color of solder mask.
  • Final finish requirement.
  • Any additional mechanical dimension requirements.           

Suggestions for Tenting Via holes:

If Liquid Photo Imageable (LPI) solder mask is required, we advise that the via holes not be tented. Tenting the via holes with LPI solder mask will result in the following problems: incomplete encapsulation of the via hole, exposed copper/metal on via holes Solder, on via hole pads and in holes, uncured solder mask in the holes, which results in peeling of LPI and strapping contamination in side the holes.

The solder mask pads for via holes can be made about 5 mils bigger than the via drill size. This will result in deposition of solder in the via holes, reduce the possibility of bridging problems during wave soldering operation.

If the via plugging is used to fill open holes with the solder mask to block air leakage during In Circuit Test, via plugged one side is the best.

We hope the above mentioned is of some help to you. If you need additional information or have any questions, suggestions, please feel free to contact us at (847) 439-5447.