Tel: (800) 404-0204
www.ironwoodelectronics.com
Leadless Surface Mount Foot Soldering Instructions
The Ironwood Electronics, leadless style, emulator foot (parts with a 'SF-' prefix and a '-L' suffix) is
designed to solder to the standard gull-wing type quad flat pack (QFP) surface mount land pattern.
Because the Ironwood emulator foot does not emulate the physical characteristics of a QFP gull-wing
package, the methods used to solder it to a target PCB are different. Several methods are possible, 3 are
listed here in order of preference:
1. Solder Paste and Reflow Oven
(a) Determine an appropriate temperature solder paste for your application.
(b) Apply a continuous bead of paste to the target PCB pads as shown in Fig. 1. Cover approximately 1/3
of the pad between the center of the pad and the outer edge. Begin with this amount and add additional
paste after reflow, if necessary (excessive paste on an initial trial will be difficult to remove).
(c) Note the target PCB QFP land pattern and the emulator foot Pin 1 locations.
(d) Align and place the emulator foot onto the solder paste and land pattern as shown in Fig. 2. 'Pick and
place' equipment or a vacuum pen, are recommended (if they will accommodate the foot), but, handling the
foot by the gold pins and placing on the land pattern by hand will suffice.
(e) Reflow target PCB with emulator foot in reflow oven (convection, IR, etc.). Time and temperature
settings will be determined by the manufactures of the solder paste and reflow oven. The Ironwood
leadless foot has a larger thermal mass than a gull-wing QFP package, and therefore, may require longer
reflow times or higher temperature settings. Surface tension between the liquid reflowing solder and the
emulator foot will center the emulator foot on the land pattern.
(f) Inspect solder fillets. Add additional so lder paste to solder deficient areas as needed or remove excess
with small tip solder iron and copper desoldering braid. If the solder has not completely reflowed, add
solder flux and repeat step (e). It may then, be necessary to increase the reflow temperature and/or time.
QFP surface
mount land
solder paste
Fig. 1 Top view of land
pattern with paste
L/3
L
QFP surface
mount land
Target
PCB
Fig. 2 Side view of emulator foot oriented
over land pattern
Page 1 of 2 LSI.doc, Rev. C
Tel: (800) 404-0204
www.ironwoodelectronics.com
Leadless Surface Mount Foot Soldering Instructions (continued)
2. Solder Paste and Hot Air Wand
Repeat steps (a) through (d) in method 1. The surface tension present between the solder and the emulator
foot in method 1, will not be present in method 2., due to the fact that only a small portion of the solder in
this method will be liquid at one time. It is necessary therefore, to align the foot over the land pattern with
greater accuracy.
(e) Reflow, with a hot air wand/gun, the solder over a few of the pads in opposite corners (diagonally) of
the land pattern.
(f) Check the foot alignment.
(g) Continue by reflowing the remaining solder paste. Add or remove solder as needed (see step (f) in
method 1.).
3. Soldering Iron
•This method has produced very good results but may be more time consuming than the other two
methods.
•Caution must be used when touching the soldering iron tip to the emulator foot. Excessive heat or
pressure may damage the pads on the side of the foot.
(a) Using a small diameter solder wire (approx. 0.015" or smaller) and a very fine tipped soldering iron,
add enough solder to two opposite corner (diagonal) pads to cover them.
(b) Align and place the emulator foot over the QFP land pattern (see steps (c) and (d) in method 1).
(c) Holding the foot in place, by pressing down gently on the gold terminal pins, place the iron tip on the
two pads to reflow the solder. This will tack and keep the foot in alig nment.
(d) Under a microscope or magnifying lens, if available, solder the remaining edge pads of the foot to the
target PCB land pattern using a liberal amount of solder (do not worry about shorts between adjacent
pads).
(e) Apply a generous amount of flux along the side of the foot.
(f) Start at one corner and pull the tip of the iron along the side of the foot to remove excess solder
deposits. Clean the tip of the iron often. Repeat this step several times starting at a point on the foot ahead
of the excess solder. Continue down the side of the foot until shorts are removed and a fillet is present
between all foot pads and target PCB pads.
(g) Repeat steps (e) and (f) for the remaining three sides.
Removing or Desoldering
Conventional methods can be used to remove a surface mount foot
from your target board, however we recommend the use of PRB Line®
D’SOLDER™.; This SMT device removal product avoids the use of
excessive heat that can compromise the integrity of our product and
your target board. The specially formulated alloy and flux make
desoldering quick and easy. This solution can be a time and money
saver for many applications. (P/N TL-DS123
Rev. C, 6/1/0, PJ, No Rev.
1. Changed document title from Leadless QFP Emulator Foot Soldering
Instructions.
2. filename: LSI.doc, Rev C” with footer autotext filename, Rev. C.
)
Page 2 of 2 LSI.doc, Rev. C
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