IEC TR 60068-3-12:2014

IEC TR 60068-3-12 ®
Edition 2.0 2014-10
TECHNICAL
REPORT
RAPPORT
TECHNIQUE
Environmental testing –
Part 3-12: Supporting documentation and guidance – Method to evaluate a
possible lead-free solder reflow temperature profile

Essais d'environnement –
Partie 3-12: Documentation d'accompagnement et guide – Méthode d'évaluation
d'un profil de température possible de brasage sans plomb par refusion
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IEC TR 60068-3-12 ®
Edition 2.0 2014-10
TECHNICAL
REPORT
RAPPORT
TECHNIQUE
Environmental testing –
Part 3-12: Supporting documentation and guidance – Method to evaluate a

possible lead-free solder reflow temperature profile

Essais d'environnement –
Partie 3-12: Documentation d'accompagnement et guide – Méthode d'évaluation

d'un profil de température possible de brasage sans plomb par refusion

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
CODE PRIX Q
ICS 19.040 ISBN 978-2-8322-1888-4

– 2 – IEC TR 60068-3-12:2014  IEC 2014
CONTENTS
FOREWORD . 3
1 Scope . 5
2 Basics . 5
3 Boards under investigation . 6
3.1 Test board approach . 6
3.2 Production board approach . 6
4 Temperature tolerances . 7
4.1 Temperature tolerances in Study A . 7
4.2 Temperature tolerance and board size influence in Study B . 8
5 Peak form and width . 9
5.1 Peak form and width in Study A . 9
5.2 Reflow oven investigation in Study B . 9
6 Classification . 10
6.1 Device classification in Study A . 10
6.2 Board classification in Study B . 12
7 Consideration for a lead-free reflow temperature profile. 13
7.1 Determined lead-free reflow temperature profile in Study A . 13
7.2 Lead-free reflow temperature profile approach in Study B . 14
8 Conclusion . 15
Bibliography . 16

Figure 1 – Curve shape for a peak temperature of at least 20 s at 230 °C and 1 s at
233 °C . 6
Figure 2 – Position of the assembled devices and temperature dependence on the
device position . 7
Figure 3 – Lower and upper temperature tolerances of the reflow solder profile . 8
Figure 4 – Temperature tolerance and board size influence . 8
Figure 5 – Hat type peak profile with 40 s at T − 5 K = 255 °C for the small devices
max
and the PCB . 9
Figure 6 – ∆T by different reflow oven capabilities . 10
Figure 7 – Representative test board measurements . 11
Figure 8 – Example of the small board (camcorder) . 13
Figure 9 – Example of the mid-size board (personal computer (PC)) . 13
Figure 10 – Lead-free reflow temperature profile for device qualification . 14

Table 1 – Measured temperatures of devices and values including lower and upper
tolerances . 11
Table 2 – Possible temperature classification of surface mount devices . 12
Table 3 – Proposed requirements for a lead-free reflow profile . 14

