In electronics, printed ISO 9001 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 component side, a mix of thru-hole and surface mount on the top just, a mix of thru-hole and surface install elements on the top and surface area mount components 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 needed leads for each part utilizing conductive copper traces. The element pads and connection traces are etched 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 agreed copper pads and traces on the leading and bottom sides of the board, or multilayer designs 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 material, such as FR-4 epoxy fiberglass, with copper plating on one or both sides. This copper plating is engraved away to form the real copper pads and connection traces on the board surfaces as part of the board manufacturing process. A multilayer board consists of a variety of layers of dielectric material that has been fertilized with adhesives, and these layers are utilized to separate the layers of copper plating. All 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 4 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 aircraft layer as the 2 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 large number of layers to make the various connections for various voltage levels, ground connections, or for connecting the lots of leads on ball grid array gadgets and other large integrated circuit bundle formats.
There are normally 2 kinds of material utilized to construct a multilayer board. Pre-preg product is thin layers of fiberglass pre-impregnated with an adhesive, and is in sheet kind, typically about.002 inches thick. Core material resembles a very thin double sided board in that it has a dielectric material, such as epoxy fiberglass, with a copper layer transferred on each side, generally.030 density dielectric material with 1 ounce copper layer on each side. In a multilayer board style, there are 2 approaches used to build up the wanted variety of layers. The core stack-up technique, which is an older technology, uses a center layer of pre-preg material with a layer of core material above and another layer of core material below. This combination of one pre-preg layer and two core layers would make a 4 layer board.
The movie stack-up method, a newer innovation, would have core material as the center layer followed by layers of pre-preg and copper material developed above and listed below to form the final number of layers required by the board style, sort of like Dagwood building a sandwich. This approach enables the producer versatility in how the board layer thicknesses are integrated to satisfy the ended up product density requirements by differing the variety of sheets of pre-preg in each layer. When the product layers are completed, 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 process of producing printed circuit boards follows the actions listed below for a lot of applications.
The procedure of identifying materials, processes, and requirements to meet the consumer's specs for the board style based upon the Gerber file information supplied with the order.
The procedure of moving the Gerber file information for a layer onto an etch resist film that is put on the conductive copper layer.
The traditional process of exposing the copper and other areas unprotected by the etch withstand movie to a chemical that eliminates the vulnerable copper, leaving the protected copper pads and traces in place; more recent processes utilize plasma/laser etching rather of chemicals to remove the copper material, enabling finer line meanings.
The process of aligning the conductive copper and insulating dielectric layers and pressing them under heat to trigger the adhesive in the dielectric layers to form a solid board product.
The process of drilling all the holes for plated through applications; a 2nd drilling procedure is utilized for holes that are not to be plated through. Details on hole area and size is included 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 needed when holes are to be drilled through a copper area but the hole is not to be plated through. Prevent this process if possible due to the fact that it adds cost to the finished board.
The procedure of using a protective masking material, 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 versus environmental damage, provides insulation, safeguards against solder shorts, and protects traces that run between pads.
The process of coating the pad locations 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 components have actually been placed.
The process of using the markings for part designations and element describes to the board. May be applied to simply the top side or to both sides if parts are mounted on both leading and bottom sides.
The procedure of separating several boards from a panel of identical boards; this procedure likewise allows cutting notches or slots into the board if needed.
A visual examination 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 means applying a voltage in between various points on the board and identifying if a current circulation takes place. Depending upon the board intricacy, this process might need a specifically developed test component and test program to incorporate with the electrical test system utilized by the board producer.