In electronics, 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 elements on the top or component 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 and surface area 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 also used to electrically connect the required leads for each element using conductive copper traces. The component pads and connection traces are engraved 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 just, double sided with 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 number of internal copper layers with traces and connections.
Single or double sided boards include 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 consists of a number of layers of dielectric material that has been fertilized 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 technologies.
In a typical 4 layer board style, the internal layers are frequently used to offer power and ground connections, such as a +5 V airplane layer and a Ground airplane layer as the 2 internal layers, with all other circuit and part connections made on the top and bottom layers of the board. Extremely complex board styles might have a a great deal of layers to make the various connections for various voltage levels, ground connections, or for connecting the numerous leads on ball grid selection devices and other large incorporated circuit package formats.
There are typically two types of material utilized to build a multilayer board. Pre-preg material is thin layers of fiberglass pre-impregnated with an adhesive, and is in sheet form, typically about.002 inches thick. Core material resembles a very thin double sided board in that it has a dielectric material, such as epoxy fiberglass, with a copper layer deposited on each side, generally.030 thickness dielectric material with 1 ounce copper layer on each side. In a multilayer board design, there are 2 techniques used to build up the wanted number of layers. The core stack-up approach, which is an older technology, utilizes a center layer of pre-preg product 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 film stack-up approach, a newer innovation, would have core material as the center layer followed by layers of pre-preg and copper product built up above and listed below to form the last variety of layers needed by the board design, sort of like Dagwood building a sandwich. This method permits the manufacturer versatility in how the board layer thicknesses are combined to satisfy the finished product density requirements by differing the variety of sheets of pre-preg in each layer. As soon as the material layers are finished, the whole stack goes through heat and pressure that causes the adhesive in the pre-preg to bond the core and pre-preg layers together ISO 9001 Accreditation into a single entity.
The procedure of manufacturing printed circuit boards follows the actions below for the majority of applications.
The procedure of figuring out products, procedures, and requirements to satisfy the consumer's specifications for the board style based upon the Gerber file details supplied with the purchase order.
The process of moving the Gerber file data for a layer onto an etch withstand movie that is put on the conductive copper layer.
The traditional process of exposing the copper and other areas unprotected by the etch withstand movie to a chemical that gets rid of the vulnerable copper, leaving the safeguarded copper pads and traces in place; newer processes utilize plasma/laser etching rather of chemicals to get rid of the copper product, allowing finer line meanings.
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 solid board material.
The procedure of drilling all of the holes for plated through applications; a 2nd drilling procedure is utilized for holes that are not to be plated through. Info on hole area and size is included 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 required when holes are to be drilled through a copper area however the hole is not to be plated through. Avoid this procedure 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 had a thin layer of solder used; the solder mask protects versus environmental damage, provides insulation, secures against solder shorts, and secures traces that run in between pads.
The process of finish the pad areas with a thin layer of solder to prepare the board for the ultimate wave soldering or reflow soldering process that will happen at a later date after the parts have been positioned.
The process of applying the markings for element designations and part details to the board. Might be applied to just the top or to both sides if components are installed on both leading and bottom sides.
The procedure of separating numerous boards from a panel of similar boards; this process also allows cutting notches or slots into the board if required.
A visual evaluation of the boards; also can be the process of inspecting wall quality for plated through holes in multi-layer boards by cross-sectioning or other approaches.
The process of looking for continuity or shorted connections on the boards by methods applying a voltage in between various points on the board and identifying if a present circulation happens. Relying on the board complexity, this process may need a specifically created test component and test program to integrate with the electrical test system utilized by the board maker.