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 design may have all thru-hole components on ISO 9001 the leading or component side, a mix of thru-hole and surface mount on the top only, a mix of thru-hole and surface area mount parts on the top and surface mount elements on the bottom or circuit side, or surface area install components on the top and bottom sides of the board.
The boards are also used to electrically link the required leads for each element utilizing conductive copper traces. The part pads and connection traces are engraved from copper sheets laminated onto a non-conductive substrate. Printed circuit boards are designed 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 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 product, such as FR-4 epoxy fiberglass, with copper plating on one or both sides. This copper plating is etched away to form the actual copper pads and connection traces on the board surface areas as part of the board production process. A multilayer board includes a variety of layers of dielectric product that has actually been fertilized with adhesives, and these layers are utilized 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 with today's innovations.
In a typical four layer board design, the internal layers are frequently used to supply power and ground connections, such as a +5 V airplane layer and a Ground aircraft layer as the 2 internal layers, with all other circuit and part connections made on the top and bottom layers of the board. Really complicated board styles might have a a great deal of layers to make the numerous connections for various voltage levels, ground connections, or for linking the lots of leads on ball grid variety devices and other big integrated circuit bundle formats.
There are usually 2 kinds of product utilized to build a multilayer board. Pre-preg material is thin layers of fiberglass pre-impregnated with an adhesive, and is in sheet type, typically about.002 inches thick. Core material is similar to an extremely thin double sided board because it has a dielectric product, such as epoxy fiberglass, with a copper layer transferred on each side, typically.030 density dielectric product with 1 ounce copper layer on each side. In a multilayer board design, there are 2 methods used to develop the preferred variety of layers. The core stack-up technique, which is an older innovation, uses a center layer of pre-preg material with a layer of core product above and another layer of core material listed below. This mix of one pre-preg layer and two core layers would make a 4 layer board.
The movie stack-up technique, a more recent innovation, would have core material as the center layer followed by layers of pre-preg and copper material developed above and listed below to form the last variety of layers required by the board design, sort of like Dagwood building a sandwich. This method permits the producer versatility in how the board layer densities are integrated to meet the ended up item density requirements by differing the number of sheets of pre-preg in each layer. Once the product 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 process of manufacturing printed circuit boards follows the steps below for many applications.
The process of figuring out materials, procedures, and requirements to satisfy the consumer's specs for the board style based upon the Gerber file information provided with the purchase order.
The procedure of moving the Gerber file information for a layer onto an etch resist film that is placed on the conductive copper layer.
The traditional procedure of exposing the copper and other areas unprotected by the etch resist movie 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 remove the copper product, allowing finer line meanings.
The procedure 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 product.
The process of drilling all of the holes for plated through applications; a 2nd drilling process is used for holes that are not to be plated through. Info on hole place and size is included in the drill drawing file.
The process of applying 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 needed when holes are to be drilled through a copper area but the hole is not to be plated through. Prevent this procedure if possible since it adds cost to the ended up board.
The procedure 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 applied; the solder mask safeguards against environmental damage, offers insulation, secures against solder shorts, and protects traces that run in between pads.
The procedure of covering the pad locations 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 components have been put.
The process of using the markings for element designations and element details 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 likewise permits cutting notches or slots into the board if needed.
A visual inspection of the boards; likewise can be the procedure of inspecting wall quality for plated through holes in multi-layer boards by cross-sectioning or other techniques.
The procedure of looking for connection or shorted connections on the boards by methods applying a voltage between numerous points on the board and identifying if a current flow happens. Relying on the board complexity, this process may need a specially designed test fixture and test program to integrate with the electrical test system utilized by the board maker.