Ironwood Electronics Leadless Surface Mount Foot Soldering Instructions - Manual

Page 1 of 2 LSI.doc, Rev. C
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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 solder 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
QFP surface
mount land
solder paste
L
L/3
Fig. 2 Side view of emulator foot oriented
over land pattern Fig. 1 Top view of land
pattern with paste
Target
PCB