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ENVIRONMENTAL TESTING –
Part 3-12: Supporting documentation and guidance –
Method to evaluate a possible lead-free solder
reflow temperature profile
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
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9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
The main task of IEC technical committees is to prepare International Standards. However, a
technical committee may propose the publication of a technical report when it has collected
data of a different kind from that which is normally published as an International Standard, for
example "state of the art".
IEC TR 60068-3-12, which is a technical report, has been prepared by IEC technical
committee 91: Electronics assembly technology.
This second edition cancels and replaces the first edition published in 2007 and constitutes a
technical revision.
– 4 – IEC TR 60068-3-12:2014  IEC 2014
This edition includes the following significant technical changes with respect to the previous
edition:
• the content has been adapted to the state-of-the-art of reflow-oven technology and
termination finishes;
• minor language adjustments were performed.
The text of this technical report is based on the following documents:
Enquiry draft Report on voting
91/1158/DTR 91/1177/RVC
Full information on the voting for the approval of this technical report can be found in the
report on voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all the parts in the IEC 60068 series, under the general title Environmental testing,
can be found on the IEC website.
The committee has decided that the contents of this publication will remain unchanged until
the stability date indicated on the IEC website under "http://webstore.iec.ch" in the data
related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
ENVIRONMENTAL TESTING –
Part 3-12: Supporting documentation and guidance –
Method to evaluate a possible lead-free solder
reflow temperature profile
1 Scope
This part of IEC 60068, which is a technical report, presents two approaches for establishing
a possible temperature profile for a lead-free reflow soldering process using SnAgCu solder
paste.
This process covers a great variety of electronic products, including a large range of package
sizes (e.g. molded active electronic components, passive components and electromechanical
components).
Study A addresses requirements needed in the production of high-reliability electronic control
units (ECU), as for example in automotive electronics. These requirements include
measurement and production tolerances.
Study B represents consumer electronics products and includes reflow oven capability, board
design and package sizes.
2 Basics
The process temperature for SnPb solder paste has a wide margin due to the liquid
temperature of the solder alloy. During reflow soldering, temperature differences between
components exist but are not critical. The process temperature of SnAgCu solder paste is
about 20 K to 30 K higher than SnPb solder paste. Furthermore, the temperature difference
between components (∆T) becomes wider and sometimes the heat resistance temperature of
components can become critical.
To avoid soldering failures which could be very harmful in safety-related applications and also
generate higher failure costs, the capability of the soldering process is very important.
A compromise between the temperature requirements of highly reliable solder joints and the
limited solder-heat resistance of the electronic components has to be sought. In addition, the
different aspects of mass production have to be considered. To achieve a reliable solder joint,
the conventional reflow soldering process with eutectic SnPb solder paste is usually
performed at a minimum peak temperature of about 203 °C at the coldest solder joint (i.e. at
least 20 K above the liquid temperature of SnPb T = 183 °C).

liquid
The selected lead-free solder is SnAgCu with a melting point at around T = 217 °C [1] . It
liquid
is a generally preferred material for lead-free reflow and wave soldering in mass production
[2]. Using SnAgCu solder paste, it is not possible to solder the coldest solder joints at least
20 K above the liquid temperature (T = 217 °C), which would result in minimum

liquid
temperatures of 237 °C. When the coldest solder joint is 237 °C, the temperature spread
between small and large components, small semiconductor, and passive components, as well
as the printed circuit board (PCB), will be too large for the components to survive the heat
impact. Despite the aim to achieve a relatively low temperature at the coldest solder joint, the
reliability of the solder joint has to be assured.
___________
Numbers in square brackets refer to the Bibliography.

– 6 – IEC TR 60068-3-12:2014  IEC 2014
To reach this target in Study A, the temperature at the coldest solder joint is taken to be
T = 230 °C, for a minimum time of 20 s, which is just 13 K above the melting temperature.
min
Considering the peak shape (see Figure 1) this condition corresponds to 1 s at 233 °C. From
a physical point of view, the risk of insufficient solder wetting during mass production is
significantly higher if the solder joint temperature is lower than the above mentioned
temperature of 230 °C. In addition, lead-free termination finishes (like tin layers with a post-
bake process or very thin NiPdAu finishes) are known to exhibit a poorer wetting behavior
than conventional SnPb pin finishes.
Coldest solder joint
20 s at 230 °C
t,  s
IEC
Figure 1 – Curve shape for a peak temperature
of at least 20 s at 230 °C and 1 s at 233 °C
The experiments had been performed under mass production conditions (850 mm/min) using
state-of-the-art reflow equipment, i.e ovens featuring multiple heating zones, full convection
and N atmosphere.
3 Boards under investigation
3.1 Test board approach
For the experiment in Study A, a special test PCB was designed. Polyimide resin with a glass
transition temperature of T = 260 °C was used as base material for the PCB. Such a test
g
board can represent the entire automotive ECU spectrum. The largest temperature difference
(∆T) between the coldest solder joint and the hottest point existing on this printed circuit
assembly (PCA) spectrum is reflected on this test board (∆T can be even larger for even more
complex PCAs). The coldest solder joint was represented by a defined thermal mass, to
represent large integrated circuits (ICs), coils or aluminium electrolytic capacitors. Its
temperature behavior was correlated with the temperatures of the coldest solder joints on
serial boards.
3.2 Production board approach
For Study B, PCB and reflow oven were taken from actual series production.

