About TQM 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 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 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 components on the top and surface install elements on the bottom or circuit side, or surface area install components on the top and bottom sides of the board.

The boards are likewise used to electrically link the required leads for each component utilizing conductive copper traces. The part pads and connection traces are etched from copper sheets laminated onto a non-conductive substrate. Printed circuit boards are developed 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 designs 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 consist of a core dielectric product, such as FR-4 epoxy fiberglass, with copper plating on one or both sides. This copper plating is engraved away to form the real 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 been impregnated with adhesives, and these layers are used to separate the layers of copper plating. All of 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 innovations.

In a common 4 layer board design, the internal layers are frequently utilized to provide power and ground connections, such as a +5 V plane layer and a Ground plane layer as the 2 internal layers, with all other circuit and part connections made on the top and bottom layers of the board. Extremely complicated board designs may have a large number of layers to make the various connections for different voltage levels, ground connections, or for linking the numerous leads on ball grid array devices and other big integrated circuit package formats.

There are normally two types of product utilized to build a multilayer board. Pre-preg product is thin layers of fiberglass pre-impregnated with an adhesive, and is in sheet kind, usually about.002 inches thick. Core product is similar to an extremely thin double sided board because it has a dielectric product, such as epoxy fiberglass, with a copper layer transferred on each side, usually.030 thickness dielectric material with 1 ounce copper layer on each side. In a multilayer board style, there are two methods utilized to build up the desired variety of layers. The core stack-up technique, which is an older innovation, uses a center layer of pre-preg product with a ISO 9001 consultants layer of core material above and another layer of core material below. This combination of one pre-preg layer and two core layers would make a 4 layer board.

The film 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 final number of layers required by the board style, sort of like Dagwood building a sandwich. This approach enables the manufacturer versatility in how the board layer densities are combined to fulfill the finished item thickness requirements by differing the number of sheets of pre-preg in each layer. As soon as the material layers are finished, the whole stack undergoes 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 many applications.

The procedure of identifying materials, processes, and requirements to fulfill the consumer's requirements for the board style based upon the Gerber file details supplied with the purchase order.

The process of transferring the Gerber file information for a layer onto an etch withstand film that is placed on the conductive copper layer.

The traditional process of exposing the copper and other areas unprotected by the etch resist movie to a chemical that eliminates the unprotected copper, leaving the secured copper pads and traces in location; newer processes use plasma/laser etching instead of chemicals to get rid of the copper product, enabling finer line meanings.

The procedure of aligning 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 material.

The procedure of drilling all the holes for plated through applications; a second drilling process is used for holes that are not to be plated through. Information on hole place and size is consisted of 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 required when holes are to be drilled through a copper location but the hole is not to be plated through. Prevent this process if possible since it includes expense to the ended up board.

The process of applying a protective masking material, a solder mask, over the bare copper traces or over the copper that has had a thin layer of solder used; the solder mask secures versus environmental damage, supplies insulation, protects versus solder shorts, and safeguards traces that run in between pads.

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

The procedure of using the markings for element designations and part lays out to the board. Might be applied to just the top 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 also permits cutting notches or slots into the board if required.

A visual evaluation of the boards; likewise 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 ways applying a voltage between various points on the board and determining if an existing flow takes place. Depending upon the board complexity, this process might need a specifically developed test fixture and test program to integrate with the electrical test system used by the board manufacturer.