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In electronics, printed circuit boards, or PCBs, are utilized 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 part leads in thru-hole applications. A board style may have all thru-hole parts on the leading or element side, a mix of thru-hole and surface mount on the top just, a mix of thru-hole and surface area install parts on the top and surface install components on the bottom or circuit side, or surface install parts on the leading and bottom sides of the board.
The boards are also utilized to electrically link the needed leads for each component using conductive copper traces. The component pads and connection traces are engraved 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 only, double sided with 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 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 manufacturing process. A multilayer board includes 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 aligned and 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 typical four layer board design, the internal layers are often used to offer power and ground connections, such as a +5 V airplane layer and a Ground airplane layer as the 2 internal layers, with all other circuit and element connections made on the leading and bottom layers of the board. Very intricate board designs may have a a great deal of layers to make the various connections for various voltage levels, ground connections, or for linking the numerous leads on ball grid variety devices and other big incorporated circuit package formats.
There are generally two types of product utilized to construct a multilayer board. Pre-preg product is thin layers of fiberglass pre-impregnated with an adhesive, and remains in sheet kind, usually about.002 inches thick. Core product resembles a really thin double sided board because it has a dielectric material, such as epoxy fiberglass, with a copper layer deposited on each side, normally.030 density dielectric product with 1 ounce copper layer on each side. In a multilayer board design, there are 2 approaches utilized to build up the desired number of layers. The core stack-up method, which is an older technology, uses a center layer of pre-preg product with a layer of core product 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 film stack-up technique, a newer innovation, would have core material as the center layer followed by layers of pre-preg and copper material built up above and listed below to form the last variety of layers needed by the board style, sort of like Dagwood developing a sandwich. This technique enables the maker flexibility in how the board layer thicknesses are combined to meet the ended up product density requirements by varying the number of sheets of pre-preg in each layer. Once the product layers are finished, the whole stack is subjected to 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 producing printed circuit boards follows the steps below for the majority of applications.
The procedure of determining materials, procedures, and requirements to fulfill the consumer's specs for the board style based upon the Gerber file details provided with the purchase order.
The procedure of moving the Gerber file data for a layer onto an etch resist film that is put on the conductive copper layer.
The standard procedure of exposing the copper and other areas unprotected by the etch resist film to a chemical that gets rid of the vulnerable copper, leaving the secured copper pads and traces in location; newer procedures utilize plasma/laser etching rather of chemicals to get rid of the copper product, allowing finer line definitions.
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 solid board material.
The procedure of drilling all the holes for plated through applications; a 2nd drilling process 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 required when holes are to be drilled through a copper area but the hole is not to be plated through. Prevent this process if possible since it includes cost to the ended up board.
The process of using a protective masking product, a solder mask, over the bare copper traces or over the copper that has actually had a thin layer of solder used; the solder mask protects against ecological damage, supplies insulation, safeguards against solder shorts, and secures traces that run 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 process that will take place at a later date after the elements have been positioned.
The procedure of using the markings for component designations and element outlines to the board. Might be used to just the top side or to both sides if elements are installed on both leading and bottom sides.
The process of separating multiple boards from a panel of similar boards; this procedure also permits cutting notches or slots into the board if needed.
A visual examination of the boards; likewise 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 checking for connection or shorted connections on the boards by methods applying a voltage between different points on the board and determining if a present circulation happens. Relying on the board complexity, this process might need a specifically designed test fixture and test program to incorporate with the electrical test system used by the board producer.
ISO 9001 Accreditation Consultants