SMT/THR PCB-COMPONENTS

3 THE SMT PROCESS
FOR MODULES WITH THR COMPONENTS
3.4 The placement process
Automatic sequential placement is one of
the placement processes that is used
most frequently in the SMT process. Use
is made of both pick & place systems
and of collect & place systems (chip
shooter). In the pick & place station, only
one components is taken from the
component feeder by means of a vacuum
pipette, and is placed on the pcb.
Pick & Place head transports SL-SMT 3.5
By contrast, a chip shooter transports
several components to the corresponding
placement position and deposits them
there.
Packaging of the components is the
basis for the use of both processes.
A distinction is made between tape-onreel,
tray, tube and bulk. The pick & place
process with tape-on-reel or tray has
established itself for leaded terminal
elements.
The following parameters must be
observed with regard to the optimum
placement suitability of leaded terminal
elements and thus easy integration
into the placement process with usual
standard placement systems:
Tray packaging accord. to IEC 286-5
• packaging in line with standards:
fully automatic feeding of the
terminal elements with tape-on-reel
or tray is possible
• dimensional stability of the
component: lowest possible water
absorption during storage under
normal climatic conditions ensuring
pitch fidelity of the component
• suction surface of the component:
determined in relation to the weight
or size for the use of standardised
vacuum nozzles
• precision of the pin end position:
smallest possible tolerances
(in addition to hole position and
machine placement tolerance)
prevent problems caused by collision
of the component with the PCB
This results in the following
requirements for leaded terminal
elements:
• minimised weight for an placement
speed that is as high as possible
• minimised component length for a
high rotation and transport speed
and thus maximum placement
performance
• minimised height to avoid a
restriction of the travel height
over the PCB and thus to prevent
collisions
Tape-on-reel packaging accord. to IEC 286-3
• minimised tooling effort by using
components in high packed numbers
to achieve lower product and tooling
costs
12 APPLICATION INFORMATION