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 mount applications or through rilled holes in the board and copper pads for soldering the component leads in thru-hole applications. A board design might have all thru-hole parts 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 install components on the top side See more here and surface area install parts on the bottom or circuit side, or surface area install elements on the top and bottom sides of the board.
The boards are also used to electrically connect the required leads for each component utilizing conductive copper traces. The part pads and connection traces are engraved 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 agreed 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 variety 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 real copper pads and connection traces on the board surface areas as part of the board manufacturing process. A multilayer board includes a variety of layers of dielectric product that has actually been impregnated with adhesives, and these layers are used to separate the layers of copper plating. All of 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 typical 4 layer board style, the internal layers are often utilized to supply 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 element connections made on the top and bottom layers of the board. Really intricate board styles may have a large number of layers to make the different connections for different voltage levels, ground connections, or for linking the many leads on ball grid selection gadgets and other large incorporated circuit bundle formats.
There are usually two kinds of material utilized to build a multilayer board. Pre-preg material is thin layers of fiberglass pre-impregnated with an adhesive, and remains in sheet type, 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 design, there are 2 techniques used to build up the preferred number of layers. The core stack-up technique, which is an older innovation, utilizes a center layer of pre-preg product with a layer of core product above and another layer of core material listed below. This combination 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 product developed above and listed below to form the last number of layers required by the board design, sort of like Dagwood building a sandwich. This approach permits the maker versatility in how the board layer thicknesses are integrated to fulfill the completed item density requirements by differing the variety of sheets of pre-preg in each layer. When the product layers are finished, the entire stack undergoes 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 manufacturing printed circuit boards follows the steps listed below for most applications.
The process of determining products, procedures, and requirements to meet the consumer's specs for the board design based on the Gerber file info supplied with the order.
The process of transferring the Gerber file data for a layer onto an etch resist movie that is placed on the conductive copper layer.
The conventional process of exposing the copper and other locations 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 processes use plasma/laser etching instead of chemicals to get rid of the copper material, allowing finer line definitions.
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 procedure of drilling all the holes for plated through applications; a 2nd drilling process is utilized for holes that are not to be plated through. Info on hole area and size is contained in the drill drawing file.
The procedure of applying 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 required when holes are to be drilled through a copper location but the hole is not to be plated through. Avoid this procedure if possible because it adds expense to the ended up board.
The procedure of applying 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 versus ecological damage, provides insulation, secures against solder shorts, and protects traces that run between pads.
The procedure of finish 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 parts have actually been put.
The procedure of using the markings for part classifications and part lays out to the board. Might be applied to just the top or to both sides if components are mounted on both leading and bottom sides.
The process of separating numerous boards from a panel of similar boards; this process also enables cutting notches or slots into the board if required.
A visual assessment of the boards; likewise can be the procedure of examining wall quality for plated through holes in multi-layer boards by cross-sectioning or other techniques.
The procedure of looking for continuity or shorted connections on the boards by ways applying a voltage between numerous points on the board and figuring out if an existing flow happens. Relying on the board intricacy, this procedure may require a specifically designed test component and test program to integrate with the electrical test system used by the board manufacturer.