APPLICATION NOTE
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VE-Trac] Direct / Direct SiC
Assembly Guide
AND9989/D
This document is intended to be a guide to correctly assemble all
VE−Trac Direct family of modules. It covers the recommended tools,
materials and components needed to mount the power module to thecooler and the gate driver printed circuit board to the power module.
Using the module beyond the limits and recommendation in thisguide requires additional tests and verification by the user.
APPLIES TO THE FOLLOWING PARTS
NVHxxxS75LxSPx

IGBT 6pak /w Press−fit pins, pin−fin &Flat back series

NVXRxxSxxMxSPx

SiC 6pak /w Press−fit pins, pin−fin &Flat back series

Figure 1.

© Semiconductor Components Industries, LLC, 2019

November, 2023 − Rev. 7

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Publication Order Number:
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INTRODUCTION

order to avoid unnecessary mechanical stress on theassembly it is important to follow the recommended
assembly order to correctly install the power module into theend application power converter. Be sure to follow thedetailed guidelines explained in this document for each step
listed.

VE−Trac Direct represents a family of power modules
specifically designed for Electric Vehicle (EV) traction
application. This document is intended to serve as a guidefor Si−IGBT and SiC MOSFET version of the product. It
also includes the various terminal and heatsink variations. In

Figure 2. Example VE−Trac Direct Power Module Top View (right) Bottom View (left)
Recommended mounting order for the assembly forpress−fit:

4. Secure the PCB to the power module
5. Solder the press−fit pins to the PCB

1. Align PCB to the power module.
2. Press−in the PCB to the press fit pins
3. Prepare cooler with the sealing ring
4. Attach the power module with PCB to the cooler
5. Secure the module to the cooler
6. Secure the PCB to the power module
7. Connect the module terminals to the end
application power converter

PRINTED CIRCUIT BOARD (PCB) ASSEMBLYPCB Requirements for Press−fitting Only

All VE−Trac Direct power modules have a uniquepress−fit pin design suitable for standard FR4 printed circuitboards with tin plating. The PCB material must be compliant
with IEC 60249−2−4 or IEC 60249−2−5 for double sided
PCBs. For multi−layer PCBs the material must be compliant
to IEC 60249−2−11 or IEC 60249−2−12. The requirements
for the press−fit pin holes are summarized below for a std.
1.6 mm thick PCB and the component keep out zone aroundeach press−fit pin hole:

Recommended mounting order for the assembly forpress−fit pins with soldering:

1. Prepare cooler with the sealing ring
2. Attach the power module to the cooler
3. Align PCB to the power module and insert until
resting on the case mounting domes

Figure 3. Press−fit Hole Definitions for PCB and Component Keep Out Zone around each Press−fit Holewww.onsemi.com
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It should be noted that slotting to reduce forces on thepress−fit pin is not recommended for a press−fit onlyinterface. But if slots are being added, it is necessary to keepthem out of the defined keep−out zones.

The table below summarizes the specifications fora 1.6 mm thick two layer PCB. The force required for
insertion and extraction is specified in the next section.

Table 1. REQUIREMENTS FOR PCB FOR PRESS−FITTING#

Description

Min

Typ

Max

1

Initial (Drill) hole diameter (mm)2

Copper thickness in press−fit hole (mm)

25

1.15
50

3

Metallization (Sn) in press−fit hole (mm)

10

15

4

Final hole diameter (mm)15Annular ring (mm)300

6Hole to Hole pattern tolerance

7

Metal type on circuit board

8

Metal type on pin

1.04

1.09

±100 mmTin
Sn/Ni to mitigate whisker growth

In addition to the press−fit holes, it is also necessary tohave the holes in the PCB for the guide pins. The

requirement for the guide pin holes are listed in the tablebelow.

