In electronic devices, printed circuit boards, or PCBs, are utilized to mechanically support electronic components which have their connection leads soldered onto copper pads in surface install applications or through rilled holes in the board and copper pads for soldering the part leads in thru-hole applications. A board design may have all thru-hole parts on the leading or element side, a mix of thru-hole and surface area mount on the top just, a mix of thru-hole and surface area mount elements on the top side and surface area install parts on the bottom or circuit side, or surface mount parts on the top and bottom sides of the board.
The boards are also utilized to electrically connect the needed leads for each element using conductive copper traces. The part pads and connection traces are engraved 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 styles 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 product, 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 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 of 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 technologies.
In a common 4 layer board design, the internal layers are often utilized to supply power and ground connections, such as a +5 V airplane 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 designs may have a a great deal of layers to make the different connections for various voltage levels, ground connections, or for connecting the lots of leads on ball grid range gadgets and other big incorporated circuit bundle formats.
There are usually two kinds of product used to build a multilayer board. Pre-preg material is thin layers of fiberglass pre-impregnated with an adhesive, and is in sheet kind, normally about.002 inches thick. Core material resembles a very thin double sided board because it has a dielectric product, such as epoxy fiberglass, with a copper layer deposited on each side, usually.030 thickness dielectric material with 1 ounce copper layer on each side. In a multilayer board design, there are two techniques used to develop the wanted variety of layers. The core stack-up technique, which is an older innovation, utilizes a center layer of pre-preg material with a layer of core product above and another layer of core product below. This mix 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 developed above and listed below to form the final variety of layers needed by the board style, sort of like Dagwood constructing a sandwich. This technique enables the manufacturer flexibility in how the board layer densities are integrated to satisfy the ended up item density requirements by varying the number of sheets of pre-preg in each layer. When the material layers are finished, the entire stack goes through 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 See more of producing printed circuit boards follows the steps below for most applications.
The process of identifying materials, processes, and requirements to meet the customer's specs for the board design based on the Gerber file information provided with the purchase order.
The process of moving the Gerber file information for a layer onto an etch resist film that is put on the conductive copper layer.
The standard process of exposing the copper and other locations unprotected by the etch resist movie to a chemical that removes the unprotected copper, leaving the secured copper pads and traces in location; more recent processes use plasma/laser etching rather of chemicals to remove the copper material, permitting 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 strong board material.
The process of drilling all the holes for plated through applications; a 2nd drilling procedure is used for holes that are not to be plated through. Info on hole place 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 put 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 procedure if possible because it adds expense to the finished board.
The process of applying a protective masking product, 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 against ecological damage, provides insulation, protects versus solder shorts, and protects traces that run between pads.
The procedure of finish the pad locations 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 elements have been put.
The process of applying the markings for part designations and element outlines to the board. Might be applied to simply the top side or to both sides if components are mounted on both top and bottom sides.
The procedure of separating several boards from a panel of identical boards; this process also allows cutting notches or slots into the board if needed.
A visual examination of the boards; also can be the procedure of inspecting wall quality for plated through holes in multi-layer boards by cross-sectioning or other techniques.
The process 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 an existing circulation takes place. Depending upon the board intricacy, this process may require a specially developed test component and test program to integrate with the electrical test system utilized by the board manufacturer.