Benefits of TQM Systems in Modern Enterprises

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 area install applications or through rilled holes in the board and copper pads for soldering the component leads in thru-hole applications. A board design may have all thru-hole parts on the top or component side, a mix of thru-hole and surface area mount on the top side only, a mix of thru-hole and surface area mount elements on the top and surface area install parts on the bottom or circuit side, or surface area mount elements on the leading 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 agreed copper pads and traces on one side of the board only, 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 include 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 real copper pads and connection traces on the board surface areas as part of the board production procedure. A multilayer board consists of a variety of layers of dielectric material that has actually been fertilized with adhesives, and these layers are used to separate the layers of copper plating. All these layers are lined up and after that 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 typical four layer board design, the internal layers are often used to supply power and ground connections, such as a +5 V plane layer and a Ground plane layer as the 2 internal layers, with all other circuit and component connections made on the top and bottom layers of the board. Really complex 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 array devices and other large integrated circuit package formats.

There are typically 2 kinds of product used to build a multilayer board. Pre-preg material is thin layers of fiberglass pre-impregnated with an adhesive, and remains in sheet kind, normally about.002 inches thick. Core material is similar to an extremely thin double sided board in that it has a dielectric material, such as epoxy fiberglass, with a copper layer transferred on each side, normally.030 density dielectric product with 1 ounce copper layer on each side. In a multilayer board style, there are two methods used to build up the wanted number of layers. The core stack-up method, which is an older technology, utilizes a center layer of pre-preg material with a layer of core material above and another layer of core product below. This mix of one pre-preg layer and two core layers would make a 4 layer board.

The film stack-up approach, a more recent technology, 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 required by the board style, sort of like Dagwood constructing a sandwich. This technique allows the maker flexibility in how the board layer thicknesses are combined to fulfill the finished item thickness requirements by varying the number of sheets of pre-preg in each layer. When the material layers are finished, the entire stack is subjected to 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 below for the majority of applications.

The process of determining materials, processes, and requirements to satisfy the consumer's requirements for the board design based upon the Gerber file details supplied with the purchase order.

The process of transferring the Gerber file information for a layer onto an etch withstand movie that is put on the conductive copper layer.

The traditional process of exposing the copper and other areas unprotected by the etch withstand film to a chemical that removes the unguarded copper, leaving the safeguarded copper pads and traces in location; newer procedures use plasma/laser etching instead of chemicals to remove the copper material, enabling finer line meanings.

The process of lining up the conductive copper and insulating dielectric layers and pushing 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 second drilling process is used for holes that are not to be plated through. Info on hole location 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 positioned in an electrically charged bath of copper.

This is required when holes are to be drilled through a copper area but the hole is not to be plated through. Avoid this process if possible due to the fact that it adds cost to the finished board.

The procedure of applying a protective masking material, a solder mask, over the bare copper traces or over the copper that has actually had a thin layer of solder applied; More interesting details here the solder mask safeguards against ecological damage, provides insulation, secures against solder shorts, and secures traces that run in between pads.

The process of coating the pad locations with a thin layer of solder to prepare the board for the eventual wave soldering or reflow soldering procedure that will take place at a later date after the parts have been put.

The procedure of using the markings for part designations and element details to the board. Might be applied to just the top or to both sides if elements are mounted on both leading and bottom sides.

The process of separating numerous boards from a panel of similar boards; this procedure also permits cutting notches or slots into the board if needed.

A visual examination of the boards; likewise 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 connection or shorted connections on the boards by methods using a voltage in between different points on the board and figuring out if an existing flow happens. Relying on the board complexity, this procedure may require a specifically designed test component and test program to incorporate with the electrical test system utilized by the board maker.