In electronics, printed circuit boards, or PCBs, are used to mechanically support electronic components 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 part leads in thru-hole applications. A board design might have all thru-hole elements on the leading or element side, a mix of thru-hole and surface area install on the top side only, a mix of thru-hole and surface install components on the top side and surface mount components on the bottom or circuit side, or surface area install components on the top and bottom sides of the board.
The boards are also utilized to electrically link the required leads for each component using conductive copper traces. The element pads and connection traces are etched from copper sheets laminated onto a non-conductive substrate. Printed circuit boards are created as single agreed 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 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 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 production procedure. A multilayer board consists of 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 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 normal 4 layer board style, the internal layers are typically utilized to offer power and ground connections, such as a +5 V airplane layer and a Ground plane layer as the two internal layers, with all other circuit and component connections made on the top and bottom layers of the board. Very complex 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 many leads on ball grid variety devices and other large incorporated circuit bundle formats.
There are generally 2 kinds of product utilized to construct a multilayer board. Pre-preg material is thin layers of fiberglass pre-impregnated with an adhesive, and remains in sheet kind, typically about.002 inches thick. Core material is similar to an extremely thin double sided board in that it has a dielectric product, such as epoxy fiberglass, with a copper layer deposited on each side, generally.030 density dielectric product with 1 ounce copper layer on each side. In a multilayer board style, there are two techniques used to build up the preferred variety of layers. The core stack-up method, which is an older innovation, 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 2 core layers would make a 4 layer board.
The film stack-up approach, a newer innovation, would have core product as the center layer followed by layers of pre-preg and copper product developed above and below to form the last number of layers required by the board design, sort of like Dagwood building a sandwich. This approach permits the manufacturer versatility in how the board layer thicknesses are integrated to satisfy the ended up item thickness requirements by differing the variety of sheets of pre-preg in each layer. Once the product layers are finished, the entire stack is subjected to 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 making printed circuit boards follows the actions below for a lot of applications.
The procedure of identifying products, procedures, and requirements to satisfy the customer's requirements for the board design based on the Gerber file details provided with the purchase order.
The procedure of moving the Gerber file information for a layer onto an etch withstand film that is put on the conductive copper layer.
The traditional process of exposing the copper and other locations unprotected by the etch resist movie to a chemical that gets rid of the unprotected copper, leaving the secured copper pads and traces in location; newer procedures utilize plasma/laser etching instead of chemicals to get rid of the copper product, allowing finer line meanings.
The procedure of lining up 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 of the holes for plated through applications; ISO 9001 Accreditation Consultants a second drilling procedure is utilized for holes that are not to be plated through. Details on hole place and size is included in the drill drawing file.
The process of applying copper plating to the pads, traces, and drilled through holes that are to be plated through; boards are put in an electrically charged bath of copper.
This is required when holes are to be drilled through a copper area however the hole is not to be plated through. Avoid this process if possible due to the fact that it adds expense to the completed board.
The process of using a protective masking product, a solder mask, over the bare copper traces or over the copper that has actually had a thin layer of solder applied; the solder mask protects against environmental damage, offers insulation, safeguards against solder shorts, and secures traces that run between pads.
The procedure of covering the pad areas 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 parts have been positioned.
The process of applying the markings for element designations and part details to the board. Might be used to just the top or to both sides if parts are installed on both leading and bottom sides.
The procedure of separating multiple boards from a panel of similar boards; this process also allows cutting notches or slots into the board if needed.
A visual assessment of the boards; likewise can be the process of inspecting wall quality for plated through holes in multi-layer boards by cross-sectioning or other approaches.
The procedure of looking for connection or shorted connections on the boards by means using a voltage in between numerous points on the board and determining if an existing circulation happens. Relying on the board intricacy, this process may require a specifically developed test fixture and test program to incorporate with the electrical test system used by the board producer.