The Components of A Leading-Edge QM System

In electronic devices, printed circuit boards, or PCBs, are utilized 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 part leads in thru-hole applications. A board design may have all thru-hole components on the top or component side, a mix of thru-hole and surface area mount on the top side just, a mix of thru-hole and surface install parts on the top and surface area install parts on the bottom or circuit side, or surface install parts on the top and bottom sides of the board.

The boards are also utilized to electrically connect the required leads for each part utilizing conductive copper traces. The element pads and connection traces are etched 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 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 product, such as FR-4 See more here 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 manufacturing process. A multilayer board consists of a number of layers of dielectric material that has actually been impregnated with adhesives, and these layers are used to separate the layers of copper plating. All of these layers are lined up 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 common four layer board design, the internal layers are typically used 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 element connections made on the top and bottom layers of the board. Extremely intricate board designs might have a a great deal of layers to make the numerous connections for various voltage levels, ground connections, or for connecting the numerous leads on ball grid array devices and other big integrated circuit plan formats.

There are usually two types of product utilized to construct a multilayer board. Pre-preg material is thin layers of fiberglass pre-impregnated with an adhesive, and is in sheet type, normally about.002 inches thick. Core product is similar to a really thin double sided board in that it has a dielectric material, such as epoxy fiberglass, with a copper layer transferred on each side, typically.030 density dielectric material with 1 ounce copper layer on each side. In a multilayer board design, there are two techniques utilized to build up the preferred variety 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 material above and another layer of core product listed below. This combination of one pre-preg layer and 2 core layers would make a 4 layer board.

The movie stack-up technique, a newer technology, would have core product as the center layer followed by layers of pre-preg and copper product developed above and listed below to form the final number of layers required by the board style, sort of like Dagwood constructing a sandwich. This technique enables the producer versatility in how the board layer thicknesses are combined to fulfill the completed product thickness requirements by varying the variety of sheets of pre-preg in each layer. Once the product layers are completed, the entire stack goes through 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 producing printed circuit boards follows the steps listed below for a lot of applications.

The procedure of identifying materials, procedures, and requirements to fulfill the customer's requirements for the board design based on the Gerber file info supplied with the purchase order.

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

The standard process of exposing the copper and other areas unprotected by the etch resist movie to a chemical that removes the unguarded copper, leaving the safeguarded copper pads and traces in location; more recent procedures utilize plasma/laser etching rather of chemicals to remove the copper material, permitting finer line meanings.

The process 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 solid board material.

The process of drilling all of the holes for plated through applications; a second drilling process is used for holes that are not to be plated through. Details on hole area and size is consisted of 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 put 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. Prevent this procedure if possible because it adds expense to the finished board.

The procedure 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 applied; the solder mask safeguards against ecological damage, provides insulation, protects against 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 ultimate wave soldering or reflow soldering procedure that will take place at a later date after the components have actually been put.

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

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

A visual assessment 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 approaches.

The procedure of checking for connection or shorted connections on the boards by ways applying a voltage in between different points on the board and determining if a present circulation takes place. Depending upon the board complexity, this process might require a specifically developed test fixture and test program to integrate with the electrical test system utilized by the board maker.