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Technical Glossary


Technical Glossary
 
PCB Glossary
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Acid Trap,
A feature of copper tracking which captures excess etching chemistry during processing resulting in under or over etching.

Analogue circuit,
This is a type of circuit where the variation of the voltage is the signal quantity. These circuits have short signal paths with large areas of screening.

Annular Ring,
The width of the copper pad area that remains after a hole is drilled through a pad.

Aperture,
This is the shape and size of the tool which draws or flashes pads or tracks respectively. The early vector plotters created tracks and pads by shining a light through selected apertures in a wheel, which was indexed over photographic film. Each aperture is referred to as a "D" code, the term arising from the adapted original machine NC language where it meant "drill"tool. Photographic films are now plotted using laser raster plotters, where all the shapes and sizes are produced in software, and there is no limitation of a mechanical wheel.

Aperture List,
The list of the shapes and sizes of the apertures used to create pads and tracks.

Artwork,
The photographic tool used to manufacture a printed circuit board. Usually this is film work, but could be hand laid with tape, or could refer to the Gerber files themselves.

ATE,
Automatic (Automated) Test Equipment

Auto-routing,
The process by which a CAD layout package automatically places copper tracking and components in accordance with the connectivity defined by the net-list.
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Bare Board,
This refers to a bare board to distinguish it from a populated pcb.

Base Material,
This is the material which forms the structural and insulating layer between the copper layers.

Bed of nails electrical tester,
A machine which by way of an adaptor jig ("the test jig"), connects every test point of a board under test to an input channel on a computer. the computer scans the test points and compares the connectivity to either a net list file or to the connectivity of a learnt "golden" board. Bill of Materials, (BOM).
A document that sets out quantity required, manufacturer's part numbers, device descriptions, value, type or size, and reference designators.

Blind Via,
This is a copper plated hole which passes from the surface of a PCB and terminates at a copper feature on an inner layer. It does not pass all the way through the PCB.

Breakout,
This is a PCB fault where part of a drilled hole cuts through its associated copper pad.

Bridging,
A PCB fault where excess solder or copper causes a short between 2 adjacent copper features.

Buried Via,
A buried via is a copper plated hole which interconnects between 2 internal layers of a multi-layer PCB. They are not visible externally.

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CEM-1,
Epoxy paper laminate with glass fabric coating

CEM-3,
Epoxy felt laminate with glass fabric coating

Chamfer,
Usually applied to an edge connector area of a PCB to relieve the sharp edges where the PCB is inserted into an edge connector.

Circuit,
The copper connections which allow electrical currents to pass between components, and create a functioning electrical or electronic device.

Circuit Boards,
See Printed circuit board

Circuit Layer,
One of the layers of a PCB containing conductors, including tracking, ground and voltage planes.

Component Hole,
The holes through which leaded components are fitted.

Conductor Spacing,
The gap between adjacent copper tracks

Controlled impedance,
This is defined in ohms, commonly 70 ohm or 50 ohm. It is a characteristic of a copper track which is governed by the dielectric constant of the base laminate, the width of the track, the thickness of the dielectric, and the thickness of the copper track, and the configuration of the adjacent copper features.

Copper foils,
Often used in multilayer printed circuit board construction, copper foils are commonly available in 18 micron, 35 micron, and 70 micron thicknesses.

Coverlay,
This is a material applied to the outside layers of a flexible circuit to insulate the copper conductor. Coverlays are normally produced with a drilling process. Limitations of the drilling process only allow round or oval holes. Square openings or dense features are not practical.

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Design Rules Check,
Normally checked by a computer program, features on the circuit which breach design rules are identified. Checks undertaken include: track to track gaps, track to pad gaps, annular ring sizes, track to board edge gaps, acid trap detection, unterminated track checks, legend to pad clearance, solder resist clearance, etc.

Desmear,
When multilayer printed circuit boards are drilled, the drill cuts through lands of copper on the inner and outer layers. Resin from the base laminate is smeared over the exposed copper where plated copper must eventually form a connection. This resin must be removed to ensure a sound electrical connection will be made by the plated copper. This is the desmear process.

