PCBs are rugged, inexpensive, and can be highly reliable. They require much more layout effort and higher initial cost than either wire-wrapped or point-to-point constructed circuits, but are much cheaper and faster for high-volume production. Much of the electronics industry's PCB design, assembly, and quality control needs are set by standards that are published by the IPC organization.photomask is usually prepared with a photoplotter from data produced by a technician using CAM, or computer-aided manufacturing software. Laser-printed transparencies are typically employed for phototools; however, direct laser imaging techniques are being employed to replace phototools for high-resolution requirements.
PCB milling uses a two or three-axis mechanical milling system to mill away the copper foil from the substrate. A PCB milling machine (referred to as a 'PCB Prototyper') operates in a similar way to a plotter, receiving commands from the host software that control the position of the milling head in the x, y, and (if relevant) z axis. Data to drive the Prototyper is extracted from files generated in PCB design software and stored in HPGL or Gerber file format.
"Additive" processes also exist. The most common is the "semi-additive" process. In this version, the unpatterned board has a thin layer of copper already on it. A reverse mask is then applied. (Unlike a subtractive process mask, this mask exposes those parts of the substrate that will eventually become the traces.) Additional copper is then plated onto the board in the unmasked areas; copper may be plated to any desired weight. Tin-lead or other surface platings are then applied. The mask is stripped away and a brief etching step removes the now-exposed original copper laminate from the board, isolating the individual traces.

The additive process is commonly used for multi-layer boards as it facilitates the plating-through of the holes (to produce conductive vias) in the circuit board.

[edit] Lamination
Some PCBs have trace layers inside the PCB and are called multi-layer PCBs. These are formed by bonding together separately etched thin boards.

[edit] Drilling
Holes, or vias, through a PCB are typically drilled with tiny drill bits made of solid tungsten carbide. The drilling is performed by automated drilling machines with placement controlled by a drill tape or drill file. These computer-generated files are also called numerically controlled drill (NCD) files or "Excellon files". The drill file describes the location and size of each drilled hole.

When very small vias are required, drilling with mechanical bits is costly because of high rates of wear and breakage. In this case, the vias may be evaporated by lasers. Laser-drilled vias typically have an inferior surface finish inside the hole. These holes are called micro vias.

It is also possible with controlled-depth drilling, laser drilling, or by pre-drilling the individual sheets of the PCB before lamination, to produce holes that connect only some of the copper layers, rather than passing through the entire board. These holes are called blind vias when they connect an internal copper layer to an outer layer, or buried vias when they connect two or more internal copper layers and no outer layers.

The walls of the holes, for boards with 2 or more layers, are plated with copper to form plated-through holes that electrically connect the conducting layers of the PCB. For multilayer boards, those with 4 layers or more, drilling typically produces a smear comprised of the bonding agent in the laminate system. Before the holes can be plated through, this smear must be removed by a chemical de-smear process, or by plasma-etch.

[edit] Exposed conductor plating and coating
The places to which components will be mounted are typically plated, because bare copper oxidizes quickly, and therefore is not readily solderable. Traditionally, any exposed copper was plated with solder by hot air solder levelling (HASL). This solder was a tin-lead alloy, however new solder compounds are now used to achieve compliance with the RoHS directive in the EU, which restricts the use of lead. Other platings used are OSP (organic surface protectant), immersion silver (IAg), immersion tin, electroless nickel with immersion gold coating (ENIG), and direct gold. Edge connectors, placed along one edge of some boards, are often gold plated.

Electrochemical migration (ECM) is the growth of conductive metal filaments on or in a printed circuit board (PCB) under the influence of a DC voltage bias.[1][2]

[edit] Solder resist
Areas that should not be soldered to may be covered with a polymer solder resist (solder mask) coating. The solder resist prevents solder from bridging between conductors and thereby creating short circuits. Solder resist also provides some protection from the environment.

[edit] Printed circuit assembly
After the printed circuit board (PCB) is completed, electronic components must be attached to form a functional printed circuit assembly[3][4], or PCA (sometimes called a "printed circuit board assembly" PCBA). In through-hole construction, component leads are inserted in holes. In surface-mount construction, the components are placed on pads or lands on the outer surfaces of the PCB. In both kinds of construction, component leads are electrically and mechanically fixed to the board with a molten metal solder.