T,  °C
4 Temperature tolerances
4.1 Temperature tolerances in Study A
For tolerances during temperature profiling, different systematic failures shall be considered.
First of all, there is an error associated with the temperature measurement itself. The
measurement was performed in the centre on top of the packages with a well defined and
repeatable preparation technique. Nevertheless, the failure due to preparation had to be fixed
within ±1,0 K. In addition, the thermocouple (NiCrNi), together with the evaluation unit has an
accuracy of ±1,5 K for pre-selected thermocouples. According to IEC 60584-2 [6] the NiCrNi
thermocouples, class K, tolerance class 1 are specified with a tolerance of ±1,5 K for just the
thermocouple itself without the measurement unit. Based on suppliers indication and own
measurements, the furnace tolerance based on furnace load is ±0,5 K and the furnace
tolerance for long term stability is ±2,5 K.
– Thermocouple with measurement unit:
±1,5 K
– Preparation of thermocouple:
±1,0 K
– Furnace load variation:
±0,5 K
– Long term stability of furnace:
±2,5 K
Because these variations are independent, the Gaussian error propagation can be applied,
which results in a total tolerance of ±3,0 K, due to measurement errors and variations in mass
production. The tolerance of –3,0 K results in the requirement to profile the coldest solder
joint at 236 °C, instead of 233 °C (i.e. 233 °C + 3,0 K). This tolerance is known as the “lower
tolerance”. In addition to the measurement errors and variations due to mass production, the
influences of the test board have to be considered. The measured temperatures of the
electronic components depend also on the position on the test board because of the
longitudinal and transversal temperature spread in the furnace and along the test board (see
Figure 2). These temperature differences are the result of the heat flow conditions in the
furnace and around the test board. The actual temperature of a device can be up to 3,5 K
higher than the measured values at the position where the device is mounted on the test
board. The temperature dependence on the device position was measured independently
before measuring the device temperatures on the assembled test board.
Temperature
Transversal temperature profile
Longitudinal
temperature
profile
Device position
Direction of
on test board
transportation
IEC
Figure 2 – Position of the assembled devices
and temperature dependence on the device position
The thermal mass on the test board, which represents the coldest solder joint on the serial
boards, was designed to include the relevant position-dependent tolerances. The upper
temperature tolerances consist of the position-dependent temperature tolerances of 2 K to
3,5 K and the above mentioned +3 K. This leads to a total upper tolerance of 5 K to 6,5 K.

– 8 – IEC TR 60068-3-12:2014  IEC 2014
Regarding the whole temperature window of the lead-free soldering process, a total position-
dependent temperature tolerance of 8 K to 9,5 K has to be added to the measured ∆T spread
of the devices (see Figure 3).
Upper tolerances (measurement, equipment
and position on test board 5,0 K to 6,5 K)
Measured ∆T between coldest solder joint
and hottest device within each class
∆T devices
236 °C
Lower tolerances (measurement and equipment)
3 K
233 °C
20 s at 230 °C corresponds to 1 s at 233 °C
Minimum temperature requirement; 20 s at 230 °C
20 s 230 °C
IEC
NOTE Electronic devices are divided into three temperature classes.
Figure 3 – Lower and upper temperature tolerances of the reflow solder profile
4.2 Temperature tolerance and board size influence in Study B
In the consumer board study, the measured temperature includes lower temperature tolerance
and upper temperature tolerance. Therefore at the coldest solder joint temperature of 230 °C,
the "worst-case" temperature becomes 227 °C (i.e. 230 °C – 3 K) which is still 10 K higher
than the melting point of the SnAgCu solder alloy (see Figure 4).
∆T = 20 K
∆T between coldest solder joint and hottest
∆T = 15 K
component within the board          →
∆T = 10 K
230 °C →
Total tolerance 3 K
Minimum condition for high reliable soldering
227 °C min.
Temperature: 230 °C
13 K
Soldering time: 10 s to 30 s
Melting point of the SnAgCu: 217 °C         →
IEC
Figure 4 – Temperature tolerance and board size influence

