The Functional Aspects of a Present-day QM System

In electronics, 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 part leads in thru-hole applications. A board design might have all thru-hole parts on the top or element side, a mix of thru-hole and surface install on the top side only, a mix of thru-hole and surface area mount parts on the top side and surface area mount parts on the bottom or circuit side, or surface area mount elements on the leading and bottom sides of the board.

The boards are likewise used to electrically link the needed leads for each element 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 leading and bottom sides of the board, or multilayer designs with copper pads and traces on 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 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 includes a variety of layers of dielectric product that has actually been fertilized with adhesives, and these layers are utilized to separate the layers of copper plating. All of 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 technologies.

In a common 4 layer board design, the internal layers are often utilized to supply 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 component connections made on the top and bottom layers of the board. Really complex board designs might have a large number of layers to make the various connections for various voltage levels, ground connections, or for connecting the lots of leads on ball grid array devices and other big integrated circuit bundle formats.

There are normally two types of material utilized to build a multilayer board. Pre-preg material is thin layers of fiberglass pre-impregnated with an adhesive, and is in sheet kind, generally about.002 inches thick. Core material is similar to an extremely thin double sided board in that it has a dielectric product, such as epoxy fiberglass, with a copper layer transferred on each side, typically.030 thickness dielectric material with 1 ounce copper layer on each side. In a multilayer board design, there are 2 techniques utilized to build up the preferred variety of layers. The core stack-up approach, which is an older innovation, uses 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 approach, a newer technology, would have core material as the center layer followed by layers of pre-preg and copper material built up above and listed below to form the final number of layers required by the board style, sort of like Dagwood building a sandwich. This approach allows the maker versatility in how the board layer densities are integrated to satisfy the finished product thickness requirements by varying the variety of sheets of pre-preg in each layer. When the material layers are finished, 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 process of manufacturing printed circuit boards follows the actions listed below for most applications.

The procedure of determining materials, processes, and requirements to meet the client's requirements for the board design based upon the Gerber file information offered with the purchase order.

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

The traditional process of exposing the copper and other locations unprotected by the etch resist movie to a chemical that eliminates the unguarded copper, leaving the protected copper pads and traces in place; more recent processes utilize plasma/laser etching instead of chemicals to eliminate the copper material, enabling finer line definitions.

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

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

The procedure of using copper plating to the pads, traces, and drilled through ISO 9001 Accreditation holes that are to be plated through; boards are positioned 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 finished board.

The process 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 safeguards against ecological damage, offers insulation, safeguards against solder shorts, and protects traces that run between pads.

The procedure of coating the pad locations 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 parts have been placed.

The process of applying the markings for component designations and component details to the board. May be applied to simply the top or to both sides if components are mounted on both top and bottom sides.

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

A visual inspection of the boards; likewise can be the procedure of examining wall quality for plated through holes in multi-layer boards by cross-sectioning or other techniques.

The procedure of checking for connection or shorted connections on the boards by means applying a voltage in between numerous points on the board and figuring out if a present flow happens. Depending upon the board complexity, this process might require a specially designed test component and test program to integrate with the electrical test system utilized by the board producer.