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A New Approach to Process Qualification – SIR Testing + Functional Components
The experiment will build test vehicles with soldering materials susceptible to electrical leakage and electrochemical failures. The test vehicles will be tested using a test instrument designed to power and record the outputs of functional and dummy components.
Technical Paper
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Authored By:
Mike Bixenman
Magnalytix, LLC
TN, USA
Terry Munson
Foresite Inc.
IN, USA
Summary
Process Qualification requires key elements: boards from your supplier, mixed technology assembly, functional components from approved vendors, and SIR test patterns on the same PCBA. This is the next step in assessing the materials and processes interacting during the multiple soldering/cleaning operations. This test vehicle is designed to assess the residues from solder paste from the reflow, laser soldering, and wave solder / selective solder, as well as thermal chemical effects on specific component packages and circuit performance, compared to SIR measurements.
What does this mean? SIR testing is the traditional assessment of the residues from the solder paste and wave solder processes but doesn’t include the PCB cleanliness or component cleanliness, nor does the SIR assess the over-fluxing or rework/brush cleaning effects. With this new approach, we have designed a series of sensitive functional effects next to SIR patterns on one eight-layer board.
The experiment will build test vehicles with soldering materials susceptible to electrical leakage and electrochemical failures. The test vehicles will be tested using a test instrument designed to power and record the outputs of functional and dummy components.
Conclusions
Combining functional and SIR testing enables the design authority to detect parasitic residue effects on sensitive parts of critical circuits while detecting the impact of process residues on SIR circuits. Understanding the material effects under SIR conditions and the interactive effects of the collective of residues from the multiple soldering/cleaning, or soldering and No-Clean operations, on the functional circuits and their interactivity in typical operation conditions provides process data to enable a reliable design. The goal is to show the effect of why a short in one area will crash a separate part of the circuit with just a few ohms of leakage or sensitive circuits that may or may not recover. SIR misses the effect of circuit sensitivity on functional performance. Test instrumentation and test vehicle design are the first steps in creating this understanding.
Initially Published in the SMTA Proceedings
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