circuit board Fabrication And Drilling Process:
There are two reasons for through-hole drilling printed circuit boards:
Create an opening through the board that will permit a subsequent process to form an electrical connection between top, bottom, and internal conductor pathways.
To permit the board component mounting through with structural integrity and precision of location.
The quality of a hole drilled through a printed circuit board is measured by its ability to interface with the following fabrication processes: plating, soldering, and forming a highly reliable, non-degrading electrical and mechanical connection.
Imaging:
The process that patterns the metal conductor to form the circuit. This PCB Fabrication process involves a multistep integration of imaging materials, imaging equipment, and processing conditions with the metallization process to reduce the master pattern on a substrate.
ElectroPlating:
Electroplating is the coating of an electrically conductive object with a layer of metal using electrical current. The result is a thin, smooth, even coat of metal on the object. A new genre of high-density interconnect (HDI) boards is making the transition from leading edge to mainstream. These printed circuit boards are characterized by combining a series of complexity features that include buried and blind vias, high-aspect ratio plating, small-hole plating, and fine lines and spaces side by side with ground plane areas of different sizes.
Etching Process
Etching Process is one of the major steps in the chemical processing of subtractive printed boards. It is the removal of copper, to achieve the desired circuit patterns. Etching is also used for surface preparation with minimal metal removal (microetching) during innerlayer oxide coating and electroless or electrolytic planting. Technical, economic, and environmental needs for practical process control have brought about major improvements in etching techniques. Batchtype operations, with their variable etching rates and long downtimes, have been replaced completely with continuous, constant-etch-rate processes.
Solder Resist Application:
Permanent solder resists may be applied to the PWB by any of several techniques or pieces of equipment. Screen printing of liquid solder resists is the most common and the liquid-photoprint solder resists are applied by curtain coating, roll coating, or blank-screen-printing techniques.
Liquid Photoprint: For some liquid-photoprint solder resists, a screen-printing technique is used to apply the resist in a controlled manner to the surface of the PWB. The screen has no image and serves only to control the thickness and waste of the liquid solder resist. There is no registration of the screen, since there is no image. The actual solder resist image will be obtained by exposing the coated PWB with ultraviolet light energy and the appropriate phototool image. The unexposed solder resist areas defined by the phototool are washed away during the development step of the PCB fabrication process.
Surface Finishes:
Surface Finish is about connectivity. It is at the surface where a connection from the board to a device occurs. Initially soldering and insertion were the preferred methods for connecting components to the printed board and the circuit board to the system. The dominant method of assembly was wave soldering. Hot-air solder leveling (HASL) was the finish of choice for component holed on the board. The evolution from through-hole components to surface-mount components offered great opportunities to reduce the size and weight of the final electronic product. Surface-mount pads required screen pastes and reflow assembly.
Final PCB Fabrication Test
Advances in packaging technology resulting in finer board geometry, including the various forms of high-density interconnection (HDI), have combined with increasing data rates to put significant pressure on the electrical test area. Fixture construction is more expensive and requires improved process control.
