LSM-16A C&D Technologies., LSM-16A Datasheet - Page 11

• Manufacturer Part Number: LSM-16A
• Description: Non-isolated, 13-80w Smt Dc/dc Converters
• Manufacturer: C&D Technologies.

Tape & Reel Surface Mount Package
Murata Power Solutions’ LSM series DC/DC converters are the only higher-
current (16A) SMT DC/DCs that can be automatically “pick-and-placed” using
standard vacuum-pickup equipment (nozzle size and style, vacuum pressure
and placement speed may need to be optimized for automated pick and place)
and subsequently reflowed using high-temperature, lead-free solder.
assembled by their vendors with high-temperature solder (usually Sn96.5/
Ag3.5 with a melting point of +221°C) so that you may attach them to your
board using low-temperature solder (usually Sn63/Pb37 with a melting point
of +183°C). Conceptually straightforward, this “stepped” solder approach has
its limitations, and it is clearly out of step with an industry trending toward
the broad use of lead-free solders. Are you to experiment and develop reflow
profiles from other vendors that ensure the components on those DC/DC never
exceed 215–216°C? If those components get too hot, “double-reflow” could
compromise the reliability of their solder joints. Virtually all these devices
demand you “cool down” the Sn63 profile you are likely using today.
Virtually all SMT DC/DCs today are unprotected “open-frame” devices
250
200
183
150
100
221
50
0
50
Sn96.5/Ag3.5 Melting Point
Sn63/Pb37 Melting Point
100
www.murata-ps.com
PCB TEMPERATURE INSIDE THE HEAT SHIELD
150
Figure 6. Reflow Solder Profile
Time (Seconds)
200
solders no one else has. Nevertheless, we have a simple and practical, straight-
forward approach that works. We assemble our LSM SMT DC/DCs using a
high-temperature (+216°C), lead-free alloy (Sn96.2%, Ag2.5%, Cu0.8%,
Sb0.5%). The LSM design ensures co-planarity to within 0.004 inches (100µm)
of the unit’s copper leads. These leads are gold-plated with a nickel underplate.
See Mechanical Data for additional information.
ing the package leads, provides thermal insulation to internal components
during reflow and its smooth surface ideally doubles as the vacuum pick-up
location also. The insulation properties of the heat shield are so effective that
temperature differentials as high as 50°C develop inside-to-outside the shield.
Oven temperature profiles with peaks of 250–260°C and dwell times exceed-
ing 2 minutes above 221°C (the melting point of Sn96.5/Ag3.5) are easily
achieved.
MPS is not exempted from the Laws of Physics, and we do not have magic
The disposable heat shield (patent pending), which has a cutaway expos-
250
Non-Isolated, 13-80W SMT DC/DC Converters
HEAT SHIELD OUTSIDE TEMPERATURE
Technical enquiries email: [e-mail], tel:
LSM-16A D12 Models
300
MDC_LSM 16A D12 Models.A03 Page 11 of 12
350
400
[phone]