In electronics, printed circuit boards, or PCBs, are utilized 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 element leads in thru-hole applications. A board style might have all thru-hole elements on the top or element side, a mix of thru-hole and surface area install on the top just, a mix of thru-hole and surface area mount parts on the top side and surface area install parts on the bottom or circuit side, or surface install components on the leading and bottom sides of the board.
The boards are likewise utilized to electrically connect the required leads for each part using conductive copper traces. The part pads and connection traces are etched from copper sheets laminated onto a non-conductive substrate. Printed circuit boards are developed as single sided with copper pads and traces on one side of the board just, double agreed 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 include a core dielectric material, 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 surfaces as part of the board manufacturing 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 4 layer board style, the internal layers are often utilized to provide power and ground connections, such as a +5 V aircraft layer and a Ground aircraft layer as the 2 internal layers, with all other circuit and element connections made on the leading and bottom layers of the board. Really complicated board styles may have a a great deal of layers to make the different connections for different voltage levels, ground connections, or for linking the many leads on ball grid variety gadgets and other big integrated circuit bundle formats.
There are typically two types of material used to construct 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 really thin double sided board in that it has a dielectric product, such as epoxy fiberglass, with a copper layer transferred on each side, usually.030 density dielectric material with 1 ounce copper layer on each side. In a multilayer board design, there are 2 techniques used to build up 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 product above and another layer of core product below. This combination of one pre-preg layer and two core layers would make a 4 layer board.
The film stack-up technique, a more recent technology, would have core product as the center layer followed by layers of pre-preg and copper material built up above and listed below to form the last number of layers required by the board design, sort of like Dagwood constructing a sandwich. This technique permits the producer versatility in how the board layer thicknesses are combined to meet the finished item thickness requirements by varying the number of sheets of pre-preg in each layer. Once the material layers are completed, the entire stack undergoes 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 manufacturing printed circuit boards follows the steps listed below for many applications.
The procedure of figuring out materials, procedures, and requirements to meet the consumer's specs for the board design based on the Gerber file details supplied with the purchase order.
The process of moving the Gerber file data for a layer onto an etch resist movie that is placed on the conductive copper layer.
The conventional procedure of exposing the copper and other areas unprotected by the etch resist movie to a chemical that eliminates the unguarded copper, leaving the secured copper pads and traces in location; more recent procedures utilize plasma/laser etching ISO 9001 Certification Consultants instead of chemicals to eliminate the copper product, enabling finer line meanings.
The process 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 strong board material.
The process of drilling all of the holes for plated through applications; a second drilling procedure is utilized for holes that are not to be plated through. Info on hole location and size is contained in the drill drawing file.
The process 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 area however the hole is not to be plated through. Avoid this process if possible due to the fact that it adds expense to the finished board.
The procedure of applying 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 safeguards against ecological damage, provides insulation, safeguards against solder shorts, and protects traces that run in between pads.
The procedure of finishing the pad locations with a thin layer of solder to prepare the board for the eventual wave soldering or reflow soldering procedure that will occur at a later date after the components have actually been positioned.
The process of using the markings for element designations and part describes to the board. Might be used to simply the top or to both sides if parts are mounted on both top and bottom sides.
The process of separating multiple boards from a panel of similar boards; this procedure likewise enables cutting notches or slots into the board if needed.
A visual evaluation of the boards; also can be the process of examining wall quality for plated through holes in multi-layer boards by cross-sectioning or other techniques.
The procedure of checking for continuity or shorted connections on the boards by ways applying a voltage in between numerous points on the board and identifying if a current circulation takes place. Relying on the board complexity, this procedure might require a specifically developed test fixture and test program to incorporate with the electrical test system used by the board manufacturer.