11 Environmental Requirements and SMT Specifications
11.1 PCB Bending
The PCB follows IPC-A-600J for PCB twist and warpage < 0.75% or 7.5 mil per inch.
11.2 Handling Environment
11.2.1 Terminals
The product is mounted with motherboard through land-grid array (LGA). To prevent poor soldering, do not make
skin contact with the LGA portion.
11.2.2 Falling
The mounted components will be damaged if the product falls or is dropped. Such damage may cause the
product to malfunction.
11.3 Storage Condition
11.3.1 Moisture Barrier Bag Before Opened
A moisture barrier bag must be stored in a temperature of less than 30°C with humidity under 85% RH. The
calculated shelf life for the dry-packed product will be 24 months from the date the bag is sealed.
11.3.2 Moisture Barrier Bag Open
Humidity indicator cards must be blue, < 30%.
11.4 PCB Assembly Guide
The wireless MCU modules are packaged in a substrate base Leadless Quad Flatpack (QFM) package. The
modules are designed with pull back leads for easy PCB layout and board mounting.
11.4.1 PCB Land Pattern & Thermal Vias
We recommended a solder mask defined land pattern to provide a consistent soldering pad dimension in order
to obtain better solder balancing and solder joint reliability. PCB land pattern are 1:1 to module soldering pad
dimension. Thermal vias on PCB connected to other metal plane are for thermal dissipation purpose. It is critical
to have sufficient thermal vias to avoid device thermal shutdown. Recommended vias size are 0.2mm and
position not directly under solder paste to avoid solder dripping into the vias.
11.4.2 SMT Assembly Recommendations
The module surface mount assembly operations include:
• Screen printing the solder paste on the PCB
• Monitor the solder paste volume (uniformity)
• Package placement using standard SMT placement equipment
• X-ray pre-reflow check - paste bridging
• Reflow
• X-ray post-reflow check - solder bridging and voids
SWRS263A – FEBRUARY 2021 – REVISED JUNE 2022
56
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