 | Number of layers: Limit the number of layers as much as
possible. If higher quantities are anticipated, spend the extra time and
money in engineering to minimize layer count. Layout engineering is a one
time expense, manufacturing is not! |
| Quantities ordered: Order the higher quantities whenever
possible. You may be better off maintaining a higher inventory of say 3 or 5
months worth. Smaller runs mean your board house is less likely to panelize
and maximize the number of images on a panel. Larger runs are simply more
efficient. If your board manufacturer has to stock them until you need them,
you can bet there is a hidden charge somewhere. |
| Delivery time: Quick delivery greatly influences board
prices. Allow as much time as schedule permits. Don't ask for a rush only to
find out a special order chip or transformer has a 10 week delivery and you
cannot proceed with assembly. Longer lead times allow your board house
flexibility for other quick turn work, so yours can be at lower cost. |
| Number of hole sizes: Limit the number of hole sizes. Each
additional size adds to the cost. Layout designers have considerable
flexibility since hole sizes can be .007 - .015 larger than component lead
sizes. |
| Small hole size: Try not to use hole sizes smaller than
.028. They limit stack drilling, and drilling one board at a time greatly
increases machine time. Drills also break more often and copper plating
becomes more difficult. Holes .021 and smaller must be stack drilled 1 deep.
Holes .022 thru .027 can be stack drilled 2 deep. Holes .028 and larger can
be stack drilled 3 deep. |
| Annular ring: Try to provide pads that are .020 larger than
hole size. Planned annular ring of .010 is good design criteria. Allowances
must be made for etching, lamination, drill position, front to back layer
registration and film stability. Smaller annular ring is certainly possible,
but at the expense of lower yields and increased manufacturing difficulty
which results in higher cost. |
| Hole tolerance: If possible, do not specify hole size
tolerances any smaller than +/-.003. Boards are usually pre-drilled .003 to
.004 larger than the finished holes size to allow for copper plating inside
the hole. Drilling and copper plating is a very critical step in
manufacturing circuit boards. Tight tolerances just increase problems and
lowers yields. A lot of material and labor go into a multilayer before its
drilled and plated. If it's out of tolerance, it's all scrap. |
| Copper weight: Do not specify 2 oz. copper unless you are
sure you need it. 2 oz. material cost about 40% more than 1 oz. |
| Via and Component Pads: Keep vias and component pads a
minimum of .050 away from connector gold-plated fingers. This will simplify
the tape process and prevent exposed bare copper after hot air solder
leveling. |
| Internal cut-outs: Avoid these if at all possible. These and
very large holes require special routing. Also, make the board as small as
possible. |
| Mil-P-5511OD boards: If you require Mil boards, look into
manufacturing the prototypes to best commercial standards such as IPC600.
The quality will probably be the same, but at much lower cost. |
| Standards: Adopt PCB design, artwork and manufacturing
standards: By adopting standards, you will insure your product can be
manufactured for the lowest cost possible. Your artwork should be of such
quality that literally any board house can build it without problems. Also
provide the manufacturer with a drill file, a fabrication detail drawing,
and gerber data instead of film whenever possible. 
|
|
Bill
Of Materials |
|
Final
Netlist |
|
Hardcopy
of the Schematics |
|
Spec
Sheets for all parts (including: footprint, pin spacing, lead size, drill
size, silkscreen shape and connector pin numbering assignments). |
|
Any
special instructions on layer stack-up (i.e. Signal, Ground & Power
Planes). |
|
Drawing
showing board size and any mounting holes (with required placement). |
|
Any
mechanical specifications like part height restrictions. |
|
Silkscreen
text identification, including Part Numbers and Revisions. |
|
Any
signals requiring special routing |
|
Any
placement requirements or restrictions (Please include any placement ideas
in the packages). |
