In electronics, printed circuit boards, or PCBs, are used to mechanically support electronic elements 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 element leads in thru-hole applications. A board design may have all thru-hole parts on the top or element side, a mix of thru-hole and surface area install on the top just, a mix of thru-hole and surface install parts on the top side and surface area mount parts on the bottom or circuit side, or surface install parts on the top and bottom sides of the board.
The boards are also utilized to electrically link the required leads for each component utilizing conductive copper traces. The component pads and connection traces are etched from copper sheets laminated onto a non-conductive substrate. Printed circuit boards are designed 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 designs with copper pads and traces on top and bottom of board with a variable variety 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 real copper pads and connection traces on the board surfaces as part of the board manufacturing process. A multilayer board includes a number 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 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 design, the internal layers are frequently utilized to supply power and ground connections, such as a +5 V plane layer and a Ground aircraft layer as the two internal layers, with all other circuit and part connections made on the leading and bottom layers of the board. Extremely intricate board designs might have a a great deal of layers to make the various connections for various voltage levels, ground connections, or for connecting the lots of leads on ball grid array gadgets and other big incorporated circuit bundle formats.
There are generally two types of product used to build 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 material resembles a very thin double sided board in that 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 approaches used to develop the preferred number of layers. The core stack-up technique, which is an older innovation, uses a center layer of pre-preg product with a layer of core material above and another layer of core product below. This mix of one pre-preg layer and two core layers would make a 4 layer board.
The film stack-up method, a newer innovation, would have core material as the center layer followed by layers of pre-preg and copper product developed above and listed below to form the final number of layers needed by the board style, sort of like Dagwood building a sandwich. This method permits the manufacturer versatility in how the board layer thicknesses are combined to fulfill the ended up product thickness requirements by varying the number of sheets of pre-preg in each layer. When the material layers are completed, the whole 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 process of manufacturing printed circuit boards follows the actions below for the majority of applications.
The procedure of determining products, processes, and requirements to meet the customer's requirements for the board style based upon the Gerber file details supplied with the purchase order.
The procedure of moving the Gerber file data for a layer onto an etch withstand film that is put on the conductive copper layer.
The standard process of exposing the copper and other locations unprotected by the etch resist movie to a chemical that removes the unprotected copper, leaving the protected copper pads and traces in place; more recent procedures use plasma/laser etching instead of chemicals to get rid of the copper product, permitting finer line meanings.
The process 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 strong board product.
The procedure of drilling all the holes for plated through applications; a second drilling procedure is utilized for holes that are not to be plated through. Information on hole area and size is consisted of in the drill drawing file.
The process 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 needed when holes are to be drilled through a copper area but the hole is not to be plated through. Avoid this procedure if possible due to the fact that it adds cost to the ended up board.
The process of using a protective masking product, a solder mask, over the bare copper traces or over the copper that has had a thin layer of solder used; the solder mask secures against environmental damage, provides insulation, protects versus solder shorts, and safeguards traces that run in between pads.
The process 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 components have been placed.
The procedure of using the markings for part classifications and component outlines to the board. May be applied to just the top side or to both sides if elements are mounted on both leading and bottom sides.
The procedure of separating several boards from a panel of identical boards; this process also enables cutting notches or slots into the board if ISO 9001 Accreditation Consultants
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 techniques.
The procedure of looking for connection or shorted connections on the boards by ways using a voltage between various points on the board and determining if a present circulation occurs. Relying on the board complexity, this process might need a specifically designed test fixture and test program to integrate with the electrical test system used by the board maker.