Application Note AN-0801

VISHAY SEMICONDUCTORS
www.vishay.com
Modules
Application Note AN-0801
Mounting Instructions for MTP Modules
By Kevin Liu
INTRODUCTION
This application note introduces Vishay´s MTP
rectifier-switch modules and discusses the assembly and
PCB issues involved in their use.
Vishay´s MTP modules are distinguished by these key
features:
MTP modules are designed to provide reliable performance
in rugged 20 A to 100 A industrial applications. A single
housing is used to integrate power components, providing
higher power density. Various die selections are available in
several configurations. An integrated thermal sensor is also
offered as an option.
• Compact and easy to mount
• Fully isolated
• Low profile package suitable for assembly on PCB
• Low junction to case thermal resistance
These attributes allow MTP modules to fit into existing
assembly processes using standard reflow profiles or press
fit mechanical contact.
Important factors in the assembly process are:
• Heatsink design
• PCB design
• Power leads size/area
• Distance from adjacent heating parts
• Solder alloy choice
• Reflow profile
• Protection against electrostatic discharge (ESD)
Recommendations for each of these items and
requirements for mounting MTP modules to the PCB are
discussed in the following sections.
Fig. 1 - Example of MTP Module (solder pin)
ESD PROTECTION
IGBT, MOSFET, and diode modules are sensitive to ESD.
All MTP modules are ESD-protected during shipment with
an antistatic tube. Anyone handling or working with the
modules during the assembly process must wear a
conductive grounded wristband.
Fig. 2 - Example of MTP Module (press fit)
Revision: 13-Dec-13
The contact surface of the heatsink must be flat, with a
recommended tolerance of < 0.03 mm (< 1.18 mils) and a
levelling depth of < 0.02 mm (< 0.79 mils), according to
DIN/ISO 1302. In general, a milled or machined surface is
satisfactory if prepared with tools in good working
condition. The heatsink mounting surface must be clean,
with no dirt, corrosion, or surface oxide. It is very important
to keep the mounting surface free from particles exceeding
0.05 mm (2 mils) in thickness.
Document Number: 95002
1
For technical questions within your region: [email protected], [email protected], [email protected]
THIS DOCUMENT IS SUBJECT TO CHANGE WITHOUT NOTICE. THE PRODUCTS DESCRIBED HEREIN AND THIS DOCUMENT
ARE SUBJECT TO SPECIFIC DISCLAIMERS, SET FORTH AT www.vishay.com/doc?91000
APPLICATION NOTE
HEATSINK SPECIFICATION
Application Note AN-0801
www.vishay.com
Vishay Semiconductors
Mounting Instructions for MTP Modules
MOUNTING OPERATION
SOLDER TO PCB
Inspect the module to ensure that the contact surface of the
base is clean, and that there are no lumps or bulges on the
baseplate that could damage the base or reduce heat
transfer across the surfaces.
The PCB must be designed with appropriate tolerances on
its hole diameters.
Make a uniform coat on the heatsink mounting surfaces or
on module baseplate with a good quality thermal compound
is recommended; direct application with a roller or spatula is
also suitable. The test conditions for thermal resistance
values on the datasheet specify a uniform layer of thermal
compound with a thickness in the range of 0.08 mm (3.1
mils) to 0.1 mm (4 mils). The thermal conductivity of the
compound should not be less than 1.5 W/mK.
Bolt the module to the heatsink using the two fixing holes.
An even amount of torque should be applied for each
individual mounting screw. An M5 screw should be used
with lock washers. A torque wrench, accurate in the
specified range, must be used to achieve optimum results
when mounting the module. The first mounting screw
should be tightened to one third of the recommended
torque; the second screw should then be tightened to the
same torque. Full tightening of both the screws can then be
completed applying the recommended torque (see data in
bulletins). Over-tightening the mounting screw may result in
deformation of the package, which would increase the
thermal resistance and damage the semiconductors. After a
period of three hours, check the torque with a final
tightening in opposite sequence to allow the spread of the
compound.
The module base-plate planarity can vary from slightly
concave to convex with convexity typically 0.05 mm (2 mils)
when measured between the two fixing holes. This provides
for an optimal contact area with the heatsink (Fig. 3).
