The Elements of A Leading-Edge TQM 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 style might have all thru-hole components on the top or element side, a mix of thru-hole and surface area install on the top side just, a mix of thru-hole and surface mount elements on the top and surface area install parts on the bottom or circuit side, or surface area mount elements on the top and bottom sides of the board.

The boards are likewise used to electrically connect the needed leads for each component using conductive copper traces. The component pads and connection traces are etched from copper sheets laminated onto a non-conductive substrate. Printed circuit boards are developed as single agreed 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 styles 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 ISO 9001 Accreditation 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 production procedure. A multilayer board includes a number of layers of dielectric material that has been fertilized with adhesives, and these layers are used to separate the layers of copper plating. All these layers are lined up 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 innovations.

In a normal four layer board style, the internal layers are typically used 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 component connections made on the top and bottom layers of the board. Really complex board styles may have a large number of layers to make the different connections for various voltage levels, ground connections, or for connecting the lots of leads on ball grid variety devices and other large incorporated circuit bundle formats.

There are typically two types of product used to construct a multilayer board. Pre-preg material is thin layers of fiberglass pre-impregnated with an adhesive, and remains in sheet form, generally about.002 inches thick. Core product resembles an extremely thin double sided board in that it has a dielectric material, such as epoxy fiberglass, with a copper layer transferred on each side, normally.030 thickness dielectric product with 1 ounce copper layer on each side. In a multilayer board design, there are 2 approaches utilized to develop the preferred variety of layers. The core stack-up approach, which is an older technology, utilizes a center layer of pre-preg material with a layer of core material 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 movie stack-up method, a newer innovation, would have core product as the center layer followed by layers of pre-preg and copper material developed above and below to form the last variety of layers needed by the board style, sort of like Dagwood constructing a sandwich. This method permits the producer flexibility in how the board layer densities are integrated to meet the finished item density requirements by differing the number of sheets of pre-preg in each layer. Once the material layers are completed, the whole stack goes through 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 making printed circuit boards follows the actions below for most applications.

The process of identifying materials, procedures, and requirements to meet the consumer's specs for the board design based on the Gerber file details supplied 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 process of exposing the copper and other locations unprotected by the etch withstand film to a chemical that removes the unprotected copper, leaving the secured copper pads and traces in place; more recent procedures use plasma/laser etching rather of chemicals to eliminate the copper product, allowing finer line definitions.

The procedure 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 strong board material.

The process of drilling all the holes for plated through applications; a second drilling procedure is used for holes that are not to be plated through. Information on hole location 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 put 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 due to the fact that 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 actually had a thin layer of solder applied; the solder mask safeguards against ecological damage, provides insulation, secures versus solder shorts, and protects traces that run between pads.

The process of finishing the pad areas 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 been put.

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

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

A visual evaluation of the boards; also can be the procedure of inspecting wall quality for plated through holes in multi-layer boards by cross-sectioning or other approaches.

The process of looking for connection or shorted connections on the boards by means applying a voltage between numerous points on the board and figuring out if an existing flow takes place. Relying on the board complexity, this process may require a specially designed test component and test program to integrate with the electrical test system used by the board maker.