Packaging used in the manufacture of oscillators and quartz crystals can absorb moisture from the atmosphere while in storage. When these parts are subjected to the high temperatures seen during reflow soldering, the moisture in the package expands into steam and can cause micro-fractures within the package or worse. These can result in destruction of the wire bonds within the package and thus product failure. The wire bonds form the electrical connection between the IC die and the metal lead-frame and as such are often encased in plastic during the molding process.
The occurrence of such incident to occur can be attributed to the following:
- the type of plastic used and the finish on this plastic
- the humidity, temperature, and time of storage
This issue became of increasing importance after the introduction of lead-free solder and the consequential rise in the maximum peak temperature seen during reflow soldering.
To cope with this issue, one needs to quantify how susceptible specific oscillator and crystal designs are to moisture ingress, so to recommend minimum storage requirements to minimize any potential damage. The two international standards used in electronics regarding moisture are:
- JDEC-STD-020 Moisture/Reflow Sensitivity Classification for Non-hermetic Solid-State Surface Mount Devices which defines moisture exposure levels, reflow profiles and pass criteria. Components are graded from levels 1 to 6, thus giving a standardized way to classify a component.
- JDEC-STD-033 Handling, Packing Shipping and Use of Moisture/Reflow Sensitive Surface Mount Devices, follows on from the first standard and recommends specific storage conditions depending upon the classification number attributed in JDEC-STD-020.
The JDEC standards provide a framework for the manufacturer of the component to both assess the appropriate MSL level and consequently specify the packaging, handling, and labelling requirements that each subsequent company in the supply chain must follow. Each Receiving department can then clearly identify the requirements upon receipt of the goods and pass this on down the chain. Since electronics components being to pass through many different companies between manufacturing and assembly into the finished end product is quite common, no misconceptions should be inserted into the chain which may result in increased cost or delivery time due to unnecessary packaging restrictions.
For additional information regarding Effects of Moisture for Oscillators or other RF / microwave topics, please contact your local Dynamic Engineers sales representative or Inquiry@DynamicEngineers.com