Small size PCB
・Digital camera
・Camcorder
Small
Mid size PCB
devices
・PC
Large
・Set top box
devices
Very large
devices
Large size PCB
・Non consumer products
5 Peak form and width
5.1 Peak form and width in Study A
The requirements were to maintain a temperature of at least 230 °C for 20 s at the coldest
solder joint, and to limit the peak package temperature of the smallest devices (e.g. SOT23,
small LQFP, TopLEDs and passive components) to T ≤ 260 °C. In order to meet these
peak
requirements, a soak-type preheating, as well as a hat type soldering peak were necessary in
the investigation. The soak-type preheating allowed the temperatures of the individual
packages to be close to each other upon entering the peak zone (see Figure 7). The hat type
form of the soldering peak was used to minimize the temperature differences between the
individual packages during reflow soldering. After conducting the experiment, it was
discovered that the hat type form of the soldering peak required a soak time of 40 s at
T − 5 K = 255 °C for the hottest devices on the PCB (see Figure 5).
max
40 s at 255 °C
PCB
LQFP 14 × 14
LQFP 20 × 20
Coldest solder joint
20 s at 230 °C
t,  s
IEC
NOTE Temperature tolerances are included.
Figure 5 – Hat type peak profile with 40 s at T − 5 K = 255 °C
max
for the small devices and the PCB
5.2 Reflow oven investigation in Study B
Figure 6 shows temperature profiles on quad flat package (QFP) leads and a 1608 size
surface mounting device (SMD) resistor using the same board but different reflow ovens. The
reflow oven of Maker B, having more heating zones than the oven of Maker A, shows a wider
temperature spread ∆T in the temperature profile than the oven of Maker A. Thus, the
temperature spread ∆T does not depend primarily on the number of heating zones of the
reflow oven but on the design of the reflow oven.
The peak reflow temperature for smallest components may vary according to the reflow oven
being used. Also board size and board design are other factors affecting the peak reflow
temperature.
T,  °C
– 10 – IEC TR 60068-3-12:2014  IEC 2014
Maker A
Maker B
7 zones
12 zones
∆T ≈ 15 °C
230 °C
230 °C
∆T ≈ 20 °C
QFP Lead
1608 R
IEC
Figure 6 – ∆T by different reflow oven capabilities
6 Classification
6.1 Device classification in Study A
To classify the non-hermetic solid-state surface-mount devices into temperature groups with
respect to the reflow peak, the heat capacity and heat conductivity should be taken into
consideration. To simplify the study, the component similarity with respect to the composition
(molded silicon) is taken into account and only the package volume and thickness are
considered. In Figure 7, some typical temperature measurements of molded components
using the described test board with a soak preheating and a hat-type reflow soldering peak
are shown. The transportation speed was 850 mm/min and the temperature measurements
were performed centrally on the top of the packages. In total, the temperature profiles for 19
characteristic molded package types and several passive and electromechanical devices were
measured on a multiple heating zone reflow oven with full convection. Between the coldest
solder joint and the PCB itself, a temperature difference of 13 K was measured. Small plastic
components like small connectors, switches or TopLEDs showed even higher peak package
temperatures with a temperature difference of 17 K from the coldest solder joint [3], [4].

