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 area install applications or through rilled holes in the board and copper pads for soldering the part leads in thru-hole applications. A board style might have all thru-hole parts on the leading or element side, a mix of thru-hole and surface area mount on the top side only, a mix of thru-hole and surface area mount components on the top side and surface mount parts on the bottom or circuit side, or surface area install components on the leading and bottom sides of the board.
The boards are also utilized to electrically link the required leads for each element using conductive copper traces. The element pads and connection traces are engraved 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 leading and bottom sides of the board, or multilayer styles 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 include a core dielectric product, such as FR-4 epoxy fiberglass, with copper plating on one or both sides. This copper plating is engraved away to form the actual copper pads and connection traces on the board surface areas as part of the board production process. A multilayer board includes a variety of layers of dielectric product that has been fertilized with adhesives, and these layers are utilized to separate the layers of copper plating. All of these layers are aligned 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 technologies.
In a common 4 layer board design, the internal layers are frequently utilized to supply power and ground connections, such as a +5 V aircraft layer and a Ground airplane layer as the 2 internal layers, with all other circuit and component connections made on the leading and bottom layers of the board. Extremely complicated board designs might have a large number of layers to make the different connections for various voltage levels, ground connections, or for connecting the many leads on ball grid range gadgets and other big incorporated circuit plan formats.
There are usually two types of material utilized to build a multilayer board. Pre-preg product is thin layers of fiberglass pre-impregnated with an adhesive, and remains in sheet type, normally about.002 inches thick. Core product is similar to a really thin double sided board in that it has a dielectric product, such as epoxy fiberglass, with a copper layer transferred on each side, typically.030 density dielectric material with 1 ounce copper layer on each side. In a multilayer board style, there are two approaches used to develop the preferred number of layers. The core stack-up technique, 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 material below. This combination of one pre-preg layer and 2 core layers would make a 4 layer board.
The film stack-up technique, 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 below to form the final number of layers required by the board design, sort of like Dagwood constructing a sandwich. This approach permits the producer flexibility in how the board layer thicknesses are integrated to fulfill the finished item thickness requirements by varying the number of sheets of pre-preg in each layer. As soon as the material layers are completed, 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 steps listed below for many applications.
The process of figuring out products, processes, and requirements to meet the consumer's requirements for the board design based on the Gerber file information offered with the purchase order.
The procedure of transferring the Gerber file information for a layer onto an etch resist film that is placed on the conductive copper layer.
The conventional procedure of exposing the copper and other areas unprotected by the etch withstand movie to a chemical that gets rid of the unprotected copper, leaving the secured copper pads and traces in location; more recent processes utilize plasma/laser etching instead of chemicals to eliminate the copper product, allowing finer line meanings.
The ISO 9001 Accreditation Consultants procedure of lining up the conductive copper and insulating dielectric layers and pushing them under heat to trigger the adhesive in the dielectric layers to form a solid board material.
The process of drilling all the holes for plated through applications; a second drilling process is utilized for holes that are not to be plated through. Information on hole place 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 positioned in an electrically charged bath of copper.
This is needed when holes are to be drilled through a copper location but the hole is not to be plated through. Prevent this procedure if possible due to the fact that it adds expense to the completed board.
The process of using a protective masking material, 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 secures against ecological damage, offers insulation, secures against solder shorts, and protects traces that run in between pads.
The process of covering the pad areas with a thin layer of solder to prepare the board for the ultimate wave soldering or reflow soldering procedure that will occur at a later date after the elements have actually been positioned.
The process of applying the markings for component designations and part lays out to the board. May be applied to just the top side or to both sides if components are installed on both leading and bottom sides.
The process of separating numerous boards from a panel of similar boards; this procedure likewise permits cutting notches or slots into the board if needed.
A visual assessment of the boards; also can be the procedure of inspecting wall quality for plated through holes in multi-layer boards by cross-sectioning or other methods.
The process of looking for connection or shorted connections on the boards by methods using a voltage between different points on the board and determining if a current flow occurs. Relying on the board complexity, this process might require a specially developed test fixture and test program to incorporate with the electrical test system used by the board producer.