non-wet open

**Non-wet open** is the **solder joint defect where solder fails to wet one or both mating surfaces, leaving an electrical open** - it often stems from oxidation, contamination, or inadequate thermal activation. **What Is Non-wet open?** - **Definition**: Solder remains separated from pad or termination with little to no metallurgical bonding. - **Root Causes**: Surface oxidation, poor flux activity, and insufficient time above liquidus are common drivers. - **Appearance**: May show rounded solder shape without expected fillet spread on target surface. - **Detection**: Found through AOI, X-ray patterns, and continuity testing depending on package visibility. **Why Non-wet open Matters** - **Functional Failure**: Creates immediate opens or unstable contact behavior. - **Yield Loss**: Can produce significant first-pass defects in fine-pitch and array assemblies. - **Process Signal**: Non-wet trends indicate cleanliness, storage, or profile-control problems. - **Reliability**: Marginal wetting can degrade further under thermal and mechanical stress. - **Cost**: Rework and retest burden increases when non-wet root causes are not quickly contained. **How It Is Used in Practice** - **Surface Control**: Manage board and component oxidation with proper storage and handling. - **Flux Matching**: Use flux chemistry compatible with finish type and process atmosphere. - **Thermal Verification**: Ensure profile provides adequate activation and wetting window. Non-wet open is **a critical wetting-failure defect in solder-joint formation** - non-wet open reduction depends on strict surface-condition control and validated flux-thermal process matching.