PCB and small devices
BGA
Coldest solder joint
t,  s
IEC
NOTE Temperature tolerances are included.
Figure 7 – Representative test board measurements
Table 1 shows the measured temperatures and the temperatures achieved when the lower
and upper tolerances are being added. Temperatures shown are for several characteristic
molded devices with different peak temperatures.
Table 1 – Measured temperatures of devices and values
including lower and upper tolerances
Temperature
Measured Lower Including Upper Including
Device value tolerance lower tolerance upper
tolerance tolerance
°C °C °C °C °C
Coldest solder joint 233,0 3,0 236,0 – –
Plastic leaded chip 234,0 3,0 237,0 6,0 243,0
carrier PLCC52
TO263 239,5 3,0 242,5 5,0 247,5
Ball grid array (BGA) 240,5 3,0 243,5 6,0 249,5
(24 mm x 24 mm)
Low-profile quad flat 243,5 3,0 246,5 6,0 252,5
package (LQFP) (14 mm
x 14 mm)
Small outline transistor 247,0 3,0 250,0 5,0 255,0
(SOT) devices
The upper tolerance is dependent on the position of the device on the PCB. The lower tolerance of 3,0 K
represents the value that the minimum solder joint temperature has to be raised to, due to the mentioned
measurement and process tolerances.

In these examples, the maximum temperature difference between actual measured and
tolerance corrected values was 9 K. These corrected temperatures represent the theoretically
possible maximum package temperatures for the devices during reflow soldering. Referring to
molded components (most active components) their internal structure is very similar. The
specific heat capacity and the thermal conductivity do not deviate significantly (metal-based
lead frame or interposer/silicon/mold compound). Therefore, it is possible to create
temperature classes for the solder-heat resistance referring to volume and thickness of such
molded devices. However, a similar approach is not feasible for the wide range of passive and

T,  °C
– 12 – IEC TR 60068-3-12:2014  IEC 2014
electromechanical components. Some of these (non-molded) components reached peak
temperatures of 260 °C. In addition, many of the small molded components are commonly
qualified with a 260 °C peak temperature reflow profile. Therefore, the upper temperature
device group was defined as the 260 °C class. Furthermore, a class of 250 °C for large
molded components and a class of 245 °C for very large molded components was defined.
Table 2 shows a possible temperature classification of non-hermetic solid state surface mount
devices referring to volume and thickness of the devices.
Table 2 – Possible temperature classification of
surface mount devices
3 3 3 3
Thickness / Volume <350 mm 350 mm to 2 000 mm >2 000 mm
260 (– 0) °C 260 (– 0) °C 260 (– 0) °C
<1,6 mm
1,6 mm to 2,5 mm 260 (– 0) °C 250 (– 0) °C 250 (– 0) °C
260 (– 0) °C 250 (– 0) °C 245 (– 0) °C
>2,5 mm
NOTE The package volume excludes external terminals and non-integral heat sinks.

6.2 Board classification in Study B
Between the coldest solder joint and the hottest component package or PCB ∆T ranks from
1 K for small boards to 9 K for mid-size boards.
Figure 8 shows temperature profiles of the PCB surface and under the BGA on the small
board. The maximum temperature under the BGA is 229 °C with 20 s above 225 °C and the
maximum temperature of the PCB is 230 °C.
Figure 9 shows temperature profiles of the PCB surface and under the BGA on the mid-size
board. The maximum temperature under the BGA is 228 °C with 26 s above 225 °C and the
maximum temperature of the PCB is 237 °C.
From this study, ∆T between coldest solder joint and hottest component package or PCB
could be assumed as follows (refer to Figure 4):
small size board (e.g., digital camera, camcorder) 10 K;
mid-size board (e.g., personal computer (PC), set top box) 15 K;
large board (e.g., non-consumer product) 20 K.

