In the electronics industry, printed circuit boards are widely used. In fact, the majority of components, appliances, devices, etc. cannot be completed without a printed circuit board. Circuit boards act as mechanical support wherein the connection leads are soldered onto the copper pads.
Some circuit boards have drilled holes where leads are soldered through and through. Some circuit boards can be surface-mounted while some are through-hole although there are circuit boards that incorporate both designs.
There are circuit boards with surface-mounted and through-hole designs on the top only, bottom only, top sides, bottom sides and surface- mounted at the top and through-hole at the bottom.
Regardless of the design, the printed circuit boards pass through several basic procedures. First is setting up. The procedure involves the identification of the requirements of the customers including the materials and specifications of the printed circuit board. Some vendors used the Gerber file in communicating the required circuit boards design in their purchase order. Information needed include numbers of layer, materials and thickness, finish plating, copper weight, dimensions and sizes of the holes.
Second is imaging. Imaging involves the transfer of the specs of the layer based on Gerber file and onto the etch-resist film. The film will be placed on the conductive layer which is usually made from copper.
Third is etching –
Etching is a traditional process wherein the copper will be exposed as well as the resist film-unprotected areas. A chemical will be used in removing the unprotected copper, leaving protected pads and traces. Some manufacturers are using laser etching in removing copper for finer lines and dots definitions.
Fourth is multilayer pressing. Pressing means to align the layers of conductive copper and dielectric insulation and heat press them. Heat pressing activates the adhesive thereby forming a solid printed circuit board material.
Fifth is drilling –
Holes are drilled onto the pressed boards especially for plated through applications. However, a second drilling may be required for the holes that need not be plated through. A drill drawing file is created to guide the process specifically the location and size of the holes to be drilled.
Sixth is plating –
Plating is the application of copper plating onto the pads, traces, lines and dots. This also applies on drilled through holes that need plating. Circuit boards are put on an electrically charged copper bath.
Seventh is masking –
The process will be proceed to masking is a second drilling is not necessary. Masking is the application of a protected material which is typically solder mask above the copper traces or copper where solder is thinly applied.
Solder masks will protect the printed circuit board against the elements such as environmental damages and solder shorts. It will also provide insulation while protecting the traces running between copper pads.
Eighth is finishing. Finishing requires coating copper pads with solder. A thin layer is enough to prepare the circuit board for soldering which will occur after placing all the necessary components.
Ninth is silk screening. Silk screening is the application of markings where the components will be designated. Through this, component outlines will be created onto the circuit board.
The process is only applicable on the top side for surface-mounted applications and on top and bottom sides for both surface-mounted and through-hole applications.
Tenth is routing. This procedure involves the separation of the multiple boards from the panel of identical boards. The process may require cutting slots or notches into the circuit board if deemed necessary.
Eleventh is quality controlling. The circuit board will be inspected visually for wall quality among others. The quality controller may perform a cross-sectioning to determine the integrity of the layers in multilayer circuit boards.
Twelfth is electrical testing. The circuit board will be checked for short connections and continuity. Voltage will be applied between two points to determine if current is flowing smoothly or not. Test programs and fixtures usually depend on the complexity of the circuit board.
There are no cutting corners when it comes to creating printed circuit boards. Anyhow, if passing through all these processes means manufacturing high quality circuit boards.