Smart Businesses Use State-of-the-Art Quality Systems

In electronics, printed circuit boards, or PCBs, are utilized to mechanically support electronic parts which have their connection leads soldered onto copper pads in surface area 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 have all thru-hole elements on the leading or part side, a mix of thru-hole and surface area mount on the top side only, a mix of thru-hole and surface mount parts on the top side and surface install elements on the bottom or circuit side, or surface area mount elements on the top and bottom sides of the board.

The boards are likewise utilized to electrically connect 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 created as single sided with copper pads and traces on one side of the board only, double sided with copper pads and traces on the top and bottom sides of the board, or multilayer styles 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 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 real copper pads and connection traces on the board surfaces as part of the board production procedure. A multilayer board consists of a variety 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 then bonded into a single board structure under heat and pressure. Multilayer boards with 48 or more layers can be produced with today's innovations.

In a common 4 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 aircraft layer as the 2 internal layers, with all other circuit and component connections made on the leading and bottom layers of the board. Very intricate board styles might have a large number of layers to make the different connections for different voltage levels, ground connections, or for connecting the many leads on ball grid array devices and other large incorporated circuit package formats.

There are generally two types of product utilized to construct a multilayer board. Pre-preg material is thin layers of fiberglass pre-impregnated with an adhesive, and is in sheet type, generally about.002 inches thick. Core product is similar to a really thin double sided board because it has a dielectric material, such as epoxy fiberglass, with a copper layer deposited on each side, generally.030 density dielectric material with 1 ounce copper layer on each side. In a multilayer board style, there are 2 techniques used to develop the desired variety of layers. The core stack-up technique, which is an older innovation, utilizes a center layer of pre-preg material with a layer of core material above and another layer of core material listed below. This mix of one pre-preg layer and two core layers would make a 4 layer board.

The movie stack-up approach, a ISO 9001 Accreditation Consultants newer innovation, 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 variety of layers required by the board design, sort of like Dagwood developing a sandwich. This technique enables the producer versatility in how the board layer densities are integrated to fulfill the completed item thickness requirements by differing the variety 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 making printed circuit boards follows the actions below for many applications.

The process of identifying materials, procedures, and requirements to meet the client's specifications for the board style based on the Gerber file details provided with the order.

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

The conventional procedure of exposing the copper and other locations unprotected by the etch resist film to a chemical that eliminates the unguarded copper, leaving the protected copper pads and traces in location; newer processes use plasma/laser etching rather of chemicals to remove the copper product, enabling finer line meanings.

The procedure 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 solid board material.

The procedure of drilling all of the holes for plated through applications; a 2nd drilling process is used for holes that are not to be plated through. Info on hole area and size is contained 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 placed in an electrically charged bath of copper.

This is needed when holes are to be drilled through a copper area but the hole is not to be plated through. Avoid this process if possible due to the fact that it includes expense to the completed board.

The process of applying a protective masking product, a solder mask, over the bare copper traces or over the copper that has had a thin layer of solder applied; the solder mask secures against environmental damage, offers insulation, secures against solder shorts, and safeguards 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 happen at a later date after the elements have been positioned.

The procedure of using the markings for element classifications and component outlines to the board. Might be used to simply the top or to both sides if elements are mounted on both leading and bottom sides.

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

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

The process of looking for continuity or shorted connections on the boards by methods applying a voltage in between various points on the board and determining if a current circulation occurs. Relying on the board intricacy, this procedure may require a specifically designed test component and test program to integrate with the electrical test system utilized by the board producer.