Temperature profile
Temperature profile
- PCB surface    230 °C
- Under the BGA  229 °C
PCB surface
Under the BGA
IEC
Figure 8 – Example of the small board (camcorder)
Temperature profile
Temperature profile
- PCB surface
237 °C max.
- Under the BGA
228 °C max.
PCB surface
Under the BGA
IEC
Figure 9 – Example of the mid-size board (personal computer (PC))
7 Consideration for a lead-free reflow temperature profile
7.1 Determined lead-free reflow temperature profile in Study A
The performed measurements and the given considerations lead to a possible reflow profile,
which covers the described requirements of lead-free mass production (see Figure 10). Once
a device is qualified, using this reflow profile, it can be used in a wide range of electronic
control units. To assess the components resistance to solder heat the devices should be
subjected to a soldering simulation by subjecting them to this temperature profile at least
three times. This is necessary to ensure the reliability of the device after more than one reflow
soldering process. Soldering in mass production shall be performed below this limiting
temperature line to ensure that the device will not be stressed too much during the reflow
process. Therefore, the proposed reflow profile could help define the borders between the

– 14 – IEC TR 60068-3-12:2014  IEC 2014
device suppliers and the device assemblers. Figure 10 shows a lead-free reflow temperature
profile for device qualification regarding the solder heat resistance.
T(solid) 217 °C
Ramp down
Ramp up
from T(max.)
to 150 °C
6 K/s
3 K/s
t,  s
IEC
NOTE Temperature profile not to scale.
Figure 10 – Lead-free reflow temperature profile for
device qualification
Table 3 presents proposed requirements for a lead-free device qualification reflow
temperature profile given in numbers.
Table 3 – Proposed requirements for a lead-free reflow profile

Profile features Small devices Large Very large
Pre-heat
Ramp-up rate to 150 °C 3 K/s (average value over 10 s)
Time from 190 °C to 200 °C Min. 110 s
Peak
Ramp-up rate from 200 °C to T 0,5 K/s – 3 K/s (average value over 10 s)
peak
Time above T (min. 217 °C) Min. 90 s
solidus
Peak temperature T 260 (–0) °C 250 (–0) °C 245 (–0) °C
peak
Time above T – 5 K Min. 40 s Min. 30 s Min. 30 s
peak
Cooling
Ramp-down rate from T (min. 217 °C) Up to 6 K/s (average value over 10 s) device dependent
solidus
General
Time 25 °C to T Min. 300 s
peak
7.2 Lead-free reflow temperature profile approach in Study B
The maximum temperature of the package body during the reflow process not only depends
on volume and thickness, but also depends on construction, materials used and other factors.
Therefore, the resistance to soldering heat test conditions for reflow soldering using SnAgCu,
as described in IEC 60068-2-58 [5], covers the majority of the consumer electronics,
assuming components are mounted on a large size board (∆T = 20 K).

T,  °C
8 Conclusion
Based on measurements performed on state-of-the-art technology furnaces, a process for
lead-free soldering using SnAgCu solder paste was developed. The determined lead-free
temperature profile covers the requirements of mass production assembly with respect to the
solder-heat resistance. The molded (non-hermetic solid state) devices could be divided into
three maximum temperature classes of 260 °C, 250 °C and 245 °C (a classification of the
passive and electromechanical components was not achieved). For automotive ECU
applications as shown in Study A, all passive and electromechanical devices should be
considered as elements of the 260 °C class until further measurements of single parts are
performed. Using this process, most electronic control units can be soldered in compliance
with the process-capability requirements. In order to reduce the peak temperature below
260 °C, further evaluation is necessary. Improvements of the furnace technology may reduce
the position-dependent tolerances and mass production tolerances (especially the long term
stability and the longitudinal temperature spread across the board).

