TQM Systems Assessment

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

The boards are also used to electrically link the required leads for each component 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 created as single sided with 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 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 surface areas as part of the board production process. A multilayer board consists of a number of layers of dielectric material that has actually been fertilized with adhesives, and these layers are utilized to separate the layers of copper plating. All these layers are aligned 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 innovations.

In a common 4 layer board design, the internal layers are frequently utilized to provide 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 part connections made on the leading and bottom layers of the board. Extremely complex board designs may have a a great deal of layers to make the numerous connections for various voltage levels, ground connections, or for connecting the many leads on ball grid variety gadgets and other large incorporated circuit plan formats.

There are typically two kinds of material used to build a multilayer board. Pre-preg product is thin layers of fiberglass pre-impregnated with an adhesive, and is in sheet kind, generally about.002 inches thick. Core product resembles an extremely thin double sided board in that it has a dielectric product, such as epoxy fiberglass, with a copper layer deposited on each side, usually.030 thickness dielectric material with 1 ounce copper layer on each side. In a multilayer board style, there are 2 approaches utilized to build up the desired variety of layers. The core stack-up method, which is an older technology, uses 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 two core layers would make a 4 layer board.

The film stack-up approach, a newer innovation, would have core material as the center layer followed by layers of pre-preg and copper product built up above and listed below to form the last number of layers required by the board design, sort of like Dagwood building a sandwich. This approach permits the maker versatility in how the board layer thicknesses are combined to fulfill the completed item thickness requirements by varying the variety of sheets of pre-preg in each layer. When the product layers are finished, the whole 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 process of making printed circuit boards follows the steps listed below for many applications.

The process of determining materials, procedures, and requirements to satisfy the client's specs for the board style based upon the Gerber file information supplied with the purchase order.

The process of moving the Gerber file information for a layer onto an etch resist film that is put 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 removes the vulnerable copper, leaving the safeguarded copper pads and traces in place; newer procedures use plasma/laser etching rather of chemicals to eliminate the copper material, 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 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. Information on hole location 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 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 because it adds cost to the finished board.

The process of using a protective masking product, a solder mask, over the bare copper traces or over the copper that has had a thin layer of solder applied; the solder mask secures versus ecological damage, offers insulation, protects versus solder shorts, and protects traces that run in between pads.

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

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

The procedure of separating several boards from a panel of identical boards; this process likewise permits cutting notches or slots into the board if required.

A visual examination of the boards; likewise can be the procedure of checking 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 ways applying a voltage in between numerous points on the board and identifying if an existing flow happens. Depending upon the board intricacy, this procedure might need a specially created test fixture and test program to sneak a peek at these guys integrate with the electrical test system used by the board manufacturer.