Ublox NEO-M8U Quick setup guide

NEO-M8U
u-blox M8 Untethered Dead Reckoning module including
3D inertial sensors
Hardware Integration Manual

Abstract
This document describes the features and specifications of NEO-M8U, a high-
performance
untethered dead reckoning module with 3D sensors. The module includes the u-
blox M8 concurrent
GNSS engine with reception of GPS, GLONASS, BeiDou, Galileo and QZSS signals.
www.u-blox.com
UBX-15016700 - R07

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Document Information
Title NEO-M8U
Subtitle u-blox M8 Untethered Dead Reckoning module including 3D inertial sensors
Document type Hardware Integration Manual
Document number UBX-15016700
Revision and date R07 18-Apr-2019
Document status Production Information
Product status Corresponding content status
In Development /
Prototype
Objective Specification Target values. Revised and supplementary data will be published later.
Engineering Sample Advance Information Data based on early testing. Revised and supplementary data will be published later.
Initial Production Early Production Information Data from product verification. Revised and supplementary data may be published later.
Mass Production /
End of Life
Production Information Document contains the final product specification.
European Union regulatory compliance
NEO-M8U compile with all relevant requirements for RED 2014/53/EU. The NEO-M8U
Declaration of
Conformity (DoC) is available at www.u-blox.com within Support > Product resources > Conformity Declaration.
This document applies to the following products:
Product name Type number ROM/FLASH version PCN reference
NEO-M8U NEO-M8U-04B-00 FLASH FW 3.01 UDR 1.21 N/A
u-blox or third parties may hold intellectual property rights in the products, names, logos and designs included in this
document. Copying, reproduction, modification or disclosure to third parties of this document or any part thereof is only
permitted with the
express written permission of u-blox.
The information contained herein is provided “as is” and u
-blox assumes no liability for its use. No warranty, either express or
implied, is given, including but not limited
to, with respect to the accuracy, correctness, reliability and fitness for a particular
purpose of the information. This document may be revised by u
-blox at any time without notice. For the most recent
documents, visit www.u
-blox.com.
Copyright © u
-blox AG.

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Contents
Document Information................................................................................................................................ 2
Contents .......................................................................................................................................................... 3
1Hardware description ........................................................................................................................... 5
1.1 Overview........................................................................................................................................................5
1.2 Configuration ...............................................................................................................................................5
1.3 Connecting power .......................................................................................................................................5
1.3.1 VCC: Main supply voltage .................................................................................................................5
1.3.2 V_BCKP: Backup supply voltage......................................................................................................5
1.3.3 VDD_USB: USB interface power supply .........................................................................................6
1.3.4 VCC_RF: Output voltage RF .............................................................................................................6
1.4 Interfaces......................................................................................................................................................6
1.4.1 UART .....................................................................................................................................................6
1.4.2 USB ........................................................................................................................................................6
1.4.3 Display Data Channel (DDC) .............................................................................................................7
1.4.4 SPI ..........................................................................................................................................................7
1.4.5 TX Ready signal...................................................................................................................................8
1.5 I/O pins...........................................................................................................................................................8
1.5.1 Electromagnetic interference on I/O lines.....................................................................................8
2Design ..................................................................................................................................................... 10
2.1 Pin description...........................................................................................................................................10
2.1.1 Pin name changes.............................................................................................................................11
2.2 Minimal design...........................................................................................................................................11
2.3 Layout: Footprint and paste mask ........................................................................................................11
12
2.4 Antenna.......................................................................................................................................................12
2.4.1 Antenna design with passive antenna.........................................................................................12
2.4.2 Active antenna design.....................................................................................................................13
3Untethered Dead Reckoning........................................................................................................... 15
3.1 Implementation .........................................................................................................................................15
3.2 Installation..................................................................................................................................................15
3.3 Initialization and Calibration...................................................................................................................15
4Migration from NEO-M8L to NEO-M8U ...................................................................................... 16
4.1 Hardware migration NEO-M8L to NEO-M8U ......................................................................................16
5Product handling................................................................................................................................. 17
5.1 Packaging, shipping, storage and moisture preconditioning ..........................................................17
5.2 Soldering .....................................................................................................................................................17
5.3 EOS/ESD/EMI precautions......................................................................................................................20
5.4 Applications with cellular modules........................................................................................................23
Appendix ....................................................................................................................................................... 25
AGlossary ................................................................................................................................................. 25

