SMT Stencil Glossary

A
Aspect ratio
The ratio of the thickness of the PCB to the diameter of its smallest via hole. A via hole with aspect ratio greater than three may be susceptible to cracking.

B
Ball Grid Array (BGA)
An IC package with solder balls that are arranged in a grid pattern and act as the input/output points.

Bridging
Errant molten solder that spans two conductors (bridges) to complete an unwanted connection, causing an electrical short.

C
CAD/CAM Systems
A computer-aided design/manufacturing method for translating circuit designs into actual products. They may assist in performing all steps in artwork generation.

Check Plot
Check Plots are PDF images of what holes we intend to cut for you. You will need to reply with approval if you receive this.

Convection/IR
A solder reflow oven for SMD interconnect that combines convection and infrared (IR) radiation heating.

Conveyor
A PCB transporting system for moving assemblies to various processes. An edge conveyor supports the boards at opposite sides; the mesh conveyor fully supports the board; the secondary conveyor is located below the edge mechanism to catch fallen components during solder reflow.

D
Dewetting
A defect owing to inadequate cleaning via flux in which the solder coating recedes, leaving irregular material deposits.

Dispensing (syringe)
Application of adhesives by pressurized (hydraulic or pneumatic) force for a specific period required to emit an "appropriate" amount of material through the needle and onto the target location.

Due Date
This is the date that you would like the stencil to arrive at your location.

E
Epoxy
A polymeric family of thermosetting resins generally used for adhering components to metallic or substrate surfaces.

F
Fiducial Data
Fiducials are alignment marks to align the stencil to the board. In most cases ONLY automatic printers use fiducials.

Fine Pitch
A center-to-center lead distance of surface mount packages of 0.025" or less.

Flip Chip
A leadless structure that is electrically and mechanically connected to the substrate via contact lands or solder bumps.

Frame Size
This is the size frame specified by the printer manufacturer to be used in your printer.

L
Land
A portion of a conductive pattern usually, but not exclusively, used for component connection, attachment or both.

Land Pattern
Component mounting sites located on the substrate that are intended for the interconnection of a compatible surface mount component.

Lead Pitch
The distance between successive center of the leads of a component package. The lower the lead pitch, the smaller the package area for a given pin count in a package.

Lead Free Application
This will help us to determine if we need to apply any special design rules for solder paste release.

N
No-clean paste
A very low-residue soldering paste having a solids content between 2.1 and 2.8 percent by weight.

No-clean soldering
A soldering process that uses a specially formulated solder paste that does not require the residues to be cleaned after solder processing.

P
Pad
A portion of a conductive pattern usually, but not exclusively, used for the connection, attachment or both of components.

Panelized Boards
Are you printing individual boards or a panel of more than one up?

Part Number
This is an identification number for your project that will be etched on the stencil.

Pick-and-place
A programmable method of component placement using machines to automatically pick parts from a feeder, then move to a precise location on a PCB and place them in the correct site.

Placement Rate
The speed of a complete component placement cycle beginning with component/part pick-up, move to the placement site and the return to the feeding source.

Preheat
That part of the solder reflow process at which a board is conditioned for peak temperatures via heating from ambient.

Printed Circuit Assembly (PCA)
General term for a PCB fully assembled with all electrical, electromechanical and mechanical components.

Printer Name
This helps us to ensure the correct stencil size is being ordered. Enter N/A for hand printing.

Q
Quad Flat Pack (QFP)
A term used for SMT packages with leads on all four sides. Most commonly used to describe packages with gull wing leads. Also known as a flat pack, but flat packs may have gull wing leads on either two or four sides.

R
Reflow Soldering
A process of joining metallic surfaces through the mass heating/cooling of preplaced solder paste between two surfaces (i.e., component leads and PCB pads).

Repair
Restoring the functional capability of a defective.

Rework
Repetition of a manufacturing process to bring an assembly into compatibility with a spec or contract requirement.

S
Squeegee
A rubber or metal blade used in stencil printing to wipe solder paste across the stencil's face, forcing the material through the patterned apertures and onto the PCB.

Solder Ball
A defect in which small spheres of solder separate from the main body of material forming the solder joint. Causes include excessive oxides or moisture in the solder paste.

Special Instructions
Include any special requests, comments, concerns or questions here.

Stencil
A metal sheet bearing a circuit pattern cut into the material. The most common materials is stainless steel.

Stencil File(s)
This is the solder paste layer that you want laser cut into the stencil.

Stencil Side
This acts as a more detailed identifier of the stencil and will be engraved with the part number.

Stencil Thickness
This is the thickness of the stainless steel you want your stencil made from. We can choose for you based upon your design.

Surface Mount Technology (SMT)
A method of assembling PCBs or hybrid circuits in which components are mounted onto the surface rather than inserted into through-holes.

V
Vacuum pickup
A parts handling instrument through which a vacuum force secures and holds them for placement.