ECE Projects Lab
Surface Mount Technology
What is SMT?
Surface Mount Technology
Used primarily in industry
Same circuitry with much smaller
components
Was not intended for individual soldering,
but gaining popularity
SMT Components
“Reflow”
a thermal process in which solder paste is
used to electrically connect components to
their attachment pads. It is the most
common means to attach a surface
mounted component to a circuit board
“Reflow temperature” is the temperature at
which the solder paste changes state from
solid to liquid
SMT Board
Why SMT (advantages)?
Much smaller size
Components on both sides of board
Leads can be much shorter reducing
inductance and resistance thereby
increasing performance
Prototyping is more indicative of the final
product
How to SMT solder (techniques)
Fine tip soldering
– Uses conventional soldering techniques on a
much smaller scale
Hot plate reflow
– Useful for single ICs with limited footprint
Oven reflow
– Uses soldering paste and reflows entire board
How to SMT rework
Solder wick
– Uses fine mesh conductive Copper braid.
Heat and capillary action pulls excess solder
away
Hot air reflow
– Uses hot air to reflow the solder with
components present
De-Solder vacuum plunger/sucker
– Uses small negative pressure to suck up
excess solder
Fine Tip Soldering
Conventional Equipment
Useful for Larger
components
Causes eye strain
Requires a steady
hand
Fine Tip Soldering
Specialized Fine-tip tools
Hot-Air Rework
Station AM6500 by
JBC
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–
–
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Fine tip solder tools
Desoldering tools
Hot tweezers
Hot air gun
Hot plate reflow
useful for smaller
boards as heat
distribution on a
hotplate is far less
uniform than a
convection oven
end point is
monitored visually
Oven reflow
Typical Reflow oven
– Large and bulky
– Expensive $$$ 
Cuisinart TOB 165
– Just as good
– A small fraction of the
cost
Oven Reflow Overview
After applying solder
paste and setting
components, the
board is inserted to
be “cooked”
End result is a
perfectly soldered
board for a fraction of
the cost (no eye strain
either)
Reflow Profile
The temperature of
the reflow process
must:
– be precise enough to
not damage IC’s
through excess heat
– be sufficient for reflow
of solder
Oven Reflow Steps
Apply soldering paste
Cook!
Set IC’s and components
Touch up (here using solder wick)
Industrial SMT Movie
Silicon Run II
Copper Solder Wick (rework)
useful for removing
excess solder
braided copper mesh is
used to remove solder
via capillary action
Fine-tip or conventional
soldering iron is used for
heating braid and solder
Hot air reflow (rework)
Hot-Air Rework
Station AM6500 by
JBC
–
–
–
–
Fine tip solder tools
Desoldering tools
Hot tweezers
Hot air gun
How hot air reflow works
Hot air used to
desolder IC
Vacuum extractor
pulls IC after solder
flows
De-Solder vacuum plunger/sucker
(rework)
Uses small vacuum
to pull solder away
from board
Hand-held manual
version
Heated tip &
vacuum combined
on SMT rework
station
Summary
Fine tip soldering is hard, but essential
sometimes
Hotplate or Oven reflow are great for
creating a whole board at once
Rework techniques include Copper wick,
Hot-air reflow, and de-solder vacuuming
ECE Projects Lab can do it all
Credits/Work cited
http://en.wikipedia.org/wiki/Surface-mount_technology
– General SMT info
http://www.heinc.com/jbc/repair.html
– Hot air reflow station website
http://www.bidservice.com/Browses/NF_Detailed_Item_View_new.a
sp?ProductID=20069
– Place to purchase typical reflow oven
http://www.seattlerobotics.org/encoder/200006/oven_art.htm
– Another group that has done a similar project with a toaster oven
http://www.circuitcellar.com/library/print/0704/Lacoste_168/
– Thermal profile for a toaster oven
Design Lab Website
Presentations available
Online Reflow Tutorial
http://www.ee.duke.edu/DesignLab/
Thanks!