IEC 60749-21:2025

Overview

IEC 60749-21:2025 - Semiconductor devices: Mechanical and climatic test methods - Part 21: Solderability defines a standardized procedure for verifying the solderability of device package terminations intended for attachment with tin‑lead (SnPb) or lead‑free (Pb‑free) solder. The standard covers the common “dip and look” solderability test for through‑hole, axial and surface‑mount devices (SMDs) and provides an optional simulated board‑mounting (reflow) solderability procedure for SMDs. It also specifies optional ageing (preconditioning) methods. This test is normally considered destructive unless otherwise specified in a device specification.

Key topics and technical requirements

• Test methods
  • Dip‑and‑look solderability testing for through‑hole, axial and SMD packages.
  • Optional simulated board mounting (reflow) solderability test for SMDs to mimic application soldering.
• Preconditioning / ageing
  • Optional steam ageing and high‑temperature storage conditions to simulate field or process exposure.
  • Steam ageing arrangement requires specimens placed at least 40 mm above the water surface to avoid condensate dripping.
• Test apparatus and materials
  • Solder bath: minimum 40 mm depth and ~300 ml volume (capable of holding ≥1 kg solder); temperature control within ±5 °C.
  • Dipping device: controlled immersion/emersion rates and dwell time.
  • Optical inspection: microscope magnification 10×–20× for visual assessment after soldering.
  • SMD reflow equipment: stencil/screen, squeegee or spatula, test substrate, solder paste, reflow oven and flux‑removal solvent.
• Flux and solder
  • Standard activated rosin flux compositions defined for SnPb and Pb‑free testing (colophony + diethylammonium hydrochloride in isopropanol), with precise composition limits described.
• Limitations
  • The method does not evaluate thermal stress effects during soldering; see IEC 60749‑15 or IEC 60749‑20 for thermal stress tests.
  • For quantitative wetting balance tests, refer to IEC 60068‑2‑69.

Practical applications and users

• Who uses it
  • Semiconductor manufacturers and device packaging engineers for product qualification.
  • Contract test laboratories and QA/reliability teams for incoming inspection and lot acceptance.
  • PCB assemblers and process engineers for process validation and solderability troubleshooting.
  • Procurement and compliance personnel for supplier qualification of termination finishes.
• Why it’s used
  • To verify terminal finishes are wettable by SnPb or Pb‑free solders.
  • To simulate assembly conditions (dip or reflow) and assess effects of ageing on solderability.
  • To support reliability assessments, failure analysis and manufacturing yield improvements.

Related standards

• IEC 60749‑15, IEC 60749‑20 - thermal stress and solder joint reliability.
• IEC 60068‑2‑69 - wetting balance test method (qualitative/quantitative wetting).
• IEC 61190 series - solder alloys and flux requirements referenced for materials.

This 2025 edition (Edition 3.0) updates certain operating conditions to reflect current working practices while maintaining the established dip‑and‑look and simulated reflow solderability frameworks for semiconductor device package terminations.