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Related documents ................................................................................................................................... 27
Revision history .......................................................................................................................................... 27
Contact.......................................................................................................................................................... 28

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1Hardware description
1.1 Overview
The NEO-M8U is an Untethered Dead Reckoning module bringing the benefits of dead reckoning to a
wider range of road-vehicle applications by eliminating the need for a speed or wheel-tick connection
to the vehicle. The module uses built-in gyroscope and accelerometer sensors and features the high
performance u-blox M8 concurrent positioning engine. Available in the NEO industry standard
leadless chip carrier (LCC) package, it is easy to integrate and combines exceptional positioning
performance with highly flexible power, design, and connectivity options. SMT pads allow fully
automated assembly with standard pick & place and reflow-soldering equipment for cost-efficient,
high-volume production enabling short time-to-market.
☞For more about product features see the NEO-M8U Data Sheet [1].
☞To determine which u-blox product best meets your needs, see the product selector tables on the
u-blox website www.u-blox.com.
1.2 Configuration
The configuration settings can be modified using UBX protocol configuration messages (see u-blox 8
/ u-blox M8 Receiver Description Including Protocol Specification
[2]). The modified settings remain
effective until power-down or reset. If these settings have been stored in BBR (Battery Backed RAM),
then the modified configuration will be retained, as long as there is no backup battery supply interrupt.
For NEO-M8U modules, the configuration can be saved permanently in SQI flash.
1.3 Connecting power
The NEO-M8U positioning module has up to three power supply pins: VCC, V_BCKP and VDD_USB.
1.3.1 VCC: Main supply voltage
The VCC pin provides the main supply voltage. During operation, the current drawn by the module can
vary by some orders of magnitude. For this reason, it is important that the supply circuitry be able to
support the peak power for a short time (see the
NEO-M8U Data Sheet [1] for specification).
☞When switching from backup mode to normal operation or at start-up, the NEO-M8U module must
charge the internal capacitors in the core domain. In certain situations, this can result in a
significant current draw. It is important that the power supply or low ESR capacitors at the module
input can deliver this current/charge.
☞Use a proper GND concept. Do not use any resistors or coils in the power line.
1.3.2 V_BCKP: Backup supply voltage
If the module supply has a power failure, the V_BCKP pin supplies the real-time clock (RTC) and
battery backed RAM (BBR). Use of valid time and the GNSS orbit data at start-up will improve the
GNSS performance, as with hot starts, warm starts, AssistNow Autonomous and AssistNow Offline.
If no backup battery is connected, the module performs a cold start at power up.
☞A backup supply voltage should be provided to the NEO-M8U to enable navigation by Dead
Reckoning before the first GNSS fix.

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☞Avoid high resistance on the V_BCKP line: During the switch from main supply to backup supply,
a short current adjustment peak can cause high voltage drop on the pin with possible
malfunctions.
☞If no backup supply voltage is available, connect the V_BCKP pin to VCC.
☞As long as power is supplied to the NEO-M8U module through the VCC pin, the backup battery is
disconnected from the RTC and the BBR to avoid unnecessary battery drain (see Figure 1). In this
case, VCC supplies power to the RTC and BBR.
Figure 1: Backup battery and voltage (for exact pin orientation, see the NEO-M8U Data Sheet [1])
1.3.3 VDD_USB: USB interface power supply
VDD_USB supplies the USB interface. If the USB interface is not used, the VDD_USB pin must be
connected to GND. For more information about correctly handling the VDD_USB pin, see section 1.4
1.3.4 VCC_RF: Output voltage RF
The VCC_RF pin can supply an active antenna or external LNA. For more information, see section 0
1.4 Interfaces
1.4.1 UART
NEO-M8U 3D dead reckoning module includes a Universal Asynchronous Receiver Transmitter
(UART) serial interface RXD/TXD supporting configurable baud rates. The baud rates supported are
specified in the
NEO-M8U Data Sheet [1].
The signal output and input levels are 0 V to VCC. An interface based on RS232 standard levels (+/-
12 V) can be implemented using level shifters such as Maxim MAX3232. Hardware handshake signals
and synchronous operation are not supported.
1.4.2 USB
A USB version 2.0 FS (Full Speed, 12 Mb/s) compatible interface is available for communication as an
alternative to the UART. The USB_DP integrates a pull-up resistor to signal a full-speed device to the
host. The VDD_USB pin supplies the USB interface.
u-blox provides Microsoft® certified USB drivers for Windows Vista, Windows 7, Windows 8 and
Windows 10. These drivers are available at our website at www.u-blox.com
USB external components
The USB interface requires some external components to implement the physical characteristics
required by the USB 2.0 specification. These external components are shown in Figure 2 and listed in
Table 1. To comply with USB specifications, VBUS must be connected through an LDO (U1) to pin
VDD_USB on the module.