Soldering operations must be done so as to avoid inducing
any mechanical stress from pulling or tensioning the module
pins. The module stand-off can be used to help align the
PCB and keep proper distance. MTP modules can be
soldered to the PCB using hand iron or wave soldering
processes. To prevent overheating of the device, we
suggest the soldering time not exceed 8 s to 10 s at a
temperature of 260 °C. The mounting of the module on the
heatsink can be done either before or after soldering the
module pins onto the PCB.
If the module needs to be removed from the PCB, the first
step is to unscrew it from the heatsink, followed by gentle
movement of the module to separate it from the heatsink.
Thermal grease will remain both on the heatsink surface and
on the bottom baseplate surface.
PRESS FIT TO PCB
The solder-free press fit method can be used as an
alternative for contacting MTP pins to the PCB. The major
advantages of this method are the elimination of solder
reflow and its related temperature profile.
The majority of standard FR4 PCB boards can be used with
no special requirement in terms of dimension and number of
layers. Vishay tested both FR4 125 and FR4 180 PCB
models.
MTP pins have been designed with the size and shape
required to fit into the PCB holes during the assembly
process. The contact between the pin and PCB hole will
result in a very low contact resistance (less than 500 μΩ).
Double-sided or multilayer PCBs according to IEC 60249
can be used.
As per IEC 60352-5 the PCB material should be defined with
following specifications;
• PCB hole diameter: 1.12 mm - 1.15 mm
• Copper thickness in hole: 25 μm - 50 μm
APPLICATION NOTE
• Metallization in hole: < 15 μm
• End hole diameter (after hole plating): 0.94 mm - 1.09 mm
• Copper thickness of conductors: 35 μm to 400 μm 
(typical 70 μm to 105 μm)
• Metallization of circuit board: tin (chemical)
Fig. 3 - Description of “Module Convexity”
Revision: 13-Dec-13
• Metallization of pin: tin (galvanic) 




Document Number: 95002
2
For technical questions within your region: [email protected], [email protected], [email protected]
THIS DOCUMENT IS SUBJECT TO CHANGE WITHOUT NOTICE. THE PRODUCTS DESCRIBED HEREIN AND THIS DOCUMENT
ARE SUBJECT TO SPECIFIC DISCLAIMERS, SET FORTH AT www.vishay.com/doc?91000
Application Note AN-0801
www.vishay.com
Vishay Semiconductors
Mounting Instructions for MTP Modules
Due to the wide variety of PCB construction methods and
designs available on the market, there are multiple solutions
that might be adopted by MTP module end users. Vishay
strongly suggests adhering to the specifications described
above, which have been used to test and qualify MTP
press-fit pin solutions. In principle, other methods to get tin
plating, like HAL, might be used if they can guarantee the
needed tolerances in layer thickness.
We do not recommend reusing an MTP device after it has
been de-mounted from the PCB. Even if tests conducted
during qualification showed no degradation of the press-fit
pin contact or variation of the needed press-in force after
three cycles (mount/de-mount) of the same module on three
different PCBs with 25 mm/s insertion speeds, if a MTP
module is to be reused, we suggest soldering the
connecting pins.
It is possible to utilize the same PCB after de-mounting from
the MTP module up to three times. The tests conducted
during qualification showed no degradation of the PCB hole
contact and variation of the needed press-in and pull-out
forces after three cycles (mount/de-mount) of different
modules on the same PCB with 25 mm/s insertion speed.
However, special attention must be taken to avoid pin
damage and bending during the mount/de-mount process.
PRESS-IN TOOLS
APPLICATION NOTE
The pin-to-PCB press-in operation has been defined and validated by using the tools shown in Fig. 4. We suggest adopting a
similar approach when selecting the press-in to be installed at the end user manufacturing floor.
Fig. 4 - The tool for PCB module press-in
Revision: 13-Dec-13
Document Number: 95002
3
For technical questions within your region: [email protected], [email protected], [email protected]
THIS DOCUMENT IS SUBJECT TO CHANGE WITHOUT NOTICE. THE PRODUCTS DESCRIBED HEREIN AND THIS DOCUMENT
ARE SUBJECT TO SPECIFIC DISCLAIMERS, SET FORTH AT www.vishay.com/doc?91000
Application Note AN-0801
www.vishay.com
Vishay Semiconductors
Mounting Instructions for MTP Modules
Fig. 5 - Photo of the tool for PCB module press-in
The bottom side of the press tool keeps the PCB fixed, while the top side moves and applies force directly onto the module
baseplate. Special settings have to be prepared when simultaneously mounting more than one MTP module on the same PCB.