Table 2. GUIDE PIN REQUIREMENTS#

Description

Min

Typ

1

End hole diameter of Horizontal Guide Pin

5.82 mm

5.9 mm2

End hole diameter of Rotational Guide Pin

4.82 mm

4.9 mm3

Hole to Hole dimensional toleranceMax±100 mm

PCB Mounting Tool

The top tool supports the PCB around each of the press−fit
pins to ensure an even delivery of force across the PCB
without warping of bending the PCB during the press−inprocess. The tool is made of steel to withstand the requiredpress−in forces. A hollow cylinder around each of thepress−fit pin hole in the PCB ensures that the there is no
mechanical interference between top tool and the othercomponents on the PCB. Since the SiC version of themodules have a different press−fit pin layout, it is necessary
to have a slight modified version of the top tool for SiC
modules.

For press−fitting option (not required if solderingpress−fit pins) it is highly recommended that a tool be used
to mount the PCB to the power module to ensure a proper fit
without damage to the PCB or the power module. The tool
itself is made of two parts – a top and bottom part (Figure 4).
The bottom part of the tool is made of plastic to avoid
damaging the critical baseplate surface used for sealing. It
is designed as a cradle to properly support the power moduleand protect the pin fins from damage during the PCB press
fit mounting process. The guide pins at the bottom of thepower module ensure that the module is always oriented
correctly in the bottom tool.

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Figure 4. PCB Mounting Tool for All Si−IGBT Version of the Modules is shown

It should be noted that the height of the hollow cylinders
on the top tool must such that it can clear the tallest
components on the PCB. During the press−in process the top
and bottom tools must be parallel to each other and a force
is applied in the vertical direction to complete the press−inprocess to attach the PCB to the power module.

The design for a reference PCB insertion tool is provided
below in Figures 5, 7 and 8. The reference tool design
maybe adapted for specific customer systems provided the
key concepts remain the same.

Figure 5. Bottom Tool Designwww.onsemi.com
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Figure 6. Example Use of the Actual PCB Mounting Tool

Figure 7. Top Tool Design Specifically for All Variants of Si−IGBT Modules

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Figure 8. Top Tool for All SiC−MOSFET Variants of Module

Figure 9. Detail for Top Tool for SiC Variants
Press−fit Assembly“fish−eye” of the press−fit pin is collapsing and peaks when
fully collapsed. In phase 2 the force decreases as the fish eyeslides into the PCB and in phase 3 the PCB hits the mounting
points on the module and any further increase in force is notbeneficial and may result in damage to the PCB assembly.
The lower part of the plot shows the strain on the PCB during
the press−in process. The location of the strain sensors are
identified and the force and strain measurements are alignedwith the displacement of the PCB on the x−axis.

The horizontal and rotational alignment pins on the power
module ensure that the PCB is correctly oriented on the
power module. This also ensure that all the press−fit pins arealigned on the press−fit holes on the PCB. Using the press−inprocess described in the previous section, follow thespecifications for speed and force as recommended inTable 3 and Figure 10. The press−in force plot shown in
Figure 10 can be split into 3 phases. In the first phase thewww.onsemi.com
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Figure 10. Press−in Definitions with Press−in Force versus Position Plot

Press−out operation and tool is presently not verified andis not recommended.
Table 3. RECOMMENDED PRESS−IN SPECIFICATIONS#

Description

Min

Typ

Max

1

Press−in speed

25 mm/min

2

Starting IPCB−

3

Travel distance ZPCB

1.7 mm4

Ending IPCB (after securing the PCB to the module)

12.75 mm−−

5Max. allowed force on module−−

3.5 kNPCB Requirements for Press−fit Pins with Soldering

500 mm/min
14.5 mm−
2 mm

soldered to the PCB after insertion and can result in an
increased FIT rate. For this reason soldering press−fit pins
to the PCB is NOT RECOMMENDED.
However, if there is a strong desire to solder the press−fitpins, then please follow the directions for the PCB design asstated at the start of the section for press−fit pins except for
the information stated in the table below.

onsemi’s unique press−fit pin design offers one of thelowest FIT rate connectivity between a power module and
PCB. This advantage primarily comes from the ability of thepress−fit pin to contort or temporarily deform during
insertion to form a tight yet flexible and reliable contact
between the pin and the plated through hole on the PCB.
Some of the flexibility is lost if the press−fit pins are

Table 4. PCB REQUIREMENTS FOR SOLDERING PRESS−FIT PINS#

Description

1

Initial (Drill) hole diameter (mm)2

Copper thickness in press−fit hole (mm)

Min.