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In USB self-powered mode, the power supply (VCC) can be turned off and the digital block is not
powered. In this case, since VBUS is still available, the USB host would still receive the signal indicating
that the device is present and ready to communicate. This should be avoided by disabling the LDO
(U1) using the enable signal (EN) of the VCC-LDO or the output of a voltage supervisor. Depending on
the characteristics of the LDO (U1), it is recommended to add a pull-down resistor (R11) at its output
to ensure VDD_USB is not floating if the LDO (U1) is disabled or the USB cable is not connected, i.e.
VBUS is not supplied.
☞USB bus-powered mode is not supported.
Module
VDD_USB
LDO
VDD_USB
R4
USB_DP
USB_DM
R5
C24 C23
D2
VBUS
DP
DM
GND
USB Device Connector
U1
EN R11
EN
Figure 2: USB Interface
Name Component Function Comments
U1 LDO Regulates VBUS (4.4 …5.25 V)
down to a voltage of 3.3 V.
Almost no current requirement (~1 mA) if the GNSS receiver is
operated as a USB self-powered device.
C23, C24 Capacitors Required according to the specification of LDO U1
D2 Protection
diodes
Protect circuit from overvoltage /
ESD when connecting.
Use low capacitance ESD protection such as ST Microelectronics
USBLC6-2.
R4, R5 Serial
termination
resistors
Establish a full-speed driver
impedance of 28…44 Ω
A value of 27 Ωis recommended.
R11 Resistor 100 kΩis recommended for USB self-powered setup.
Table 1: Summary of USB external components
1.4.3 Display Data Channel (DDC)
An I2C compatible Display Data Channel (DDC) interface is available with a NEO-M8U module for serial
communication with an external host CPU. The interface only supports operation in slave mode
(master mode is not supported). The DDC protocol and electrical interface are fully compatible with
the Fast-Mode of the I2C industry standard. DDC pins SDA and SCL have internal pull-up resistors.
For more information about the DDC implementation, see the
u-blox 8 / u-blox M8 Receiver
Description Including Protocol Specification
[2]. For bandwidth information, see the NEO-M8U Data
Sheet
[1]. For timing, parameters consult the I2C-bus specification [5].
☞The NEO-M8U DDCy intyerface supports serial communication with u-blox cellular modules. See
the specification of the applicable cellular module to confirm compatibility.
1.4.4 SPI
An SPI interface is available for communication to a host CPU.
☞SPI is not available in the deyfault configuration, because its pins are shared with the UART and
DDC interfaces. The SPI interface can be enabled by connecting D_SEL to ground. For speed and
clock frequency, see the
NEO-M8U Data Sheet [1].

