Quality Management Systems Reprise

In electronic devices, printed circuit boards, or PCBs, are used to mechanically support electronic components which have their connection leads soldered onto copper pads in surface 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 ISO 9001 consultants have all thru-hole elements on the leading or component side, a mix of thru-hole and surface install on the top side just, a mix of thru-hole and surface area install parts on the top side and surface area mount components on the bottom or circuit side, or surface area mount components on the leading 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 component 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 just, double agreed 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 variety of internal copper layers with traces and connections.

Single or double sided boards consist of 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 actual copper pads and connection traces on the board surfaces as part of the board manufacturing procedure. A multilayer board includes a variety of layers of dielectric product that has actually been impregnated with adhesives, and these layers are utilized to separate the layers of copper plating. All these layers are lined up and then 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 normal 4 layer board style, the internal layers are often used to provide power and ground connections, such as a +5 V plane layer and a Ground plane layer as the two internal layers, with all other circuit and element connections made on the leading and bottom layers of the board. Extremely complex board designs may have a large number of layers to make the various connections for various voltage levels, ground connections, or for linking the lots of leads on ball grid range gadgets and other big integrated circuit bundle formats.

There are generally 2 types of product utilized to build a multilayer board. Pre-preg product is thin layers of fiberglass pre-impregnated with an adhesive, and remains in sheet form, normally about.002 inches thick. Core material 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, generally.030 thickness dielectric product with 1 ounce copper layer on each side. In a multilayer board style, there are two methods utilized to develop the desired variety of layers. The core stack-up method, which is an older innovation, utilizes a center layer of pre-preg product with a layer of core product above and another layer of core product listed below. This mix of one pre-preg layer and 2 core layers would make a 4 layer board.

The film stack-up technique, a newer innovation, would have core material as the center layer followed by layers of pre-preg and copper product developed above and below to form the last number of layers required by the board design, sort of like Dagwood developing a sandwich. This method enables the manufacturer versatility in how the board layer densities are combined to fulfill the ended up item density requirements by varying the number of sheets of pre-preg in each layer. Once the material layers are completed, 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 procedure of manufacturing printed circuit boards follows the actions below for most 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 process of transferring the Gerber file data for a layer onto an etch withstand movie that is put on the conductive copper layer.

The conventional procedure of exposing the copper and other areas unprotected by the etch resist movie to a chemical that eliminates the unprotected copper, leaving the safeguarded copper pads and traces in location; more recent processes use plasma/laser etching rather of chemicals to eliminate the copper product, permitting finer line meanings.

The process of lining up 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 procedure 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 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 put in an electrically charged bath of copper.

This is required when holes are to be drilled through a copper location but the hole is not to be plated through. Avoid this procedure if possible due to the fact that it includes 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 actually had a thin layer of solder used; the solder mask secures against ecological damage, provides insulation, secures against solder shorts, and secures traces that run between pads.

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

The process of applying the markings for part designations and component describes to the board. May be used to just the top or to both sides if components are mounted on both leading and bottom sides.

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

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 procedure of looking for connection or shorted connections on the boards by ways applying a voltage in between numerous points on the board and figuring out if a current circulation occurs. Relying on the board intricacy, this procedure may need a specifically created test component and test program to integrate with the electrical test system utilized by the board producer.