DFM,
Document Exchange Format or .dxf format is files format by which many mechanical drawing programmes can share data. It is commonly the means by which PCB designs drafted on Autocad can be transferred to PCB manufacturers. Newbury Electronics can read DXF files into their PCB manufacturing software, and convert it into Gerber for PCB manufacture.

DXF,
The copper connections which allow electrical currents to pass between components, and create a functioning electrical or electronic device.

Digital Circuits,
These are characterised by a signal which is either on or off, and is typically either 0 or 5 volts or 0 and 3 volts. High speed digital circuitry is largely replacing analogue circuits.

Dielectric Constant, Dk,
That property of a dielectric that determines the electrostatic energy per unit volume for unit potential grade. The transmission speed of an electromagnetic wave in a dielectric medium is the speed of light divided by the square root of Dk. Air has a Dk of 1.0. FR4 has a Dk of 4.4.

Dielectric loss (tan d),
The energy absorbed by the dielectric media is measured by tan d. Attenuation is proportional to tan d and signal frequency. For standard FR4 multilayer printed circuit boards materials, tan d is 0.02 which translates into serious losses at at frequencies above 1 Ghz. For circuits operating at 1 Ghz or higher, a material such as PTFE with a tan d of 0.001 is preferred.

Double-sided board
PCB with a copper tracking on both sides, but no inner layers.

Drill Table,
A list of drill sizes used in making the PCB.

DPF,
Disc Plotter Format or .dpf files is a proprietary file format used by Barco for plotting PCB files. Circuit board features are defined by "contour lines" which are "filled" with copper. It is generally considered to be superior to Gerber, but it is not widely used. Newbury Electronics can read DPF files into their PCB manufacturing software, and convert it into Gerber for PCB manufacture.

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E-test Fixture and (E/T) Cost:

There will be 2 kinds of e-testing charge.
1. One is flying probe test charge, which is mainly for prototype sample lot.
There are 4 or 8 test metal needles to touch the pads quickly to make sure whether there’s open or short circuit.
The charge is relative with the Qty, and need to be paid according to every order.
2. The other is electric test fixture charge.
And the test metal needles are installed into the fixture, which is mainly for mass production with fast test speed.
The fixture is unique because it’s installed according to that PCB.
But it can be used thousands of times if there’s no change for the file.●Different E/T fixture charge The E/T fixture charge will be different according to differnt PCB, which is relative with the PNL size, the test point Qty, and the Upsin the panels. SPCB perfer to set up the e-test fixture according to shipment panel size by one time test, even the fixture charge will be much lower if set up the fixture partly, like seting up the fixture with 2ups for 6ups in the PNL to test 3 times for the whole PNL. There will be potential risk to miss test for some part of boards.


Edge Connector,
Usually this will consist of gold plated tags at the edge of the PCB which mate with an appropriate connector.

Electroless copper,
This is the copper deposited on the inside of drilled holes to a thickness of about 0.5 microns. The process is based on the catalytic deposition of copper on to all the surfaces of the substrate. Subsequently, the thickness of copper will increased by electrolytic plated copper of about 20 to 25 microns.

Electroless Nickel - Immersion Gold,
Normally this will be 0.1 microns of gold over 5 microns of nickel plated over just the copper pads. This finish provides a flat and oxidation free surface for mounting surface mount components.

Etch Factor,
The ratio of etch depth to the amount the resist is undercut during etching.

Etching,
This is the process of removing copper from copper clad laminate to create insulation between the copper tracking.

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Fiducial marker,
Usually a copper pad, this marker provides a common datum for registering other PCB layers or machines (eg pick & place) to the component placement points (copper pads) on the PCB.

Flash,
Vector plotters would "flash" an image of the pads required on PCB. Tracking would be "drawn".

Flexi-Rigid,
see Flexible Printed Circuit.

Flexi,
see Flexible Printed Circuit.

Flexi circuit,
see Flexible Printed Circuit.

Flexible Circuit,
see Flexible Printed Circuit.

Flexible circuits,
Single sided flexible circuits consist of a single copper conductor layer on a flexible dielectric film. Single sided circuits can be fabricated with or without coverlayers. Similarly, double sided circuits consist of two copper layers insulated with a dielectric normally connected with plated through holes.