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1.4.5 TX Ready signal
The TX Ready signal indicates that the receiver has data to transmit. A listener can wait on the TX
Ready signal instead of polling the DDC or SPI interfaces. The UBX-CFG-PRT message lets you
configure the polarity and the number of bytes in the buffer before the TX Ready signal goes active.
The TX Ready signal can be mapped to UART TXD (PIO 06). The TX Ready function is disabled by
default.
☞The TX Ready functionality can be enabled and configured by AT commands sent to the u-blox
cellular module supporting the feature. For more information, see the
GPS Implementation and
Aiding Features in u-blox wireless modules
[6].
1.5 I/O pins
RESET_N: Reset input
Driving RESET_N low activates a hardware reset of the system. Use this pin only to reset the module.
Do not use RESET_N to turn the module on and off, since the reset state increases power
consumption, or as a POR. With the NEO-M8U module the RESET_N pin is an input only.
D_SEL: Interface select
The D_SEL pin selects the available interfaces. SPI cannot be used simultaneously with the
UART/DDC. If open, UART and DDC are available. If pulled low, the SPI interface is available. More
information see the
NEO-M8U Data Sheet [1].
LNA_EN: LNA enable
In Power Save Mode, the system can turn on/off an optional external LNA using the LNA_EN signal in
order to optimize power consumption.
TIMEPULSE
A configurable time pulse signal is available with the NEO-M8U module. It generates pulse trains
synchronized with GPS or UTC time grid with intervals configurable over a wide frequency range. The
time pulse signal is disabled by default. For more information, see the
u-blox 8 / u-blox M8 Receiver
Description Including Protocol Specification
[2].
☞The NEO-M8U time-pulse output is configured using messages for “TIMEPULSE2”.
☞The time-pulse output must not be held LOW during start-up.
1.5.1 Electromagnetic interference on I/O lines
Any I/O signal line with a length greater than approximately 3 mm can act as an antenna and may pick
up arbitrary RF signals transferring them as noise into the GNSS receiver. This specifically applies to
unshielded lines, in which the corresponding GND layer is remote or missing entirely, and lines close
to the edges of the printed circuit board.
If, for example, a cellular signal radiates into an unshielded high-impedance line, it is possible to
generate noise in the order of volts and not only distort receiver operation but also damage it
permanently.
On the other hand, noise generated at the I/O pins will emit from unshielded I/O lines. Receiver
performance may be degraded when this noise is coupled into the GNSS antenna (see Figure 15).
To avoid interference by improperly shielded lines, it is recommended to use resistors (e.g. R>20 Ω),
ferrite beads (e.g. BLM15HD102SN1) or inductors (e.g. LQG15HS47NJ02) on the I/O lines in series.
These components should be chosen with care because they will affect also the signal rise times.

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Figure 3 shows an example of EMI protection measures on the RX/TX line using a ferrite bead. More
information can be found in section 5.3.
Figure 3: EMI Precautions Design

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2Design
2.1 Pin description
No Name I/O Description
1 SAFEBOOT_N I SAFEBOOT_N, Test-point for service use (Leave OPEN)
2 D_SEL I Interface select
3 TIMEPULSE I/O Time pulse (disabled by default). Do not pull low during reset.
Note: configured using TIMEPULSE2 messages (see
u-blox 8 / u-blox M8
Receiver Description Including Protocol Specification
[2])
4 EXTINT I External Interrupt Pin (disabled by default).
5 USB_DM I/O USB Data
6 USB_DP I/O USB Data
7 VDD_USB I USB Supply
8 RESET_N I RESET_N
9 VCC_RF O Output Voltage RF section
10 GND I Ground
11 RF_IN I GNSS signal input
12 GND I Ground
13 GND I Ground
14 LNA_EN O Antenna / External LNA control
15 Reserved - Reserved
16 Reserved - Reserved
17 Reserved - Reserved
18 SDA /
SPI CS_N
I/O DDC Data if D_SEL =1 (or open)
SPI Chip Select if D_SEL = 0
19 SCL /
SPI CLK
I/O DDC Clock if D_SEL =1(or open)
SPI Clock if D_SEL = 0
20 TXD /
SPI MISO
O Serial Port if D_SEL =1(or open)
SPI MISO if D_SEL = 0
21 RXD /
SPI MOSI
I Serial Port if D_SEL =1(or open)
SPI MOSI if D_SEL = 0
22 V_BCKP I Backup voltage supply
23 VCC I Supply voltage
24 GND I Ground
Table 2: Pinout of NEO-M8U

