In electronic devices, printed circuit boards, or PCBs, are used to mechanically support electronic parts 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 element leads in thru-hole applications. A board style might have all thru-hole components on the leading or element side, a mix of thru-hole and surface area install on the top side just, a mix of thru-hole and surface install elements on the top side and surface area install elements on the bottom or circuit side, or surface install parts on the leading and bottom sides of ISO 9001 Accreditation the board.
The boards are likewise used to electrically connect the needed leads for each part 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 agreed 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 designs with copper pads and traces on top and bottom of board with a variable number 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 production procedure. A multilayer board includes a number of layers of dielectric material that has been impregnated with adhesives, and these layers are utilized to separate the layers of copper plating. All these layers are lined up and after that 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 normal four layer board style, the internal layers are often utilized 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. Extremely intricate board styles might have a large number of layers to make the numerous connections for different voltage levels, ground connections, or for connecting the many leads on ball grid array gadgets and other big integrated circuit plan formats.
There are typically two types of material used to construct a multilayer board. Pre-preg material is thin layers of fiberglass pre-impregnated with an adhesive, and is in sheet type, normally 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 thickness dielectric material with 1 ounce copper layer on each side. In a multilayer board design, there are 2 approaches utilized to build up the wanted variety of layers. The core stack-up approach, which is an older technology, utilizes 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 film stack-up approach, a newer innovation, would have core material as the center layer followed by layers of pre-preg and copper material developed above and listed below to form the last number of layers required by the board style, sort of like Dagwood building a sandwich. This technique permits the manufacturer flexibility in how the board layer thicknesses are integrated to satisfy the finished item density requirements by differing the variety of sheets of pre-preg in each layer. Once the product layers are completed, the entire stack is subjected to 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 steps below for a lot of applications.
The procedure of identifying products, procedures, and requirements to fulfill the client's specs for the board design based on the Gerber file details supplied with the 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 standard procedure of exposing the copper and other locations unprotected by the etch resist film to a chemical that gets rid of the unprotected copper, leaving the secured copper pads and traces in location; newer procedures use plasma/laser etching rather of chemicals to remove the copper product, allowing finer line definitions.
The procedure of aligning 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 product.
The process of drilling all of the holes for plated through applications; a second drilling procedure is used for holes that are not to be plated through. Details on hole place 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 put 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 because it adds cost 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 applied; the solder mask protects versus ecological damage, provides insulation, safeguards versus solder shorts, and protects traces that run in between pads.
The process of coating the pad areas with a thin layer of solder to prepare the board for the eventual wave soldering or reflow soldering procedure that will occur at a later date after the components have actually been placed.
The procedure of applying the markings for element designations and part describes to the board. May be used to just the top or to both sides if components are installed on both top and bottom sides.
The procedure of separating several boards from a panel of similar boards; this process also permits cutting notches or slots into the board if needed.
A visual inspection of the boards; also can be the process of checking wall quality for plated through holes in multi-layer boards by cross-sectioning or other techniques.
The process of checking for connection or shorted connections on the boards by means applying a voltage between different points on the board and figuring out if an existing flow occurs. Depending upon the board complexity, this procedure may require a specifically developed test fixture and test program to integrate with the electrical test system utilized by the board maker.