Have You Ever Wondered About Quality Management Systems



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 part leads in thru-hole applications. A board design may have all thru-hole elements on the leading or part side, a mix of thru-hole and surface install on the top just, a mix of thru-hole and surface area install elements on the top and surface mount elements on the bottom or circuit side, or surface area install elements on the top and bottom sides of the board.

The boards are likewise utilized to electrically link the required leads for each part utilizing conductive copper traces. The element pads and connection traces are engraved from copper sheets laminated onto a non-conductive substrate. Printed circuit boards are developed as single agreed copper pads and traces on one side of the board just, double sided with 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 number of internal copper layers with traces and connections.

Single or double sided boards consist of a core dielectric material, 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 production process. A multilayer board consists of a variety of layers of dielectric product that has been impregnated with adhesives, and these layers are utilized to separate the layers of copper plating. All of these layers are aligned 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 normal four layer board design, the internal layers are frequently used to provide power and ground connections, such as a +5 V aircraft layer and a Ground aircraft layer as the two internal layers, with all other circuit and component connections made on the leading and bottom layers of the board. Really intricate board styles might have a large number of layers to make the different connections for various voltage levels, ground connections, or for connecting the numerous leads on ball grid range gadgets and other large integrated circuit package formats.

There are generally two kinds of material utilized to construct a multilayer board. Pre-preg material is thin layers of fiberglass pre-impregnated with an adhesive, and remains in sheet form, usually about.002 inches thick. Core product resembles an extremely thin double sided board in that it has a dielectric material, such as epoxy fiberglass, with a copper layer deposited on each side, typically.030 density dielectric material with 1 ounce copper layer on each side. In a multilayer board design, there are 2 techniques utilized to build up the desired number of layers. The core stack-up method, which is an older technology, utilizes a center layer of pre-preg product with a layer of core material above and another layer of core product 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 technology, 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 final variety of layers needed by the board style, sort of like Dagwood building a sandwich. This method permits the manufacturer versatility in how the board layer thicknesses are integrated to fulfill the ended up product thickness requirements by differing the number of sheets of pre-preg in each layer. As soon as the material layers are completed, the entire 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 producing printed circuit boards follows the actions listed below for a lot of applications.

The process of determining products, procedures, and requirements to fulfill the customer's specifications for the board design based upon the Gerber file info offered with the order.

The procedure of moving the Gerber file data for a layer onto an etch resist film that is put on the conductive copper layer.

The conventional procedure of exposing the copper and other areas unprotected by the etch resist movie to a chemical that gets rid of the unguarded copper, leaving the secured copper pads and traces in place; more recent processes use plasma/laser etching instead of chemicals to eliminate the copper product, permitting finer line meanings.

The process of aligning the conductive copper and insulating dielectric layers and pushing them under heat to activate the adhesive in the dielectric layers to form a solid board product.

The process of drilling all the holes for plated through applications; a 2nd drilling process is utilized for holes that are not to be plated through. Information on hole area and size is contained 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 put 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 since it adds cost to the ended up board.

The procedure of using a protective masking material, a solder mask, over the bare copper traces or over the copper that has had a thin layer of solder applied; the solder mask safeguards against environmental damage, provides insulation, safeguards against solder shorts, and safeguards traces Reference site that run in between pads.

The procedure of finish the pad locations 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 procedure of using the markings for part designations and component outlines to the board. May be used to simply the top side or to both sides if parts are mounted on both top and bottom sides.

The process of separating numerous boards from a panel of identical boards; this process also enables cutting notches or slots into the board if required.

A visual evaluation of the boards; also can be the procedure of inspecting wall quality for plated through holes in multi-layer boards by cross-sectioning or other methods.

The process of looking for connection or shorted connections on the boards by methods using a voltage in between numerous points on the board and figuring out if a current circulation happens. Depending upon the board complexity, this procedure may require a specially developed test fixture and test program to integrate with the electrical test system used by the board manufacturer.
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