In electronics, printed circuit boards, or PCBs, are utilized 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 top or part side, a mix of thru-hole and surface mount on the top side only, a mix of thru-hole and surface mount parts on the top and surface install components on the bottom or circuit side, or surface mount components on the top and bottom sides of the board.
The boards are also used to electrically connect the needed leads for each element using 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 agreed copper pads and traces on one side of the board only, double sided with copper pads and traces on the leading and bottom sides of the board, or multilayer designs 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 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 actual copper pads and connection traces on the board surface areas as part of the board production procedure. A multilayer board consists of a number of layers of dielectric material that has actually been impregnated with adhesives, and these layers are used 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 normal four layer board design, the internal layers are frequently used to offer power and ground connections, such as a +5 V plane 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 complicated board styles may have a large number of layers to make the different connections for various voltage levels, ground connections, or for linking the numerous leads on ball grid selection devices and other big incorporated circuit package formats.
There are usually 2 types of product used to build a multilayer board. Pre-preg material is thin layers of fiberglass pre-impregnated with an adhesive, and is in sheet kind, normally about.002 inches thick. Core material is similar to a really thin double sided board because it has a dielectric product, such as epoxy fiberglass, with a copper layer transferred on each side, generally.030 density dielectric product with 1 ounce copper layer on each side. In a multilayer board style, there are two approaches utilized to develop the desired number of layers. The core stack-up method, which is an older innovation, 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 2 core layers would make a 4 layer board.
The film stack-up method, a newer innovation, would have core material as the center layer followed by layers of pre-preg and copper material built up above and listed below to form the final number of layers required by the board design, sort of like Dagwood building a sandwich. This technique allows the producer flexibility in how the board layer densities are integrated to fulfill the finished item density requirements by varying the variety of sheets of pre-preg in each layer. When the product layers are completed, the entire 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 manufacturing printed circuit boards follows the actions below for the majority of applications.
The process of identifying materials, processes, and requirements to fulfill the client's specifications for the board style based on the Gerber file information supplied with the purchase order.
The procedure of moving the Gerber file information for a layer onto an etch ISO 9001 Accreditation Consultants
withstand movie that is placed on the conductive copper layer.
The traditional procedure of exposing the copper and other locations unprotected by the etch withstand movie to a chemical that gets rid of the unprotected copper, leaving the secured copper pads and traces in location; more recent processes utilize plasma/laser etching rather of chemicals to remove the copper product, enabling finer line definitions.
The process of aligning the conductive copper and insulating dielectric layers and pressing them under heat to trigger the adhesive in the dielectric layers to form a strong board product.
The procedure of drilling all of the holes for plated through applications; a second drilling procedure is used for holes that are not to be plated through. Details on hole area and size is contained 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 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. Avoid this procedure if possible because it adds expense to the finished board.
The procedure of applying 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 secures versus environmental damage, provides insulation, secures versus solder shorts, and protects traces that run between pads.
The procedure of covering the pad areas with a thin layer of solder to prepare the board for the ultimate wave soldering or reflow soldering procedure that will occur at a later date after the parts have actually been placed.
The process of using the markings for part classifications and element describes to the board. Might be used to just the top side or to both sides if elements are installed on both top and bottom sides.
The procedure of separating numerous boards from a panel of similar boards; this procedure likewise permits cutting notches or slots into the board if needed.
A visual examination of the boards; also can be the process of examining 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 ways using a voltage in between numerous points on the board and identifying if a current circulation happens. Depending upon the board intricacy, this procedure might need a specially created test fixture and test program to integrate with the electrical test system used by the board maker.