In electronic devices, printed circuit boards, or PCBs, are used to mechanically support electronic components which have their connection leads soldered onto copper pads in surface mount applications or through rilled holes in the board and copper pads for soldering the component leads in thru-hole applications. A board style might have all thru-hole parts on the leading or part side, a mix of thru-hole and surface install on the top just, a mix of thru-hole and surface area mount components on the top side and surface mount elements on the bottom or circuit side, or surface install parts on the leading and bottom sides of the board.
The boards are also used to electrically link the needed 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 developed as single agreed copper pads and traces on one side of the board just, double agreed copper pads and traces on the top 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 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 surfaces as part of the board manufacturing procedure. A multilayer board consists of a variety of layers of dielectric material that has actually been impregnated with adhesives, and these layers are used to separate the layers of copper plating. All these layers are aligned then bonded into a single board structure under heat and pressure. Multilayer boards with 48 or more layers can be produced ISO 9001 consultants with today's innovations.
In a common four layer board design, the internal layers are frequently utilized to provide power and ground connections, such as a +5 V aircraft layer and a Ground airplane layer as the two internal layers, with all other circuit and element connections made on the top and bottom layers of the board. Extremely complicated board designs may have a a great deal of layers to make the different connections for different voltage levels, ground connections, or for connecting the lots of leads on ball grid array gadgets and other large integrated circuit bundle formats.
There are usually 2 types of material utilized to construct a multilayer board. Pre-preg product is thin layers of fiberglass pre-impregnated with an adhesive, and remains in sheet type, generally about.002 inches thick. Core material is similar to a very thin double sided board because it has a dielectric material, such as epoxy fiberglass, with a copper layer deposited on each side, usually.030 density dielectric material with 1 ounce copper layer on each side. In a multilayer board design, there are 2 methods used to develop the preferred number of layers. The core stack-up technique, 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 material 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 technology, would have core product as the center layer followed by layers of pre-preg and copper product developed above and below to form the final number of layers required by the board style, sort of like Dagwood developing a sandwich. This method permits the maker versatility in how the board layer densities are combined to meet the ended up product thickness requirements by differing the number of sheets of pre-preg in each layer. Once the material layers are finished, the whole 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 producing printed circuit boards follows the steps below for many applications.
The procedure of figuring out products, procedures, and requirements to fulfill the customer's specs for the board design based on the Gerber file details offered with the purchase order.
The process of transferring the Gerber file data for a layer onto an etch resist movie that is placed on the conductive copper layer.
The standard process of exposing the copper and other areas unprotected by the etch withstand film to a chemical that gets rid of the unprotected copper, leaving the safeguarded copper pads and traces in location; more recent processes utilize plasma/laser etching rather of chemicals to remove the copper product, enabling finer line definitions.
The procedure of lining up 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 product.
The procedure of drilling all the holes for plated through applications; a second drilling procedure is used for holes that are not to be plated through. Information on hole area and size is consisted of 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 location however the hole is not to be plated through. Avoid this process 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 applied; the solder mask protects against environmental damage, offers insulation, protects against solder shorts, and safeguards traces that run in between pads.
The process of finishing the pad areas with a thin layer of solder to prepare the board for the ultimate wave soldering or reflow soldering procedure that will take place at a later date after the components have actually been put.
The procedure of using the markings for element designations and component lays out to the board. Might be used to simply the top or to both sides if parts are mounted on both top and bottom sides.
The process of separating numerous boards from a panel of similar boards; this process likewise allows cutting notches or slots into the board if needed.
A visual assessment of the boards; also can be the procedure of checking wall quality for plated through holes in multi-layer boards by cross-sectioning or other approaches.
The process of checking for connection or shorted connections on the boards by methods using a voltage between different points on the board and determining if an existing circulation takes place. Depending upon the board intricacy, this procedure may need a specifically designed test component and test program to incorporate with the electrical test system used by the board producer.