Flexible Printed Circuit,
A printed circuit board (pcb) manufactured on non-rigid material, commonly polyimide sheet.

Flying probe electrical tester,
A machine which electrically tests printed circuit boards by moving test probes to the nets under test. Modern machines will test at over 2000 points a minute.

FR-2,
Phenolic paper laminate

FR-3,
Epoxy paper laminate

FR-4,
This is the standard glass epoxy substrate with a glass transition temperature of 135 deg C. Its mechanical strength and in particular flexural strength and impact resistance are greatly superior to those of phenolic and epoxy paper laminates. FR stands for flame resistant.
This is an enhanced glass epoxy substrate with a glass transition temperature of 165 deg C

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Glass transition temperature (Tg),
The Tg of a resin system is the temperature at which the material transforms from a relatively rigid or glassy state to a more deformable or softened state.

Gerber Data,
This is data that encapsulates a PCB design. It is configured in a vector format and arose from an adaptation of a simple NC drill programming language widely used in the 1960's. Gerber data is unique to the PCB industry and is still the universal data format for transferring data from CAD packages to PCB manufacturers despite attempts to popularise alternatives. Gerber data is officially designated as RS-274-D (without embedded aperture codes) and RS-274-X (with embedded aperture codes).

Ground Plane,
A large area of solid or hatched copper on a printed circuit board used as an electrical ground or shield.

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HASL,
Hot Air Solder Leveled. This is a process whereby a printed circuit board is immersed for a few seconds in a vat of molten solder and then rapidly withdrawn, passing between two air knives which blast away surplus solder from the surface and the through holes. The thickness of solder is between 10 and 25 microns. The solderability and shelf life of HASL is excellent.

HPGL,
Hewlett Packard Graphics Language is commonly used for driving pen plotters. It is vector driven language similar to Gerber. Newbury Electronics can read HPGL into their PCB manufacturing software, and convert it into Gerber for PCB manufacture.

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Import net-list,
The term used to describe the process of transferring a net list from a schematic layout software to PCB design CAD software.
Inner Layer,
The layers of a circuit board that are sandwiched in between the outer copper layers. These may be tracking layers or ground plane layers.

Land,
That part of a pad surrounding a component hole or a via hole.

Lead-free solder,
These solders are based on 95% tin metal with the addition of small amounts (around 1%) of variously silver, copper, bismuth and other metals.
Standard tin/lead solder is 60% tin, 40% lead. Most lead-free solders have a melting point some 30/35 degrees C above that of 60/40 tin/lead solder. Therefore the soldering process has to be performed at temperatures of around 255 degrees C rather than the more normal 235 degrees C. The maximum temperature rating of most components is 260 degrees C, thus restricting the use of an optimum temperature.

Legend,
Silk screened component identification layer. Sometimes called an "ident".

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Micro sectioning,
A micro section is a polished sample of a cross-section of a pcb, usually through a PTH hole. It is normally mounted in clear resin. Under magnification, a micro-section is used to verify the integrity of plating down the hole.

Mil,
One thousands of an inchv Misregistration,
The mis-alignment of features, e.g. solder resist to pad misregistration.

Mixed Technology,
Describes the assembly process used when pin through hole, surface mount, and other mounting technologies are placed on the same printed circuit board.

MLPCB,
see Multilayer Printed Circuit Board

ML4,
see Multilayer Printed Circuit Board

ML6,
see Multilayer Printed Circuit Board

ML8,
see Multilayer Printed Circuit Board

MLPWB,
see Multilayer Printed Circuit Board

ML,
see Multilayer Printed Circuit Board

Moisture absorption,
Moisture is the enemy of a printed circuit board. Absorbed moisture raises Dk, expands the board, and causes thermal defects such as substrate blisters and barrel cracking during soldering. If storage time are short, or humidity is low, then moisture will not be a problem. However if the pcbs are stored in high humidity for several months or more, then they should be separated, racked and baked at 120 degrees C for 1 hour before assembly.

Multilayer Board,
A PCB with more that 2 layers.

