Circuit Internal

Circuit Internal

Fundamentals of manufacturing printed circuits

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 mount applications or through holes in the board and filled with copper pads soldering the component leads through hole applications. A board design may have all the components of the hole at the top or component, a mixture of thru-hole and surface mount on the upper side of the machine, a mix of thru-hole and surface mount components on top and the mounting surface components on the bottom or side of the circuit, or surface mount components on the top and bottom sides of the board.

The tables also are used electrically connecting cables needed for each component using conductive traces of copper. Component pads and connection traces are etched from copper sheets laminated on a nonconductive substrate. Printed circuit boards are designed as a single face with copper pads and traces on one side of the board only, Double-sided with copper pads and traces on top and bottom sides of the board, or multilayer designs with copper pads and traces on top and bottom of the board with a variable number of internal copper layers with traces and connections.

panels Single or double face composed of a dielectric core, such as fiberglass FR-4 epoxy with copper plating on one or both sides. This copper is etched away to form copper pads and connection traces in real sealing surfaces as part of board fabrication process. A multilayer board is composed of a series of layers of dielectric material that has been impregnated with adhesive, and these layers are used to separate the layers of copper plating. All these layers are aligned and then bonded into a single board structure under heat and pressure. multiple boards layers with 48 or more layers can be produced with current technologies.

In a typical family of four plate design layer, the inner layers are used often to maintain power and ground connections, such as a flat layer of +5 V and a ground plane layer as the two inner layers, with all other circuits and connections components made in the upper and lower layer of the board. very complex board designs may have a large number of layers to make different connections of different voltage levels, ground connections or cables to connect many of the ball grid array devices and other large-format integrated circuit package.

Generally There are two types of material used to construct a multilayer board. Pre-preg material is thin layers of fiberglass pre-impregnated with an adhesive, and is in the form of leaves, usually about 0.002 inches thick. Main material is similar to a very thin sheet of double-sided as it has a dielectric material, such as fiberglass epoxy with a layer of copper deposited on each side, usually .030 thickness dielectric material with one ounce copper layer on each side. In a board design multilayer, There are two methods used to build the necessary number of layers. The basic method of stack-which is an older technology, uses a center layer pre-preg material with a layer of core material above and another layer of base material below. This combination of pre-preg layer and two main layers that make a board 4 layers.

The method of the film stack-up, a new technology, there would be material at the center of the base layer followed by layers of pre-preg material and Copper built above and below to form the final number of layers required by the board design, sort of like building a Dagwood sandwich. This method allows for flexibility in how the manufacturer of thicknesses of the layers are combined board to meet the finished product thickness requirements varying the number of pre-preg sheets in each layer. Once the layers of material have been completed, the entire stack is subjected to heat and pressure that makes the adhesive pre-preg for linking the core and pre-preg layers together into a single entity.

The manufacturing process of printed circuit boards following steps for most applications:

Basic Steps for the manufacture of printed circuits:

1. Setup – the process of identifying materials, processes and requirements to meet the specifications customer for the design of the motherboard in the Gerber file information provided with the purchase order.

2. Images – the process of transferring the data file Gerber for an etch resist layer in a film that is placed on the layer of copper conductor.

3. Etching – the traditional process of exposure to copper and other areas not protected by the etch resist film to a chemical that removes the unprotected copper, leaving the protected copper pads and traces on the site, new processes use plasma / laser etching instead of chemicals to eliminate the copper material, allowing finer line definitions.

4. Multilayer Pressing – the process of aligning the conductive copper and insulating dielectric layers and pressing them by means of heat to activate the adhesive on the dielectric layers to form a solid material on board.

5. Drilling – the process of drilling any holes plated through applications, a drilling process the second is used for holes that must be plated through. Information on location and size of the hole is in the drill drawing file.

6. Coating – the application process copper pads, traces, and drilled through holes that are plated through, which together are placed in a bath copper electrical charge.

7. Second drill – this is necessary when holes are drilled through a copper area, but the hole not going through silver. Avoid as much as possible this process, as it increases the cost of finished board.

8. Masking – The process of applying a masking material of protection, a solder mask on bare copper traces or copper that has had a thin layer of solder applied, the solder mask protects against environmental damage, provides insulation, protection against short welding, and protect the trails that run between pads.

9. Finish – the coating process of the pad areas with a thin layer of solder to set the table for eventual wave soldering or reflow soldering process will occur at a later date after the components have been placed.

10. Screen printing – the process of applying for appointment marks the components and component projects to the Board. It can be applied only to the top or both sides if components are mounted on both top and bottom faces.

11. Routing – The process of separation of several cards from a panel of identical boards, this process also allows cutting notches or slots on the board if necessary.

12. Quality control – a visual inspection of the joints may also be the quality inspection process of the wall plated through holes in the boards of multiple layers cross-section or other methods.

13. Electrical Testing – the process of checking for continuity or shorted connections on the boards by applying a voltage between various points on the board and determine if a current flow. Depending on the complexity of table, this process can take a stand Specially designed test and integration test program with electrical test system used by the motherboard manufacturer.

About the Author

Jim Usery
Sales and Marketing Director
Innovative Circuits Inc.
311A S Parkway St
Corinth, MS 38834
office 662-287-2007
toll free 866-887-7381
fax 662-665-9275
email jusery@icimfg.com

At Innovative Circuits Inc., we assemble a variety of surface mount and thru-hole boards each day for our customers. We also provide printed circuit board layout design services along with conversions from thru-hole designs to surface mount designs for our customers. We do not manufacture bare printed circuit boards ourselves but we do work with a number of board houses to produce the bare boards that we use every day to assemble our customers’ products. As a result, we have become very familiar with the board manufacturing processes and we wanted to share our knowledge with others who may not have our level of exposure to printed circuit boards.

How to find internal resistance of a Cell Phone?

A cell has an open circuit voltage of 1.47V and 1.17V voltage across a load of 150 mA. What is the internal resistance of the cell? I'm not sure how to solve this given the terminal voltage and load current, is law Ohm's fair?

See the circuit breaker is a potential. While the divided voltage is measured, is not "released" the circuit. (So I_out = 0) = Vin http://en.wikipedia.org/wiki/Potential_divider the cells Vunloaded load voltage Vout = Voltage V_loaded cells when loaded. Z1 = R_internal = internal resistance of the cell circuit Z2 = = R_load resistance When there is no load connected in the circuit is R_load all purposes infinite, and in that case V_loaded = V_unloaded Applying Ohm's Law gives the following relationship Vloaded = V_unloaded R_load * / … … (+ R_internal R_load) — Ah! Now I see the problem! you do not know the load resistance or internal resistance (or R_internal R_load)! As a series circuit the current flowing through the internal resistance (= I_loaded) is the same in all parts of the circuit. The potential across different internal resistance is the difference between the charge and discharge voltages for the cell. So it is about Ohm's law! V_unloaded-V_loaded = I_loaded * R_internal R_internal = (V_unloaded-V_loaded) / I_loaded to facts known at the V_unloaded = [V 1.47 V_loaded] = 1.17 [V] I_loaded = 150 (E-3) [A] = R_internal ((1.47-1.17) / 150 (E-3)) [Ohm] R_internal = (0.3/0.15) [ Ohm] R_internal = 2] Ohm [