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2.1.1 Pin name changes
Selected pin names have been updated to agree with a common naming convention across u-blox
modules. The pins have not changed their operation and are the same physical hardware but with
updated names. The table below lists the pins that have changed name along with their old and new
names.
No Previous Name New name
14 ANT_ON LNA_EN
18 SDA
SPI CS_N
SDA /
SPI CS_N
19 SCL
SPI CLK
SCL /
SPI CLK
20 TxD
SPI MISO
TXD /
SPI MISO
21 RxD
SPI MOSI
RXD /
SPI MOSI
Table 3: Pin name changes in NEO-M8U
2.2 Minimal design
This is a minimal design for a NEO-M8U GNSS receiver.
Figure 4: NEO-M8U passive antenna design
☞Use series resistors in the UART lines to avoid electromagnetic interference as mentioned in
section
1.5.1.
2.3 Layout: Footprint and paste mask
Figure 5 describes the footprint and provides recommendations for the paste mask for NEO-M8U
modules. These are recommendations only and not specifications. Note that the copper and solder
masks have the same size and position.
To improve the wetting of the half vias, reduce the amount of solder paste under the module and
increase the volume outside of the module by defining the dimensions of the paste mask to form a T-
shape (or equivalent) extending beyond the copper mask. For the stencil thickness, see section 5.2.

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☞Consider the paste mask outline when defining the minimal distance to the next component. The
exact geometry, distances, stencil thicknesses and solder paste volumes must be adapted to the
specific production processes (e.g. soldering) of the customer.
2.4 Antenna
2.4.1 Antenna design with passive antenna
A design using a passive antenna requires more attention to the layout of the RF section. Typically, a
passive antenna is located near electronic components; therefore, care should be taken to reduce
electrical noise that may interfere with the antenna performance. Passive antennas do not require a
DC bias voltage and can be directly connected to the RF input pin RF_IN. Sometimes, they may also
need a passive matching network to match the impedance to 50 Ω.
Figure 6 shows a minimal setup for a design with a good GNSS patch antenna. For exact pin
orientation, see the
NEO-M8U Data Sheet [1].
Figure 6: Module design with passive antenna
☞Use an antenna that has sufficient bandwidth to receive all GNSS constellations. For more
information see the appendix and the
GPS Antenna Application Note [3].
Stencil: 170
µ
m
10.4 mm [409.5 mil]
14.6 mm [575 mil]
12.2 mm [480 mil]
0.8 mm
[31.5 mil]
0.6 mm
[23.5 mil]
12.2 mm [480.3 mil]
16.0 mm [630 mil]
1.0 mm
[39.3 mil]
0.8 mm
[31.5 mil]
0.8 mm
[31.5 mil]
3.0 mm
[118.1 mil]
1.0 mm
[39.3 mil]
1.1 mm
[43.3 mil]
Figure
5: NEO-M8U footprint / NEO-M8U paste mask

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Figure 7 shows a design using an external LNA and SAW to increase the sensitivity for best
performance with passive antenna. For exact pin orientation, see the
NEO-M8U Data Sheet [1].
Figure 7: Module design with passive antenna and an external LNA and SAW
The LNA_EN pin (LNA enable) can be used to turn on and off an optional external LNA.
The VCC_RF output can be used to supply the LNA with a filtered supply voltage.
☞A standard GNSS LNA has enough bandwidth to amplify GPS/GLONASS/BeiDou signals.
2.4.2 Active antenna design
An active antenna makes use of an integrated low-noise amplifier, which requires a power supply that
will contribute to the total GNSS system power consumption budget with additional 5 to 20 mA
typically.
If the supply voltage of the NEO-M8U module matches the supply voltage of the active antenna (e.g.
3.0 V), use the filtered supply voltage available at pin VCC_RF as shown in Figure 8. For exact pin
orientation, see the
NEO-M8U Data Sheet [1].
Active antenna design using VCC_RF pin to supply the active antenna
Figure 8: Active antenna design, external supply from VCC_RF
If the VCC_RF voltage does not match with the supply voltage of the active antenna, use a filtered
external supply as shown in Figure 9. For exact pin orientation, see the
NEO-M8U Data Sheet [1].

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Active antenna design powered from an external supply
Figure 9: Active antenna design, direct external supply
☞The circuit shown in Figure 9 works with all u-blox M8 modules, including modules without VCC_RF
output.

