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 area mount applications or through rilled holes in the board and copper pads for soldering the part leads in thru-hole applications. A board design may have all thru-hole components on the leading or part side, a mix of thru-hole and surface area mount on the top side only, a mix of thru-hole and surface install elements on the top side and surface mount components on the bottom or circuit side, or surface mount components on the top and bottom sides of the board.
The boards are also utilized to electrically link the required leads for each element utilizing conductive copper traces. The element pads and connection traces are etched 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 only, double sided with 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 variety 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 surface areas as part of the board manufacturing procedure. A multilayer board includes a number of layers of dielectric product that has actually been impregnated https://alice4000.wixsite.com/quality/home/iso-9001-the-global-quality-standard with adhesives, and these layers are used to separate the layers of copper plating. All these layers are lined up and 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 common four layer board design, the internal layers are frequently 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 part 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 many leads on ball grid array gadgets and other large incorporated circuit package formats.
There are normally two kinds of product utilized to build a multilayer board. Pre-preg product is thin layers of fiberglass pre-impregnated with an adhesive, and is in sheet kind, typically about.002 inches thick. Core product resembles a really thin double sided board in that it has a dielectric product, 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 two approaches utilized to develop the desired number of layers. The core stack-up approach, which is an older technology, uses a center layer of pre-preg product with a layer of core product 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 movie stack-up method, a more recent innovation, would have core material as the center layer followed by layers of pre-preg and copper material developed above and below to form the final number of layers required by the board design, sort of like Dagwood constructing a sandwich. This approach allows the producer versatility in how the board layer densities are combined to fulfill the finished item thickness requirements by varying 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 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 listed below for most applications.
The process of figuring out products, processes, and requirements to meet the consumer's specs for the board style based upon the Gerber file information offered with the purchase order.
The process of moving the Gerber file data for a layer onto an etch resist film that is put on the conductive copper layer.
The standard procedure of exposing the copper and other areas unprotected by the etch withstand film to a chemical that eliminates the unprotected copper, leaving the protected copper pads and traces in location; more recent procedures use plasma/laser etching instead of chemicals to get rid of the copper product, enabling finer line definitions.
The process 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 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. Details on hole location and size is contained 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 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 due to the fact that it adds cost to the ended up 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 secures against ecological damage, supplies insulation, protects versus solder shorts, and secures traces that run between pads.
The procedure of finishing the pad areas with a thin layer of solder to prepare the board for the eventual wave soldering or reflow soldering procedure that will happen at a later date after the elements have been put.
The procedure of applying the markings for part designations and part describes to the board. May be applied to simply the top or to both sides if parts are mounted on both leading and bottom sides.
The procedure of separating several boards from a panel of identical boards; this procedure also permits cutting notches or slots into the board if required.
A visual inspection of the boards; likewise can be the process of checking 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 means using a voltage between numerous points on the board and determining if a present circulation happens. Depending upon the board intricacy, this process might require a specially designed test fixture and test program to integrate with the electrical test system utilized by the board producer.