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 design may have all thru-hole parts on the leading or element side, a mix of thru-hole and surface mount on the top only, a mix of thru-hole and surface area mount components on the top and surface area install elements on the bottom or circuit side, or surface mount parts on the top and bottom sides of the board.
The boards are likewise utilized to electrically link the needed leads for each part 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 developed 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 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 procedure. A multilayer board includes a variety of layers of dielectric product that has actually been impregnated with adhesives, and these layers are used to separate the layers of copper plating. All of 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 with today's technologies.
In a typical four layer board style, the internal layers are typically utilized to supply power and ground connections, such as a +5 V airplane layer and a Ground plane layer as the two internal layers, with all other circuit and component connections made on the leading and bottom layers of the board. Extremely complex board designs might have a large number of layers to make the different connections for different voltage levels, ground connections, or for linking the lots of leads on ball grid selection gadgets and other big integrated circuit bundle formats.
There are normally 2 types of product used to build 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 really thin double sided board in that it has a dielectric material, such as epoxy fiberglass, with a copper layer transferred on each side, typically.030 density dielectric material with 1 ounce copper layer on each side. In a multilayer board design, there are 2 approaches utilized to develop the preferred number of layers. The core stack-up approach, which is an older technology, uses a center layer of pre-preg material with a layer of core product above and another layer of core product below. This mix of one pre-preg layer and two core layers would make a 4 layer board.
The movie stack-up technique, a newer innovation, would have core product as the center layer followed by layers of pre-preg and copper product built up above and below to form the last number of layers required by the board style, sort of like Dagwood constructing a sandwich. This method allows the maker flexibility in how the board layer densities are combined to fulfill the completed item density requirements by differing the variety of sheets of pre-preg in each layer. Once the material layers are completed, the whole stack undergoes 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 procedure of manufacturing printed circuit boards follows the steps below for a lot of applications.
The procedure of determining products, procedures, and requirements to meet the customer's specs for the board style based upon the Gerber file information provided with the purchase order.
The procedure of moving the Gerber file data for a layer onto an etch withstand movie that is placed on the conductive copper layer.
The traditional process ISO 9001 Certification Consultants of exposing the copper and other areas unprotected by the etch resist movie 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 rather of chemicals to eliminate the copper product, permitting finer line meanings.
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 solid board product.
The process of drilling all of the holes for plated through applications; a 2nd drilling process 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 placed 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. Prevent this procedure if possible since it adds expense to the finished board.
The process of using 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 protects against environmental damage, provides insulation, secures versus solder shorts, and secures traces that run between pads.
The process of finish the pad locations with a thin layer of solder to prepare the board for the ultimate wave soldering or reflow soldering process that will take place at a later date after the components have been positioned.
The procedure of using the markings for component classifications and element lays out to the board. Might be used to simply the top or to both sides if parts are installed on both top and bottom sides.
The procedure of separating several boards from a panel of identical boards; this process also allows cutting notches or slots into the board if needed.
A visual evaluation 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 techniques.
The process of checking for connection or shorted connections on the boards by ways applying a voltage between various points on the board and identifying if a present circulation happens. Depending upon the board intricacy, this process may require a specifically designed test fixture and test program to integrate with the electrical test system used by the board producer.