In electronic devices, printed circuit boards, or PCBs, are used ISO 9001 consultants 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 element leads in thru-hole applications. A board style might have all thru-hole elements on the leading or component side, a mix of thru-hole and surface area install on the top side just, a mix of thru-hole and surface area install components on the top and surface area install components on the bottom or circuit side, or surface area mount parts on the leading and bottom sides of the board.
The boards are likewise used to electrically link the needed leads for each element using conductive copper traces. The part pads and connection traces are etched from copper sheets laminated onto a non-conductive substrate. Printed circuit boards are designed as single agreed copper pads and traces on one side of the board just, double sided with copper pads and traces on the leading and bottom sides of the board, or multilayer designs 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 include a core dielectric material, such as FR-4 epoxy fiberglass, with copper plating on one or both sides. This copper plating is engraved away to form the actual copper pads and connection traces on the board surface areas as part of the board manufacturing procedure. A multilayer board consists of 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 after that bonded into a single board structure under heat and pressure. Multilayer boards with 48 or more layers can be produced with today's technologies.
In a common four layer board style, the internal layers are often used to provide power and ground connections, such as a +5 V airplane layer and a Ground aircraft 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 numerous connections for different voltage levels, ground connections, or for connecting the numerous leads on ball grid range devices and other large incorporated circuit bundle formats.
There are normally 2 kinds of product utilized 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 product is similar to an extremely thin double sided board because it has a dielectric product, such as epoxy fiberglass, with a copper layer deposited on each side, usually.030 thickness dielectric product with 1 ounce copper layer on each side. In a multilayer board design, there are 2 approaches used to develop the desired number of layers. The core stack-up approach, which is an older technology, utilizes a center layer of pre-preg material with a layer of core product above and another layer of core product listed below. This mix of one pre-preg layer and two core layers would make a 4 layer board.
The film stack-up technique, a newer technology, 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 required by the board design, sort of like Dagwood constructing a sandwich. This technique enables the manufacturer versatility in how the board layer densities are integrated to satisfy the completed item density requirements by varying the variety of sheets of pre-preg in each layer. When the material layers are finished, the whole 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 process of producing printed circuit boards follows the actions listed below for most applications.
The procedure of identifying products, processes, and requirements to fulfill the customer's requirements for the board design based upon the Gerber file info provided with the purchase order.
The process of moving the Gerber file information for a layer onto an etch withstand film that is placed on the conductive copper layer.
The traditional procedure of exposing the copper and other areas unprotected by the etch resist film to a chemical that gets rid of the unguarded copper, leaving the protected copper pads and traces in place; newer procedures utilize plasma/laser etching rather of chemicals to eliminate the copper product, allowing finer line meanings.
The process of aligning the conductive copper and insulating dielectric layers and pressing them under heat to trigger 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 procedure 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 positioned in an electrically charged bath of copper.
This is needed when holes are to be drilled through a copper area however the hole is not to be plated through. Avoid this procedure if possible since 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 environmental damage, supplies insulation, safeguards against solder shorts, and safeguards traces that run in between pads.
The process of covering the pad locations with a thin layer of solder to prepare the board for the ultimate wave soldering or reflow soldering process that will happen at a later date after the elements have been put.
The procedure of using the markings for part designations and component details to the board. May be used to simply the top side or to both sides if parts are installed on both top and bottom sides.
The process of separating several boards from a panel of similar boards; this procedure likewise allows cutting notches or slots into the board if required.
A visual examination of the boards; also can be the process of checking wall quality for plated through holes in multi-layer boards by cross-sectioning or other approaches.
The procedure of checking 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 circulation happens. Depending upon the board intricacy, this process may require a specially created test component and test program to integrate with the electrical test system used by the board producer.