There are a variety of soldering techniques used to attach components to a PCB. High volume production is usually done with machine placement and bulk wave soldering or reflow ovens, but skilled technicians are able to solder very tiny parts (for instance 0201 packages which are 0.02" by 0.01") by hand under a microscope, using tweezers and a fine tip soldering iron for small volume prototypes. Some parts are impossible to solder by hand, such as ball grid array (BGA) packages.

Often, through-hole and surface-mount construction must be combined in a single PCA because some required components are available only in surface-mount packages, while others are available only in through-hole packages. Another reason to use both methods is that through-hole mounting can provide needed strength for components likely to endure physical stress, while components that are expected to go untouched will take up less space using surface-mount techniques.

After the board has been populated it may be tested in a variety of ways:

While the power is off, visual inspection, automated optical inspection. JEDEC guidelines for PCB component placement, soldering, and inspection are commonly used to maintain quality control in this stage of PCB manufacturing.
While the power is off, analog signature analysis, power-off testing.
While the power is on, in-circuit test, where physical measurements (i.e. voltage, frequency) can be done.
While the power is on, functional test, just checking if the PCB does what it had been designed for.
To facilitate these tests, PCBs may be designed with extra pads to make temporary connections. Sometimes these pads must be isolated with resistors. The in-circuit test may also exercise boundary scan test features of some components. In-circuit test systems may also be used to program nonvolatile memory components on the board.

In boundary scan testing, test circuits integrated into various ICs on the board form temporary connections between the PCB traces to test that the ICs are mounted correctly. Boundary scan testing requires that all the ICs to be tested use a standard test configuration procedure, the most common one being the Joint Test Action Group (JTAG) standard.

When boards fail the test, technicians may desolder and replace failed components (professional term: rework).

