In electronics, printed circuit boards, or PCBs, are used to mechanically support electronic parts which have their connection leads soldered onto copper pads in surface install applications or through rilled holes in the board and copper pads for soldering the element leads in thru-hole applications. A board design may have all thru-hole components on the top or element side, a mix of thru-hole and surface mount on the top side only, a mix of thru-hole and surface area install components on the top side and surface area install parts on the bottom or circuit side, or surface mount parts on the leading and bottom sides of the board.
The boards are also used to electrically connect the needed leads for each component utilizing conductive copper traces. The element pads and connection traces are engraved from copper sheets laminated onto a non-conductive substrate. Printed circuit boards are created as single sided with copper pads and traces on one side of the board just, double agreed copper pads and traces on the top and bottom sides of the board, or multilayer styles with copper pads and traces on the top and bottom of board with a variable number of internal copper ISO 9001 consultants layers with traces and connections.
Single or double sided boards include a core dielectric product, such as FR-4 epoxy fiberglass, with copper plating on one or both sides. This copper plating is etched away to form the real copper pads and connection traces on the board surface areas as part of the board production process. A multilayer board includes a number of layers of dielectric product that has been impregnated with adhesives, and these layers are used to separate the layers of copper plating. All these layers are aligned and then bonded into a single board structure under heat and pressure. Multilayer boards with 48 or more layers can be produced with today's innovations.
In a typical 4 layer board style, the internal layers are typically used to provide power and ground connections, such as a +5 V aircraft layer and a Ground plane layer as the two internal layers, with all other circuit and component connections made on the leading and bottom layers of the board. Really intricate board styles might have a large number of layers to make the different connections for various voltage levels, ground connections, or for connecting the numerous leads on ball grid variety gadgets and other big incorporated circuit bundle formats.
There are normally two kinds of material used to construct a multilayer board. Pre-preg material is thin layers of fiberglass pre-impregnated with an adhesive, and remains in sheet kind, usually about.002 inches thick. Core material is similar to a really thin double sided board in that it has a dielectric product, such as epoxy fiberglass, with a copper layer deposited on each side, normally.030 thickness dielectric product with 1 ounce copper layer on each side. In a multilayer board style, there are 2 approaches used to develop the wanted number of layers. The core stack-up approach, which is an older innovation, utilizes a center layer of pre-preg material with a layer of core product above and another layer of core product listed below. This combination of one pre-preg layer and two core layers would make a 4 layer board.
The film stack-up method, a more recent innovation, would have core material as the center layer followed by layers of pre-preg and copper material developed above and listed below to form the last number of layers needed by the board design, sort of like Dagwood building a sandwich. This method allows the producer versatility in how the board layer densities are combined to satisfy the finished item density requirements by differing the number of sheets of pre-preg in each layer. Once the material layers are finished, the entire stack goes through heat and pressure that causes the adhesive in the pre-preg to bond the core and pre-preg layers together into a single entity.
The procedure of manufacturing printed circuit boards follows the actions listed below for the majority of applications.
The procedure of determining products, processes, and requirements to meet the customer's specifications for the board style based on the Gerber file info supplied with the order.
The process of transferring the Gerber file data for a layer onto an etch resist film that is put on the conductive copper layer.
The standard process of exposing the copper and other areas unprotected by the etch resist movie to a chemical that gets rid of the unguarded copper, leaving the secured copper pads and traces in place; newer processes use plasma/laser etching rather of chemicals to remove the copper material, enabling finer line meanings.
The process of lining up the conductive copper and insulating dielectric layers and pressing them under heat to activate the adhesive in the dielectric layers to form a solid board product.
The procedure of drilling all of the holes for plated through applications; a second drilling process is used for holes that are not to be plated through. Info on hole place and size is contained in the drill drawing file.
The process of applying copper plating to the pads, traces, and drilled through holes that are to be plated through; boards are put in an electrically charged bath of copper.
This is required when holes are to be drilled through a copper area but the hole is not to be plated through. Prevent this procedure if possible since it adds expense to the finished board.
The procedure of applying a protective masking product, a solder mask, over the bare copper traces or over the copper that has actually had a thin layer of solder used; the solder mask protects against ecological damage, offers insulation, protects against solder shorts, and secures traces that run between pads.
The procedure of coating the pad locations with a thin layer of solder to prepare the board for the eventual wave soldering or reflow soldering process that will occur at a later date after the parts have been placed.
The procedure of using the markings for component classifications and element describes to the board. Might be used to just the top or to both sides if components are mounted on both leading and bottom sides.
The process of separating numerous boards from a panel of identical boards; this procedure likewise allows cutting notches or slots into the board if needed.
A visual assessment of the boards; likewise can be the procedure of inspecting wall quality for plated through holes in multi-layer boards by cross-sectioning or other methods.
The procedure of looking for continuity or shorted connections on the boards by methods applying a voltage in between various points on the board and determining if a present circulation happens. Depending upon the board complexity, this procedure might require a specifically created test component and test program to incorporate with the electrical test system used by the board manufacturer.