In electronic devices, printed circuit boards, or PCBs, are used to mechanically support electronic elements which have their connection leads soldered onto copper pads in surface area mount applications or through rilled holes in the ISO 9001 Accreditation Consultants board and copper pads for soldering the element leads in thru-hole applications. A board style might have all thru-hole parts on the top or element side, a mix of thru-hole and surface area mount on the top side just, a mix of thru-hole and surface mount parts on the top and surface area install components on the bottom or circuit side, or surface area install parts on the leading and bottom sides of the board.
The boards are likewise utilized to electrically link the needed leads for each element utilizing 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 sided with copper pads and traces on one side of the board only, double agreed copper pads and traces on the top and bottom sides of the board, or multilayer styles with copper pads and traces on 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 etched away to form the real copper pads and connection traces on the board surfaces as part of the board manufacturing procedure. A multilayer board includes a variety of layers of dielectric material that has been impregnated with adhesives, and these layers are utilized to separate the layers of copper plating. All of these layers are lined up 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 typical four layer board design, the internal layers are typically used to provide 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 component connections made on the leading and bottom layers of the board. Really complicated board styles might have a large number of layers to make the numerous connections for different voltage levels, ground connections, or for connecting the lots of leads on ball grid array devices and other large incorporated circuit plan formats.
There are usually two kinds of product used to build a multilayer board. Pre-preg product is thin layers of fiberglass pre-impregnated with an adhesive, and is in sheet type, typically about.002 inches thick. Core product resembles a really 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 techniques used to develop the preferred number 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 product built up above and below to form the final number of layers required by the board style, sort of like Dagwood building a sandwich. This approach enables the manufacturer flexibility in how the board layer densities are combined to meet the completed product thickness requirements by differing the variety of sheets of pre-preg in each layer. When the material layers are finished, the entire stack undergoes 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 manufacturing printed circuit boards follows the actions below for many applications.
The procedure of figuring out materials, processes, and requirements to satisfy the client'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 withstand movie 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 safeguarded copper pads and traces in place; newer processes use plasma/laser etching instead of chemicals to eliminate the copper material, enabling finer line definitions.
The process 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 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 location and size is consisted of 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 positioned 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 since it adds expense to the finished 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 environmental damage, supplies insulation, safeguards versus solder shorts, and protects traces that run in between pads.
The procedure of covering the pad locations 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 elements have actually been put.
The procedure of using the markings for component designations and element outlines to the board. May be used to simply the top side or to both sides if elements are installed on both top and bottom sides.
The procedure of separating several boards from a panel of similar boards; this process likewise enables cutting notches or slots into the board if required.
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 methods.
The process of checking for connection or shorted connections on the boards by methods using a voltage between numerous points on the board and identifying if a current flow occurs. Depending upon the board intricacy, this process might require a specifically created test component and test program to integrate with the electrical test system utilized by the board manufacturer.