In electronics, printed circuit boards, or PCBs, are utilized to mechanically support electronic elements 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 part 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 mount on the top only, a mix of thru-hole and surface install components on the top and surface mount elements on the bottom or circuit side, or surface install parts on the leading and bottom sides of the board.
The boards are likewise used to electrically link the required leads for each part using conductive copper traces. The part 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 just, 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 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 actual copper pads and connection traces on the board surfaces 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 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 innovations.
In a common four layer board style, the internal layers are frequently used to supply power and ground connections, such as a +5 V plane layer and a Ground aircraft layer as the 2 internal layers, with all other circuit and element connections made on the leading and bottom layers of the board. Very complicated board designs may have a a great deal of layers to make the numerous connections for different voltage levels, ground connections, or for linking the numerous leads on ball grid selection devices and other big incorporated circuit bundle formats.
There are usually 2 types of material utilized to construct a multilayer board. Pre-preg product is thin layers of fiberglass pre-impregnated with an adhesive, and remains in sheet kind, generally about.002 inches thick. Core product is similar to an extremely thin double sided board in that it has a dielectric product, such as epoxy fiberglass, with a copper layer transferred on each side, generally.030 thickness dielectric material with 1 ounce copper layer on each side. In a multilayer board style, there are 2 approaches used to build up the desired variety of layers. The core stack-up technique, which is an older innovation, uses a center layer of pre-preg product 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 movie stack-up approach, a newer innovation, would have core material as the center layer followed by layers of pre-preg and copper product developed above and below to form the final number of layers needed by the board design, sort of like Dagwood building a sandwich. This approach permits the producer flexibility in how the board layer densities are integrated to satisfy ISO 9001 Certification Consultants the ended up product thickness requirements by differing the variety of sheets of pre-preg in each layer. As soon as the material layers are finished, the entire 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 procedure of manufacturing printed circuit boards follows the steps listed below for most applications.
The process of figuring out products, procedures, and requirements to satisfy the customer's specifications for the board style based on the Gerber file information provided with the purchase order.
The procedure of transferring the Gerber file information for a layer onto an etch withstand movie that is placed on the conductive copper layer.
The conventional process 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 secured copper pads and traces in location; more recent processes utilize plasma/laser etching rather of chemicals to get rid of the copper product, permitting 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 solid board material.
The process of drilling all the holes for plated through applications; a second drilling procedure is utilized for holes that are not to be plated through. Details 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 put 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. Prevent this process if possible due to the fact that it adds cost to the finished 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 protects versus environmental damage, provides insulation, safeguards against 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 eventual wave soldering or reflow soldering procedure that will happen at a later date after the parts have been put.
The process of using the markings for part classifications and component lays out to the board. May be used to just the top or to both sides if elements are installed on both leading and bottom sides.
The procedure of separating multiple boards from a panel of identical boards; this process also permits cutting notches or slots into the board if needed.
A visual assessment 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 looking for connection or shorted connections on the boards by methods using a voltage in between different points on the board and figuring out if a current flow occurs. Depending upon the board complexity, this process may need a specifically developed test fixture and test program to integrate with the electrical test system used by the board maker.