TQM Systems Guide

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

The boards are likewise used to electrically connect the required leads for each part 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 developed as single agreed copper pads and traces on one side of the board just, 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 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 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 surfaces as part of the board production process. A multilayer board includes Click here a variety of layers of dielectric product that has been fertilized with adhesives, and these layers are used to separate the layers of copper plating. All of these layers are aligned and after that 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 used to supply power and ground connections, such as a +5 V plane layer and a Ground aircraft layer as the two internal layers, with all other circuit and element connections made on the top and bottom layers of the board. Very complex board designs might have a large number of layers to make the various connections for different voltage levels, ground connections, or for connecting the numerous leads on ball grid variety gadgets and other big integrated circuit package formats.

There are generally two types of product utilized to construct a multilayer board. Pre-preg material is thin layers of fiberglass pre-impregnated with an adhesive, and remains in sheet type, usually about.002 inches thick. Core product resembles 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, normally.030 density dielectric material with 1 ounce copper layer on each side. In a multilayer board design, there are 2 approaches utilized to develop the wanted number of layers. The core stack-up method, which is an older innovation, utilizes a center layer of pre-preg product with a layer of core product above and another layer of core material below. This combination of one pre-preg layer and two core layers would make a 4 layer board.

The movie stack-up approach, a more recent innovation, 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 final variety of layers required by the board style, sort of like Dagwood building a sandwich. This technique allows the manufacturer flexibility in how the board layer densities are integrated to fulfill the ended up product density requirements by differing the variety of sheets of pre-preg in each layer. Once the product layers are completed, the entire stack is subjected to 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 manufacturing printed circuit boards follows the steps below for a lot of applications.

The procedure of determining products, procedures, and requirements to fulfill the consumer's requirements for the board design based on the Gerber file info provided with the purchase order.

The process of moving the Gerber file data for a layer onto an etch resist movie that is placed on the conductive copper layer.

The conventional process of exposing the copper and other areas unprotected by the etch resist movie to a chemical that removes the unprotected copper, leaving the secured copper pads and traces in place; newer processes utilize plasma/laser etching rather of chemicals to eliminate the copper product, enabling finer line meanings.

The procedure of aligning the conductive copper and insulating dielectric layers and pushing them under heat to activate 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 second drilling procedure is used for holes that are not to be plated through. Info on hole area and size is contained 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 required when holes are to be drilled through a copper location but the hole is not to be plated through. Avoid this procedure if possible since it includes expense to the ended up board.

The process of applying a protective masking product, a solder mask, over the bare copper traces or over the copper that has had a thin layer of solder used; the solder mask protects against environmental damage, supplies insulation, safeguards against solder shorts, and protects traces that run in between pads.

The procedure 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 elements have been put.

The procedure of using the markings for component classifications and component lays out to the board. May be used to simply the top side or to both sides if parts are installed on both top and bottom sides.

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

A visual inspection 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 procedure of looking for continuity or shorted connections on the boards by means using a voltage between numerous points on the board and determining if an existing circulation takes place. Depending upon the board intricacy, this procedure may need a specially created test fixture and test program to incorporate with the electrical test system utilized by the board maker.