Multilayer Printed Circuit Board,
A printed circuit board with more than 2 layers, commonly 4 layers , 6 layers or 8 layers. The internal layers of a multilayer printed circuit board may be either ground planes or tracking or a mixture of both. Connection between the layers are made by copper plated through holes.

Major defect
A defect likely to result in the failure of a unit or product by making it unusable.

Master Drawing
A document showing dimensional limits or grid locations for all parts on a PCB. Conductors and nonconductive material of a PCB ( e.g. dielectric, resist, etc.) are also shown.

Measling
An internal condition that occurs in laminated base material in which the glass fibers are separated from the resin at the weave intersection. This condition manifests itself in the form of discrete white spots below the surface of the base material. This is often caused due to thermally induced stress.

MELF, MetalElectrode Leadless Face
A component package that is cylindrical and has metalized terminations on its two ends for surface mounting. The package is commonly used for diodes, capacitors, and resistors.

Metallization
A metallic deposited on substrates and component terminations by itself, or over a base metal, to enable electrical and mechanical interconnections.

Mixed Mounting Technology
A component mounting technology that uses both through-hole and surface mount components on the same packaging and interconnecting structure.

Multilayer Board
A printed wiring board that uses more than two layers for conductor routing. Internal layers are connected to the outer layers by way of plated via holes.

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Net,
A net consists of all the points that are connected together by copper.

Net End,
A net end is a pad or plated through hole at the end of a branch of an electrical circuit. layers or ground plane layers.

Net list,
A list of net numbers and their associated X and Y coordinates, and the surface upon which they can be found. This is the basic information from which a test program for an electrical test machine can be constructed since it physically identifies the locations of the nets to be tested. Another type of net list is a CAD software design package net list which identifies connectivity between components, but does not identify their physical location.

Nick,
A cut or notch in a track or pad.

Neutralizer
An alkaline chemical added to water to improve its ability to dissolve organic acid flux residues.

Nonwetting
A condition whereby a surface has contacted molten solder, but the solder has not properly "wetted" all of the surface. The base metal remains exposed. Nonwetting is caused primarily due to impurities acting as physical barriers (intermetallic or oxide) between surfaces to be joined.

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Open,
An absence of expected circuit continuity. Two electrically connected points that are electrically separated during the process of manufacturing. The reasons may be over-etching or non-planarity of the leads at the point of connection etc.

Organic coatings,
Organic solderability preservative (OSP) coatings are organic compounds that selectively bond with copper to provide a protective layer over the copper. Benzimidazoles, benzotriazoles, imidazoles or substituted benzimidazoles are often employed to restrict copper oxidation. The organic material reacts with copper to form a thin coating which prevents moisture and air from coming into contact with the copper surface, thus preserving solderability. OSP's are cheap, but are not mechanically robust, and will not withstand multiple heat cycles.

Outgassing
De-aeration or other gaseous emission from a printed circuit board or solder joint.

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Prices
The price for each piece of board after production from original material.
●Different Price for different factorys. The price will be different more or less from different factories as different base 20 detailed processes for normal board production. material, different material in process, different process control system, different labor cost. And there are more than
For example,
  1. Base Material: the base material KB "A-level" which SPCB used to make sure reliable Quality will be higher cost than B or C level material.
  2. The chemical in plating process is ROHM HRRS to make sure copper connection and uniformity, and the cost will be higher than domestic chemical.
  3. SPCB perfer to build long cooperation with customer, and the base will be long term competitiveness through stable and professional staff who have higher level salary and training
 
PCB ; Printed Circuit Board.
Printed circuit boards are not like other components. They are not pre-built components like resistors or capacitors. They are custom made for each individual customer.

Pad,
The portion of the conductive pattern on printed circuits designated for the mounting or attachment of components.

Panel,
A piece of laminate which contains multiple images/ of a circuit.

PCB prototype,
An initial low volume production run of printed circuit boards (pcbs).

Photomech,
The department of a printed circuit board factory which uses photo-sensitive materials to print images/ on printed circuit boards.

Photoplotter,
A machine for creating a photographic image of a printed circuit board from electronic data.

