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 area install applications or through rilled holes in the board and copper pads for soldering the part leads in thru-hole applications. A board style might have all thru-hole parts on the top or part side, a mix of thru-hole and surface area mount on the top side only, a mix of thru-hole and surface install elements on the top and surface mount elements on the bottom or circuit side, or surface area install elements on the leading and bottom sides of the board.
The boards are also used to electrically link 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 just, double agreed copper pads and traces on the leading and bottom sides of the board, or multilayer designs with copper pads and traces on the top and bottom of board with a variable number of internal copper 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 ISO 9001 consultants away to form the real copper pads and connection traces on the board surface areas as part of the board production procedure. A multilayer board consists of a variety of layers of dielectric product that has actually been impregnated with adhesives, and these layers are utilized to separate the layers of copper plating. All these layers are lined up 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 common four layer board style, the internal layers are typically utilized to provide power and ground connections, such as a +5 V aircraft layer and a Ground aircraft layer as the 2 internal layers, with all other circuit and element connections made on the leading and bottom layers of the board. Very complex board designs may have a a great deal of layers to make the different connections for different voltage levels, ground connections, or for linking the numerous leads on ball grid range devices and other big integrated circuit package formats.
There are normally 2 kinds of product used to construct a multilayer board. Pre-preg product is thin layers of fiberglass pre-impregnated with an adhesive, and remains in sheet kind, typically about.002 inches thick. Core material resembles a very thin double sided board because it has a dielectric material, such as epoxy fiberglass, with a copper layer transferred on each side, typically.030 thickness dielectric product with 1 ounce copper layer on each side. In a multilayer board style, there are two techniques utilized to build up the preferred number of layers. The core stack-up method, which is an older technology, utilizes a center layer of pre-preg material with a layer of core material above and another layer of core material listed below. This combination of one pre-preg layer and two core layers would make a 4 layer board.
The film stack-up technique, a more recent innovation, would have core material as the center layer followed by layers of pre-preg and copper material built up above and below to form the final variety of layers required by the board style, sort of like Dagwood developing a sandwich. This method permits the producer flexibility in how the board layer densities are integrated to satisfy the ended up product density requirements by differing the number of sheets of pre-preg in each layer. Once the product layers are finished, the entire stack goes through 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 manufacturing printed circuit boards follows the steps below for most applications.
The process of determining products, processes, and requirements to meet the consumer's requirements for the board design based upon the Gerber file info offered with the purchase order.
The process of moving the Gerber file data for a layer onto an etch resist movie that is put on the conductive copper layer.
The conventional procedure of exposing the copper and other locations unprotected by the etch resist movie to a chemical that gets rid of the vulnerable copper, leaving the safeguarded copper pads and traces in place; newer procedures utilize plasma/laser etching instead of chemicals to remove the copper material, enabling finer line meanings.
The procedure of aligning the conductive copper and insulating dielectric layers and pushing them under heat to trigger the adhesive in the dielectric layers to form a solid board product.
The process of drilling all of the holes for plated through applications; a second drilling process is utilized for holes that are not to be plated through. Details on hole area and size is included 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 placed in an electrically charged bath of copper.
This is needed 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 includes cost to the finished board.
The process of applying a protective masking product, a solder mask, over the bare copper traces or over the copper that has had a thin layer of solder applied; the solder mask protects versus ecological damage, offers insulation, safeguards versus solder shorts, and safeguards traces that run between pads.
The process of covering the pad areas with a thin layer of solder to prepare the board for the ultimate wave soldering or reflow soldering procedure that will happen at a later date after the components have actually been put.
The process of applying the markings for component classifications and element outlines to the board. Might be applied to just the top or to both sides if components are mounted on both leading and bottom sides.
The process of separating multiple boards from a panel of similar boards; this procedure likewise allows cutting notches or slots into the board if required.
A visual inspection of the boards; likewise can be the procedure of checking wall quality for plated through holes in multi-layer boards by cross-sectioning or other approaches.
The process of looking for continuity or shorted connections on the boards by ways applying a voltage in between numerous points on the board and figuring out if a present flow takes place. Depending upon the board intricacy, this process may require a specially developed test component and test program to integrate with the electrical test system utilized by the board maker.