Insights Into Quality Management Systems

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 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 components on the top or part side, a mix of thru-hole and surface mount on the top side only, a mix of thru-hole and surface area mount components on the top and surface mount parts on the bottom or circuit side, or surface install 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 element pads and connection traces are etched 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 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 actual copper pads and connection traces on the board surfaces as part of the board manufacturing procedure. A multilayer board consists of a number 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 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 frequently utilized to provide power and ground connections, such as a +5 V aircraft 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. Very complex board styles might have a a great deal of layers to make the numerous connections for various voltage levels, ground connections, or for linking the lots of leads on ball grid array gadgets and other big integrated circuit bundle formats.

There are typically two types of material used to construct a multilayer board. Pre-preg material is thin layers of fiberglass pre-impregnated with an adhesive, and is in sheet type, typically about.002 inches thick. Core material resembles a really thin double sided board because it has a dielectric product, such as epoxy fiberglass, with a copper layer transferred on each side, usually.030 density dielectric product with 1 ounce copper layer on each side. In a multilayer board design, there are two methods used to build up the wanted variety of layers. The core stack-up technique, which is an older technology, 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 approach, a newer innovation, would have core product as the center layer followed by layers of pre-preg and copper product built up above and listed below to form the final number of layers needed by the board design, sort of like Dagwood constructing a sandwich. This method permits the maker flexibility in how the board layer densities are combined to satisfy the completed product thickness requirements by varying the number of sheets of pre-preg in each layer. As soon as the material layers are finished, the whole stack is ISO 9001 consultants 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 producing printed circuit boards follows the actions below for the majority of applications.

The procedure of determining materials, processes, and requirements to fulfill the client's specs for the board design based on the Gerber file info offered with the purchase order.

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

The standard process of exposing the copper and other locations unprotected by the etch resist film to a chemical that eliminates the unprotected copper, leaving the safeguarded copper pads and traces in place; more recent processes utilize plasma/laser etching instead of chemicals to remove the copper material, allowing finer line meanings.

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

The procedure of drilling all of the holes for plated through applications; a second drilling procedure is utilized for holes that are not to be plated through. Details on hole place and size is included 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 location 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 product, a solder mask, over the bare copper traces or over the copper that has had a thin layer of solder used; the solder mask secures against ecological damage, offers insulation, safeguards against solder shorts, and secures traces that run in between pads.

The process 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 take place at a later date after the components have actually been placed.

The process of using the markings for part classifications and component details to the board. Might be used to simply the top or to both sides if parts are installed on both leading and bottom sides.

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

A visual evaluation of the boards; likewise 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 continuity or shorted connections on the boards by ways applying a voltage in between various points on the board and determining if an existing flow happens. Relying on the board intricacy, this procedure might require a specially developed test component and test program to integrate with the electrical test system used by the board producer.