PRESS-IN
Based on the results of the qualification tests we suggest mounting the MTP module on the PCB with the following conditions:
Insertion speed in the range: 25 mm/min. to 50 mm/min. (as suggested also in IEC 60352-5)
• Minimum force to press-in each pin is 35 N.
• Maximum force to press-in each pin is 90 N.
• Therefore, the press-in force for a 20 pin MTP module should be in the range 0.7 kN to 1.8 kN.
The press-in procedure using a semiautomatic machine is illustrated below.
Alignment column
PCB
APPLICATION NOTE
Fixing plate
Fig. 6 - Step 1: Put the PCB on the assistant tool
Revision: 13-Dec-13
Document Number: 95002
4
For technical questions within your region: [email protected], [email protected], [email protected]
THIS DOCUMENT IS SUBJECT TO CHANGE WITHOUT NOTICE. THE PRODUCTS DESCRIBED HEREIN AND THIS DOCUMENT
ARE SUBJECT TO SPECIFIC DISCLAIMERS, SET FORTH AT www.vishay.com/doc?91000
Application Note AN-0801
www.vishay.com
Vishay Semiconductors
Mounting Instructions for MTP Modules
Stand-off
Alignment column
Fig. 7 - Step 2: Put the MTP module on the PCB and make sure the alignment column is aligned into stand-off.
APPLICATION NOTE
Fig. 8 - Step 3: Start the semiautomatic machine to press the press fit module into the PCB,
making sure there is no gap between the standoff and the PCB.
Fig. 9 - Step 4: Stop the machine and press-in is finished
Revision: 13-Dec-13
Document Number: 95002
5
For technical questions within your region: [email protected], [email protected], [email protected]
THIS DOCUMENT IS SUBJECT TO CHANGE WITHOUT NOTICE. THE PRODUCTS DESCRIBED HEREIN AND THIS DOCUMENT
ARE SUBJECT TO SPECIFIC DISCLAIMERS, SET FORTH AT www.vishay.com/doc?91000
Application Note AN-0801
www.vishay.com
Vishay Semiconductors
Mounting Instructions for MTP Modules
PRESS-OUT
The force to be applied in order to press-out the single pin is at least 20 N. Therefore, the force needed to press-out a 20-pin
MTP module is 0.4 kN.
To press-out the MTP module from the PCB, we suggest using the tool and pushing directly by contacting the pin’s edge. It is
not recommended to remove the device from the PCB by pulling the baseplate. The press-out setup tool is illustrated below.
PCB
Module
Remove mold
Fig. 10
MOUNTING A PCB TO THE MODULE
The MTP module housing has been designed with four stand-off lids. They can be used to tighten the PCB to the module body
by adding screws. Fig. 11 shows a schematic of a PCB connected to a MTP through screws tightened into the module’s
stand-offs.
Screw
PCB
Stand-off
MTP module
APPLICATION NOTE
Fig. 11
Screwing into a plastic cavity is a delicate operation, and care has to be taken to avoid stand-off damage. We suggest using
M2.5 x 10 self-tapping screws, in accordance with the PCB thickness, to avoid touching the bottom surface of the stand-off
cavity. The screws will self-thread into the stand-off cavity. The vertical position of the screw must also be maintained to prevent
lateral insertion. We also suggest mounting the screws in a crosswise sequence. Fox example, if the fixing holes are 1, 2, 3, and
4 in a clockwise or counter-clockwise sequence, then we suggest mounting the screws by the sequence 1 and 3, then 2 and
4. In addition, the screwdriver used should have a slow rotating speed. Typical mounting torque is 0.45 Nm ± 10 %. Do not
exceed 1 Nm to avoid screw/plastic damage.
Revision: 13-Dec-13
Document Number: 95002
6
For technical questions within your region: [email protected], [email protected], [email protected]
THIS DOCUMENT IS SUBJECT TO CHANGE WITHOUT NOTICE. THE PRODUCTS DESCRIBED HEREIN AND THIS DOCUMENT
ARE SUBJECT TO SPECIFIC DISCLAIMERS, SET FORTH AT www.vishay.com/doc?91000
Similar pages