TN0983
Technical note
Safety application guide for SPC56xL70xx family
reference manual addendum
Introduction
This document is an addendum of SPC56xL70xx Safety Application Guide.
September 2013
Doc ID 024257 Rev 2
1/6
www.st.com
Contents
TN0983
Contents
1
2
Purpose and scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Considerations on SPC56x70xx package and soldering procedures . 4
2.1
2.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Risk analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.2.1
2.2.2
2.2.3
2.2.4
Risk item . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Cause . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Risk evaluation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Item Assumption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3
Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2/6
Doc ID 024257 Rev 2
TN0983
Purpose and scope
1
Purpose and scope
The purpose of this document is to communicate to ST customers who intend to integrate
SPC56x70xx in an ASIL-D Item some additional assumptions which shall be met at item
level to preserve the SPC56x70xx integrity. The assumptions described in this document
shall be intended as additional assumptions with respect to those communicated in the
SPC56x70xx Safety Application Guide.
Doc ID 024257 Rev 2
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Considerations on SPC56x70xx package and soldering procedures
TN0983
2
Considerations on SPC56x70xx package and
soldering procedures
Introduction
SPC56x70xx package is composed by Ultra Low Alpha mold compound. Measurements
report an alpha particle emissivity of 0.00383 ± 0.00056 cp/h/cm
2
.
This value has been used in the SPC56x70xx quantitative safety analyses (see
SPC56x70xx FMEDA).
In order to ensure that this value does not increase when soldering the device on a board, a
risk analysis is made in the following chapter. The conclusions of this analysis report that
some caution must take during soldering process in order to avoid package delamination,
hence avoiding any contamination from the soldering material to the silicon contained in the
plastic package.
2.1
2.2
2.2.1
Risk analysis
Risk item
Single Event Upset randomly induced by alpha particle emission from Package material.
2.2.2
Cause
A possible cause of silicon contamination is the presence of potentially alpha-emissive
soldering material, specifically induced by Pb impurities.
2.2.3
Risk evaluation
Assuming that no delamination is present on the package and given the low migration
capability of Pb particles, the risk of having emissive material on the silicon surface is very
low.
2.2.4
Item Assumption
We recommend our customers to avoid active soldering flux and to verify the integrity of
packages after board mounting in order to eliminate the possibility of package delamination
after device mounting on board, therefore eliminating the possibility of silicon contamination
by soldering material.
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