The PCB Manufacturing Process

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A lot of effort goes into making printed circuit boards, the procedure is extremely rigorous.

PCB prototyping process

The procedure varies slightly for different types of PCB. The process for creating a board with a single layer, for example, is slightly simpler than that for multilayer boards.

For the purposes of this illustration we shall use a multilayer board because it is the type most ordered by our customers.

PCB Preparation

When we receive the information from a customer, we convert it from a Gerber file to CAM process data that is compatible with our equipment.

We also perform the first of many checks at this stage to ensure the design meets our manufacturing requirements – checking the track widths, spacing and the hole sizes to ensure our equipment is suitable for the job.

After all of these checks have been completed we can export the tool files to our equipment.

Next, we plot films of each PCB layer by using a laser photoplotter to convert the board data into a pixel image, before making sure all of the layers align with one another correctly.

Photoresist

A clean layer of photosensitive film is attached on top of the copper. This layer is called the photo resist.

Once this photoresist layer is set up, we can print a positive image onto the film discussed above and develop it. Once printed, we can etch away the excess copper and strip dry the film resist.

After a quick visual inspection the copper is oxidised before being bonded in the vacuum press.

Drilling

A PCB will start to take shape during the drilling stage. We use the program file to drill the desired holes in the CNC making sure to remove any resin smears as we go along.

After drilling and before adding other PCB layers, we place conductive film in any holes using the ‘Black Hole’ process.

The photoresist steps then need to be repeated for each layer. We laminate the dry film photoresist, print and develop the image before putting copper plate and then tin plate (as an etch resist) on tracks and down through-holes.

Stripping

We strip the photoresist off before etching to remove any unwanted excess copper. Strip the tin and complete another inspection of the tracks and holes to ensure nothing has been damaged.

Finishing touches

The PCB now looks all but finished but there are a number of steps it needs to go through before it is ready to ship.

  1. Coat with photo-defined solder resist
  2. Print solder resist image
  3. Develop solder resist
  4. Print component indent
  5. Finanl finish of ENIG Immersion Silver HAL (lead free) OSP
  6. Score
  7. Rout profile
  8. Electrical test
  9. Final inspect
  10. Pack and ship