Double-sided reflow in one reflow cycle
tible to this problem as well. No hold time
sDsrs advantages sDsrs Disadvantages
between reflow cycles, so less moisture
issues with PCBs and components. Eliminates one reflow process stage New process introduction
Only one heating process for Possible loss of components
Reduction in capital equipment
double-sided boards
Eliminating a reflow process means one
less piece of equipment is required in a
Reduction in capital equipment Gluing stage required
production line. The cost of power con-
Reduced floor space requirements New glue materials required
sumption and extraction systems for reflow
equipment is higher than any other piece
Reduced handling stages Glue curing process
of equipment on the line, and they are Increased PCB throughput speed Possible limits on component positioning
effectively halved.
Potential elimination of component
weight issues
Reduced floor space requirements
Eliminating a reflow oven reduces the
Improved solderability of OSP
floor space required in a manufacturing
circuit boards
area. Even with the need for an additional
Table 1. Advantages and disadvantages of simultaneous double-sided reflow soldering
printer or the use of a single dispenser for
both adhesive and paste, floor space is still
being saved.
Reduced handling stages
The number of handling stages is reduced
from a conventional surface mount
process, albeit only slightly reduced from a
fully double-sided reflow process.
Increased PCB throughput speed
The total process cycle time for each prod-
uct is reduced by the elimination of one
reflow soldering stage. The increased cycle
time for one printing or dispensing stage is
Figure 5. X-ray images illustrate BGA and surface mount components reflow soldered on the base of the board
still far less than the period taken to reflow during simultaneous reflow.
one side of a board.
Potential elimination of component
weight issues
In a liquid state there is a limit to com-
ponent weight during traditional double-
sided surface mount assembly. Large heavy
components can fall off the board. If
adhesive is used and cured it will increase
the range of components that can be used
on both sides of the board.
Improved solderability of OSP
circuit boards
Figure 6. Components that have been reflowed on the base of the board with the adhesive holding the parts in
There has been great debate on the ben-
place during a single reflow soldering cycle in a convection oven.
efits of using OSP: improved printing and
Figure 7. Bottom-sided images of chip resistors, BGA terminations, and a top-sided view featuring successful reflow of LED and intrusive reflow connector joints.
www.globalsmt.net Global SMT & Packaging – January 2009 – 5
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