Soldering And Cleaning Processes
This application note is designed to provide step-by-step
processing recommendations. It covers the popular SMC
soldering processes currently in use and provides recommenda-
tions and cautions for each step. Since many variations of
temperature, time, processes, cleaning agents and board types
are found in the electronics industry, you’ll want to test and
verify your own system.
The process steps, recommendations and cautions are
based on Bourns Trimpot surveys of SMC users, equipment
manufacturers and materials suppliers. Also, comments
reflect results of Bourns’ testing. Our findings suggest the
following soldering and cleaning processes:
1. SOLDERING - Forced Hot Air, Convection, IR, Vapor Phase
(In-Line), Wave (Single and Dual)
2. CLEANING - Solvent, Aqueous, Semi-Aqueous, No-Clean
On the facing page are the common methods, materials and
maximum temperature/time parameters for soldering and
cleaning processes.
1
Solder Paste
Printing
Reflow
Adhesive
Application
Flow (Wave)
2
SMC
Placement
GENERAL
Use pick-and-place
equipment with
vacuum nozzle ID size
that allows adequate
suction to pick the
SMC out of the
embossed cavity.
3
Adhesive
Cure
Flow (Wave)
4
Flux
Application
Flow (Wave)
5
GENERAL
Use the optimum
solder paste for the
pattern, printing
process, solder paste
density and solder
joint quality.
GENERAL
The adhesive must hold
the SM Component
(SMC) in correct
orientation upon place-
ment and maintain
correct trimmer position
during physical
handling before final
solder processing.
GENERAL
Use heat/time cure
method with either
convection oven or
infrared radiation.
GENERAL
Use the correct flux
to remove surface
oxides, prevent
reoxidation and
promote wetting.
RECOMMENDED
Cure using the
temperature and
times recommended
by the adhesive
manufacturer.
RECOMMENDED
Use Sn 63% Pb 37%
solder paste. Use 8 to
10 mil thickness for
solder paste print.
RECOMMENDED
• RMA
• No-clean SRB
(Synthetic resin
based)
• OA (Organic Acid)
(See caution)
RECOMMENDED
The nozzle inside
diameter (ID) should
not exceed .100 in.
(2.54mm) to ensure
adequate suction and
part alignment.
RECOMMENDED
To assure positional
stability, place a single
dot of epoxy under the
SMC.
EPOXY
CAUTION
Since solder paste
usually contains a high
percentage of activators,
you must ensure
adequate cleaning to
remove all residues,
unless no-clean (low
solids) paste is used.
CAUTION
Use enough cure
time to assure
complete adhesive
transition from fluid
to solid.
CAUTION
Avoid highly
activated fluxes.
Consult factory before
using OA.
CAUTION
Assure parts are
placed so that all
terminals are
equidistant (<4 mils)
from the solder pads.
Align terminals with
solder belt direction of
travel to avoid body
shadowing effects
during flow soldering.
CAUTION
Stability after placement
is a direct function of
the volume of adhesive
used. Use enough epoxy
to assure stability
through the cure
process.
Avoid overflow of epoxy
to solder pad and
terminal areas.
Specifications are subject to change without notice.
84
BOURNS [ BOURNS ELECTRONIC SOLUTIONS ]
