Fabricating Printed Circuit Boards

C. Murphy

June 6, 1997

The purpose of this document is to state the necessary steps for getting a printed circuit board fabricated. The basic information needed is described along with additional information needed if the board is being contract assembled.

I. Assembling the board in the shop

Before you send a board out to be fabricated, you need to make sure you have your parts list with specific manufacturer's part numbers and quantities and have given it to the secretary, along with an account number so that the parts can be ordered. This actually should have been done as soon as the board was successfully put through To Layout, but if it hasn't been done, do it NOW.

The next step is to get a quote for the fabrication of the board. There is a template letter on the PC next to the library that should be copied, filled out for your board, and faxed to board companies to quote on. To fill out the letter you will need the following information: (an example letter is attached to this document)

Standard values

Board name

Dimensions

Thickness

Board Material FR4

Cutout sizes

Number of layers

Copper weight 1oz

Surface mount, which side(s)

Smallest trace width

Smallest spacing

Number of different hole sizes

Smallest hole diameter

Largest hole diameter

Total number of holes

Any gold plating- number of areas and area sizes

Number of silkscreen layers

Number of solder mask layers

Solder mask Wet mask over bare copper

Quantity

Delivery time 2 week

Number of artworks

Make sure you put your name and phone/fax number on the letter so that the quotes come back addressed to you. The easiest way to fax this letter out is print it to WinFax. After you OK the print job, a window pops up- in that window there is a list of companies. Select the board companies and add them to the list of fax destinations- these should include Sovereign Circuits (Terry Marsh), Unicircuit, Metro Circuits, Advanced Circuits, R&D Circuits, and Proto Express. Within a day or so you should have received quotes from all of the companies. When you have selected a company and have gotten a purchase order, you are ready to send the necessary information to the selected company.

To fabricate a printed circuit board, you need the following four items:

• Artwork files for your board
• Drill file
• Aperture table file
• Fabrication drawing (example attached)

All of these items are created in Fablink.

• The artwork files are computer files that contain the necessary information for each individual layer in the board. This includes signal, power, silkscreen, solder mask, drill, and possibly paste mask layers.
• The aperture table file is a file that is used to plot the artwork. It has shapes and sizes that are needed to draw the artwork listed, and also a description of the power connection shapes.
• The drill file is a text file in excellon format that lists all of the different drill hole coordinates on your board.
• The fabrication drawing is made in Fablink as well and can be printed out and faxed to the company if the board is small enough, or it can be made into an additional artwork.

For instructions on creating any of the four items listed above, please see the E-shop document on going through Fablink

Now you need to get the files to the board company. The preferred methods are by modem or e-mail. First of all, all of the files need to be zipped together. If you are faxing over the fabrication drawing then it is not included.

On the shop PC, open ftp and get all of these files from the /pcb/mfg directory in your design area. Then zip the files together using WinZip. If the company has e-mail (Unicircuit), you can ftp the file back to your usual e-mail machine and attach it to an e-mail. If they don't have e-mail, you can modem the file directly from the shop PC to the company. Most of the board companies' modem numbers are set up in the SmartTerm sessions area.

I. Contract Assembly

If you are going to contract assemble your board, you will need a more comprehensive package of materials to get a quote on. There are also more options. A company can do the whole thing, including getting the board made, ordering all parts, and assembling, or we can supply the boards and they can get the parts and do the assembly, or we can get the boards and parts and they can just do the assembly. Beware, if we get the parts, there may be requirements that all parts be on tape or in tubes.

You should contact individual assembly companies for specific quoting requirements, but the minimum necessary information is:

• Artwork files for your board
• Aperture table file
• Bill of Materials (example attached)

These should be zipped together and sent to the company. Currently, we know of five assembly houses:

• ADCO (810)853-5525 x20 Marc Damman
• Donelly (810)606-0444
• IE&E (810)545-3245
• Debron (248)553-4335
• CCI (248)588-7220

When you get ready to have the board assembled, you will have to have the drill file, fabrication drawing (if they are having the board made), specific and final bill of materials with reference numbers for each manufacturer part, and an assembly drawing (example attached).