LSM-0.75/16-W3 MURATA [Murata Manufacturing Co., Ltd.], LSM-0.75/16-W3 Datasheet - Page 11

• Manufacturer Part Number: LSM-0.75/16-W3
• Description: Non-Isolated, Wide Input SMT DC/DC Converters
• Manufacturer: MURATA [Murata Manufacturing Co., Ltd.]

Tape & Reel Surface Mount Package
DATEL’s LSM series DC/DC converters are the only higher-current (16A) SMT
DC/DC’s 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 subse-
quently reflowed using high-temperature, lead-free solder.
Virtually all SMT DC/DC’s today are unprotected “open-frame” devices assem-
bled by their vendors with high-temperature solder (usually Sn96.5/Ag3.5
with a melting point +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 limita-
tions, 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 compro-
mise the reliability of their solder joints. Virtually all these devices demand you
“cool down” the Sn63 profile you are likely using today.
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)
Non-Isolated, Wide Input SMT DC/DC Converters
200
DATEL is not exempted from the Laws of Physics, and we do not have
magic solders no one else has. Nevertheless, we have a simple and
practical, straightforward approach that works. We assemble our LSM SMT
DC/DC’s 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 (100μ1m) of the unit’s copper leads. These units are
gold-plated with a nickel underplate. See Mechanical Data for additional
information.
The disposable heat shield (patent pending), which has a cutaway exposing
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
exceeding 2 minutes above 221°C (the melting point of Sn96.5/Ag3.5) are
easily achieved.
250
HEAT SHIELD OUTSIDE TEMPERATURE
Technical enquiries email: [e-mail], tel:
LSM-16A W3 Models
300
MDC_LSM-16A_W3.A04 Page 11 of 12
350
400
[phone]