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SMT Terms

A thru L L thru Z

L

Land Pad
 A PCB termination area.
Land Pattern Footprint Refers to the area, pad dimensions and the pattern of pads for a particular component.
Laser Cut Stencil Thin plate of steel or plastic with laser cut holes. Used in solder paste printing.
LCCC Leadless Ceramic Chip Carrier.
Lead Pb Used in most solder alloys. Legislative and market forces are eliminating this metal.
Lead Component terminal or electrical connection point.
Lead-Free Refers to solder alloy and solder joints not containing lead.
Lead-Free Solder Refers to solder alloy not containing lead.
Leadless Component An "old" phrase for surface mount component.
Lead Pitch Distance between the centers of two leads on an IC.
Liquidus Temperature The temperature above which an alloy become totally liquid.
Local Fiducial Marks Two or three small marks on the PCB are used to calculate the PCB position relative to the placement head. Calculations are then made to ensure precise placement of a particular component.

 

M

Manual Assembly Assembly process done by hand.
Matrix Tray Flat plastic matrix component carrier.
MCM Short for MultiChip Module. A single laminate or ceramic base material mounted with multiple, unpackaged integrated circuits (bare die) along with capacitors and resistors.
Melf Metal Electrode Face. Refers to a specific group of cylindrical components.
Melting Point The specific temperature at which an alloy become liquid.
Mesh Size The number of openings per inch in a mesh screen.
Metal Content The weight percent of the solder powder in a solder paste.
MicroBGA �BGA. Refers to a group of fine pitch BGA's.
MSD Moisture Sensitive Device. Components that contain moisture and have a high potential of cracking during soldering due to moist expansion.
MSL Moisture Sensitivity Level. A moisture sensitivity classification for surface mount components. See IPC/JEDEC J-STD-020.
Mulitilayer PCB Laminate with more than 2 layers of conductors forming a circuit pattern.

 

N

Ni Chemical symbol for nickel. Used under Au on PCB solder lands and on component terminals.
Nitrogen (N2) Inert gas used in the soldering process to avoid oxidation of the components, pads and solder alloy.
No-Clean Term used about flux, solder paste and solder wire that contain flux, formulated in such a way that it is not necessary to remove the remaining flux on the PCB. Acids should be encapsulated in the flux residue and the residue should work as an electrical insulator.
Nozzle A vacuum nozzle holds the component during transport from feeder unit to PCB. An adhesive nozzle is used to transfer adhesive to the PCB.

 

O

OA Organic Acid flux Classification for a water soluble flux usually containing organic acids and no rosin.
ODM Original Design Manufacturer. ODMs offer development and design services.
OEM Original Equipment Manufacturer.
Organic Solder ability Preservative OSP. Used as protective layer over cobber solder pads.
Oxidation Oxygen absorption on metal surfaces. Oxides resist solder wetting.

 

