An Overview About Modern QM Systems



In electronic devices, printed circuit boards, or PCBs, are utilized to mechanically support electronic parts which have their connection ISO 9001 Accreditation leads soldered onto copper pads in surface mount applications or through rilled holes in the board and copper pads for soldering the element leads in thru-hole applications. A board design might have all thru-hole components on the leading or component side, a mix of thru-hole and surface area mount 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 install elements on the top and bottom sides of the board.

The boards are likewise used to electrically connect the needed leads for each element utilizing conductive copper traces. The element pads and connection traces are engraved 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 only, double sided with copper pads and traces on the leading 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 include a core dielectric material, such as FR-4 epoxy fiberglass, with copper plating on one or both sides. This copper plating is etched away to form the actual copper pads and connection traces on the board surface areas as part of the board production process. A multilayer board consists of a variety of layers of dielectric material that has been impregnated with adhesives, and these layers are used to separate the layers of copper plating. All these layers are lined up 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 normal 4 layer board design, the internal layers are typically utilized to provide power and ground connections, such as a +5 V airplane layer and a Ground airplane layer as the two internal layers, with all other circuit and part connections made on the leading and bottom layers of the board. Really complex board styles may have a large number of layers to make the various connections for different voltage levels, ground connections, or for connecting the many leads on ball grid variety gadgets and other big integrated circuit package formats.

There are usually two kinds of product used to build a multilayer board. Pre-preg material is thin layers of fiberglass pre-impregnated with an adhesive, and is in sheet kind, usually about.002 inches thick. Core material resembles a very thin double sided board because it has a dielectric product, such as epoxy fiberglass, with a copper layer deposited on each side, generally.030 density dielectric product with 1 ounce copper layer on each side. In a multilayer board style, there are two approaches used to develop the wanted variety of layers. The core stack-up approach, which is an older technology, uses a center layer of pre-preg product 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 film stack-up method, a newer technology, would have core product as the center layer followed by layers of pre-preg and copper material built up above and listed below to form the last variety of layers needed by the board style, sort of like Dagwood developing a sandwich. This technique allows the manufacturer versatility in how the board layer thicknesses are integrated to fulfill the completed item density requirements by differing the number of sheets of pre-preg in each layer. As soon as the product 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 a lot of applications.

The process of determining products, procedures, and requirements to satisfy the customer's specs for the board design based upon the Gerber file info provided with the purchase order.

The process of moving the Gerber file data for a layer onto an etch withstand film that is put on the conductive copper layer.

The conventional procedure of exposing the copper and other areas unprotected by the etch resist movie to a chemical that gets rid of the unguarded copper, leaving the safeguarded copper pads and traces in location; newer processes use plasma/laser etching instead of chemicals to eliminate the copper material, allowing finer line definitions.

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 process of drilling all of the holes for plated through applications; a second drilling procedure is used for holes that are not to be plated through. Information on hole area and size is consisted of in the drill drawing file.

The process 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 needed when holes are to be drilled through a copper area but the hole is not to be plated through. Avoid this procedure if possible due to the fact that it includes expense to the completed 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 used; the solder mask safeguards against environmental damage, offers insulation, secures versus solder shorts, and secures 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 happen at a later date after the components have actually been placed.

The procedure of applying the markings for component classifications and part outlines to the board. Might be applied to simply the top side or to both sides if parts are installed on both leading and bottom sides.

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

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

The process of checking for continuity or shorted connections on the boards by ways applying a voltage in between different points on the board and figuring out if a current flow occurs. Depending upon the board complexity, this process may need a specially developed test fixture and test program to incorporate with the electrical test system used by the board maker.