A Look Inside QM Systems



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

The boards are likewise utilized to electrically link the required leads for each component utilizing conductive copper traces. The component 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 agreed copper pads and traces on the leading and bottom sides of the board, or multilayer designs 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 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 manufacturing procedure. A multilayer board consists of a variety 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 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 common four layer board design, the internal layers are frequently used to offer power and ground connections, such as a +5 V aircraft layer and a Ground aircraft layer as the two internal layers, with all other circuit and part connections made on the leading and bottom layers of the board. Very intricate board designs might have a large number of layers to make the numerous connections for various More interesting details here voltage levels, ground connections, or for connecting the many leads on ball grid variety gadgets and other big integrated circuit plan formats.

There are usually 2 types of product used to build a multilayer board. Pre-preg product is thin layers of fiberglass pre-impregnated with an adhesive, and is in sheet form, typically about.002 inches thick. Core product is similar to a very thin double sided board in that it has a dielectric material, such as epoxy fiberglass, with a copper layer deposited on each side, usually.030 thickness dielectric product with 1 ounce copper layer on each side. In a multilayer board design, there are 2 methods utilized to develop the wanted 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 material below. This combination of one pre-preg layer and two core layers would make a 4 layer board.

The film stack-up approach, a newer technology, would have core product 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 style, sort of like Dagwood building a sandwich. This technique permits the producer flexibility in how the board layer thicknesses are combined to fulfill the ended up item thickness requirements by differing the number of sheets of pre-preg in each layer. When 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 procedure of making printed circuit boards follows the steps listed below for the majority of applications.

The procedure of identifying products, processes, and requirements to meet the customer's specifications for the board design based upon the Gerber file details provided with the order.

The process of transferring the Gerber file data for a layer onto an etch withstand film that is placed on the conductive copper layer.

The conventional process of exposing the copper and other locations unprotected by the etch resist movie to a chemical that removes the unprotected copper, leaving the secured copper pads and traces in location; newer procedures utilize plasma/laser etching instead of chemicals to get rid of the copper material, permitting finer line definitions.

The procedure of lining up the conductive copper and insulating dielectric layers and pushing them under heat to trigger the adhesive in the dielectric layers to form a strong board product.

The process of drilling all the holes for plated through applications; a 2nd drilling procedure is utilized for holes that are not to be plated through. Information on hole area and size is included in the drill drawing file.

The procedure of using 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 needed when holes are to be drilled through a copper area however the hole is not to be plated through. Avoid this process if possible due to the fact that it adds expense to the finished board.

The procedure 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 secures versus environmental damage, supplies insulation, protects versus solder shorts, and safeguards traces that run between pads.

The procedure of covering the pad locations with a thin layer of solder to prepare the board for the ultimate wave soldering or reflow soldering procedure that will occur at a later date after the components have actually been placed.

The procedure of using the markings for component designations and component details to the board. May be used to just the top side or to both sides if elements are installed on both leading and bottom sides.

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

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

The process of checking for connection or shorted connections on the boards by ways applying a voltage in between various points on the board and figuring out if an existing flow happens. Relying on the board intricacy, this process might require a specially designed test fixture and test program to integrate with the electrical test system used by the board maker.