In electronic devices, printed circuit boards, or PCBs, are utilized to mechanically support electronic parts which have their connection leads soldered onto copper pads in surface area mount 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 components on the leading or component side, a mix of thru-hole and surface mount on the top only, a mix of thru-hole and surface mount parts on the top and surface mount elements on the bottom or circuit side, or surface area mount parts on the top and bottom sides of the board.
The boards are also used to electrically link the required leads for each part using 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 sided with 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 variety of internal copper layers with traces and connections.
Single or double sided boards consist of a core dielectric material, 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 manufacturing process. A multilayer board consists of a variety of layers of dielectric material that has been fertilized with adhesives, and these layers ISO 9001 Certification Consultants are used to separate the layers of copper plating. All these layers are lined up 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 4 layer board design, the internal layers are often used to provide power and ground connections, such as a +5 V aircraft layer and a Ground aircraft layer as the two internal layers, with all other circuit and element connections made on the leading and bottom layers of the board. Extremely complex board designs might have a a great deal of layers to make the different connections for different voltage levels, ground connections, or for connecting the numerous leads on ball grid selection gadgets and other big integrated circuit bundle formats.
There are generally 2 types of product utilized to construct a multilayer board. Pre-preg material is thin layers of fiberglass pre-impregnated with an adhesive, and is in sheet form, normally about.002 inches thick. Core material resembles an extremely 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 material with 1 ounce copper layer on each side. In a multilayer board design, there are two methods used to build up the preferred variety of layers. The core stack-up method, 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 product below. This mix of one pre-preg layer and 2 core layers would make a 4 layer board.
The movie stack-up technique, a newer technology, would have core product as the center layer followed by layers of pre-preg and copper material developed above and below to form the final number of layers needed by the board design, sort of like Dagwood developing a sandwich. This technique allows the manufacturer versatility in how the board layer thicknesses are integrated to fulfill the completed item density requirements by differing the number of sheets of pre-preg in each layer. Once the product layers are completed, 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 producing printed circuit boards follows the actions below for many applications.
The process of figuring out products, procedures, and requirements to satisfy the consumer's requirements for the board style based on the Gerber file info offered with the purchase order.
The procedure of moving the Gerber file data for a layer onto an etch withstand movie that is placed on the conductive copper layer.
The conventional procedure of exposing the copper and other locations unprotected by the etch resist film to a chemical that eliminates the unguarded copper, leaving the secured copper pads and traces in place; more recent procedures utilize plasma/laser etching instead of chemicals to remove the copper product, permitting finer line meanings.
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 procedure of drilling all of the holes for plated through applications; a 2nd 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 location however the hole is not to be plated through. Prevent this procedure if possible due to the fact that it adds expense to the completed board.
The procedure 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 applied; the solder mask secures versus ecological damage, provides insulation, safeguards versus solder shorts, and secures traces that run in 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 components have been put.
The procedure of using the markings for element designations and component details to the board. Might be used to just the top side or to both sides if components are mounted on both leading and bottom sides.
The process of separating several boards from a panel of identical boards; this procedure likewise permits cutting notches or slots into the board if needed.
A visual examination of the boards; also can be the process of examining 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 ways using a voltage between various points on the board and determining if an existing flow takes place. Depending upon the board complexity, this process might need a specially created test fixture and test program to integrate with the electrical test system utilized by the board producer.