409-35001
Rev C
18
of 92
The pressing process can be controlled in one of five ways:
1.
FIXED FORCE -
A connector can be pressed to a set force, such as 5 kN [.56 tons/1,124 lbs]. This is
a common technique used by hydraulic and pneumatic presses. It is the least sophisticated method
available and is the most likely to damage the PCB or connector.
2.
FIXED FORCE PER PIN -
A connector can be pressed to a set force per pin, such as 150 N [33.7 lbf]
per pin. This is slightly better than the first method because it recognizes that the force applied should
be proportional to the number of pins being pressed. It cannot, however, compensate for normal
variations in required force per pin for different connectors, in different positions, in different boards.
3.
PRESS TO HEIGHT
–
A connector can be pressed to within a programmed distance short of seating
on the board surface. This is the gentlest process possible because it exerts only enough force to
press the pins into the board. No excess force is pressed into the connector plastic or the board. This
sophisticated technique is made possible by the control available using an electric servo press head
and a rigid press structure. In order for press to height to be accurate, the board thickness must be
precisely known. This can be done using the thickness measurement probe and sequence provided.
4.
(PARS)
–
PERCENT ABOVE RANGE SAMPLE
–
A connector can be pressed with force that is
proportional to the actual resisting force detected during the pressing cycle. We call this Percent
Above Range Sample, or PARS. In this technique, the connector’s resisting force while pressing is
sampled and averaged over a distance range above final seating to the board surface. The final force
percent added assures complete seating of the connector. This is the most widely used technique
because it limits the stress to the assembly but does not require great accuracy for board thickness
measurement.
5.
FORCE GRADIENT
–
Monitors the rate of change of force to distance. This method is used for robust
connectors that need to be seated against the board surface. Generally, the force vs. distance plot will
make a steep upturn as the connector contacts the board surface. The connector stops moving so the
force rises quickly.
A minimum
slope is specified for the upturn in terms of ΔForce over ΔDistance, which corresponds to
how solidly the connector is pressed against the board. A conversion tool is provided for those
accustomed to using the legacy force gradient programming method, which uses the production graph
scaling and graph gradient angle.
Board Thickness Measurement
Board thickness measurement facilitates the press to height technique by measuring the actual thickness
of the PCB before the pressing cycle starts. If the board thickness is not measured, the program uses a
nominal thickness in height calculations.
Optional Accessories
ACAL (Automatic Calibration) Unit
There are two different units, one for a 5T machine and one for a 10T. They are used to recalibrate the
machine, which must be done annually. This accessory is bought so the company can calibrate the
machine on their own.
Bar Code Reader
The bar code reader option allows PCB serial numbers to be quickly entered for tracking purposes.
Pressing tools can also identified by bar code for efficient and accurate control. Tool identification can be
enabled by adding the Tool ID condition to the press sequence.
CBP MKII SensiPress Anvil Extension
This SensiPress option is specific to the CBP MKII machine only. There are three different dash numbers
to associate with the machine height that is bought. The extension is larger than the original received so
that the head can get closer to the table top if a smaller product needs to be pressed.
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