PCB Manufacturing at CSE

PCB manufacturing

To design a PCB, you normally use CAD/CAM tools to create the schematic diagram and then the PCB layout. From the PCB layout, GERBER and Excellon drill files are produced - this is the raw information needed in most manufacturing processes.

The manufacture of the blank PCB will be done for people from the GERBER/Excellon files they supply to David Johnson. Since the setup, drilling, plating and and milling process is technical and time consuming, prior arrangements must be made with David. It might be expected that a PCB manufacturing run will be done approximately once per week. Urgent jobs can also be accommodated, at David's discretion.

PCB fabrication is centred on a PCB milling machine, and copper plating tank and a silver plating tank. A PCB is designed using a standard CAD tool - for example, OrCad, Protel or Eagle. The resulting Gerber and Excellon files are translated into a format suitable for the milling machine. Holes are drilled on the PCB blank, and the board is then placed in the copper plating unit to plate copper through these holes.

The board is then placed on the milling machine, and isolation channels are milled around all tracks and pads. The board is then silver plated to provide a cleaner appearance and much easier surface for further working.

Note that CSE's procedures do not currently support solder masks or component legends.

VERY IMPORTANT INFORMATION

See the useful design rules for very important details on PCB design rules.
New users MUST read these rules in oder to correctly design a board.

Step by Step Procedure

(preliminary version)

Have a good idea

* Confirm with PCB support that your idea can be made and that you have the
  skills required
      eg a PCB 3metres by 3metres can't be done

* Confirm that components exist 

* Select your design tool

* Design the PCB, single, double or multi layer

* Run Error Rule Checking and particularly Design Rule Checking. 
      If you do not know what these are, talk to someone 

* Generate the Excellon/GERBER files

* Contact PCB support to organise a time to do the manufacturing
   Notify if any of your design reuires less than 0.20mm spacing between
   track/pads, etc

* This is tye time to consider rubouts

* Supply the Excellon/GERBER files to PCB support at the agreed time

* Solder up your board, and see if it works - this stage is your problem

A calculator to help with track size for current capacity for PCB layout can be found here.
A company called UltraCAD has some useful design notes at this address Topics include 'Square Waves, Pulse Rise Times, and Frequencies' and 'Maintaining Clean Power'
PCB manufacture costs depend to some extent on the number of blank PCBs required, and the size/complexity of PCBs. To have a board manufactured within the school will cost approximately $??? per sq cm. So a typical board of about 100mm x 80 mm will cost $???
Actually populating the board with components and debugging the final assembly is the responsibility of the board designer

There are number of CAD/CAM tools that are used by people within the school. The following links provide hints, tools and sometimes copies of freeware binaries :

Eagle is a schematic capture and PCB layout program used by some people within the school
Protel is a schematic capture and PCB layout program used by some people within the school
OrCad is a schematic capture and PCB layout program used by some people within the school

A Selection of tutorials can be found at these links.

Alex's Electronic Resource Library '
ChipCentre's Online Apps and tools have a large selection of interesting documentation/. The cross-talk tutorial looks good

This is the milling machine. This drills holes (eg vias) through a copper plated fibreglass blank. After copper plating these holes, it then mills isolation channels around tracks, creating the final PCB

This is the thermal press. It bonds extra layers (prepreg) to a PCB blank, creating a multi layer board.

This is the copper/silver plating unit. The large tank in the middle is the copper plating tank - you can see the attachments for the power supply. Typically 50 amps is passed through a copper sulphate/acid solution which plates the holes in a board.
The tanks to the left are cleaning and surface preparation tanks for copper plating.
The tanks to the right are the silver plating tanks (this is chemical plating rather than electro plating).

Tank 1 - BlackHole SP Conditioner is a single component, silghtly alkaline solution designed to clean copper surfaces and condition dielectric surfaces of the PCBs. It is used in praparation for through-holee plating.

Tank 2 - Water Spray Tank for rinsing.

Tank 3 - BlackHole SP Starter is a silghtly alkaline carbon black based, liquid suspension. The bath coats the substrate and copper material with carbon providing the means to electrolytically copper plate the hole walls.

Tank 4 - Microclean Spray Tank is a sodium persulphate based solution. It removes dried BlackHole Starter material from all copper surfaces, including innerlayers, by penetrating the BlackHole coating and etching the copper surfaces. This lifts the BlackHole coating from the copper surfaces while giving those surfaces a micro-roughened structure for subsequent processing steps.

Tank 5 - Copper Plating Tank.

Tank 6 - Sterling Acid Cleaner is a single component immersion acid cleaner formulated to remove oils, smut, oxides and fingerprints.

Tank 7 - DI Water rinse tank.

Tank 8 - Sterling Predip tank.

Tank 9 - Sterling Siler tank is an immersion process for a silver deposit on copper.

And this is a finished PCB blank. You can see several completed circuit boards. the colour of the board is due to the final silver plating. This is less likely to tarnish compared to a blank copper finish, and in particular facilitates soldering of components.