Quality Management Systems Mind-sets

In electronic devices, printed circuit boards, or PCBs, are utilized to mechanically support electronic elements which have their connection leads soldered onto copper pads in surface area install applications or through rilled holes in the board and copper pads for soldering the component leads in thru-hole applications. A board style 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 mount parts on the top and surface mount components on the bottom or circuit side, or surface area mount parts on the top and bottom sides of the board.

The boards are also used to electrically link the needed leads for each component utilizing conductive copper traces. The component pads and connection traces are etched from copper sheets laminated onto a non-conductive substrate. Printed circuit boards are designed 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 number 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 engraved away to form the actual copper pads and connection traces on the board surface areas as part of the board manufacturing process. A multilayer board consists of a number of layers of dielectric material that has actually been impregnated with adhesives, and these layers are used to separate the layers of copper plating. All of 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 common four layer board style, the internal layers are often utilized to supply 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 part 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 numerous connections for different voltage levels, ground connections, or for linking the lots of leads on ball grid range devices and other large integrated circuit bundle formats.

There are normally 2 types of product utilized to build a multilayer board. Pre-preg material is thin layers of fiberglass pre-impregnated with an adhesive, and remains in sheet kind, usually about.002 inches thick. Core material resembles a very thin double sided board in that 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 2 approaches used to build up the wanted 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 material above and another layer of core product listed below. This combination of one pre-preg layer and 2 core layers would make a 4 layer board.

The film stack-up technique, a more recent 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 constructing a sandwich. This approach enables the producer versatility in how the board layer thicknesses are integrated to fulfill the completed product density requirements by differing the number of sheets of pre-preg in each layer. Once the product layers are completed, the entire 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 procedure of manufacturing printed circuit boards follows the steps below for many applications.

The procedure of figuring out products, procedures, and requirements to fulfill the client's requirements for the board style based on the Gerber file information offered with the order.

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

The traditional procedure of exposing the copper and other areas unprotected by the etch resist film to a chemical that eliminates the unprotected copper, leaving the secured copper pads and traces in place; more recent processes utilize plasma/laser etching rather of chemicals to get rid of the copper material, allowing finer line meanings.

The procedure of aligning the conductive copper and insulating dielectric layers and pushing them under heat to activate the adhesive in the dielectric layers to form a solid board material.

The process of drilling all of the holes for plated through applications; a 2nd drilling procedure is used for holes that are not to be plated through. Details on hole place and size is consisted of in the drill drawing file.

The procedure 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 but the hole is not to be plated through. Prevent this procedure if possible since it adds cost to the completed 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 safeguards versus ecological damage, offers insulation, secures against solder shorts, ISO 9001 Certification Consultants and safeguards traces that run in between pads.

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

The procedure of applying the markings for component classifications and component outlines to the board. Might be used to just the top side or to both sides if components are installed on both leading and bottom sides.

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

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 process of checking for continuity or shorted connections on the boards by means using a voltage between different points on the board and determining if an existing flow happens. Relying on the board complexity, this process might need a specifically designed test fixture and test program to integrate with the electrical test system utilized by the board manufacturer.