Quality Management Systems - Their Framework and Benefits



In electronics, printed circuit boards, or PCBs, are utilized to mechanically support electronic components 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 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 parts on the top side and surface area mount parts on the bottom or circuit side, or surface install components on the top and bottom sides of the board.

The boards are also utilized to electrically link the required leads for each part utilizing conductive copper traces. The component 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 agreed copper pads and traces on the leading and bottom sides of the board, or multilayer styles 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 include a core dielectric material, such as FR-4 epoxy fiberglass, with copper plating on one or both sides. This copper plating is etched away to form the actual copper pads and connection traces on the board surface areas as part of the board production procedure. A multilayer board includes a variety of layers of dielectric product that has actually been fertilized with adhesives, and these layers are used to separate the layers of copper plating. All 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 design, the internal layers are typically used to offer power and ground connections, such as a +5 V airplane layer and a Ground aircraft layer as the 2 internal layers, with all other circuit and element connections made on the top and bottom layers of the board. Extremely 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 many leads on ball grid range devices and other big integrated circuit plan formats.

There are typically 2 kinds of product used to construct a multilayer board. Pre-preg material is thin layers of fiberglass pre-impregnated with an adhesive, and remains in sheet type, typically about.002 inches thick. Core product is similar to an extremely thin double sided board because it has a dielectric material, such as epoxy fiberglass, with a copper layer deposited on each side, normally.030 density dielectric material with 1 ounce copper layer on each side. In a multilayer board design, there are 2 techniques used to develop the preferred number of layers. The core stack-up approach, which is an older innovation, uses a center layer of pre-preg material with a layer of core product 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 movie stack-up technique, a newer innovation, would have core material as the center layer followed by layers of pre-preg and copper material built up 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 maker flexibility in how the board layer densities are integrated to meet the finished item density 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 making printed circuit boards follows the steps below for a lot of applications.

The procedure of determining products, procedures, and requirements to satisfy the customer's requirements for the board style based on the Gerber file info offered with the purchase order.

The procedure of transferring the Gerber file data for a layer onto an etch withstand film that is placed on the conductive copper layer.

The conventional process of exposing the copper and other areas unprotected by the etch resist film to a chemical that gets rid of the vulnerable copper, leaving the safeguarded copper pads and traces in place; more recent procedures utilize plasma/laser etching rather of chemicals to eliminate the copper material, allowing finer line definitions.

The process of aligning the conductive copper and insulating dielectric layers and pressing them under heat to activate the adhesive in the dielectric layers to form a ISO 9001 consultants solid board material.

The procedure of drilling all the holes for plated through applications; a 2nd drilling procedure 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 put in an electrically charged bath of copper.

This is needed when holes are to be drilled through a copper area however the hole is not to be plated through. Prevent this procedure if possible because it adds cost to the ended up board.

The procedure of applying 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 environmental damage, provides insulation, secures 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 ultimate wave soldering or reflow soldering process that will take place at a later date after the elements have been positioned.

The process of using the markings for element classifications and part details to the board. Might be applied to just the top side or to both sides if components are installed on both leading and bottom sides.

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

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

The process of looking for continuity or shorted connections on the boards by methods using a voltage between numerous points on the board and identifying if a present circulation occurs. Depending upon the board intricacy, this process might need a specially designed test component and test program to incorporate with the electrical test system used by the board producer.