Question: There has been some request by our customers asking how long products can be stored before solderability becomes a concern. Assuming the following storing conditions, Humidity-10-70% Temperature 12-30C. Does the IPC cover anything on shelf life of soldered components?
Answer: In researching your component shelf life inquiry, I contacted a member of the IPC Component and Wire Solderability Task Group. Many key issues need to be considered; solderability protection type, quality of process and materials used in applying solderability protection, duration of time from when the solderability protection was applied, packaging used in component storage, environment used to store component until soldered, and handling methods used on the component until soldered.
Solderability of component leads is included in EIA/IPC/JEDEC J-STD-002D Solderability Tests for Component Leads, Terminations, Lugs, Terminals and Wires. The Scope, Purpose, Method Classification, and Coating Durability clauses may lead you (supplier or user) to make the correct decisions for the product.
1.1 Scope This standard prescribes test methods, defect definitions, acceptance criteria, and illustrations for assessing the solderability of electronic component leads, terminations, solid wires, stranded wires, lugs, and tabs. This standard also includes a test method for the resistance to dissolution/dewetting of metallization. This standard is intended for use by both vendor and user.
1.2 Purpose Solderability evaluations are made to verify that the solderability of component leads and terminations meets the requirements established in this standard and to determine that storage has had no adverse effect on the ability to solder components to an interconnecting substrate. Determination of solderability can be made at the time of manufacture, at receipt of the components by the user, or just before assembly and soldering.
Method Classification 1.3 and Visual Acceptance Criteria Tests 1.3.1 lists the various test methods that may be used in evaluating SnPb and Pb-free solderability. These condition categories are listed in Table 3-3 for Preconditioning. The table includes preconditioning with steam or dry bake, exposure parameters (time), and finishes being used. When purchasing components the usage of Table 3-3 is of the highest importance.
The user shall specify to the vendor, as part of the purchase agreement, the required coating durability and preconditioning category.
Clause 1.4 Coating Durability lists Category 1 and 2. Category 1 – Minimum Coating Durability Intended for surfaces that will be soldered within a short period of time (e.g., up to six months) from the time of testing and are likely to experience a minimum of thermal exposures before soldering. Category 2 – Typical Coating Durability Intended for surfaces whose solderability may become degraded from storage of longer than six months or from multiple thermal exposures.