Glossary of PCB Assembly Terms

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Accumulating Conveyor
Stores a number of boards from the upstream line and releases them one at a time into the downstream line. The standard length is normally 72 inches and is used ahead of any operation in a line that has a variable cycle time. One example would be on the output of a re-flow oven, allowing the oven to be ahead of some manual assembly or test operation. The Accumulating conveyor utilizes a special low friction, continually running, edge carry chain that allows the boards to "accumulate" against a stop at the end that then releases them one at a time when the next operation calls for a board.

Automatic Optical Inspection. Uses television and computer technology to look at and make an inspection of a PCB or other object.

A condition that causes the machine to stop, requiring operator intervention to resume operation.

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Board Loader
Takes bare unpopulated PCBs from a stack and feeds them one at a time to the production line. Dyna3 offers BBLs that hold an 18-inch or a 6-inch stack of boards.
Board Inverter  
Used to turn a board over when processing 2-sided boards. Example after side one is complete, turn over before the screen printer for the second side. Edge Carry only.

Buffer Storage
An edge carry conveyor that accepts boards from the upstream line and either passes them through or stores them within the machine for future processing. Depending on the requirements of your process FIFO or LIFO are available. An example would be on the output of an oven to allow it to empty in the event of a downstream stoppage. Buffers are also available with removable storage units called “magazines” for off line storage or moving. See Magazine Storage.

Board Cleaner
A machine used in the production line to remove solder residue and other foreign material acquired during assembly from the PCB. These cleaners can be Inline or batch type, the latter requiring the boards to be loaded into the machine prior to washing similar to the kitchen dishwasher.

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Case Controlled
Continuous run conveyor without PLC control.
The product transfer electrical interface “handshaking” that occurs between two adjacent machines. The standard used is SMEMA 1.2

Control Functions
E-Stop: Push for Emergency Stop, twist & pull out to reset.
Start/Reset: Push to start, If in E-Stop press to reset.
Release: In Audit mode releases stopped PCB.
Audit/Bypass: Select Audit/Bypass Audit-Stops PCB waiting for operator to press.
Release; Bypass-passes product through.

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Mechanically engaged switch located on the electrical enclosure door and wired into the machine power circuit designed to remove AC supply power when the door is opened.

Any location after the present or reference machine position within the in-line configuration of assembly machines.

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Edge Carry Conveyor
Uses a narrow belt or chain that contacts just the edge of the PCB, not interfering with components or leads on the bottom side of the board.

Edge Contact
Width of the belt contact along the edge of a board in an Edge Carry Conveyor. Dyna3 normal maximum is 0.187 inches although narrower edge clearances are available. May also be called Edge Clearance.

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An operational or component failure condition that causes the machine to stop immediately requiring attention to resume operation.

Flat Belt
Utilizes a wide flat belt to carry the product. Dyna3 Flat Belt Conveyors are available up to 24-inch widths.

Follow the
See: Width Adjustment Types

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Hand Crank
Width Adjust
  See: Width Adjustment Types

Heavy Duty
Dyna3 offers a line of Heavy Duty Edges long, 24 inches wide and weighting up to 75 lbs Carry Conveyor products that are capably of handling boards up to 42 inches

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Incline/Decline Conveyor
Used as an interface between the exit height of a specific wave solder machine and a specific downstream line height. Normally Flat Belt but Edge Carry available. Cooling fan hoods are also an option. May also be referred to as a Wave Exit conveyor.

Mechanically engaged switch located on the hinged and removable machine guards and wired into the machine E-STOP circuit.

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Light Curtain
The use of multiple photocell and light sources arranged to form a “curtain” of light beams, which will detect a person, or object that pass through the curtain. When normally used in product detection situations two or more photocells must “see” the object to confirm its presence. This is done to prevent “false” recognition if for some reason only one light beam is broken. Also used as a safety shield around potentially hazardous machinery. An array of sensors is used to create a “curtain” of light and any light beam broken by a person will stop machine operation.

Lift Gate
A conveyor that an operator manually lifts, like a drawbridge, to allow a walkway in a production line. Normally used for maintenance access.

Line Height
Height of the Line above the floor. The SMEMA standard is 37.5 inches +/- 0.5”.

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A portable enclosure used to hold PCBs or product. These allow manual movement from one process to another. As an example: rejected product to a rework station or movement of product between production areas that are separated by a large distance.

Magazine Loader
Accepts PCBs for the upstream line and stores them in a removable enclosure called a "magazine”. This is a convenient way to collect defective boards for movement to a rework station.

Magazine Unloader
Removes PCBs from the magazine placing product into the production line.

Multi-Magazine Loader/Unloader
Loads and unloads PCBs to and from magazines to the production line. Up to 5 magazines are buffered (2 empty, 2 full, and 1 in process).

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The adjacent machine that receives product transferred out from previous (feeding) machine.

National Fire Protection Association (
Sets electrical and fire safety standards for industry.