Typ.

Max.

1.7
20

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Table 4. PCB REQUIREMENTS FOR SOLDERING PRESS−FIT PINS (continued)#

Description

Min.

Typ.

Max.

1.62

1.701

3

Metallization (NiAu) in press−fit hole (mm)4Final hole diameter (mm)

1.539

7

5

Annular ring (mm)650

6Hole to Hole pattern tolerance

7

Component keep out zone around the press−fit initial drill hole center on
PCB

8Metal type on circuit board

9

Metal type on pin±100 mm≥ 4 mm radius from center
NiAu
Sn/Ni to mitigate whisker growth

The description of the parameters above are defined in
Figure 3. Soldering the press−fit pins to the PCB makes themechanical assembly less compliant and thus the PCB
requires slotting to decouple the solder joints from shockand vibration from the mounting points on the module andeliminate any potential mechanical oscillations.

It is critical that when soldering the press−fit pins to the
PCB the assembly process steps should be flowed as listed
in the first section of this document.

Figure 11. Recommended Slots for the PCB, used with Si IGBT Modules, to minimize the Effects of Vibration

soldering time must not exceed the values shown in the tablebelow. The power, tip size and working temperature of theiron must be adjusted such that it does not exceed thespecified limits. When soldering is complete, the joint
should be inspected according to IPC−A−610G for press−fit
pins.

Only hand/automated soldering with a soldering iron isrecommend. For the PCB requirements as stated in Table 1,
following the annular ring size recommendation for thesolder option. Soldering the pins should only be attempted
after the PCB is securely mounted to the module with therecommended screws. This minimizes the mechanical stresson the solder pins. According to IEC 68 section 2, thewww.onsemi.com
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Description

#

Unit

Typ.

Max.

°C

280

315

4

1

Max. solder tip temperature2

Solder Times

3Max. module housing temperature during soldering°C

4

Module PCB mounting dome temperature during
soldering

°C

Min.

Comment

7
225

100

150

Figure 12. Example Illustration of Soldered Press−fit Pin
Attaching PCB to Power Module

selected according to the thickness of the PCB. For a typical
PCB with a thickness of 1.6 mm the following self−tapping
screw type and length is recommended with recommended
torque and speed shown in Table 5:

The PCB should be attached to the power module withscrews only after the power module is attached to theheatsink assembly. The length of the screws should be
EJOT Delta PT WN5451 30x10

The length of the recommended mounting screws must be selected according to thethickness of the PCB. Using other screw types can permanently damage the mounting
points on the plastic module.

Table 5. PCB MOUNTING SCREW SPECIFICATIONS#

Description

Min

Typ

Max

0.5 Nm0.55 Nm

1

Mounting torque for PCB Screw

0.45 Nm

2

Screw speed

400 rpm

It is necessary to follow the screw in sequence for the PCB
mounting screws as shown in Figure 13.

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600 rpmAND9989/D

Figure 13. PCB Mounting Screw in Sequence
HEATSINK ASSEMBLY

module. A cooling liquid, like a 50/50 mix of Ethylene
Glycol and water is passed though the pin−fin structure tocool the module.
• The pin−fin structure allows a maximum particle size of
1.5 mm to pass through.

Power dissipated in the module must be effectively
removed from the module without exceeding the maximum
rated operating temperature of the module as specified in its
data sheet.
To do this all VE−Trac Direct modules have an array ofpin−fins at the bottom of the isolated Cu base plate of the

When mounting the module great care should be taken to not damage the Ni plating or
structure of the pin−fins. Also avoid contamination, scratches or other damage to thearea (Figure 14) of the base plate that will seal the module to the cooler.
Ensure that the cooling medium is compatible with the cooler material, Ni plate baseplate of the power module and other parts of the cooling loop.

