In electronics, printed circuit boards, or PCBs, are used to mechanically support electronic components 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 design may have all thru-hole parts on the leading or element side, a mix ISO 9001 Certification Consultants of thru-hole and surface install on the top just, a mix of thru-hole and surface area install parts on the top side and surface mount parts on the bottom or circuit side, or surface install components on the leading and bottom sides of the board.
The boards are likewise used to electrically link 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 created as single agreed copper pads and traces on one side of the board just, double agreed copper pads and traces on the leading 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 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 surface areas as part of the board production procedure. A multilayer board consists of a variety of layers of dielectric product that has been impregnated 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 innovations.
In a common 4 layer board style, the internal layers are frequently used to supply power and ground connections, such as a +5 V plane layer and a Ground airplane layer as the two internal layers, with all other circuit and element connections made on the leading and bottom layers of the board. Extremely intricate board styles may have a large number of layers to make the numerous connections for different voltage levels, ground connections, or for linking the many leads on ball grid array devices and other large integrated circuit plan formats.
There are generally 2 kinds of product utilized to build a multilayer board. Pre-preg material is thin layers of fiberglass pre-impregnated with an adhesive, and remains in sheet kind, usually about.002 inches thick. Core product resembles a very thin double sided board in that it has a dielectric product, such as epoxy fiberglass, with a copper layer deposited on each side, generally.030 density dielectric product with 1 ounce copper layer on each side. In a multilayer board design, there are two approaches utilized to develop the desired variety of layers. The core stack-up method, 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 product below. This combination of one pre-preg layer and 2 core layers would make a 4 layer board.
The movie stack-up technique, a newer technology, would have core product as the center layer followed by layers of pre-preg and copper product developed above and below to form the last number of layers needed by the board style, sort of like Dagwood building a sandwich. This technique allows the manufacturer versatility in how the board layer densities are integrated to fulfill the finished product density requirements by differing the variety of sheets of pre-preg in each layer. As soon as the material layers are finished, the entire stack goes through 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 making printed circuit boards follows the actions below for most applications.
The process of identifying materials, procedures, and requirements to meet the consumer's requirements for the board design based upon the Gerber file information supplied with the purchase order.
The procedure of moving the Gerber file data 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 resist movie to a chemical that eliminates the unprotected copper, leaving the safeguarded copper pads and traces in location; more recent procedures utilize plasma/laser etching instead of chemicals to remove the copper product, allowing finer line meanings.
The 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. Info on hole location and size is included 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 positioned in an electrically charged bath of copper.
This is required when holes are to be drilled through a copper area however the hole is not to be plated through. Prevent this process if possible because it includes expense to the completed board.
The process of applying 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 protects against ecological damage, offers insulation, protects versus solder shorts, and secures traces that run between pads.
The procedure of covering the pad areas with a thin layer of solder to prepare the board for the eventual wave soldering or reflow soldering procedure that will take place at a later date after the components have been positioned.
The process of applying the markings for element classifications and component lays out to the board. Might be used to just the top or to both sides if components are installed on both leading and bottom sides.
The process of separating numerous boards from a panel of identical boards; this procedure likewise permits cutting notches or slots into the board if required.
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 approaches.
The procedure of looking for connection or shorted connections on the boards by means using a voltage in between numerous points on the board and identifying if a present flow takes place. Relying on the board intricacy, this process might need a specifically created test component and test program to integrate with the electrical test system utilized by the board producer.