Present Day Quality Management System Advantages

In electronics, printed circuit boards, or PCBs, are used to mechanically support electronic parts 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 element leads in thru-hole applications. A board style may have all thru-hole components on the top or component side, a mix of thru-hole and surface area install on the top just, a mix of thru-hole and surface install elements on the top side and surface area mount elements on the bottom or circuit side, or surface area install parts on the top and bottom sides of the board.

The boards are also used to electrically connect the required leads for each part using conductive copper traces. The element pads and connection traces are engraved from copper sheets laminated onto a non-conductive substrate. Printed circuit boards are designed as single agreed 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 the 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 real copper pads and connection traces on the board surface areas as part of the board production procedure. A multilayer board consists of a number of layers of dielectric product that has actually been fertilized with adhesives, and these layers are utilized 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 technologies.

In a normal four layer board design, the internal layers are often used to offer 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 part connections made on the top and bottom layers of the board. Extremely complicated board styles might have a large number of layers to make the numerous connections for different voltage levels, ground connections, or for linking the numerous leads on ball grid range gadgets and other large incorporated circuit bundle formats.

There are normally two types of material utilized to construct a multilayer board. Pre-preg product is thin layers of fiberglass pre-impregnated with an adhesive, and is in sheet kind, normally about.002 inches thick. Core product is resource similar to a very thin double sided board in that it has a dielectric product, such as epoxy fiberglass, with a copper layer deposited on each side, typically.030 thickness dielectric product with 1 ounce copper layer on each side. In a multilayer board style, there are 2 techniques used to build up the preferred variety of layers. The core stack-up approach, which is an older innovation, uses a center layer of pre-preg material with a layer of core product above and another layer of core product below. This mix of one pre-preg layer and 2 core layers would make a 4 layer board.

The movie stack-up approach, 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 number of layers required by the board style, sort of like Dagwood building a sandwich. This approach allows the maker versatility in how the board layer densities are combined to fulfill the finished product thickness requirements by differing the number of sheets of pre-preg in each layer. When the product layers are finished, 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 process of making printed circuit boards follows the actions below for many applications.

The procedure of figuring out products, processes, and requirements to satisfy the consumer's specifications for the board style based on the Gerber file info supplied with the purchase order.

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

The conventional procedure of exposing the copper and other locations unprotected by the etch withstand film to a chemical that removes the unprotected copper, leaving the protected copper pads and traces in place; newer processes use plasma/laser etching instead of chemicals to eliminate the copper product, permitting finer line meanings.

The procedure of lining up the conductive copper and insulating dielectric layers and pressing them under heat to activate the adhesive in the dielectric layers to form a strong 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. Details on hole location and size is included 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 positioned in an electrically charged bath of copper.

This is required when holes are to be drilled through a copper location however the hole is not to be plated through. Prevent this procedure if possible due to the fact that it adds expense to the finished board.

The process of using 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, safeguards versus solder shorts, and secures traces that run in between pads.

The process of finishing the pad locations with a thin layer of solder to prepare the board for the eventual wave soldering or reflow soldering process that will take place at a later date after the parts have actually been positioned.

The procedure of applying the markings for part classifications and element details to the board. May be used to simply the top or to both sides if parts are installed on both leading and bottom sides.

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

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 approaches.

The procedure of checking for connection or shorted connections on the boards by means using a voltage between different points on the board and identifying if a current flow occurs. Relying on the board intricacy, this process might require a specifically created test component and test program to incorporate with the electrical test system used by the board producer.