– 16 – IEC TR 60068-3-12:2014  IEC 2014
Bibliography
[1] MOON, BÖTTINGER, KATTNER, BIANCANIELLO, HANDWERKER: "Experimental and
Thermodynamic Assessment of Sn-Ag-Cu solder alloys", J. Electr. Mat., Vol. 29, No.
10 (2000), pp. 1122-1135
[2] NIMMO, Kay: "Second European Lead-Free Soldering Technology Roadmap",
soldertec, Feb. 2003
[3] KIRCHNER, KLEIN, BEINTNER, BRAUER, HOLZ, FEUFEL: "The Development of a
Qualification Temperature Profile for Lead-free Reflow Soldering", Proceedings of 5th
IPC JEDEC Lead-free Conference San Jose, Mar. 2004
[4] GÖRTLER, ZETTNER, SCHOTTENLOHER, KIRCHNER, KLEIN: "Reaction of Passive
and Active Electronic Components on the Heat Impact During Lead-free Reflow
Soldering", Proceedings of the 7th IPC JEDEC International Lead-free Conference,
Frankfurt, Oct. 2004
[5] IEC 60068-2-58, Environmental testing – Part 2-58: Tests – Test Td: Test methods for
solderability, resistance to dissolution of metallization and to soldering heat of surface
mounting devices (SMD)
[6] IEC 60584-2, Thermocouples – Part 2: Tolerances

_____________
– 18 – IEC TR 60068-3-12:2014  IEC 2014

SOMMAIRE
AVANT-PROPOS . 19
1 Domaine d'application . 21
2 Notions fondamentales . 21
3 Cartes étudiées . 22
3.1 Approche de la carte d'essai . 22
3.2 Approche de la carte de fabrication . 23
4 Tolérances de température . 23
4.1 Tolérances de température dans l'étude A . 23
4.2 Tolérance de température et influence des dimensions de la carte dans
l'étude B . 25
5 Forme et largeur de pic de brasage . 26
5.1 Forme et largeur de pic dans l'étude A . 26
5.2 Etude du four de refusion dans l'étude B . 27
6 Classification . 28
6.1 Classification des dispositifs dans l'étude A . 28
6.2 Classification des cartes dans l'étude B . 30
7 Considérations relatives à un profil de température de refusion sans plomb . 32
7.1 Profil de température de refusion sans plomb déterminé dans l'étude A . 32
7.2 Approche du profil de température de refusion sans plomb dans l'étude B . 34
8 Conclusion . 34
Bibliographie . 35

Figure 1 – Forme de courbe pour une température de crête d'au moins 20 s à 230 °C
et 1 s à 233 °C . 22
Figure 2 – Position des dispositifs assemblés et de la dépendance de la position du
dispositif par rapport à la température . 24
Figure 3 – Tolérances de température inférieure et supérieure du profil de brasage par
refusion . 25
Figure 4 – Tolérance de température et influence des dimensions de la carte . 26
Figure 5 – Profil de crête de type chapeau avec 40 s à T – 5 K = 255 °C pour les
max
petits dispositifs et le PCB . 27
Figure 6 – ∆T pour différentes caractéristiques du four de refusion . 28
Figure 7 – Mesures de cartes d'essai représentatives . 29
Figure 8 – Exemple de petite carte (caméscope). 31
Figure 9 – Exemple de carte de taille moyenne (PC) . 32
Figure 10 – Profil de température de refusion sans plomb pour la qualification des
composants . 33

Tableau 1 – Températures mesurées des dispositifs et valeurs incluant les tolérances
inférieures et supérieures . 29
Tableau 2 – Classification en température possible des dispositifs à montage en
surface . 30
Tableau 3 – Exigences proposées pour un profil de température de refusion . 33

COMMISSION ÉLECTROTECHNIQUE INTERNATIONALE
____________
ESSAIS D'ENVIRONNEMENT –
Partie 3-12: Documentation d'accompagnement et guide –
Méthode d'évaluation d'un profil de température
...