Design Guide & Applications Manual
F
or Maxi, Mini, Micro Family DC-DC Converters and Configurable Power Supplies
Maxi, Mini, Micro Design Guide Rev 4.4 vicorpower.com
Page 72 of 88
Apps. Eng. 800-927-9474 800 735.6200
15. Surface Mount Socketing System (SurfMate)
SurfMate is a surface-mount connector system for use
with pin-compatible Maxi, Mini, Micro Family converters
and input / front-end modules. For the first time, circuit-
b
oard designers and assemblers have the ability to surface
mount high-density DC-DC converters having current
r
atings up to 50 A. (Table 15–1)
SurfMate utilizes a pair of surface-mounted headers that
contain sockets to accept the input and output pins of the
module. (Table 15–2) The SurfMate header assembly is
compatible with any thickness PC board, does not
increase the module mounting height above the board,
and is available for all three standard module size: Maxi,
Mini, and Micro (full, half, and quarter bricks).
SurfMates are available packaged in standard recyclable
JEDEC-style trays for use with automated pick-and-place
equipment and are compatible with standard reflow
solder operations. After reflow, the modules are simply
inserted into the SurfMates. Any secondary soldering
operation used for through-hole sockets or pins can now
be entirely eliminated —reducing manufacturing time and
eliminating dual processes.
This unique interconnect scheme combines the inherent
flexibility of component power designs with the manufac-
turing efficiency of surface-mount assembly.
PRINTED CIRCUIT BOARD DESIGN AND SOLDER
GUIDELINES FOR THE SURFMATE SOCKETING SYSTEM
Recommended PCB layout drawings for SurfMates are
provided in the following links. All unspecified PCB dimen-
sional tolerances comply with ANSI/IPC-D-300 for Class
“B” boards. DXF versions of the PCB outlines are available
in the SurfMate section of the
Vicor mechanical drawings
web page.
Recommended PCB Construction. The SurfMate system
is capable of very high current-carrying capacity. We
therefore recommend a multilayer PCB with 3-ounce
copper and internal power and ground planes. Consult
the drawings for the recommended size and quantity of
via holes for carrying current to the internal planes.
Solder Mask and Pad. Two solder mask keep-out areas
are recommended. The larger area encompasses the
complete pad area at either end. It ensures the proper
height of the 3-ounce solder pads to the surrounding
laminate. This provides for the optimum gap between the
SurfMate and the PCB 0.0042" ±0.0004" (0,106 mm
±0,010 mm), minimizing the solder paste thickness
required for quality solder joints. Without this solder mask
keep-out area, the gap may widen, (see “Flush-Mounted
Pads”), requiring thicker solder paste to fill the larger gap.
The smaller solder mask keep-out areas are circular, and
are located on each pad, for the solder joint between the
PCB and the SurfMate. The remainder of the pad has a
c
overing of solder mask. The solder paste is dispensed in
a rectangular area covering the soldering area and part of
t
he solder mask area. During soldering, the paste will
migrate away from the solder mask area to the soldering
area, providing ample volume for quality solder joints.
Each pad features a non-plated through hole in the center
of the pad to provide a venting function. It is normal for
the solder joint to have a slight void centered on this
through hole.
Solder Paste. Solder paste thickness requirements will
vary depending on whether the board pads are flush or
elevated from the laminate.
Elevated Pads (preferred). The ideal height for elevated
pads is 0.0042"( 0,106 mm) ±10%. This can be achieved
by using a 3-ounce copper surface layer. With this height,
a minimum solder paste thickness of 0.006" should be
used. Thicker stencils of between 0.008" (0,203 mm) and
0.012" (0,305 mm) are preferred.
Flush-Mounted Pads. For boards with flush-mounted
pads a minimum of 0.010" (0,254 mm) solder paste
should be used. Preferred thickness is between 0.012"
(0,305 mm) and 0.016" (0,406 mm).
Placement. SurfMate locating pins will engage in the cor-
responding PCB holes with a light push of the SurfMate
into the solder paste. The SurfMate should not be taped
or adhered in place. The surface tension of the solder
during reflow will center the SurfMate parts on the PCB,
resulting in accurate positioning.
Equipment and Solder. Soldering of SurfMates should
be done using either an infrared or convection oven
reflow process. Solder type Sn63Pb37, or equivalent, with
a eutectic temperature of 361°F (183°C) should be used.
Higher temperature solder is not
recommended.
Standoffs. Mounting standoffs are required for SurfMate
applications. The location for standoff holes is shown on
the PCB layout. A selection chart of recommended
standoff kits is provided in this section.
Module Pins. SurfMates must be used with modules with
the “S” or “F” pin style.
Module Insertion / Extraction. Sockets and modules are
rated for up to 5 insertions and extractions before requiring
replacement. When installing a module, lightly place it
into position so that all pins are properly aligned over each
socket. Then apply even pressure by uniformly tightening
each of the mounting screws through the mounting slots
on the baseplate into the pcb mounted standoffs. For
