JN516X Datasheet, PDF (91/94 Pages) NXP Semiconductors – IEEE802.15.4 Wireless Microcontroller

B.4.2 PCB Design and Reflow Profile
PCB and land pattern designs are key to the reliability of any electronic circuit design.
The Institute for Interconnecting and Packaging Electronic Circuits (IPC) defines a number of standards for electronic
devices. One of these is the "Surface Mount Design and Land Pattern Standard" IPC-SM-782 [3], commonly referred
to as “IPC782". This specification defines the physical packaging characteristics and land patterns for a range of
surface mounted devices. IPC782 is also a useful reference document for general surface mount design techniques,
containing sections on design requirements, reliability and testability. NXP strongly recommends that this be referred
to when designing the PCB.
NXP also provide application note AN10366, “HVQFN application information” [6], which describes the reflow
soldering process. The suggested reflow profile, from that application note, is shown in Figure 54. The specific paste
manufacturers guidelines on peak flow temperature, soak times, time above liquids and ramp rates should also be
referenced.
Figure 54: Recommended Reflow Profile for Lead-free Solder Paste (SNAgCu) or PPF Lead Frame
B.4.3 Moisture Sensitivity Level (MSL)
If there is moisture trapped inside a package, and the package is exposed to a reflow temperature profile, the
moisture may turn into steam, which expands rapidly. This may cause damage to the inside of the package
(delamination), and it may result in a cracked semiconductor package body (the popcorn effect). A package’s MSL
depends on the package characteristics and on the temperature it is exposed to during reflow soldering. This is
explained in more detail in [7].
Depending on the damage after this test, an MSL of 1 (not sensitive to moisture) to 6 (very sensitive to moisture) is
attached to the semiconductor package.
© NXP Laboratories UK 2013
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