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3Untethered Dead Reckoning
3.1 Implementation
The NEO-M8U 3D Untethered Dead Reckoning module makes use of GNSS and internal gyroscope
and accelerometer sensors only with no need or provision for speed pulse or forward/reverse
information.
3.2 Installation
In order to achieve good performance, the NEO-M8U hardware needs to be mounted in the vehicle in
such a way that its alignment is stable to within 2°. It is important that the mounting design minimizes
vibration and mechanical resonance.
Figure 10: NEO-M8U with IMU sensor frame
3.3 Initialization and Calibration
The benefits of dead reckoning are available once the receiver has completed its initialization phase
following installation. Initialization parameter values are subsequently stored in the battery-backed
RAM (BBR) for immediate use, and may also be saved in Flash memory. The duration of the
initialization depends on the quality of the GNSS signals as well as the dynamics encountered by the
vehicle.
For details on Initialization and calibration, see the
u-blox 8 / u-blox M8 Receiver Description Including
Protocol Specification
[2].
☞Note that the performance of the UDR solution relies on a stable sensor location and orientation
with respect to the vehicle frame. The module must be mounted securely within the vehicle.
☞To read more about mandatory and optional configuration parameters, see the UDR configuration
section of
u-blox 8 / u-blox M8 Receiver Description Including Protocol Specification [2].

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4Migration from NEO-M8L to NEO-M8U
4.1 Hardware migration NEO-M8L to NEO-M8U
u-blox is committed to ensuring that NEO-M8U are backwards compatible to NEO-M8L. It is highly
advisable that customers consider a design review with the u-blox support team to ensure the
compatibility of key functionalities.
Pin
NEO-M8L NEO-M8U Remarks for Migration
Pin Name Typical Assignment Pin Name Typical Assignment
1 SAFEBOOT_N Leave open. SAFEBOOT_N Leave open. No difference
2 D_SEL selects the interface D_SEL selects the interface No difference
3 TIMEPULSE Timepulse (1PPS) TIMEPULSE Timepulse (1PPS) No difference
4 WHEELTICK Wheel-tick input EXTINT External Interrupt Pin
(disabled by default).
No problem, disabled by default.
5 USB_DM USB Data USB_DM USB Data No difference
6 USB_DP USB Data USB_DP USB Data No difference
7 VDD_USB USB Supply VDD_USB USB Supply No difference
8 RESET_N Reset input RESET_N Reset input No difference
9 VCC_RF Can be used for active
antenna or external
LNA supply
VCC_RF Can be used for active
antenna or external LNA
supply
No difference
10 GND GND GND GND No difference
11 RF_IN GNSS signal input RF_IN GNSS signal input No difference
12 GND GND GND GND No difference
13 GND GND GND GND No difference
14 LNA_EN1
Used to turn on and off
an optional external
LNA
LNA_EN Used to turn on and off an
optional external LNA
No difference
15 FWD Forward/reverse input
for speed pulse
RESERVED Leave open. If it was connected on NEO-M8L,
OK to do the same on NEO-M8U.
16 RESERVED2Leave open. RESERVED Leave open. If it was connected on NEO-M8L,
OK to do the same on NEO-M8U.
17 RESERVED2Leave open. RESERVED Leave open. If it was connected on NEO-M8L,
OK to do the same on NEO-M8U.
18 SDA DDC Data / SPI CS_N SDA DDC Data / SPI CS_N No difference
19 SCL DDC Clock / SPI SCK SCL DDC Clock / SPI SCK No difference
20 TXD Serial Port / SPI MISO TXD Serial Port / SPI MISO No difference
21 RXD Serial Port / SPI MOSI RXD Serial Port / SPI MOSI No difference
22 V_BCKP Backup Supply Voltage
V_BCKP Backup Supply Voltage No difference
23 VCC Supply voltage VCC Supply voltage No difference
24 GND GND GND GND No difference
Table 4: Pin-out comparison NEO-M8L vs. NEO-M8U
☞For software migration and an overall description of the module software operation, see the u-blox
8 / u-blox M8 Receiver Description Including Protocol Specification
[2].
1In NEO-M8L documentation prior to firmware ADR 4.00 the pin 14 name was ANT_ON. The functionality of the pin 14 remains
the same, keeping the backward compatibility.
2In NEO-M8L documentation prior to firmware ADR 4.00 pin name was NC.