Photo resist or plating resist,
A light sensitive film, which when exposed to UV light under a photographic mask, polymerises and becomes hardened. The soft unexposed areas may be developed away (washed off) with the use of alkaline chemistry often in a conveyorised processor.

Plated Through Hole,
A hole in which electrical connection is made between internal or external conductive patterns, or both, by the plating of metal on the wall of the hole.

Polyimide laminate,
A high temperature laminate system with a Tg of around 250 degrees C. Suitable for applications with working temperatures of over 200 degrees C.

Printed Wiring Board,
See printed circuit board

Printed Circuit Board,
A sheet of glass reinforced plastic upon which is etched a copper pattern of conductive tracks to provide an electrical inerconnect between electronic components which are either soldered to copper pads on the printed circuit board (pcb), or mounted through holes drilled in the printed circuit board (pcb).

PWB,
PWB=PCB. See printed circuit board
 
Quotation
About quotation form

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Resist,
A coating material that is used to mask or protect selected areas of a circuit board from etching or plating processes.

Router,
A machine that profiles laminate to the shape and size of the required printed circuit board.

RS-274-X,
A variant of Gerber data which contains aperture shape information in addition to the usual tool selection and movement commands.

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Set Up Charge
Set up charge is mainly for engineering and artwork film, and it will be paid for one time only if there’s no change for the Gerber file.
And an engineer in the factory will check the original Gerber file from customer to find whether there’s obvious errors against real production capability.
and then need to translate into the tools and language for inner production.Meanwhile, as the production of PCB, the lines and solder mask will be produced
like camera needing film, which is unique for that PCB.

Scoring,
The process of part cutting through laminate with twin rotary cutters which leaves a thin web of material. This web may be broken by "snapping" after assembly.

Screen Printing,
The transfer of a pattern onto a surface by forcing a suitable material through a screen with a squeegee.

Short circuit,
Erroneous low resistance connections between two or more networks or isolated points.

Silver finish,
A silver coating can be used in place of HASL. The silver coating over the copper pads consists of a sub micron silver deposit with an organic top layer to prevent tarnishing and retain solderability. The coating claims to combine the benefits of metallic and organic coatings without the drawbacks. It has good solderability, flat and uniform topography, and a bright appearance. During soldering, the silver dissolves into the joint and the bond forms directly with the active copper surface.

Single Sided Board,
The department of a printed circuit board factory which uses photo-sensitive materials to print images/ on printed circuit boards.

SMOBC,
Solder Mask Over Bare Copper. This is to distinguish this more modern process from "solder mask over tin/lead"

SMT,
A solder mask ensures that solder is only placed on the printed circuit board in those areas where it is required. i.e. on component land areas.

Solder Mask, Solder Resist,
A hole in which electrical connection is made between internal or external conductive patterns, or both, by the plating of metal on the wall of the hole.

Solder Side,
On printed circuit boards with components on only one side, the side of the PCB that is opposite to the component side.

Solderability,
This is the ability of solder to wet a component quickly. It is influenced by thermal demand of the components, wettability and resistance to soldering heat of the components.

Step & Repeat,
The number of duplicate images/ placed on a panel in both the X axis and Y axis.

Surface Mount Technology, (SMT).
Components are mounted directly on to printed circuit boards rather than by wires passing through holes. Most modern printed circuit boards will use SMD technology.

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Teardrop,
A teardrop refers to the shape of a pad which tapers evenly into its associated track.

Tester,
A machine that checks a PCB for the connectivity of its circuits from the design net list.

Thermal Relief,
Through holes are connected to ground planes by way of thermal relief pads, otherwise the heat sink effect of the ground plane would render the temperature in the through hole during soldering insufficient to form a good connection.

Track,
An electrical connection between two or more points on a PCB.


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Underwriters Laboratories (UL),
The U.S. based safety standard certification organization. US insurance companies will not issue product liability insurance without UL approval of products. In respect of electrical goods, the UL is largely interested in fire hazards and electrical insulation. FR4 laminate is approved to the 94-V0 rating.
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Via,
A plated through hole which makes a connection from one side of a printed circuit board to the other without having a component lead inserted.
 
 
     
   

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