In electronics, printed circuit boards, or PCBs, are used to mechanically support electronic parts 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 may have all thru-hole parts on the leading or component side, a mix of thru-hole Visit this site and surface install on the top side just, a mix of thru-hole and surface area mount elements on the top and surface area install parts on the bottom or circuit side, or surface install components on the top and bottom sides of the board.
The boards are likewise used to electrically connect the required leads for each component utilizing conductive copper traces. The component 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 sided with copper pads and traces on the top and bottom sides of the board, or multilayer styles 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 consist of a core dielectric product, 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 surfaces as part of the board manufacturing process. A multilayer board consists of a number of layers of dielectric material that has been fertilized with adhesives, and these layers are used to separate the layers of copper plating. All of these layers are aligned then 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 four layer board style, the internal layers are often utilized to supply power and ground connections, such as a +5 V plane layer and a Ground plane layer as the 2 internal layers, with all other circuit and element connections made on the top and bottom layers of the board. Extremely intricate board designs may have a large number of layers to make the various connections for various voltage levels, ground connections, or for linking the many leads on ball grid range devices and other large integrated circuit plan formats.
There are generally 2 kinds of product used to build 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 because it has a dielectric product, 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 two techniques utilized to build up the desired variety of layers. The core stack-up method, which is an older technology, uses a center layer of pre-preg product with a layer of core material above and another layer of core product listed below. This combination of one pre-preg layer and two core layers would make a 4 layer board.
The film stack-up approach, a newer technology, 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 variety 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 product density requirements by varying the number of sheets of pre-preg in each layer. Once the material layers are completed, the entire 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 steps listed below for most applications.
The procedure of determining products, processes, and requirements to satisfy the client's requirements for the board style based upon the Gerber file info supplied with the purchase order.
The procedure of transferring the Gerber file data for a layer onto an etch withstand movie that is put on the conductive copper layer.
The standard process of exposing the copper and other locations unprotected by the etch resist movie to a chemical that gets rid of the unguarded copper, leaving the safeguarded copper pads and traces in location; more recent processes utilize plasma/laser etching instead of chemicals to get rid of the copper material, permitting 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 strong board product.
The process of drilling all of the holes for plated through applications; a second drilling procedure is used for holes that are not to be plated through. Information on hole area and size is included 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 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. Avoid this procedure if possible since it adds cost 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 had a thin layer of solder applied; the solder mask secures versus ecological damage, provides insulation, safeguards versus solder shorts, and protects 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 occur at a later date after the components have been placed.
The process of applying the markings for part designations and element describes 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 multiple boards from a panel of similar boards; this procedure likewise permits cutting notches or slots into the board if required.
A visual evaluation of the boards; likewise can be the process of checking wall quality for plated through holes in multi-layer boards by cross-sectioning or other techniques.
The process of looking for continuity or shorted connections on the boards by methods using a voltage in between numerous points on the board and determining if an existing flow takes place. Relying on the board intricacy, this procedure might require a specifically designed test component and test program to incorporate with the electrical test system utilized by the board producer.