In electronics, printed circuit boards, or PCBs, are utilized to mechanically support electronic elements 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 design might have all thru-hole components on the top or element side, a mix of thru-hole and surface install on the top side just, a mix of thru-hole and surface area install elements on the top and surface install components on the bottom or circuit side, or surface area mount parts on the leading and bottom sides of the board.
The boards are likewise utilized to electrically connect the required leads for each component utilizing conductive copper traces. The part pads and connection traces are etched from copper sheets laminated onto a non-conductive substrate. Printed circuit boards are designed as single sided with 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 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 etched away to form the actual copper pads and connection traces on the board surfaces as part of the board production process. A multilayer board consists of a number of layers of dielectric product that has been fertilized with adhesives, and these layers are used Reference site 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 technologies.
In a typical 4 layer board style, the internal layers are typically utilized to supply power and ground connections, such as a +5 V aircraft layer and a Ground aircraft layer as the two internal layers, with all other circuit and element connections made on the leading and bottom layers of the board. Really complex board designs might 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 array gadgets and other big integrated circuit package formats.
There are usually 2 kinds of material utilized to construct a multilayer board. Pre-preg material is thin layers of fiberglass pre-impregnated with an adhesive, and remains in sheet type, normally about.002 inches thick. Core material resembles an extremely thin double sided board because it has a dielectric product, such as epoxy fiberglass, with a copper layer deposited on each side, typically.030 thickness dielectric product with 1 ounce copper layer on each side. In a multilayer board design, there are two approaches utilized to build up 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 listed below. This combination of one pre-preg layer and 2 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 product built up above and below to form the last number of layers needed by the board design, sort of like Dagwood building a sandwich. This technique allows the manufacturer versatility in how the board layer densities are combined to fulfill the completed item thickness requirements by differing the variety of sheets of pre-preg in each layer. As soon as the product layers are finished, 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 producing printed circuit boards follows the steps below for most applications.
The procedure of figuring out products, procedures, and requirements to meet the customer's requirements for the board style based upon the Gerber file information offered with the order.
The process of moving the Gerber file data 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 locations unprotected by the etch resist film to a chemical that gets rid of the vulnerable copper, leaving the safeguarded copper pads and traces in location; newer procedures use plasma/laser etching instead of chemicals to get rid of the copper material, allowing finer line meanings.
The process of aligning the conductive copper and insulating dielectric layers and pressing them under heat to activate 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 2nd drilling process is utilized for holes that are not to be plated through. Information on hole area and size is contained 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 positioned 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 procedure if possible due to the fact that it adds expense to the completed 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 versus ecological damage, provides insulation, safeguards against solder shorts, and safeguards traces that run between pads.
The process of covering the pad areas with a thin layer of solder to prepare the board for the eventual wave soldering or reflow soldering process that will take place at a later date after the parts have been put.
The procedure of applying the markings for part classifications and part details to the board. May be used to simply the top or to both sides if components are mounted on both top and bottom sides.
The procedure of separating several boards from a panel of similar boards; this procedure also allows cutting notches or slots into the board if needed.
A visual evaluation of the boards; likewise can be the process of inspecting 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 numerous points on the board and determining if an existing flow occurs. Relying on the board complexity, this process may need a specially developed test fixture and test program to incorporate with the electrical test system utilized by the board producer.