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Pallet / Carrier
A frame used to hold a PCB during assembly. These are used primarily for manual assembly on a “slide line” or to hold smaller or odd shaped boards as they pass through a wave solder machine. In many applications, PCBs are irregular in shape and size, large and heavy, or have special components or devices that require masking. In such cases the pallet carrier is an ideal solution to an otherwise difficult situation. Dyna3 fabricates a wide variety of circuit board carriers to meet any application.

PCB or
Printed Circuit Board
The “Printed Circuit Board” replaced point-to-point wiring beginning in the 1960s. The PC boards start out with a thin solid copper sheet bonded to a fiberglass board. The circuits are not “printed” on the board but rather those areas of the copper not required to create the circuit are etched away by a photographic process. This leaves only the interconnections that you see on the Printed Circuit Board creating wiring for the circuit.

Pick & Place Machine
Automatically “picks” components from a supply, normally a roll, or bin and “places” them on the PCB in their appointed spot. Depending on the technology used in certain model machines these may referred to as “Chip Shooters.”

Programmable Logic Controller. (Simple Computer)

Power Width Adjust
See “Width Adjustment Types”

The adjacent machine that transfers product into next machine.

Progressive Assembly
Manual assembly line with workstations spaced along the line where each worker adds components to the PCB. Unlike a “manual slide line”, built in conveyors move boards along the line.

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Quick Width
  See: Width Adjustment Types

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Reflow Oven
PCBs are carried through the Oven on edge carry chains or a moving wire mesh belt while the temperature is raised to very specific settings to melt the paste screened on the board there by soldering the components.

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Selective Solder Machine
Solders only areas on the PCBs programmed in to the machine. Uses a small fountain of Solder. Sometimes used for components that were manually placed or added after the reflow process.

Screen Printer
Uses a silkscreen like process to put flux & solder in the form of a “paste” on PCBs where the component leads mount.

Shuttle Gate
An Edge Carry conveyor that automatically extends and retracts to deliver boards across a normally open walkway in the production line. There are two types. “Extend to deliver” or “extend to receive”.

Shuttle Transfer Table
Used to distribute product between two parallel processes using a horizontal moving table. For example two can be used to allow two production lines to share a single reflow oven.

Slide Line
An assembly line where PCBs are moved along manually by the workers from station to station as parts are inserted in the board. These look like long workstations with workers spaced every 3 or 4 feet along the line, sometimes working from both sides of the line. Slide lines are available with the rails flat or tilted at an angle.

Surface Mount Equipment Manufacturers Association sets standards used within the SMT industry. Dyna3 most often refers to the SMEMA Mechanical Equipment Interface Standard 1.2 Electrical Interface. Communication protocol between machines for example. Complete information on this standard is available at the IPC Association Connecting Electronics Industries website (

SMT or Surface Mount Technology
The component leads only touch pads on the “surface” of the PCB. They are held in place by the stickiness of the paste, which contains solder and flux, until they pass through the Reflow oven, which actually melts the paste soldering them in place. This enhances full automation of the assembly process as well as making better use of the space on the board.

Surface Mount Technology Association (

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Through Hole Process
Component leads are placed in holes in the PCB at points where they are to be soldered. The hole is then filled with solder to complete the process.

Movement of product into, across, and then out from the machine conveyor.
Transfer Conveyor  
Incorporates intelligent control like a PLC (Programmable Logic Controller) or computer to control the movement of boards or product.

Transfer Workstation
An Edge Carry or Flat Belt conveyor that incorporates a work surface, light and shelf for easy human interface with product as it passes on the line.

Used to rotate boards where changes in direction of the production line are encountered. Normally 90 degrees but could be any angle. Also can be used to divert defective product from the main line after an inspection station or introduce reworked product into the line before inspection.

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Any location before the present or reference machine position within the in-line configuration of assembly machines.

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A condition that requires attention before the operation of the machine is affected.

Wave Exit Conveyor
Used as an interface between the exit height of a specific wave solder machine and a specific downstream line height. Normally Flat Belt but Edge Carry available. Cooling fan hoods are also an option.

Wave Solder Machine
Passes the PCBs over a “wave”or weir of solder within the machine that just makes contact with the bottom of the board soldering the components. Wave Soldering is used mainly in the through hole manufacturing process. As a rule the boards travel up an incline within the machine making the output of wave solder machines higher than the input. There is no standard exit height and may vary from model to model so exit conveyors are custom made to match a specific model solder machine.

Width Adjustment Types
Quick Width Adjust: Manually unlock handles and slide the adjustable rail to desired width.

Hand Crank Width Adjust: Moves the adjustable rail by turning a hand crank.

Power Width Adjust: Manually operated motorized width adjustment. Push one button to send adjustable rail away from the fixed rail a 2nd button to bring adjustable rail closer to the fixed rail a digital width readout is available.

Follow the Leader: Linking many machines to progressively move the adjustable rails to the width setting on a master unit.

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Zone 2X, 3X etc.
This refers to how may “segments” or zones a given conveyor unit has. Each zone is a separate conveyor section placed end to end with others in a single frame “rail” so that a PCB can be moved from zone to zone.

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