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 area install applications or through rilled holes in the board and copper pads for soldering the component leads in thru-hole applications. A board style may have all thru-hole elements on the top or element side, a mix of thru-hole and surface install on the top side just, a mix of thru-hole and surface mount parts on the top side and surface mount parts on the bottom or circuit side, or surface area install components on the top and bottom sides of the board.
The boards are also used to electrically link the needed leads for each element 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 sided with copper pads and traces on the top and bottom sides of the board, or multilayer styles 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 consist of 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 real copper pads and connection traces on the board surfaces as part of the board production procedure. A multilayer board consists of a variety of layers of dielectric product that has been impregnated with adhesives, and these layers are utilized to separate the layers of copper plating. All these layers are aligned 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 4 layer board design, the internal layers are typically utilized to provide power and ground connections, such as a +5 V plane layer and a Ground airplane layer as the two internal layers, with all other circuit and part connections made on the top and bottom layers of the board. Really complex board styles might have a large number of layers to make the numerous connections for various voltage levels, ground connections, or for linking the numerous leads on ball grid variety gadgets and other large integrated circuit package formats.
There are usually two types of product used to build a multilayer board. Pre-preg material is thin layers of fiberglass pre-impregnated with an adhesive, and is in sheet kind, usually about.002 inches thick. Core material is similar to an extremely thin double sided board in that it has a dielectric material, such as epoxy fiberglass, with a copper layer deposited on each side, generally.030 thickness dielectric product with 1 ounce copper layer on each side. In a multilayer board style, there are 2 techniques utilized to develop the preferred number of layers. The core stack-up technique, 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 approach, a more recent innovation, would have core product as the center layer followed by layers of pre-preg and copper material built up above and listed below to form the last number of layers required by the board design, sort of like Visit this site Dagwood developing a sandwich. This method permits the maker versatility in how the board layer thicknesses are integrated to meet the finished item thickness requirements by differing the number of sheets of pre-preg in each layer. Once 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 making printed circuit boards follows the actions listed below for the majority of applications.
The procedure of figuring out products, procedures, and requirements to fulfill the consumer's specs for the board design based upon the Gerber file information provided with the purchase order.
The procedure of moving the Gerber file data for a layer onto an etch withstand film that is placed on the conductive copper layer.
The traditional process of exposing the copper and other locations unprotected by the etch withstand movie to a chemical that gets rid of the unguarded copper, leaving the secured copper pads and traces in place; more recent processes utilize plasma/laser etching rather of chemicals to remove the copper product, allowing finer line meanings.
The procedure of lining up 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 material.
The procedure of drilling all the holes for plated through applications; a 2nd drilling process is used for holes that are not to be plated through. Info 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 however the hole is not to be plated through. Prevent this procedure if possible since it adds cost to the ended up board.
The process of applying a protective masking material, 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 versus ecological damage, supplies insulation, protects versus solder shorts, and secures traces that run between pads.
The procedure of finish the pad areas with a thin layer of solder to prepare the board for the ultimate 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 part designations and component describes to the board. Might be used to simply the top or to both sides if parts are mounted on both top and bottom sides.
The process of separating numerous boards from a panel of identical boards; this procedure likewise allows cutting notches or slots into the board if required.
A visual evaluation of the boards; also can be the procedure of examining 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 methods applying a voltage between different points on the board and determining if an existing flow occurs. Depending upon the board intricacy, this procedure may require a specially designed test fixture and test program to integrate with the electrical test system used by the board manufacturer.