In electronics, printed circuit boards, or ISO 9001 Accreditation Consultants PCBs, are used to mechanically support electronic components 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 element leads in thru-hole applications. A board style may have all thru-hole components on the top or component side, a mix of thru-hole and surface area mount on the top just, a mix of thru-hole and surface area install elements on the top side and surface area install parts on the bottom or circuit side, or surface mount elements on the leading and bottom sides of the board.
The boards are also utilized to electrically connect the needed leads for each element 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 only, double sided with 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 variety 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 real copper pads and connection traces on the board surface areas as part of the board manufacturing process. A multilayer board includes a number of layers of dielectric material that has actually been fertilized with adhesives, and these layers 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 innovations.
In a typical 4 layer board style, the internal layers are typically utilized to supply power and ground connections, such as a +5 V airplane layer and a Ground aircraft layer as the two internal layers, with all other circuit and part connections made on the leading and bottom layers of the board. Extremely complex board styles may have a a great deal of layers to make the different connections for various voltage levels, ground connections, or for connecting the lots of leads on ball grid range devices and other large integrated circuit plan formats.
There are usually two types of material used to construct a multilayer board. Pre-preg material is thin layers of fiberglass pre-impregnated with an adhesive, and is in sheet kind, generally about.002 inches thick. Core material is similar to an extremely thin double sided board because it has a dielectric material, such as epoxy fiberglass, with a copper layer deposited on each side, usually.030 density dielectric product with 1 ounce copper layer on each side. In a multilayer board style, there are 2 methods utilized to develop the wanted variety of layers. The core stack-up approach, which is an older technology, utilizes a center layer of pre-preg material with a layer of core material above and another layer of core product below. This mix of one pre-preg layer and two core layers would make a 4 layer board.
The movie stack-up technique, a newer technology, would have core material as the center layer followed by layers of pre-preg and copper material built up above and listed below to form the last variety of layers needed by the board design, sort of like Dagwood building a sandwich. This technique enables the maker versatility in how the board layer densities are combined to satisfy the ended up item thickness requirements by differing the number of sheets of pre-preg in each layer. As soon as 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 procedure of manufacturing printed circuit boards follows the actions listed below for most applications.
The process of figuring out materials, procedures, and requirements to satisfy the customer's specifications for the board style based upon the Gerber file information supplied with the purchase order.
The process of transferring the Gerber file data for a layer onto an etch resist film that is put on the conductive copper layer.
The standard procedure of exposing the copper and other locations unprotected by the etch withstand film to a chemical that gets rid of the vulnerable copper, leaving the protected copper pads and traces in location; newer procedures utilize plasma/laser etching rather of chemicals to eliminate the copper material, enabling finer line definitions.
The process of aligning the conductive copper and insulating dielectric layers and pushing them under heat to trigger 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 2nd drilling process is utilized for holes that are not to be plated through. Details on hole area and size is contained in the drill drawing file.
The process of using 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 location but the hole is not to be plated through. Prevent this process if possible because it adds expense to the finished 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 safeguards against ecological damage, offers insulation, secures against solder shorts, and protects traces that run between pads.
The process of finish the pad locations with a thin layer of solder to prepare the board for the ultimate wave soldering or reflow soldering procedure that will happen at a later date after the elements have actually been positioned.
The process of applying the markings for component designations and element details to the board. May be applied to just the top side or to both sides if parts are mounted on both leading and bottom sides.
The procedure of separating multiple boards from a panel of similar boards; this procedure also enables cutting notches or slots into the board if required.
A visual evaluation of the boards; also can be the process of inspecting wall quality for plated through holes in multi-layer boards by cross-sectioning or other techniques.
The process of checking for connection or shorted connections on the boards by ways applying a voltage in between numerous points on the board and figuring out if a current circulation happens. Relying on the board complexity, this procedure may require a specially developed test component and test program to integrate with the electrical test system utilized by the board manufacturer.