Selecting
the proper solder paste for surface mount assembly requires consideration
and planning since there are
several factors that influence the applications and characteristics
of solder paste. Solder paste can be produced with no clean,
water soluble and RMA flux. The factors which must be taken into
account
include activity, tack
time,
printablilty,
cleanability, insulation and corrosion resistance.
All alloys are made from virgin metals that
meet or exceed specifications QQ-S-571, ASTM B32 and J-STD-006.
Other alloys may be available upon
request. The typical composition of solders for SMT and electronic
assembly applications are Sn63 and Sn62. However, alloys with melting
temperatures below the conventional
melting point of 183°C are being used for temperature sensitive
devices. Those assemblies requiring higher tensile strength utilize
the high temperature silver bearing alloys.
Qualitek solder powders are manufactured under inert atmosphere and strictly controlled
processes. The result is a high quality powder, characterized by uniform particle size
distribution, low oxide content, and high purity alloy compositions.
The solder particle shape and distribution effect the behavior and characteristics of
solder paste. Qualitek employs a state-of-the-art Laser Particle Size Analyzer to
determine the particle size range and to monitor the powder atomizing process. Scanning
Electron Microscope (SEM) is also used to observe the shape for the degree of sphericity
and the surfaces of powder for satellites. Other techniques include the oxide analysis. |
