State Of The Art Quality Management System Advantages



In electronics, printed circuit boards, or PCBs, are used to mechanically support electronic elements 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 element leads in thru-hole applications. A board style might have all thru-hole parts on the leading or element side, a mix of thru-hole and surface mount on the top side only, a mix of thru-hole and surface mount components on the top side and surface area install parts on the bottom or circuit side, or surface area mount parts on the top and bottom sides of the board.

The boards are also used to electrically connect the needed leads for each part using conductive copper traces. The element pads and connection traces are etched 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 agreed copper pads and traces on the leading and bottom sides of the board, or multilayer designs with copper pads and traces on 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 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 production process. A multilayer board includes a number of layers of dielectric material that has actually been impregnated with adhesives, and these layers are utilized to separate the layers of copper plating. All of 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 4 layer board style, the internal layers are often utilized to supply 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 element connections made on the leading and bottom layers of the board. Very intricate board designs may have a a great deal of layers to make the various connections for different voltage levels, ground connections, or for linking the numerous leads on ball grid variety devices and other big incorporated circuit plan formats.

There are usually 2 types of product used to construct a multilayer board. Pre-preg product is thin layers of fiberglass pre-impregnated with an adhesive, and remains in sheet form, generally about.002 inches thick. Core product resembles an extremely thin double sided board because it has a dielectric material, such as epoxy fiberglass, with a copper layer transferred on each side, generally.030 density dielectric material with 1 ounce copper layer on each side. In a multilayer board design, there are two approaches used to develop the desired 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 material 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 film 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 listed below to form the final number of layers needed by the board style, sort of like Dagwood building a sandwich. This method allows the manufacturer versatility in how the board layer densities are integrated to fulfill the completed product density requirements by varying the variety of sheets of pre-preg in each layer. When the material layers are finished, 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 procedure of producing printed circuit boards follows the steps listed below for the majority of applications.

The process of identifying materials, procedures, and requirements to satisfy the consumer's specifications for the board style based on the Gerber file info provided with the order.

The procedure of moving the Gerber file data 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 locations unprotected by the etch resist movie to a chemical that gets rid of the unguarded copper, leaving the protected copper pads and traces in location; more recent procedures use plasma/laser etching rather of chemicals to eliminate the copper product, permitting finer line definitions.

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

The process of drilling all the holes for plated through applications; a 2nd 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 using 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 completed 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 against ecological damage, supplies insulation, protects against solder shorts, and secures traces that run in between pads.

The procedure of coating the pad areas with a thin layer of solder to prepare the board for the eventual wave soldering or reflow soldering process that will occur at a later date after the components have actually been positioned.

The process of applying the markings for element designations and component describes to the board. Might be used to just the top side or to both sides if elements are mounted on both top and bottom sides.

The process of separating several boards from a panel of identical boards; this process also allows cutting notches or slots into the board if needed.

A visual inspection of the boards; also can be the procedure of checking wall quality for plated through holes in multi-layer More interesting details here boards by cross-sectioning or other methods.

The process of checking for connection or shorted connections on the boards by means using a voltage between different points on the board and figuring out if an existing circulation occurs. Depending upon the board complexity, this process may need a specially designed test fixture and test program to incorporate with the electrical test system used by the board producer.