Moisture Sensitivity and Its Effect on CDSOT23-SM712

Analysis of Failure Causes Related to Moisture Sensitivity in CDSOT23-SM712 and Solutions

Introduction

The CDSOT23-SM712 is a component used for protecting circuits from electrical surges or voltage spikes, typically in the form of transient voltage suppression ( TVS ). Moisture sensitivity is a key factor that can lead to failure in these components, particularly in environments with high humidity or when not properly stored or handled. This analysis explores the causes of failure due to moisture sensitivity, the impact it has on the CDSOT23-SM712, and provides detailed, step-by-step solutions to prevent such failures.

Understanding the Failure Causes

Moisture Absorption and Damage to the Component The CDSOT23-SM712, like many other surface-mount devices, is made with materials that can absorb moisture over time. These materials include the soldering pad, leadframe, and packaging. Moisture absorption during storage or handling can lead to internal stress within the component. When the device is soldered onto a PCB and exposed to heat during reflow soldering or operation, the trapped moisture turns into steam, expanding and causing delamination of the package, cracks, or even complete failure of the component. The failure mechanism often manifests as a short circuit, open circuit, or degraded functionality, resulting in the device no longer being able to protect the circuit as intended. Effect of High Humidity on the Device High humidity accelerates the process of moisture absorption. If the CDSOT23-SM712 is stored in a humid environment without proper packaging or moisture control, it becomes more susceptible to the failure mentioned above. Electrostatic discharge (ESD) can also become a concern in these conditions. Moisture can increase the risk of electrical shorts or even partial discharge, which may cause the component to malfunction or fail completely.

Steps to Identify the Fault

Visual Inspection Inspect the CDSOT23-SM712 for any visible signs of damage, such as cracks, delamination, or blistering on the package surface. These can be signs that moisture damage has occurred during handling or storage. Functional Testing Check the performance of the component by testing for proper voltage suppression behavior. If the CDSOT23-SM712 does not protect the circuit from surges or voltage spikes as expected, this could be an indication of internal damage caused by moisture. Check Storage and Handling Conditions Review the conditions under which the component was stored and handled. If the component was exposed to high humidity or not properly baked before use, this can confirm that moisture sensitivity is the cause of failure.

Solutions to Prevent Moisture Sensitivity Failures

Proper Storage and Packaging Use moisture barrier bags for storing the CDSOT23-SM712. These bags are designed to protect components from moisture during storage and transport. Humidity indicator cards inside the moisture barrier bags will help monitor the moisture levels and ensure that the component is kept in a dry environment. Store in dry conditions: The ideal storage humidity level should be under 60% relative humidity (RH) to prevent moisture absorption by the components. Baking the Component Before Soldering If the CDSOT23-SM712 has been exposed to high humidity or improperly stored, it should be baked before use. Baking should be done at a temperature of 125°C for 24 hours to remove any absorbed moisture from the component. This step is crucial before reflow soldering to avoid any internal damage from moisture during the soldering process. Use of Dry Cabinets Consider using a dry cabinet for storage of moisture-sensitive components like CDSOT23-SM712. These cabinets are designed to maintain a low and controlled humidity environment, reducing the risk of moisture absorption. Handling with Care Always handle moisture-sensitive components with antistatic bags and proper ESD protection during assembly and testing. Avoid touching the component directly to minimize exposure to moisture from skin oils and humidity. Ensure that soldering environments are properly controlled, and the soldering iron or reflow oven is set to optimal temperature and time parameters to prevent thermal stress on the component. Reflow Soldering Control Set up proper reflow soldering profiles that consider the moisture sensitivity of the CDSOT23-SM712. Make sure the reflow temperature is controlled to prevent thermal shock from the rapid release of trapped moisture. Following the JEDEC standard for moisture sensitivity and the recommended baking procedures will help to avoid sudden failures.

Conclusion

Moisture sensitivity is a common cause of failure in electronic components like the CDSOT23-SM712. By ensuring proper storage, handling, and baking procedures, you can prevent damage due to moisture absorption. Regular inspections, testing, and adherence to moisture control guidelines will ensure the reliability and longevity of these components. Taking these steps will not only prevent failure but also enhance the overall performance of your circuit protection systems.