494
P. Vianco and M. Neilsen
Methods and Qualification Requirements for Surface Mount Solder Attachments,”
IPC-9701 (IPC; Bannockburn, IL). First, there are the use environments of consumer
electronics, which include household appliances, office equipment, and personal
electronics such as smart phones, lap-top computers, etc. The second category is
high-reliability electronics, which encompasses products used in telecommunications equipment, commercial aircraft avionics, military weapons, satellite hardware,
and space flight systems. This category also includes automobile electronics as well
as monitoring systems used in the exploration of fossil fuel reserves (oil wells)
or the development of renewable energy industry (geothermal wells, solar electric
components, etc.). Automotive and energy system electronics are considered highreliability because they are exposed to very harsh environments and/or pose one or
more high-consequence, failure scenarios.
Each of the two use categories can be described according to the details of the environment that affect the reliability of stacked package solder interconnections. The
three primary environments are: (1) temperature fluctuations; (2) mechanical vibration; and (3) mechanical shock. A conservative approximation, which is not without
its detractors, is to assume that the electronics experience the equivalent temperature
cycle, mechanical shock loads, etc. that are present in the external environmental.
This assumption is conservative because, in the case of temperature cycling, there
can be a significant time delay between the external temperature profile and that
experienced by a component buried into the interior of the system. The magnitude
of the time delay depends upon the location of the component inside of the product
and the thermal conduction of materials located between the two locations.
Vibration conditions are characterized by frequency, power spectral density (a
measure of amplitude versus frequency), and direction of the load [22]. The loading
direction is described by Cartesian coordinates; or, the vibration is random and occurs
equally in all directions.
Mechanical shock refers to the loads experienced over a very short time duration,
typically 1–5 ms [23]. Mechanical shock is simulated by a “drop shock” test when
personal electronics are dropped to a hard surface. Shock conditions are also important in high-reliability military, space, and satellite hardware that must survive the
rigors of a launch and/or impact environment.
An important factor when considering (mechanical) shock and vibration environments is coupling between the external condition and the environment at the
site of the stacked package. Internal structures can dampen the outside shock and
vibration amplitudes. However, it is equally possible that, in the absence of suitable engineering controls, shock and vibration loads can be amplified by activating
characteristic frequencies of the PWA or its mount structures, leading rapidly to a
damaged assembly.
P. Vianco and M. Neilsen
Methods and Qualification Requirements for Surface Mount Solder Attachments,”
IPC-9701 (IPC; Bannockburn, IL). First, there are the use environments of consumer
electronics, which include household appliances, office equipment, and personal
electronics such as smart phones, lap-top computers, etc. The second category is
high-reliability electronics, which encompasses products used in telecommunications equipment, commercial aircraft avionics, military weapons, satellite hardware,
and space flight systems. This category also includes automobile electronics as well
as monitoring systems used in the exploration of fossil fuel reserves (oil wells)
or the development of renewable energy industry (geothermal wells, solar electric
components, etc.). Automotive and energy system electronics are considered highreliability because they are exposed to very harsh environments and/or pose one or
more high-consequence, failure scenarios.
Each of the two use categories can be described according to the details of the environment that affect the reliability of stacked package solder interconnections. The
three primary environments are: (1) temperature fluctuations; (2) mechanical vibration; and (3) mechanical shock. A conservative approximation, which is not without
its detractors, is to assume that the electronics experience the equivalent temperature
cycle, mechanical shock loads, etc. that are present in the external environmental.
This assumption is conservative because, in the case of temperature cycling, there
can be a significant time delay between the external temperature profile and that
experienced by a component buried into the interior of the system. The magnitude
of the time delay depends upon the location of the component inside of the product
and the thermal conduction of materials located between the two locations.
Vibration conditions are characterized by frequency, power spectral density (a
measure of amplitude versus frequency), and direction of the load [22]. The loading
direction is described by Cartesian coordinates; or, the vibration is random and occurs
equally in all directions.
Mechanical shock refers to the loads experienced over a very short time duration,
typically 1–5 ms [23]. Mechanical shock is simulated by a “drop shock” test when
personal electronics are dropped to a hard surface. Shock conditions are also important in high-reliability military, space, and satellite hardware that must survive the
rigors of a launch and/or impact environment.
An important factor when considering (mechanical) shock and vibration environments is coupling between the external condition and the environment at the
site of the stacked package. Internal structures can dampen the outside shock and
vibration amplitudes. However, it is equally possible that, in the absence of suitable engineering controls, shock and vibration loads can be amplified by activating
characteristic frequencies of the PWA or its mount structures, leading rapidly to a
damaged assembly.