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Figure 14. Bottom View of the Power Module Showing the Critical Sealing Area on the Pin−fin Baseplateexample shown is designed by onsemi and available from
Quanzhou Shengda Rubber Products Co., Ltd. It is designed
to fit in a groove, which must be designed in the cooler asshown in the reference cooler section.
There are multiple vendors suppling similar seals and also
more sophisticated sealing rings with alignment and locking
features that prevent the sealing ring from moving duringassembly. Suggested suppliers include Dichtomatik GmbHand Fabri−tech Components Inc.
Please note that the sealing options mentioned in thissection worked well in power module qualification tests.
However, it is necessary to perform system qualification testby the customer to determine if it meets their specificapplication requirements.

Cooling Jacket Requirements• Roughness of the cooler sealing area as shown in
Figure 14: ≤ RZ25 (DIN EN ISO 1302)• Cooler flatness in the module sealing area: ≤ 50 mm

Not meeting the above described requirements may
damage the power module or may not result in a proper seal
between the module and cooler. It is recommended that thecooler material be AlMgSi0.5 or another alternative whichis compatible with a Cu baseplate with Ni plating and which
can meet the mechanical stress required for the application.

Sealing

A triple wiper seal with the specifications shown in
Figure 14 with EPDM 50 material is recommended. The

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Figure 15. Recommended Drawing for the EPDM O−ring Seal and the Groove for the Cooler

We do not recommend the use of silicon gasket or any other methods to seal the module to thecooler.

Reference Cooler for Pin−fin Base Plate Modules

requirements described in Cooling Jacket Requirements
section are met and the proper trade−off consideration is
given to the thermal resistance/impedance, pressure drop
and flow rates. So, the reference design shown in Figure 16
should be considered as an example design.

The reference cooler design can be used as a guide bycustomers to develop their own cooler designs. The thermal
data shown in the data sheet for VE−Trac Direct products are
all measured using this reference cooler. The cooler can be
designed in different ways as long as the minimum

Figure 16. Reference Cooler Design for the VE−Trac Direct Family of Power Modules
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Reference Cooler for Flat−back Base Plate Modules

material or a direct cooled option where the coolant is in
direct contact with the module base plate (see Figure 17).

For the flat back version of the module there is an option
to use a cold plate (indirect cooling) with an interface

Figure 17. Indirect versus Direct Cooling for Flat Back Module

See Figure 18 for a reference cooler with diamond pin fin
turbulizer structure that is designed to generate turbulenceof the coolant to better cool the module with minimal presure
drop. The design details of the diamond pin−fin cooler can
be available upon request via onsemi sales.

There are suppliers, Wieland Microcool for example,
offering ready solutions for the indirect cooling option.
However, indirect coolers do not give assembly
commonality with a direct cooling approach. onsemi offers
a reference solution for direct cooling of flat back modules.

Figure 18. Diamond Pin−fin Cooler for Direct Cooling for Flat Back Modules
Table 6. PERFORMANCE COMPARISON OF CRITICAL PARAMETERS AT 10 LPM FOR DIRECT VERSUSINDIRECT COOLING
Heatsink Solution

Rth.j−f @ 10 LPM, 65C (5C/W)

DP (Y)

Indirect cooling /w Wieland Microcool solution

0.145

414

Direct cooling /w onsemi diamond pin−fin

0.154

122

• Max. screw speed: 400 RPM• Effective length of screw in cooler: 6 mm

Mounting Hardware and Method

The Power module baseplate is designed to be fixed to thecooler with M4 screws. A standard screw M4x10 ISO 4762
(DIN 912 A2) with washer M4 ISO 7090 (DIN 125 A2) may
be used in combination with the following specifications:• Mounting torque: 1.8 / 2.0 / 2.2 nm (min./typ./max.)

A list of recommended screws are shown in the tablebelow.

