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An Analysis of Archimedes Screw Design Parameters
An Analysis of Archimedes Screw Design Parameters and their
Influence on Dispensing Quality for Electronics Assembly Applications.
Daryl Santos and Sunil Chhabra
State University of New York at Binghamton
Binghamton, NY - 13902
Tel: (607) 777-4769; Fax: (607) 777-4094; Email: santos@binghamton.edu
Douglass Dixon, Wendy Cummings, Sergio Porcari and Steven Rocco Marongelli
Universal Instruments Corporation
Binghamton, NY - 13902
Tel: (607) 779-4630; Fax: (607) 779-7212; Email: dixond@uic.com
ABSTRACT
Dispensing any fluid material onto a mixed technology printed circuit board (PCB) substrate has two basic
requirements: applying the material to the exact location required, and dispensing a dot of exact volume.
Due to the decreasing pad sizes, and the typical density required in the material pattern, these are major
challenges [3]. There are two basic types of dispensing mechanisms that are used for practical production:
the Archimedes Metering Valve (AMV) and the Positive Displacement Pump [5]. The performance of the
Archimedes Screw in the AMV depends a great deal on screw design and operating conditions. The
principle geometric variables of the Archimedes Screw are the channel depths, i.e., the radial distance
between the cylinder surface and root diameter of the screw, the pitch of the screw, the type of threads and
the number of channels through which the material can flow. The dimensions of the nozzle, such as the
nozzle ID and stand off height, and the rheological properties of the material also influence the parameters
required for a consistent dot. Dispensing with an AMV is based on the laws of momentum, fluid dynamics,
energy, and mass transport. The amount of material dispensed depends upon the pitch of threads, depth of
cut, type of thread, length of screw, the number of starts, and angle of rotation of the screw. The quantity
of material dispensed increases with an increase in depth of cut, decrease in pitch, increase in encoder
counts, and increasing the number of channels. This paper studies the effect of different geometric
variables of the screw, and the screw-nozzle combination that optimizes the quantity of material dispensed
without affecting dot consistency.
