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In electronics, printed circuit boards, or PCBs, are utilized to mechanically support electronic parts which have their connection leads soldered onto copper pads in surface mount applications or through rilled holes in the board and copper pads for soldering the element leads in thru-hole applications. A board style might have all thru-hole components on the top or element side, a mix of thru-hole and surface mount on the top side just, a mix of thru-hole and surface area mount elements on the top side and surface mount elements on the bottom or circuit side, or surface area mount components on the top and bottom sides of the board.
The boards are also utilized to electrically connect the needed leads for each part utilizing conductive copper traces. The component pads and connection traces are engraved from copper sheets laminated onto a non-conductive substrate. Printed circuit boards are developed as single agreed copper pads and traces on one side of the board only, double agreed copper pads and traces on the leading and bottom sides of the board, or multilayer styles with copper pads and traces on top and bottom of board with a variable number of internal copper layers with traces and connections.
Single or double sided boards consist of 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 actual copper pads and connection traces on the board surface areas as part of the board production process. A multilayer board consists of a number of layers of dielectric material that has been fertilized 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 normal four layer board design, the internal layers are frequently utilized to supply power and ground connections, such as a +5 V aircraft layer and a Ground airplane layer as the two internal layers, with all other circuit and element connections made on the top and bottom layers of the board. Extremely complicated board styles may have a a great deal of layers to make the different connections for different voltage levels, ground connections, or for linking the lots of leads on ball grid variety gadgets and other big integrated circuit package formats.
There are typically two kinds of material used to construct a multilayer board. Pre-preg product is thin layers of fiberglass pre-impregnated with an adhesive, and remains in sheet form, generally about.002 inches thick. Core product resembles an extremely thin double sided board because it has a dielectric material, such as epoxy fiberglass, with a copper layer transferred on each side, generally.030 thickness dielectric material with 1 ounce copper layer on each side. In a multilayer board design, there are 2 approaches utilized to build up the preferred number of layers. The core stack-up approach, which is an older technology, uses a center layer of pre-preg material with a layer of core product above and another layer of core material below. This mix of one pre-preg layer and two core layers would make a 4 layer board.
The film stack-up approach, a newer technology, would have core product as the center layer followed by layers of pre-preg and copper product developed above and below to form the final variety of layers needed by the board style, sort of like Dagwood developing a sandwich. This technique enables the manufacturer versatility in how the board layer densities are combined to fulfill the completed product density requirements by varying the number of sheets of pre-preg in each layer. When the material layers are finished, the whole stack undergoes heat and pressure that triggers the adhesive in the pre-preg to bond the core and pre-preg layers together into a single entity.
The procedure of making printed circuit boards follows the actions listed below for most applications.
The procedure of figuring out products, processes, and requirements to fulfill the client's specs for the board style based upon the Gerber file details supplied with the order.
The process of moving the Gerber file data for a layer onto an etch resist film that is put on the conductive copper layer.
The traditional process of exposing the copper and other areas unprotected by the etch resist movie to a chemical that removes the unprotected copper, leaving the protected copper pads and traces in location; newer procedures use plasma/laser etching rather of chemicals to get rid of the copper product, permitting finer line definitions.
The procedure of aligning the conductive copper and insulating dielectric layers and pushing them under heat to activate the adhesive in the dielectric layers to form a solid board product.
The process of drilling all the holes for plated through applications; a second drilling process is utilized for holes that are not to be plated through. Information on hole location and size is consisted of in the drill drawing file.
The procedure of using copper plating to the pads, traces, and drilled through holes that are to be plated through; boards are positioned in an electrically charged bath of copper.
This is required when holes are to be drilled through a copper location but the hole is not to be plated through. Prevent this procedure if possible due to the fact that it adds cost to the ended up board.
The process of applying a protective masking material, a solder mask, over the bare copper traces or over the copper that has had a thin layer of solder used; the solder mask safeguards against environmental damage, supplies insulation, safeguards versus solder shorts, and protects traces that run in between pads.
The procedure of covering the pad areas with a thin layer of solder to prepare the board for the eventual wave soldering or reflow soldering process that will happen at a later date after the components have been put.
The procedure of applying the markings for part designations and component outlines to the board. Might be used to simply the top or to both sides if elements are installed on both top and bottom sides.
The process of separating numerous boards from a panel of similar boards; this procedure likewise enables cutting notches or slots into the board if needed.
A visual examination of the boards; likewise can be the process of examining wall quality for plated through holes in multi-layer boards by cross-sectioning or other methods.
The process of looking for continuity or shorted connections on the boards by means using a voltage in between numerous points on the board and determining if a present flow takes place. Depending upon the board intricacy, this procedure might require a specially created test component and test program to incorporate with the electrical test system used by the board manufacturer.
ISO 9001 consultants