[edit] Protection and packaging
PCBs intended for extreme environments often have a conformal coat, which is applied by dipping or spraying after the components have been soldered. The coat prevents corrosion and leakage currents or shorting due to Electronic Structural Components, Metalworking and Fabrication Services, Engineering Design Software, Connectors, Sheet Metal Patterning or Rigidizing or Suppliers, Printed Circuit Boards (PCB), Sheet Metal Fabrication, Sockets, Printed Circuit Artwork, Printed Circuit Board (PCB) Layout Services, Printed Circuit Boards (PCB) to Specification available from Douglas Electronics Inc based in San Leandro, CA. Click the links below to visit our website or contact us via our profile page. More...
Eagle Contract Services LLC Santa Clara, CA, USA
www.China-low-cost-PCB.org//www.China-low-cost-PCB.org....electrical engineering.eagle-contract.com
Engineering Services, Printed Circuit Consultancy or Design or Production Services, Electronic Cable Assemblies or Harnesses, Engineering Design Software, Electromechanical Assembly Production or Services, Electronic Contract Manufacturing Services, Mechanical Assembly Services, Printed Circuit Board (PCB) Assemblies, Printed Circuit Board (PCB) Assembly, Printed Circuit Board (PCB) Design, Printed Circuits, Procurement Services, Surface Mounted (SM) Assembly Services, Controller Displays, Printed Circuit Board (PCB) Fabrication Services, Printed Circuit Board (PCB) Layout Services available from Eagle Contract Services LLC based in Santa Clara, CA. Click the links below to visit our website or contact us via our profile page. More...
Surface Mount Prdt Dvlpt Milpitas, CA, USA
www.China-low-cost-PCB.org//www.China-low-cost-PCB.org....electrical engineering.smpd.com
Engineering Services, Computer Software, Electrical and Electronic Technical Services, Subcontract Assembly Services, Mathematical or Statistical Software, Process Control Software, Statistical Software, Printed Circuit Board (PCB) Assemblies, Printed Circuit Board (PCB) Design, Surface Mounted (SM) Assembly Services, Control Software, Purchasing Software, Printed Circuit Board (PCB) Layout Services, Manufacturing System Software available from Surface Mount Prdt Dvlpt based in Milpitas, CA. Click the links below to visit our website or contact us via our profile page. More...
East Bay Consulting San Leandro, CA, USA
www.China-low-cost-PCB.org//www.China-low-cost-PCB.org....electrical engineering.eastbayconsulting.com
Engineering Services, Electrical and Electronic Technical Services, Engineering Design Software, Embedded Control Systems, Printed Circuit Board (PCB) Design, Product Design, Printed Circuit Board (PCB) Layout Services, Printed Circuit Board (PCB) Testing, Systems Design available from East Bay Consulting based in San Leandro, CA. Click the links below to visit our website or contact us via our profile page. More...
CAD Design, Inc. Poway, CA, USA
www.China-low-cost-PCB.org//www.China-low-cost-PCB.org....electrical engineering.caddesignsd.com
CAD Design offers complete skillfull design services for the electronics market
EMS - a Division of Sandberg Industries, Inc. Santa Ana, CA, USA
www.China-low-cost-PCB.org//www.China-low-cost-PCB.org....electrical engineering.sandberg.com
EMS (Electronic Manufacturing Services) is your outsource resource for electronic PCB/SMT assembly work, wiring services, wire wrapping and legacy hardware upgrading. Low to medium volumes, confidential projects, complexity, and conformance to difficult specifications… we deliver the quality required. Our defense, aerospace, medical device, telecommunications, and commercial customers demand EMS’ high reliability and quality conformance. Our additional Mexican facilities allows EMS to be a truly outsource (off-shore) resource. More...
Schmart BOARD Fremont, CA, USA
www.China-low-cost-PCB.org//www.China-low-cost-PCB.org....electrical engineering.schmartboard.com
Schmart boards are pre-traced printed circuit boards that are connectable like building blocks. We call this patent pending product, "Electronic Circuit Building Blocks". They allow one to build electronic circuits on a Schmart Board block by block, and then connect the blocks together to form a functional board. Schmart board supports both through-hole and surface mount components! More...
SunMan Engineering, Inc. San Jose, CA, USA
www.China-low-cost-PCB.org//www.China-low-cost-PCB.org....electrical engineering.sunmantechnology.com
SunMan Engineering provides engineering turnkey services from concept to prototyping. Services include prototyping, PCB design and layout, fabrication, and assembly, as well as circuit design (digital / analog), FPGA and CPLD design and product development. More...
AGT Technologies Woodland Hills, CA, USA
www.China-low-cost-PCB.org//www.China-low-cost-PCB.org....electrical engineering.agttech.com
OEM Electronic Components service,buy and sell exclusively with OEMs.
Design Solutions Newport Beach, CA, USA
www.China-low-cost-PCB.org//www.China-low-cost-PCB.org....electrical engineering.designsolutions.com
Engineering Services, Manufacturing Services, Printed Circuit Board (PCB) Design, Printed Circuit Board (PCB) Layout Services available from Design Solutions based in Newport Beach, CA. Click the links below to visit our website or contact us via our profile page. More...
GDA Technologies Sunnyvale, CA, USA
www.China-low-cost-PCB.org//www.China-low-cost-PCB.org....electrical engineering.gdatech.com
GDA Technologies is a leading Electronic Design Services (EDS) and Silicon Intellectual Property (SIP) solution provider for the Embedded, Networking, and Consumer Electronics Markets, 10 G Mac/1G Mac, SPI 4. Fully synthesizable RTL box, verification environment, FPGA prototype platform. More...
All material, graphics Redondo Beach, CA, USA
www.China-low-cost-PCB.org//www.China-low-cost-PCB.org....electrical engineering.calpak-usa.com
Computer Services, Computer Network Services, Printed Circuit Consultancy or Design or Production Services, Test and Measurement Instrumentation, Software Development and Programing Design, Computer Hardware Design and Development, Computer Hardware Design, Computer Software Design, Computer Software Development, Computer Software Engineers, Mechanical Computer Aided Design (CAD), Panels to Specification, Printed Circuit Board (PCB) Design, Process Engineering, Through Hole Relays, Test Fixtures, Stack Test Instrumentation, Factory Automation, Printed Circuit Board (PCB) Layout Services, Business Exchange Services available from All material, graphics based in Redondo Beach, CA. Click the links below to visit our website or contact us via our profile page. More...
CA Design San Jose, CA, USA
www.China-low-cost-PCB.org//www.China-low-cost-PCB.org....electrical engineering.cadesign.net
Printed Circuit Consultancy or Design or Production Services, Printed Circuit Board (PCB) Assembly, Printed Circuit Board (PCB) Layout Computer Aided Design (CAD), Printed Circuit Board (PCB) Layout Services available from CA Design based in San Jose, CA. Click the links below to visit our website or contact us via our profile page. More...
CompServ Fremont, CA, USA www.China-low-cost-PCB.org//www.China-low-cost-PCB.org....electrical engineering.compservsales.com
Engineering Services, Printed Circuit Consultancy or Design or Production Services, Engineering Project Design, Manufacturing Services, Medical Equipment, Bare Printed Circuit Boards (PCB), Printed Circuit Board (PCB) Fabrication Services, Printed Circuit Board (PCB) Layout Services available from CompServ based in Fremont, CA. Click the links below to visit our website or contact us via our profile page. More... (http://dx.doi.org/10.1016/j.ejor.2007.03.042)
^ Ayob M. and Kendall G. (2005) A Triple Objective Function with a Chebychev Dynamic Pick-and-place Point Specification Approach to Optimise the Surface
[edit] External links
Wikibooks Practical Electronics has a page on the topic of
PCB LayoutWikimedia Commons has media related to:
Printed Circuit Board
[edit] Design guidelines
PWB/PCB Design – Analog, RF & EMC Considerations in Printed Wiring Board Design
High Frequency Laminate Information by Chet Guiles
EMC Design Guideline Collection on the Clemson Vehicular Electronics Laboratory web site
SN100CL Minimum Thickness Guidelines on Saturn Electronics website.

