Quality Systems - Their Structure and Advantages

In electronic devices, printed circuit boards, or PCBs, are used to mechanically support electronic elements 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 component side, a mix of thru-hole and surface install on the top side just, a mix of thru-hole and surface area install parts on the top side and surface area mount parts on the bottom or circuit side, or surface mount components on the top and bottom sides of the board.

The boards are also utilized to electrically connect the needed leads for each component utilizing conductive copper traces. The part pads and connection traces are engraved 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 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 top and bottom of board with a variable number 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 surfaces 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 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 Your Domain Name today's innovations.

In a common 4 layer board style, the internal layers are often utilized to supply 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 component connections made on the leading and bottom layers of the board. Very intricate board designs might have a large number of layers to make the different connections for various voltage levels, ground connections, or for connecting the numerous leads on ball grid selection devices and other large integrated circuit bundle formats.

There are typically two types of product used to build a multilayer board. Pre-preg product is thin layers of fiberglass pre-impregnated with an adhesive, and is in sheet form, generally about.002 inches thick. Core material 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, usually.030 thickness dielectric product with 1 ounce copper layer on each side. In a multilayer board style, there are two techniques used to develop the desired number of layers. The core stack-up method, which is an older technology, uses a center layer of pre-preg product with a layer of core product above and another layer of core material below. This mix of one pre-preg layer and two core layers would make a 4 layer board.

The movie stack-up method, a newer technology, would have core material as the center layer followed by layers of pre-preg and copper product built up above and below to form the last variety of layers needed by the board design, sort of like Dagwood building a sandwich. This technique enables the manufacturer flexibility in how the board layer densities are integrated to satisfy the finished item thickness requirements by varying the variety of sheets of pre-preg in each layer. When the material layers are completed, the entire 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 steps listed below for most applications.

The process of identifying products, procedures, and requirements to meet the client's requirements for the board design based upon the Gerber file information provided with the purchase order.

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

The traditional procedure of exposing the copper and other locations unprotected by the etch resist movie to a chemical that gets rid of the unprotected copper, leaving the safeguarded copper pads and traces in location; more recent procedures use plasma/laser etching rather of chemicals to get rid of the copper product, permitting 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 solid board product.

The process 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 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 needed when holes are to be drilled through a copper location however the hole is not to be plated through. Prevent this procedure if possible because it includes expense to the completed board.

The procedure of using a protective masking product, 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 protects versus ecological damage, provides insulation, protects against solder shorts, and secures traces that run in between pads.

The process of finish the pad locations 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 parts have actually been placed.

The process of applying the markings for part designations and component outlines to the board. Might be used to simply the top side or to both sides if elements are installed on both leading and bottom sides.

The procedure 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 examination 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 approaches.

The process of checking for connection or shorted connections on the boards by means using a voltage in between various points on the board and figuring out if a current circulation occurs. Relying on the board intricacy, this procedure may require a specifically developed test component and test program to integrate with the electrical test system used by the board maker.