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5Product handling
5.1 Packaging, shipping, storage and moisture preconditioning
For information pertaining to reels and tapes, Moisture Sensitivity levels (MSL), shipment and
storage information, as well as drying for preconditioning see the
NEO-M8U Data Sheet [1].
Population of Modules
☞When populating the modules, make sure that the pick and place machine is aligned to the copper
pins of the module and not on the module edge.
5.2 Soldering
Soldering paste
Use of "No Clean" soldering paste is highly recommended, as it does not require cleaning after the
soldering process has taken place. The paste listed in the example below meets these criteria.
Soldering Paste: OM338 SAC405 / Nr.143714 (Cookson Electronics)
Alloy specification: Sn 95.5/ Ag 4/ Cu 0.5 (95.5% Tin/ 4% Silver/ 0.5% Copper)
Melting Temperature: 217 °C
Stencil Thickness: See section 2.3
The final choice of the soldering paste depends on the approved manufacturing procedures. The
paste-mask geometry for applying soldering paste should meet the recommendations.
☞The quality of the solder joints on the connectors (’half vias’) should meet the appropriate IPC
specification.
Reflow soldering
A convection type-soldering oven is highly recommended over the infrared type radiation oven.
Convection heated ovens allow precise control of the temperature, and all parts will heat up evenly,
regardless of material properties, thickness of components and surface color.
As a reference, see the "IPC-7530 Guidelines for temperature profiling for mass soldering (reflow and
wave) processes”, published in 2001.
Preheat phase
During the initial heating of component leads and balls, residual humidity will be dried out. Note that
this preheat phase will not replace prior baking procedures.
•Temperature rise rate: max. 3 °C/s. If the temperature rise is too rapid in the preheat phase it may
cause excessive slumping.
•Time: 60 - 120 s. If the preheat is insufficient, rather large solder balls tend to be generated.
Conversely, if performed excessively, fine balls and large balls will be generated in clusters.
•End Temperature: 150 - 200 °C. If the temperature is too low, non-melting tends to be caused in
areas containing large heat capacity.
Heating/ Reflow phase
The temperature rises above the liquidus temperature of 217°C. Avoid a sudden rise in temperature
as the slump of the paste could become worse.
•Limit time above 217 °C liquidus temperature: 40 - 60 s
•Peak reflow temperature: 245 °C

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Cooling phase
A controlled cooling avoids negative metallurgical effects (solder becomes more brittle) of the solder
and possible mechanical tensions in the products. Controlled cooling helps to achieve bright solder
fillets with a good shape and low contact angle.
•Temperature fall rate: max 4 °C/s
☞To avoid falling off, the NEO-M8U module should be placed on the topside of the motherboard
during soldering.
The final soldering temperature chosen at the factory depends on additional external factors like
choice of soldering paste, size, thickness and properties of the base board, etc. Exceeding the
maximum soldering temperature in the recommended soldering profile may permanently damage the
module.
Figure 11: Recommended soldering profile
☞NEO-M8U modules must not be soldered with a damp heat process.
Optical inspection
After soldering the NEO-M8U module, consider an optical inspection step to check that:
•The module is properly aligned and centered over the pads
•All pads are properly soldered
•No excess solder has created contacts to neighboring pads, or to nearby pad stacks and vias
Cleaning
In general, cleaning the populated modules is strongly discouraged. Residues underneath the
modules cannot be easily removed with a washing process.
•Cleaning with water will lead to capillary effects where water is absorbed in the gap between the
baseboard and the module. The combination of residues of soldering flux and encapsulated water
leads to short circuits or resistor-like interconnections between neighboring pads.
•Cleaning with alcohol or other organic solvents can result in soldering flux residues flooding into
the two housings, areas that are not accessible for post-wash inspections. The solvent will also
damage the sticker and the ink-jet printed text.
•Ultrasonic cleaning will permanently damage the module, in particular the quartz oscillators.
The best approach is to use a "no clean" soldering paste and eliminate the cleaning step after the
soldering.

