User Manual

APEX/APEX LT
Datasheet (Preliminary Rev 0.2) www.lsr.com Page 16 of 20
14.2 Reflow Soldering
A convection soldering oven is recommended over the infrared radiation type oven.
Convection ovens allow more precise temperature control, and more even heating of parts
regardless of material composition, thickness, or color.
Consider the IPC-7530 Guidelines for temperature profiling for mass soldering processes,
reflow and wave, published 2001.
14.2.1 Preheat Phase
Initial heating of component leads and solder paste balls, for removal of residual humidity.
Note: the preheat phase is not intended to replace prior baking procedures.
• Temperature rise rate: 1-4ºC/sec
Note: excessive slumping can result if the temperature rise is too rapid.
• Time: 60-120 seconds
Note: If the preheat is insufficient, large solder balls tend to be generated. Conversely, if
preheat is excessive, small and large balls will be generated in clusters.
• End Temperature: 150-200ºC
14.2.2 Heating/Reflow Phase
The temperature rises above the liquidus temperature of the solder paste selected. Avoid a
sudden rise in temperature as any slump of the solder paste could become worse.
• Limit time above liquidus temperature to 20-40 seconds.
• Peak reflow temperature: 230-250ºC
14.2.3 Cooling Phase
A controlled cooling phase avoids unwanted metallurgical effects of the solder, and possible
mechanical tensions in the products. Controlled cooling helps achieve the brightest possible
solder fillets with a good shape and low contact angle.
• Temperature fall rate: max 3ºC/sec
14.3 Pb-free Soldering Paste
Use of “No Clean” soldering paste is strongly recommended, as it does not require cleaning
after the soldering process. The pastes listed in the examples below meet these criteria.
14.3.1 Soldering Paste: Indium 5.1 (Indium Corporation of America)
Alloy Specification: SAC305 - Sn Zinc 96.5%/Ag Silver 3.0%/Cu Copper 0.5%
Alloy Specification: SAC387 - Sn Zinc 95.5%/Ag Silver 3.8%/Cu Copper 0.7%
Melting Temperature: 217ºC
14.3.2 Soldering Paste: LFSOLDER TLF-206-93F (Tamura Kaken [UK] Ltd.)
Alloy Specification: Sn Zinc 95.5%/Ag Silver 3.9%/Cu Copper 0.6%
Melting Temperature: 216-221ºC