Everything About Quality Management Systems



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 install 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 elements on the leading or element side, a mix of thru-hole and surface area mount on the top side only, a mix of thru-hole and surface area install elements on the top and surface mount components on the bottom or circuit side, or surface install components on the top and bottom sides of the board.

The boards are likewise used to electrically link the needed leads for each component using conductive copper traces. The part 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 only, double agreed 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 include 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 material that has been fertilized with adhesives, and these layers are used to separate the layers of copper plating. All these layers are aligned 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 4 layer board style, the internal layers are typically utilized to supply power and ground connections, such as a +5 V aircraft layer and a Ground airplane layer as the 2 internal layers, with all other circuit and part connections made on the leading and bottom layers of the board. Really complicated board designs might have a a great deal of layers to make the various connections for various voltage levels, ground connections, or for connecting the numerous leads on ball grid selection devices and other large integrated circuit package formats.

There are typically two kinds of product utilized to build a multilayer board. Pre-preg product is thin layers of fiberglass pre-impregnated with an adhesive, and remains in sheet type, usually about.002 inches thick. Core product resembles an extremely thin double sided board because it has a dielectric product, such as epoxy fiberglass, with a copper layer transferred on each side, usually.030 density dielectric material with 1 ounce copper layer on each side. In a multilayer board style, there are 2 methods used to develop the wanted number of layers. The core stack-up approach, which is an older innovation, 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 movie stack-up approach, a more recent technology, would have core material as the center layer followed by layers of pre-preg and copper product developed above and below to form the last variety of layers needed by the board style, sort of like Dagwood building a sandwich. This method allows the maker versatility in how the board layer densities are combined to fulfill the completed item thickness requirements by differing the variety of sheets of pre-preg in each layer. Once the product layers are finished, 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 making printed circuit boards follows the steps listed below for a lot of applications.

The process of determining products, processes, and requirements to fulfill the consumer's specs for the board style based on the Gerber file details supplied with the order.

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

The traditional process of exposing the copper and other areas unprotected by the etch withstand film to a chemical that gets rid of the unprotected copper, leaving the secured copper pads and traces in location; more recent processes use plasma/laser etching instead of chemicals to eliminate the copper material, permitting finer line meanings.

The procedure 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 process of drilling all the holes for plated through applications; a 2nd drilling procedure is used for holes that are not to be plated through. Details on hole area and size is included 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 placed 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 process if possible since it adds expense to the ended up 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 applied; the solder mask secures versus environmental damage, supplies insulation, secures against solder shorts, and secures traces that run between pads.

The process of covering 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 components have actually been positioned.

The procedure of using the markings for element classifications and component lays out to the board. Might be applied to simply the top side or to both sides if components are mounted on both leading and bottom sides.

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

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 methods.

The process of checking for continuity or shorted connections on the boards by ways applying a voltage between numerous points on the board and determining if See more a present flow takes place. Depending upon the board complexity, this procedure might require a specifically developed test component and test program to incorporate with the electrical test system used by the board producer.