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Repeated reflow soldering
Only single reflow soldering processes are recommended for boards populated with NEO-M8U
modules. The NEO-M8U module should not be submitted to two reflow cycles on a board populated
with components on both sides in order to avoid upside down orientation during the second reflow
cycle. In this case, the module should always be placed on that side of the board, which is submitted
into the last reflow cycle. The reason for this (besides others) is the risk of the module falling off due
to the significantly higher weight in relation to other components.
Two reflow cycles can be considered by excluding the above described upside down scenario and
taking into account the rework conditions described in section Product handling
.
☞Repeated reflow soldering processes and soldering the module upside down are not
recommended.
Wave soldering
Base boards with combined through-hole technology (THT) components and surface-mount
technology (SMT) devices require wave soldering to solder the THT components. Only a single wave
soldering process is encouraged for boards populated with NEO-M8U modules.
Hand soldering
Hand soldering is allowed. Use a soldering iron temperature setting equivalent to 350 °C. Place the
module precisely on the pads. Start with a cross-diagonal fixture soldering (e.g. pins 1 and 15), and
then continue from left to right.
Rework
The NEO-M8U module can be unsoldered from the baseboard using a hot air gun. When using a hot
air gun for unsoldering the module, a maximum of one reflow cycle is allowed. In general, we do not
recommend using a hot air gun because this is an uncontrolled process and might damage the
module.
⚠Attention: use of a hot air gun can lead to overheating and severely damage the module. Always
avoid overheating the module.
After the module is removed, clean the pads before placing and hand soldering a new module.
⚠Never attempt a rework on the module itself, e.g. replacing individual components. Such actions
immediately terminate the warranty.
In addition to the two reflow cycles, manual rework on particular pins by using a soldering iron is
allowed. Manual rework steps on the module can be done several times.
Conformal coating
Certain applications employ a conformal coating of the PCB using HumiSeal®or other related coating
products. These materials affect the HF properties of the NEO-M8U module and it is important to
prevent them from flowing into the module. The RF shields do not provide 100% protection for the
module from coating liquids with low viscosity; therefore, care is required in applying the coating.
☞Conformal Coating of the module will void the warranty.
Casting
If casting is required, use viscose or another type of silicon pottant. The OEM is strongly advised to
qualify such processes in combination with the NEO-M8U module before implementing this in the
production.
☞Casting will void the warranty.

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Grounding metal covers
Attempts to improve grounding by soldering ground cables, wick or other forms of metal strips
directly onto the EMI covers is done at the customer's own risk. The numerous ground pins should be
sufficient to provide optimum immunity to interferences and noise.
☞u-blox makes no warranty for damages to the NEO-M8U module caused by soldering metal cables
or any other forms of metal strips directly onto the EMI covers.
Use of ultrasonic processes
Some components on the u-blox M8 module are sensitive to Ultrasonic Waves. Use of any Ultrasonic
Processes (cleaning, welding etc.) may cause damage to the GNSS Receiver.
☞u-blox offers no warranty against damages to the NEO-M8U module caused by any Ultrasonic
Processes.
5.3 EOS/ESD/EMI precautions
When integrating GNSS positioning modules into wireless systems, careful consideration must be
given to electromagnetic and voltage susceptibility issues. Wireless systems include components
that can produce Electrical Overstress (EOS) and Electro-Magnetic Interference (EMI). CMOS devices
are more sensitive to such influences because their failure mechanism is defined by the applied
voltage, whereas bipolar semiconductors are more susceptible to thermal overstress. The following
design guidelines are provided to help in designing robust yet cost effective solutions.
⚠To avoid overstress damage during production or in the field it is essential to observe strict
EOS/ESD/EMI handling and protection measures.
⚠To prevent overstress damage at the RF_IN of your receiver, never exceed the maximum input
power (see the
NEO-M8U Data Sheet [1]).
Electrostatic discharge (ESD)
Electrostatic discharge (ESD) is the sudden and momentary electric current that flows
between two objects at different electrical potentials caused by direct contact or
induced by an electrostatic field. The term is usually used in the electronics and other
industries to describe momentary unwanted currents that may cause damage to
electronic equipment.
ESD handling precautions
ESD prevention is based on establishing an Electrostatic Protective Area (EPA). The EPA can be a
small working station or a large manufacturing area. The main principle of an EPA is that there are no
highly charging materials near ESD sensitive electronics, all conductive materials are grounded,
workers are grounded, and charge build-up on ESD sensitive electronics is prevented. International
standards are used to define typical EPA and can be obtained for example from International
Electrotechnical Commission (IEC) or American National Standards Institute (ANSI).
GNSS positioning modules are sensitive to ESD and require special precautions when handling.
Particular care must be exercised when handling patch antennas, due to the risk of electrostatic
charges. In addition to standard ESD safety practices, the following measures should be taken into
account whenever handling the receiver.