P

Pad Land or solder pad A PCB termination area.
Panel Cluster panel A PCB panel usually containing an array of identical PCB's. After end assembly the PCB's are separated.
Parts Per Million PPM Unit commonly used in statistics.
Paste In Hole A SMT technique used to solder through hole / leaded components. Solder paste is printed onto the through-hole solder pad, part inserted and reflow soldered.
Pattern Repeat A placement method where each PCB in a panel is completely populated before moving on to the next.
Pb Chemical symbol for lead. Used in some solder alloys.
Pb-Free Refers to solder alloy and solder joints not containing lead.
PBGA Plastic Ball Grid Array. As Ball Grid Array with a thin BT resin epoxy PCB base substrate.
PCA Printed Circuit Assembly. Completed PCB unit.
PCB Mask Repair Material This material is used to affect the repair of PCB and can be either air, heat or UV cured.
PCB Printed Circuit Board. Substrate with conductors forming a circuit pattern.
PCBA Printed Circuit Board Assembly Completed PCB unit.
PCB Support Pins or plates supporting the PCB during a process.
Peak Temperature The maximum temperature reached in the soldering process.
pH A liquid acidity and alkalinity measurement unit. Scale 1 - 14, 1 acid, 7 neural and 14 alkaline.
Pick and Place P&P Refers to the process where the components are picked up from a feeding unit, moved and placed onto the PCB solder pads.
Pick and Place Head P&P Head Refers to the head in a placement machine, picking up the components from a feeding unit, moving and placing them on the PCB solder pads.
Pin In Paste A SMT technique used to solder through hole / leaded components. Solder paste is printed onto the through-hole solder pad, part inserted and reflow soldered.
Piston Pump Dispensing unit using a piston to force the adhesive onto the PCB.
Pitch The distance between the centers of two leads on an IC. Or the distance between the components in a tape carrier. Or the distance between two tape adjacent sprocket holes (4 mm).
Placement A manual, semi-automatic or fully automatic component assembly process.
Placement Head P&P Head Refers to the head in a placement machine, picking up the components from a feeding unit and moving and placing them on the PCB solder pads.
Placement Program Computer data containing placement sequence and other necessary information that the placement machine requires.
Plastic Ball Grid Array PBGA Like a Ball Grid Array with a thin BT resin epoxy PCB base substrate.
PLCC Plastic Leaded Chip Carrier Refers to a specific group of IC packages with J-lead on four sides.
Popcorning Internal delamination of a BGA due to moist expansion inside the BGA housing.
PPM Parts Per Million Unit commonly used in statistics.
Preform Solder preform A preformed shape of solder alloy. Usually flux containing.
Preheat Refers to the part of the soldering profile where the PCB is heated from ambient temperature until reaching the chosen preheat temperature.
Process Control A manual or automatic procedure set up to monitor the process in question.
Profiler A unit recording the soldering profile during the soldering process at a number of locations.
Proto or prototype Small number of initial assemblies to help prove out the electrical and functional design
PTH Plated Through Hole Hole in a double sided or multi layer printed circuit board electrical connecting the layers.
PWB Printed Wiring Board Substrate with conductors forming a circuit pattern.
P&P Pick and Place. Refers to the process where the components are picked up from a feeding unit and moved to and placed on the PCB solder pads.
P&P Head Pick and Place Head Refers to the head in a placement machine, picking up the components from a feeding unit and moving and placing them on the PCB solder pads.

 

Q

QFP Quad Flat Package Refers to a specific group of IC packages with leads on all four sides.

 

R

R Rosin flux Flux usually containing 40% solids (Rosin) and 60% solvents.
RA Short for Rosin Activated flux. Classification for an aggressive flux, containing 1 - 5 % activators.
Reballing
Reflow Oven Equipment used to solder SMD mounted PCB's.
Reflow Period Refers to the part of the soldering profile, after the equalization period, used to melt the solder paste and form the solder joints.
Reflow Process The process, where the mounted PCB is heated in a furnace by a hot atmosphere or IR radiation in specific stages, finally melting the solder paste and thereby forming the solder joints.
Reflow Soldering The mounted PCB is heated in a furnace by a hot atmosphere or IR radiation in specific stages, finally melting the solder paste and thereby forming the solder joints.
Reflow Temperature The temperature at which the reflow soldering are performed. Usually described as a window. E.g. 215 - 230�C.
Reliability The products, PCB's, solder joints ability to fulfil the specifications required.
Repair Rework or Touch-Up Refers to a process where a defective unit or part is changed into a working condition.
Repeatability The ability to deliver consistent results.
Resin Chemically synthesized rosin.
Rework Repair Refers to a process where a defective unit or part is changed into a working condition.
Rheology Material viscous and flow property.
RoHS Restriction of the use of certain Hazardous Substances in electrical and electronic equipment. EU directive 2002/96/EC banning a number of substances in electronic devices.
RoHS Compliance Refers to materials that comply with the EU RoHS directive.
Rosin Natural rosin extracted from pine trees.
RMA Rosin Mildly Activated flux. Classification for an moderate flux containing less than 1% activators.
Rosin Activated RA Classification for an aggressive flux, containing 1 - 5 % activators.

