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 area install 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 components 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 area mount components on the top side and surface area install parts on the bottom or circuit side, or surface area install elements on the top and bottom sides of the board.
The boards are likewise utilized to electrically link the required leads for each element utilizing conductive copper traces. The component pads and connection traces are engraved from copper sheets laminated onto a non-conductive substrate. Printed circuit boards are developed as single sided with 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 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 real copper pads and connection traces on the board surface areas as part of the board manufacturing process. A multilayer board includes a variety of layers of dielectric product that has been impregnated with adhesives, and these layers are used to separate the layers of copper plating. All of 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 typical four layer board style, the internal layers are typically utilized to offer power and ground connections, such as a +5 V plane layer and a Ground aircraft layer as the two internal layers, with all other circuit and part connections made on the leading and bottom layers of the board. Really intricate board designs may have a a great deal of layers to make the numerous connections for various voltage levels, ground connections, or for connecting the numerous leads on ball grid array devices and other big integrated circuit package formats.
There are generally two kinds of product used to construct a multilayer board. Pre-preg product is thin layers of fiberglass pre-impregnated with an adhesive, and remains in sheet kind, normally about.002 inches thick. Core material resembles a very thin double sided board in that it has a dielectric product, such as epoxy fiberglass, with a copper layer deposited on each side, normally.030 density dielectric material with 1 ounce copper layer on each side. In a multilayer board design, there are two methods utilized to develop the preferred 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 material above and another layer of core material below. This mix of one pre-preg layer and 2 core layers would make a 4 layer board.
The film stack-up approach, a more recent innovation, 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 design, sort of like Dagwood building a sandwich. This approach enables the producer versatility in how the board layer densities are combined to fulfill the completed item density requirements by differing the number of sheets of pre-preg in each layer. As soon as the product layers are completed, the whole 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 of manufacturing printed circuit boards follows the actions below for many applications.
The process of determining products, procedures, and requirements to meet the consumer's requirements for the board style based on the Gerber file info supplied with the purchase order.
The process of transferring the Gerber file data for a layer onto an etch resist film that is placed on the conductive copper layer.
The standard process of exposing the copper and other areas unprotected by the etch resist film to a chemical that eliminates the vulnerable copper, leaving the secured copper pads and traces in place; more recent processes utilize plasma/laser etching rather of chemicals to remove the copper material, enabling finer line definitions.
The process of aligning 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 material.
The procedure of drilling all the holes for plated through applications; a 2nd drilling procedure is used for holes that are not to be plated through. Information on hole place and size is consisted of in the drill drawing file.
The procedure of applying copper plating to the pads, traces, and drilled through holes that are to be plated through; boards are placed in an electrically charged bath of copper.
This is needed when holes are to be drilled through a copper location but the hole is not to be plated through. Avoid this process if possible due to the fact that it adds cost to the completed board.
The process of using a protective masking product, a solder mask, over the bare copper traces or over the copper that has actually had a thin layer of solder used; the solder mask protects versus ecological damage, offers insulation, secures against solder shorts, and secures 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 process that will occur at a later date after the components have been put.
The process of applying the markings for part designations and component outlines to the board. May be applied 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 inspection 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 approaches.
The procedure of looking for continuity or shorted connections on the boards by methods applying a voltage in between various points on the board and figuring out if a present circulation takes place. Depending upon the board intricacy, this procedure might require a specifically designed test component and test program to integrate ISO 9001 with the electrical test system utilized by the board maker.