LSM10A-D5 Datasheet, PDF (12/13 Pages) Murata Manufacturing Co., Ltd. – Single Output, Non-Isolated, 5VIN, 0.8-3.3VOUT, 10A, DC/DCs in SMT Packages

LSM-10A D5 Models
Tape & Reel Surface Mount Package
Single Output, Non-Isolated, 5VIN, 0.8-3.3VOUT, 10A, DC/DC's in SMT Packages
DATEL's LSM series DC/DC converters are the only higher-current (10A)
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 subsequently reflowed using high-temperature, lead-free solder.
Virtually all SMT DC/DC's today are unprotected "open-frame" devices
assembled 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 melt-
ing 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.
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 leads 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 tem-
perature 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.
250
221
200
183
150
100
50
0
Sn96.5/Ag3.5 Melting Point
Sn63/Pb37 Melting Point
HEAT SHIELD OUTSIDE TEMPERATURE
PCB TEMPERATURE INSIDE THE HEAT SHIELD
50
100
150
200
250
300
Time (Seconds)
Figure 6. Reflow Solder Profile
350
400
www.murata-ps.com
Technical enquiries email: [e-mail], tel: [phone]
MDC_LSM10A-D5.B01 Page 12 of 13