 

S

SAC alloy
Sb Chemical symbol for antimony which is a metal used in some solder alloys.
Screen Mesh A woven stainless steal or polyester fiber mesh attached with emulsion, used in the screen printing process.
Screen Printing Solder paste or adhesive printed through a mesh screen.
Self-Alignment or Swimming When a component moves on the solder pads due to the surface tension of the molten solder alloy.
Selica Gel Moisture absorbing crystals. Used in Dry-Packs to maintain a low moist level.
Short or solder bridge An unintentional mechanical and electrical short between two component terminals or solder pads.
Single Layer PCB Single layer printed circuit board. Laminate with one conductive layer forming a circuit pattern.
Silver Ag Metal used as protective layer on component terminals, PCB solder pads and in some solder alloys.
SIR Surface Insulation Resistance.
Skew Component misalignment from its target position.
Slump Solder paste spreading after printing.
SMC Surface Mount Component Component designed for PCB surface mounting.
SMD Surface Mounted Device PCB mounted with SMC's.
SMD Solder Mask Defined Pad that are defined by the solder mask.
SMEMA Surface Mount Equipment Manufacturers Association Provides standards for mechanical equipment interface, fiducial marks etc.
SMT Surface Mount Technology A technology where components are attached directly onto the PCB surface.
SMTA Surafec Mount Technical Association (see www.smta.org)
Sn tin Metal used as a primary ingredient in solder alloys.
Snap Off The distance between the stencil and the PCB in the printing situation.
SO Small Outline Refers to a specific group of IC packages with leads on two sides.
Soak Period or Stabilization Period Refers to the part of the soldering profile, after preheat, used to equalize the components temperature differences before raising the PCB temperature above the solder alloys melting point.
SOIC Short for Small Outline Integrated Circuit. See SO.
SOJ Short for Small Outline J-lead package. Refers to a specific group of IC packages with J-lead on two sides.
Solderability The ability of the solder to wet a solder land.
Solder Alloy A material made by melting two or more metals together.
Solder Bead A solder ball positioned at the side of the component. Usually seen at chips.
Solder Bridge Short An unintentional mechanical and electrical short between two component terminals and solder pads.
Solder Joint Joint Mechanical and electrical connection between component terminal and PCB solder pad.
Solder Mask Solder protection coating masking selected areas of the PCB surface.
Solder Paste A homogeneous paste of solder particles, flux, solvents and additives. Used in the SMT reflow soldering process.
Solder Preform A preformed shape of solder alloy. Usually flux containing.
SolderQuik� a polyimide stencil used to quickly rework area array and multi-leaded components while repairing solder mask
Solder Wire A wire of solder alloy containing flux. Used for hand soldering.
Solder Thief A special designed solder land positioned outside the real SMC solder pads used to attract excess solder and thereby avoid solder bridges. Used in wave soldering process.
Solidus Temperature The temperature just below the point where the alloy become liquidus.
Solvent A liquid cleaning agent and ingredient in some fluxes and solder pastes.
SOP Small Outline Package Refers to a specific group of IC packages.
SOT Small Outline Transistor Refers to a specific group of transistor and diode packages.
SPC Statistical Process Control A method used to continuously monitor a process and thereby be able to reduce product failure.
Spray Fluxer Fluxer unit used in a wave soldering machine to apply flux to the bottom side of the PCB by spraying it through a nozzle or an ultrasonic transducer.
Squeegee A metal or rubber blade used in solder paste / adhesive printing. By an angled movement across the stencil or screen the squeegee force the solder paste or adhesive through the stencil apertures and onto the PCB surface.
SSOP Shrink Small Outline Package Refers to a specific group of small IC packages.
Stabilization Period Soak period. Refers to the part of the soldering profile, after preheat, used to equalize the components temperature differences before raising the PCB temperature above the solder alloys melting point.
Stencil Thin plate of steel, brass or plastic with etched or laser cut holes. Used in solder paste printing.
Stencil Printing Solder paste printing through a metal stencil.
StencilQuik�- a polyamide-based stencil used to quickly rework area array devices and other multi-leaded components that repairs solder mask damage underneath the part
Step & Repeat A placement method where one particular component is placed on each PCB in a panel before placing the next component.
Stick Plastic tube component carrier.
Stick Feeder Unit used to feed components from plastic tube carrier into the placement machine.
Substrate An insulating material on which the components are placed, soldered and forming a circuit.
Surface Tension The attraction force on the surface of a liquid.
Swimming in self-Alignment. When a component moves on the solder pads due to the surface tension of the molten solder alloy.