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Table 7. LIST OF RECOMMENDED SCREWS TO ATTACH THE POWER MODULE TO THE COOLER
Hardware Type

Description

M4x10 ISO 4762 screw
M4 ISO 7090 Washer

Standard M4 screw and separate washer

M4x10 ISO 7380−2 A2

M4 screw with integrated washer

M4x10 ISO 7380−2 A2 TX

TX20 head M4 screw with integrated washer

Figure 19. Recommended Screws to Secure the Power Module to the Cooler

When assembling the power module to the baseplate, it isimportant to follow the sequence as shown in Figure 20.
This is the only recommended sequence to affix the screws.

Figure 20. Screw Order and Sequence to Assemble the Power Module to the Cooler

To correctly install the power module to the cooler, it isnecessary to secure the module during the mounting process

to prevent the module from tilting or rotating. There are tworecommended methods to secure the module:

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plated and well suited for screw type fastening includingself−clinching fasteners and welding processes.

1. Multi−step screw mounting: Screws 1 and 2 aresecured to the lowest torque setting (0.4 – 0.6 Nm)
to avoid tilting the module during the assembly
process. Next screws are fixed to positions 3
through 8 also at the lowest torque setting. Finally,follow the sequence 1−8 again and secure thescrews to its final specified torque.
2. Module Clamping Method: This method is better
suited for higher volume production process. Afterthe module with the PCB assembly is place in thecooler the module can be clamped with a total
force FS = 2 kN during the screw−in process. The
clamping force can be applied in the area where
the PCB mounting screw holes are located asshown in Figure 20.

Terminal Connection Options

Different combinations of the power terminal, busbar,
screw and nut are possible. Some of the acceptable
stack−ups are shown in Figure 21.
Standard M4 self−clinching nuts can be used in the M5screw holes found on the power terminals. In this case an M4
Screw is used to connect the power terminal to the busbar.
Several example terminal connection options are shown
below with respect to connecting the power module to bus
bars. Alternatively, you can have an M5 self−clinching nut
on the busbar and use an M5 screw to secure the connection.
Check chart in Table 8 to determine the correct torquesetting for different options.

POWER TERMINAL CONNECTIONSThere are several options to connect the module power
terminals to bus bars. The copper power terminals are tin

Figure 21. Different Option to Mount to the Power Converter System
Table 8. TORQUE SETTINGS FOR THE DIFFERENT MOUNTING OPTIONSMounting Torque (nm)Mounting
Option #

Min

Typ

Max

A, B

M5 ISO 4762 Screw
M5 ISO 7090 Washer
M5 ISO 4032 Nut

3.6

4.0

4.4

A, B

M5 ISO 7380−2−A2 (TX) Screw
M5 ISO 6923 Nut

3.6

4.0

4.4

C

M4 ISO 7380−2−A2 (TX)
M4 self−clinching nut e.g. PEM S−M4−0ZI

1.8

2.0

2.2

D

M5 ISO 7380−2−A2 (TX) Screw
M5 self−clinching nut

3.6

4.0

4.4

HardwareWeldingn/aLimitations

to the bus bars. Figure 22 shows the maximum allowed
forces at 25°C in all axis for the module power terminals andthe press−fit pins.

The mounting process should results in a system that will
limit the forces acting on the power terminals when secured

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Figure 22. Allowed Forces and Direction on the Module Power Terminals
SYSTEM ASSEMBLY REQUIREMENTS

metal heatsinks, bus bars or fastening hardware caninadvertently reduce the creepage and clearance distances in
the assembly. It is critical to check the assembly to ensure theminimum required creepage and clearance are met as shownin Figure 23.

Creepage and Clearance Requirements

Care should be taken not to encroach on the creepage andclearance requirements of the module as specified in the
product data sheet. Additional external components, like

Figure 23. Minimum Required Creepage and Clearance Requirements
Current Sensor Integration

current sensors. But this is not the only option. Ultimately
the selection of current sensors is depended on several end
application requirements and power converter package
design.

