QM Systems - Their Design and Advantages

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

The boards are likewise utilized to electrically link the needed leads for each part using 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 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 designs 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 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 surfaces as part of the board manufacturing procedure. A multilayer board includes a number of layers of dielectric product that has actually been impregnated 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 typical four layer board style, the internal layers are typically utilized 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 component connections made on the leading and bottom layers of the board. Really complicated board designs might have a large number of layers to make the numerous connections for different voltage levels, ground connections, or for connecting the numerous leads on ball grid range devices and other big integrated circuit bundle formats.

There are normally 2 types of material utilized to construct a multilayer board. Pre-preg material is thin layers of fiberglass pre-impregnated with an adhesive, and is in sheet type, typically about.002 inches thick. Core product is similar to an extremely 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 density dielectric material with 1 ounce copper layer on each side. In a multilayer board style, there are two techniques used to develop the preferred number of layers. The core stack-up technique, which is an older innovation, utilizes a center layer of pre-preg product with a layer of core material above and another layer of core material listed below. This combination of one pre-preg layer and two core layers would make a 4 layer board.

The movie stack-up technique, a more recent technology, would have core material as the center layer followed by layers of pre-preg and copper material developed above and listed below to form the final number of layers needed by the board design, sort of like Dagwood building a sandwich. This approach enables the maker versatility in how the board layer densities are combined to fulfill the completed product density requirements by differing the variety of sheets of pre-preg in each layer. As soon as 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 process of producing printed circuit boards follows the steps listed below for most applications.

The procedure of determining products, procedures, and requirements to satisfy the consumer's requirements for the board style based on the Gerber file details offered with the purchase order.

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

The traditional procedure of exposing the copper and other areas unprotected by the etch withstand 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 remove the copper product, allowing finer line definitions.

The process 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 product.

The procedure of drilling all the holes for plated through applications; a second drilling process is utilized for holes that are not to be plated through. Details on hole area 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 required when holes are to be drilled through a copper location however the hole is not to be plated through. Prevent this process if ISO 9001 Certification Consultants possible due to the fact that 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 had a thin layer of solder applied; the solder mask protects against ecological damage, supplies insulation, safeguards against solder shorts, and protects traces that run in between pads.

The procedure of finish the pad areas with a thin layer of solder to prepare the board for the eventual wave soldering or reflow soldering procedure that will occur at a later date after the elements have been positioned.

The process of using the markings for element designations and element describes to the board. May be used to simply the top side or to both sides if elements are mounted on both top and bottom sides.

The process of separating multiple boards from a panel of similar boards; this procedure also enables cutting notches or slots into the board if required.

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

The procedure of looking for connection or shorted connections on the boards by ways using a voltage in between various points on the board and figuring out if an existing flow takes place. Relying on the board complexity, this process may need a specially created test fixture and test program to incorporate with the electrical test system used by the board producer.