 

T

TAB Tape Automated Bonding A process where a taped IC chip is bonded directly onto a PCB.
Tact Time The time a placement head use to pickup and place one component.
Tape Paper or plastic embossed / blister component carrier.
Tape Carrier The paper or plastic embossed / blister carrier tape in which the components are stored in pockets.
Tape Cover A clear plastic film covering the components stored in the tape carrier.
Tape Automated Bonding TAB A process where a taped IC chip is bonded directly onto a PCB.
Tape feeder Unit used to feed components from tape into the placement machine.
Tape Pitch The distance between the components in a tape carrier. Available in 4 mm intervals.
Tape width The width of the tape carrier. 8, 12,16, 24, 32, 44, 56 and 72 mm.
Temperature Profile A profile showing the temperature over a period of time. In soldering the profile usually consist of 4 phases; preheat, stabilization, reflow and cooling.
Terminal Component lead or electrical connection point.
Tg Glass transition temperature. The temperature at which a material changes from hard to soft state.
Tin Sn Primary metal found in many solder alloys.
Theta Amount of rotation.
Thixotropic Adhesive or solder paste characteristic of becoming more fluid when in motion.
Time Above Liquidus Refers to the period of time at which the solder alloy is liquidus.
Tomb Stoning A component flipped to a vertical position on one solder pad.
Tooling Hole Non plated holes used for PCB alignment during processing.
Touch Less Centering Component centering using vision or laser alignment.
TQFP Thin Quad Flat Package Refers to a group of thin IC packages with leads on all four sides.
Tray Waffle tray Flat plastic matrix component carrier.
Tray Elevator Tray Handler Tray component feeding unit supplying the component into the placement machine.
TSOP Thin Small-Outline Package Refers to a package type usually used for memory ICs.
TSQFP Thin Shrink Quad Flat Package Group of small and thin IC packages with leads on four sides.
TSSOP Thin Shrink Small Outline Package Refers to a specific group of small and thin IC packages.
Turret Head A placement head unit with multiple heads, rotating parallel to the PCB.

 

U

Underfilling A filling material is injected under the component. Usually used on Flip-Chip applications to improve reliability.
Ultraviolet Refers to energy transfer by ultraviolet wavelength radiation. Used in some curing systems.
UV Ultraviolet Refers to energy transfer by ultraviolet wavelength radiation. Used in some curing systems.

 

V

Vapor Phase Soldering A method of condensation heating where the PCB is lowered into a hot vapor. The vapor condensates at the PCB surface and thereby heats it.
Via Hole A plated through-hole connecting PCB layers.
Vibratory Feeder A vibrating bowl and or track or tray system used to feed a mass of the same parts components to the placement machine.
Viscosity It is commonly perceived as a liquids� "thickness", or resistance to pouring. Viscosity describes a fluid's internal resistance to flow
VOC Volatile Organic Compound A organic fluid that rapidly vaporizes.
Void An enclosed space devoid of solder inside a solder fillet. Primarily caused by solder encapsulated out-gassing of solvents.
Volatile Organic Compound VOC A organic fluid that rapidly vaporizes.

 

W

Waffle Tray Flat plastic matrix component carrier.
Water Soluble Flux Flux usually containing organic acids and no rosin. Classified OA.
Wave Soldering A soldering process where the PCB�s are soldered by passing a wave of molten solder alloy.
WEEE Waste Electric and Electronic Equipment EU directive 2002/96/EC with the purpose of preventing electronic equipment waste and increase reuse and recycling.
Wetting A solder alloys� ability to flow and wet a metal surface.
Wetting Balance An instrument used to measure wetability.
Wire Bonding A die connection method attaching aluminum or gold wires between the pads of a bare IC and the component lead.

 

X

X-axis Horizontal movement axis that is usually left to right.
X-Ray Inspection Typical inspection technique for area array device used to determine the existence of bridges, shorts and inconsistent solder melting.

 

Y

Y-axis Horizontal movement axis that is is usually front to back.
Yield-The percentage of acceptable PWB assemblies after a given process step.

 

Z

Z-axis Vertical movement axis that is is usually up and down.

 

SOLDERING TIPS

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