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Surface Mounting SMT LED Indicator Components
Application Note 1060
Contents
• Surface Mount LED Indicators
• Standard EIA Tape and Reel Packaging
• Moisture Barrier Envelope Packaging
• PC Board Pad Design
• Automatic Placement Equipment Considerations
• Solder Paste
• Reflow Soldering
Surface Mount LED Indicators
Circuit board assemblies using surface mount technology
(SMT) are now common and SMT LED indicators are being
used on many of these SMT board assemblies. There are
currently three basic types of Avago Technologies SMT
LED indicator components:
a. HLMP/A/T-6/7/P/Qxxxx domed and flat top
subminiature lamps with formed leads:
• Option 011 “gull wing” leads.
• Option 021 “yoke” leads.
• Option 031 “Z-bend” leads.
b. ASMT-Cxxx and HSMx-Cxxx/Sxxx chip LEDs.
c. HSMx-Axxx, ASMC-PRxx, ASMT-SWxx PLCC LEDs.
All these LED indicator components types may be
mounted to a printed circuit (pc) board using automatic
placement equipment and attached using a reflow solder
process.
This application note provides information on how to suc-
cessfully attach SMT LED indicators onto a pc board.
Standard EIA Tape and Reel Packaging
SMT LED lamps are packaged tape and reel in accordance
with EIA Standard 481, Taping of Surface Mount Compo-
nents for Automatic Placement. Reel and tape dimensions
conform to EIA standards with individual SMT LED lamps
in the embossed carrier tape spaced on 4 mm (0.157 in.)
centers. Detail tape and reel dimensions are stated in in-
dividual product data sheets.
Moisture Barrier Envelope Packaging
The optical grade materials used in SMT LED components
absorb moisture directly from the air. Moisture absorbed
in SMT LED components that have been reflow soldered
to a pc board is typically a minor concern. However,
moisture absorption in SMT LED components prior to
reflow soldering is of serious concern. If moisture is
absorbed by SMT LED components prior to soldering, the
entrapped moisture turns to superheated steam during
the solder process. The pressure of this superheated
stem fractures the packages of the components causing
catastrophic failure. Therefore, it is of vital importance to
protect SMT LED components from a absorbing moisture
prior to soldering.
To protect the SMT LED components from moisture ad-
sorption during shipping and handling, reels for SMT
LED components may be packaged in moisture barrier
envelopes, as illustrated in Figure 1.
Each envelope contains desiccant. To assure the moisture
barrier seal, it is important to protect these envelopes
from being punctured by sharp objects such as staples.
Once opened, SMT LED components should be handled
in accordance with the recommendations for their ap-
propriate moisture sensitivity classification. The Joint
Industry Standard J-STD-020, Moisture/Reflow Sensitivity
Classification for Plastic Integrated Circuit Surface Mount
Devices, issued by the EIA/JEDEC JC-14.1 Committee es-
tablishes the necessary handling recommendations for
each moisture sensitivity classification. For information
on the appropriate moisture sensitivity classification of
Avago Technologies SMT LED components, please refer to
application note AN 5305.
PC Board Land Pattern Design
The design of the pc board metallic attachment pads
(land pattern) is important to assure both positions on
and attachment to an SMT board assembly. Solder coated
one ounce copper pads are best for reflow soldering.
