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84 SMT007 MAGAZINE I NOVEMBER 2025 solder wets component terminations and other suit- able surfaces for soldering. The two most common methods are the dip-and-look method and the wet- ting balance method. • Dip-and-look (qualitative): Specimens are fluxed and dipped into a solder bath under defined conditions, then inspected against acceptance criteria for coverage, de-wetting, non-wetting, and other visual indicators. It's a quick, comparative, go/no-go screen well- suited to incoming inspection or finish com- parisons. • Wetting balance (quantitative): A load cell records the net wetting force vs. time as the specimen is immersed in solder, yielding a wetting curve from which metrics such as time-to-zero force (wetting time), maximum wetting force, and slope can be extracted. This method provides numeric data for pro- cess development, alloy/flux studies, and aging evaluations. Standards in Common Use Several specifications define test setups, precon- ditioning, fluxes, solder alloys, acceptance criteria, and reporting requirements. The most frequently applied are IPC-J-STD-002, MIL-STD-883 Method 2003, and MIL-STD-202 Method 208, each tailored to specific component types and applications. Dip-and-look Test Method This method is a comparative, visually inspected immersion test: Parts are fluxed and dipped into a solder bath under defined conditions, then judged for wetting and defects. It's popular because it is: • Simple and fast: No complex instrumentation and is well-suited to shop-floor screening and finish comparisons • Low cost: Minimal capital outlay vs. wetting balance systems • Broadly accessible: Short training curve; easy to deploy at incoming inspection or on pro- duction lines Inherent limitations This type of evaluation is inherently subjective, as results depend heavily on the inspector's judgment, viewing conditions, and consistency of evaluation. Without tight standardization, variations in outcomes are common. Additionally, the method is qualita- tive—it provides only a basic go/no-go indication of wetting behavior, such as coverage, non-wetting, de-wetting, or pinhole presence, rather than quanti- tative data like force or time measurements. Another significant limitation is that the results are highly sensitive to process conditions. Factors such as flux activity, solder bath cleanliness, tem- perature, dwell time, immersion speed and angle, and specimen preparation can all strongly influence the outcome. Best use cases Despite these limitations, this approach remains valuable in several contexts. It is well-suited for rapid screening of components and board finishes, where speed is a priority. It is also useful for com- paring fluxes, solder pastes, or alloys to understand their practical wetting performance. Additionally, it is often the preferred choice for production line checks, where efficiency and cost-effectiveness are more important than absolute precision. How to reduce subjectivity (quick wins) To improve consistency and minimize subjectivity, several straightforward measures can be imple- mented. Standardizing inspection conditions—includ- ing illumination, magnification, and viewing angle, for example, by using a fixed light box and loupe—helps ensure more reliable observations. Inspectors should also use reference photographs or "golden sam- K N O C K I N G D OW N T H E B O N E P I L E F i g u re 1 : D i p - a n d - l o o k s o l d e ra b i l i t y te st . ▼