Quality Management Systems Review



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 mount applications or through rilled holes in the board and copper pads for soldering the part leads in thru-hole applications. A board design may have all thru-hole elements on the leading or component side, a mix of thru-hole and surface area mount on the top just, a mix of thru-hole and surface install parts on the top side and surface install components on the bottom or circuit side, or surface install parts on the top and bottom sides of the board.

The boards you can find out more are also used to electrically link the required leads for each component 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 designed as single agreed 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 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 surfaces as part of the board manufacturing process. A multilayer board consists of 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 aligned 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 four layer board style, the internal layers are often used to supply power and ground connections, such as a +5 V aircraft layer and a Ground airplane layer as the 2 internal layers, with all other circuit and component connections made on the top and bottom layers of the board. Extremely intricate board styles may have a a great deal of layers to make the different connections for various voltage levels, ground connections, or for linking the lots of leads on ball grid selection gadgets and other large integrated circuit plan formats.

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

The movie stack-up method, a more recent technology, would have core product as the center layer followed by layers of pre-preg and copper product developed above and below to form the last variety of layers needed by the board style, sort of like Dagwood building a sandwich. This technique allows the producer flexibility in how the board layer thicknesses are combined to satisfy the ended up item thickness requirements by varying the number of sheets of pre-preg in each layer. Once the material layers are completed, the whole stack undergoes heat and pressure that triggers the adhesive in the pre-preg to bond the core and pre-preg layers together into a single entity.

The process of manufacturing printed circuit boards follows the actions below for a lot of applications.

The procedure of determining materials, processes, and requirements to meet the consumer's specs for the board style based upon the Gerber file information provided with the order.

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

The conventional process of exposing the copper and other locations unprotected by the etch withstand movie to a chemical that removes the unprotected copper, leaving the safeguarded copper pads and traces in location; newer procedures utilize plasma/laser etching rather of chemicals to get rid of the copper product, allowing 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 product.

The procedure of drilling all the holes for plated through applications; a 2nd drilling process 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 using copper plating to the pads, traces, and drilled through holes that are to be plated through; boards are placed in an electrically charged bath of copper.

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

The procedure of using 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 used; the solder mask secures versus ecological damage, offers insulation, protects versus solder shorts, and protects traces that run between pads.

The procedure of finish 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 components have been put.

The process of applying the markings for part classifications and element lays out to the board. May be used to simply the top side or to both sides if parts are installed on both leading and bottom sides.

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

The procedure of checking for continuity or shorted connections on the boards by means applying a voltage in between various points on the board and figuring out if an existing flow happens. Relying on the board complexity, this procedure may require a specifically created test fixture and test program to integrate with the electrical test system used by the board producer.