In electronic devices, printed circuit boards, or PCBs, are used to mechanically support electronic parts 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 part leads in thru-hole applications. A board design might have all thru-hole elements on the leading or component side, a mix of thru-hole and surface install on the top just, a mix of thru-hole and surface mount components on the top side and surface area install elements on the bottom or circuit side, or surface mount elements on the leading and bottom sides of the board.
The boards are likewise utilized to electrically link the required leads for each element 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 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 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 production procedure. A multilayer board consists of a number of layers of dielectric material 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 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 normal four layer board design, the internal layers are typically used to supply power and ground connections, such as a +5 V plane 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. Very intricate board styles might have a a great deal of layers to make the different connections for different voltage levels, ground connections, or for connecting the numerous leads on ball grid range devices and other big integrated circuit package formats.
There are typically two types of product used to construct a multilayer board. Pre-preg product 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 a really thin double sided board in that it has a dielectric product, such as epoxy fiberglass, with a copper layer deposited on each side, typically.030 density dielectric product with 1 ounce copper layer on each side. In a multilayer board design, there are 2 methods used to develop the desired variety of layers. The core stack-up approach, which is an older innovation, utilizes 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 2 core layers would make a 4 layer board.
The movie stack-up method, a more recent innovation, would have core product as the center layer followed by layers of pre-preg and copper ISO 9001 consultants material built up above and listed below to form the last variety of layers needed by the board style, sort of like Dagwood constructing a sandwich. This approach allows the manufacturer versatility in how the board layer thicknesses are combined to meet the finished item density requirements by differing the number of sheets of pre-preg in each layer. As soon as the material layers are finished, the whole stack goes through heat and pressure that triggers 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 most applications.
The process of figuring out products, processes, and requirements to fulfill the client's specs for the board design based upon the Gerber file information supplied with the order.
The process of transferring the Gerber file information for a layer onto an etch withstand film that is put on the conductive copper layer.
The traditional procedure of exposing the copper and other areas unprotected by the etch withstand film to a chemical that removes the unprotected copper, leaving the safeguarded copper pads and traces in location; newer procedures use plasma/laser etching instead of chemicals to remove the copper product, permitting 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 strong board product.
The procedure of drilling all the holes for plated through applications; a second drilling procedure is used for holes that are not to be plated through. Details on hole location and size is contained 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 put 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 process if possible due to the fact that it includes expense to the finished board.
The procedure 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 used; the solder mask secures against environmental damage, offers insulation, protects versus solder shorts, and safeguards traces that run between pads.
The procedure of coating the pad locations 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 elements have been positioned.
The process of applying the markings for element classifications and component details to the board. May be used to just the top or to both sides if elements are installed on both top and bottom sides.
The process of separating numerous boards from a panel of similar boards; this process likewise allows cutting notches or slots into the board if needed.
A visual assessment of the boards; also can be the procedure of checking wall quality for plated through holes in multi-layer boards by cross-sectioning or other approaches.
The procedure of looking for continuity or shorted connections on the boards by methods applying a voltage between numerous points on the board and figuring out if a current flow occurs. Relying on the board intricacy, this process may need a specially created test fixture and test program to integrate with the electrical test system used by the board manufacturer.