IEC TR 60068-3-12:2007

Environmental testing - Part 3-12: Supporting documentation and guidance - Method to evaluate a possible lead-free solder reflow temperature profile

Presents two approaches to establish a possible temperature profile for a lead-free reflow soldering process using SnAgCu solder paste. The presented process window covers a great variety of electronic products, including a large range of package sizes (molded active electronic components, passive components and electromechanical components)

General Information

• Status: Published
• Publication Date: 11-Mar-2007
• ICS: 19.040 - Environmental testing
• Technical Committee: TC 91 - Electronics assembly technology
• Drafting Committee: WG 3 - TC 91/WG 3
• Current Stage: DELPUB - Deleted Publication
• Completion Date: 17-Oct-2014

Relations

• Revised: IEC TR 60068-3-12:2014 - Environmental testing - Part 3-12: Supporting documentation and guidance - Method to evaluate a possible lead-free solder reflow temperature profile
• Effective Date: 05-Sep-2023

Standards Content (Sample)

TECHNICAL IEC
REPORT TR 60068-3-12
First edition
2007-03
Environmental testing –
Part 3-12:
Supporting documentation and guidance –
Method to evaluate a possible lead-free solder
reflow temperature profile
Reference number
IEC/TR 60068-3-12:2007(E)
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TECHNICAL IEC
REPORT TR 60068-3-12
First edition
2007-03
Environmental testing –
Part 3-12:
Supporting documentation and guidance –
Method to evaluate a possible lead-free solder
reflow temperature profile
© IEC 2007 ⎯ Copyright - all rights reserved
No part of this publication may be reproduced or utilized in any form or by any means, electronic or
mechanical, including photocopying and microfilm, without permission in writing from the publisher.
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– 2 – TR 60068-3-12 ¤ IEC:2007(E)
CONTENTS
FOREWORD.4
1 Scope.6
2 Basics .6
3 Boards under investigation .7
3.1 Test board approach .7
3.2 Production board approach .7
4 Temperature tolerances.8
4.1 Temperature tolerances in Study A.8
4.2 Temperature tolerance and board size influence in Study B .9
5 Peak form and width.10
5.1 Peak form and width in Study A.10
5.2 Reflow oven investigation in Study B.10
6 Classification.11
6.1 Device classification in Study A.11
6.2 Board classification in Study B .12
7 Consideration for a lead-free reflow temperature profile .14
7.1 Determined lead-free reflow temperature profile in Study A .14
7.2 Lead-free reflow temperature profile approach in Study B .15
8 Conclusion .15
Bibliography.16
Table 1 – Measured temperatures of devices and values including lower and upper
tolerances.12
Table 2 – Possible temperature classification of nonhermetic solid state surface mount
devices referring to volume and thickness of the devices .12
Table 3 – Proposed requirements for a lead-free device qualification reflow
temperature profile in numbers .14
Figure 1 – Curve shape for a peak temperature of at least 20 s at 230 °C and 1 s at
233 °C .7
Figure 2 – Position of the assembled devices and temperature dependence on the
device position.8
Figure 3 – Lower and upper temperature tolerances of the reflow solder profile .9
Figure 4 – Temperature tolerance and board size influence .9
Figure 5 – Hat type peak profile with 40 s at T – 5 K = 255 °C for the small devices
max
and the PCB .10
Figure 6 – ΔT by different reflow oven capabilities .11
Figure 7 – Representative test board measurements .11
Figure 8 – Example of the small board (camcorder) .13
Figure 9 – Example of the mid-size board (PC) .13

TR 60068-3-12 ¤ IEC:2007(E) – 3 –
Figure 10 – Lead-free reflow temperature profile for device qualification regarding to
the solder heat resistance.14

– 4 – TR 60068-3-12 ¤ IEC:2007(E)
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ENVIRONMENTAL TESTING –
Part 3-12: Supporting documentation and guidance –
Method to evaluate a possible lead-free solder reflow temperature profile
FOREWORD
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IEC 60068-3-12, which is a technical report, has been prepared by IEC technical
committee 91: Electronics assembly technology.
The text of this technical report is based on the following documents:
Enquiry draft Report on voting
91/601A/DTR 91/636A/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.

TR 60068-3-12 ¤ IEC:2007(E) – 5 –
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 maintenance result date indicated on the IEC web site 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.
A bilingual version of this publication may be issued at a later date.

– 6 – TR 60068-3-12 ¤ IEC:2007(E)
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 serves as a Technical Report and 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 (molded active electronic components, passive components and electromechanical
components).
Study A addresses requirements needed in the production of automotive electronic control
units (ECU). These requirements include, but are not limited to, 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 (ΔT) becomes wider and sometimes heat resistance temperature of
components is exceeded.
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 devices has to be found. In addition, the
different aspects of mass production have to be covered. 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
= 183 °C).
least 20 K above the liquid temperature of SnPb T
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
...