[edit] Standards and specifications
Association Connecting Electronics Industries (IPC)
MIL-PRF-31032, Performance Specification Printed Circuit Board/Printed Wiring Board
MIL-PRF-55110, Performance Specification for Rigid Printed Circuit Board/Printed Wiring Board
MIL-PRF-50884, Performance Specification for Flexible and Rigid-Flexible Printed Circuit Board/Printed Wiring Board

[edit] Do-it-yourself (DIY) guides
Making PCBs using DIY cnc hardware
Making PCBs with a laser printer and photo paper, no UV machine needed anymore.
More detailed PCB DIY making with laser printer
Making PCBs by hand using an etch-resist pen (no printer or special paper needed)
Open Source Hardware Initiative (open hardware).

[edit] Others
First PCB Patent - Patent No 2,756,485 - Process of Assembling Electrical Circuits (pdf)
List of PCB trade shows
General Information on Printed Board Programs
PCB Trace Impedance Calculator
Retrieved from "http://en.wikipedia.org/wiki/Printed_circuit_board"
Categories: Electrical engineering | Electronics manufacturing | Electronic engineering | Electricity distribution
ViewsArticle Discussion Edit this page History Personal toolsLog in / create account Navigation
Main page
Contents
Featured content
?esky
Dansk
Deutsch
Eesti
Espa?ol
Fran?ais
???
Hrvatski
Bahasa Indonesia
íslenska
Italiano
?????
Lietuvi?
Magyar
Nederlands
日咕語
?Norsk (bokm?l)?
Polski
Português
Roman?
Русский
Simple English
Sloven?ina
Српски / Srpski
Suomi
Svenska
???
Ti?ng Vi?t
Türk?e
Ькра?нська

This page was last modified on 14 August 2008, at 19:34. All text is available under the terms of the GNU Free Documentation License. (See Copyrights for details.)
Wikipedia? is a registered trademark of the Wikimedia Foundation, Inc., a U.S. registered 501(c)(3) tax-deductible nonprofit charity.
Privacy policy About Wikipedia Disclaimers Monster HomeMy Monster Find Jobs Post Resume Money Education Career Advice Job Fairs ?
Send this job to a friend See all THINK ENERGY GROUP opportunities





Job Information

Location:

Email me a copy of my application
Privacy Notice: We’ll save your name, resume, and the email address you've entered so that we can contact you about the status of your application if necessary, and for our internal reporting purposes. We will not disclose your e-mail address to anyone other than this employer.Step 2:
Add your own cover letter or note below. To send your resume without a note, leave this box empty.

Note: Use plain text only. HTML is not supported.Invalid
Character Count: 0 (4,000 character limit)

Printed Circuit Board (PCB) Design
Printed Circuit Board (PCB) Development
Printed Circuit Board (PCB) Wiring
Printed Circuit Board (PCB) Procurement
Printed Circuit Board (PCB) Testing
Printed Circuit Board (PCB) Engraving
Printed Circuit Board (PCB) Soldering
More >>

About Kellysearch
About us
Add your company
Advertise with us
Find related content
Documents Library
News
Web Search
What's New


Advanced Search Browse Subjects Hot New Releases Bestsellers the new york times? best sellers Libros en espa?ol Bargain Books Textbooks

Shortcuts to Savings Around Our Store
? Gold Box
Extra savings on different products every day.
? Outlet
? Friday Sale
? Deals & Bargains
? Wish List
? Shopping List
? Gift Organizer

--------------------------------------------------------------------------------

? Your Media Library