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The majority of Discrete Semiconductors are rugged. Some, like
FETs and Schottky’s need special care to protect against electrostatic discharge
Resources contains information relative to ESD considerations.
Parts classified as
“Class 1” in terms of ESD sensitivity should be placed in dry nitrogen
storage until required for usage. Perform manual handling of die by using sharp
tweezers with excellent point alignments. Failure to use the correct tools, or
using tweezers with improperly bent or mis-aligned points, can result in costly
Plastic parts shall have appropriate classification
labeling. Refer to JEP-A-113 for classification.
Transients can be
generated by poor contact to the device under test (DUT) by test equipment, when
an uncontrolled high voltage briefly is generated, or while trying to force a
desired programmed level of test current. Therefore, precautions are necessary
in test equipment selection or maintenance of electromechanical features; for
example, test clip contacts where poor electrical continuity may occur. If the
DUT has tarnished leads from prior high temperature testing, such as HTRB or
burn-in operations, then leads should be cleaned before testing.
Lead bending of
axial leaded diodes, before insertion into a PC board, should not be done in
such close proximity to the body to force a bend up to and into the body itself.
This excessive “tight bend” may stress glass body diodes or transmit undesired
forces internally into the active die element for plastic body diodes as well.
This is less critical on double-slug glass diodes where the lead is welded or
brazed to a larger diameter slug before entering a glass to metal seal region.
In most examples, a 90-degree bend should be at least 1/8 inch or three lead
diameters from the body, whichever is greater.
Recommend that leads be supported adjacent to the body before the bend is
temperatures and times for diodes are typically 260°C for 10 seconds maximum. Solder profiles will
generally be much lower and shorter in time than these maximums when using
commonly used solders such as 63/37% Sn/Pb, 60/40% Sn/Pb, or 62/36/2% Sn/ Pb/Ag.
Actual time and temperature is determined by overall thermal mass of PC boards
and parts, along with considerations of other part sensitivity. For most
through-hole axial lead diodes, the body does not directly see these
temperature-time extremes; however, surface mount (SM) does. Common surface
mounting processes used in the industry are accomplished by using convection or
infrared belt furnace, vapor phase reflow, or wave soldering equipment. SM
packages may be affixed temporarily to the circuit board with a fast curing
adhesive system between package body and board (separate from the defined
solderable footprint) to accommodate soldering. Where the body is suddenly
exposed to soldering temperatures (such as in wave soldering), recommend a
preheat step be included that is within 100 C of the final soldering
temperature, to minimize thermal shock effects on the body of the part.
If PC board level
coatings are used after solder mounting, they should be carefully selected to
avoid stressing parts, particularly glass body designs. When used, they should
be silastic or pliable to minimize stresses that may be induced by differences
in coefficient of expansion or other transmitted forces imparted from PC board
flexure. Rigid epoxy coatings have, for example, been known to crack glass body
parts including those board coatings applied in a relatively thin layer. This
may be partly stimulated by stresses imparted on a part, when rigid coatings are
placed in the narrow standoff relief space between the PC board and a glass body