There are many options for integrating the phase current
sensors with the module. Some of the most standard readyto use options are provided by LEM’s HAH3DR series of

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VISUAL MARKINGS

Standard markings for the power module is shown below in
Figure 24 and explained in Table 9.

Traceability and Identification

For automotive applications, proper identification ofmaterials and traceability is an important aspect of quality.

Figure 24. Module Identification Labels and Markings

The 2D Code is readable with most 2D scanners
compatible with the IEC 24720 and IEC 16022 standard.

Certain apps for reading QR codes on android smart phones
can also read the 2D codes on the module.

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Table 9. EXPLANATION OF VISUAL MARKINGS ON THE MODULE
MarkerDescription

COMPANY LOGO

onsemi Logo

2D CODE 1

Date Code (YYWW) + Assembly Location (XX) + Assembly Lot Number + S/N

2D CODE 2

Assy. Lot Number + S/N

SITE AND DATE CODE

Assembly location (XX) and date code (YYWW)

P/N NUMBER

14 Character Product part number

Storage and Shipping

to IEC 60721−3−1, class 1K2 should be followed andstorage time should not exceed 2 years. Below is a summaryof the recommended storage parameters:

Transporting and storing the modules requires care to
avoid extreme shock, vibration and environments. The
recommended storage conditions for the module according

Table 10. SUMMARY OF RECOMMENDED STORAGE CONDITIONS
Maximum air temperature

40°C

Minimum air temperature+5°C

Maximum relative humidity

85

%

5

%

Minimum relative humidity
Condensation

Not Allowed

Precipitation

Not Allowed

Icing

Not Allowed

VE−Trac is a trademark of Semiconductor Components Industries, LLC dba “onsemi” or its affiliates and/or subsidiaries in the United States and/or othercountries.
onsemi,, and other names, marks, and brands are registered and/or common law trademarks of Semiconductor Components Industries, LLC dba “onsemi” or its affiliates
and/or subsidiaries in the United States and/or other countries. onsemi owns the rights to a number of patents, trademarks, copyrights, trade secrets, and other intellectual property.
A listing of onsemi’s product/patent coverage may be accessed at www.onsemi.com/site/pdf/Patent−Marking.pdf. onsemi reserves the right to make changes at any time to any
products or information herein, without notice. The information herein is provided “as−is” and onsemi makes no warranty, representation or guarantee regarding the accuracy of theinformation, product features, availability, functionality, or suitability of its products for any particular purpose, nor does onsemi assume any liability arising out of the application or useof any product or circuit, and specifically disclaims any and all liability, including without limitation special, consequential or incidental damages. Buyer is responsible for its products
and applications using onsemi products, including compliance with all laws, regulations and safety requirements or standards, regardless of any support or applications information
provided by onsemi. “Typical” parameters which may be provided in onsemi data sheets and/or specifications can and do vary in different applications and actual performance mayvary over time. All operating parameters, including “Typicals” must be validated for each customer application by customer’s technical experts. onsemi does not convey any licenseunder any of its intellectual property rights nor the rights of others. onsemi products are not designed, intended, or authorized for use as a critical component in life support systems
or any FDA Class 3 medical devices or medical devices with a same or similar classification in a foreign jurisdiction or any devices intended for implantation in the human body. Should
Buyer purchase or use onsemi products for any such unintended or unauthorized application, Buyer shall indemnify and hold onsemi and its officers, employees, subsidiaries, affiliates,and distributors harmless against all claims, costs, damages, and expenses, and reasonable attorney fees arising out of, directly or indirectly, any claim of personal injury or deathassociated with such unintended or unauthorized use, even if such claim alleges that onsemi was negligent regarding the design or manufacture of the part. onsemi is an Equal
Opportunity/Affirmative Action Employer. This literature is subject to all applicable copyright laws and is not for resale in any manner.

ADDITIONAL INFORMATIONONLINE SUPPORT: www.onsemi.com/support
For additional information, please contact your local Sales Representative at
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TECHNICAL PUBLICATIONS:Technical Library: www.onsemi.com/design/resources/technical−documentation
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