|Ask the Experts|
May 13, 2020
Shelf Life Limit for Soldering Old Components
We are contract EMS provider and we have some customers with restrictions on how old electronic components can be when soldered. Some customers allow up to 3 years, some allow up to 5 years after the date of manufacture.
Is there a guideline by IPC or other sources that we can follow based on the class of the PCB assembly?
|Expert Panel Responses|
I am not aware of an IPC standard that suggests that the age of a component is a reason to NOT use it. The "mother of all standards" that covers electronic assembly, IPC/EIA J-STD-001 "Requirements for Soldered Electrical and Electronic Assemblies" does not appear to cover this subject, that I was able to find.
The real question is, why do your customers have such a requirement? A "standard" saying otherwise may not be an effective way to convince your customers that older components are OK to use. Typically, component age can affect solderability. If this is their reason, proper storage (low RH atmosphere cabinets) can help preserve the solderability of components for many years. However, your customer may have other reasons such as the mean-time to failure recommendations specified by the manufacture of the component.
Have the conversation with your customer to understand their requirements.
Senior Project Engineer
Electronic Controls Design Inc
Component shelf life is really an OEM specification and I would expect the OEM to determine shelf life based on a couple items -
One - a specific characteristic of the component that derogates over time. E.g. internal plated contacts becoming tarnished or lubricant for moving parts drying out.
Two - solderability - finish/plating of the component maintaining required solderability to support manufacturing. In this case regardless of the age of the component a simple solderability test can be performed to prove out the finish/plating is still acceptable.
These types of boiler plate contractual requirements really put the customer in bad position as components become obsolete and fall into the legacy category, causing the customer/supply chain to either break the contractual rules or incur overhead in processing deviations. Not to say there is not a place for component shelf life, but it should be up to the OEM.
Director of Corporate Quality Assurance
Delta Group Electronics Inc.
The IPC standard J-STD-002C, Solderability Tests for Components Leads, Terminations, Lugs, Terminals and Wires, addresses solderability testing that should be used to assess the solderability of components prior to assembly. IPC standard J-STD-003C, Solderability Tests for Printed Boards, addresses the solderability of PCBs.
Based on your question it appears as if you might be assembling an end-of-life product which often requires the use of legacy components that are typically no longer a currently manufactured part. If this is the case you need to assess your component supply chain to ensure the manufacture date, storage conditions, and shipping packaging, etc. as in some cases legacy components are sourced from the ‘grey market’ either due to small lot size or simply limited availability from the component OEM.
As a general recommendation a sampling of legacy components should be subjected to a solderability test, the most common of which is a zero force wetting balance test. If the samples pass this test they should be suitable for board level assembly, but if they fail the component leads should be re-tinned before board assembly avoiding costly post-soldering rework and repair.
Active components, including semiconductors, oscillators, and diodes, etc., can be accepted, if less than 2 years old. They must pass Solderability Test (J-STD-002A and J-STD-003b), if between 2 to 5 years old. They cannot be used unless it is for LTB or approved via e-SDR, if more than 5 years old.
Passive components, including resistors, capacitors (except for Aluminium Electrolytic Capacitors Described in 3.4), can be used up to 5 years provided there are no evidence of the corrosion.
Aluminium electrolytic capacitors (wet type): less than 1 year old from component manufacture date. If older than 1 year, suppliers must seek component manufacturer recommendations, treatment/reforming procedure based on the component manufacturers.
Mechanical hardware, including sheet metal, fastener hardware can be used up to 5 years provided there is no evidence of the corrosion.
Miscellaneous, including connectors, transformers can be used up to 5 years provided there is no evidence of the corrosion.
Finish PCBA can be used up to 5 years provided there is no evidence of the corrosion.
Moisture sensitive components floor life shall follow J-STD-033b for floor life classification and reflow/bake procedures.
Director of Sales and Marketing
One way is to contact the component's manufacturer. In some cases they might recertify or extend the shelf life. However, this option is not cost effective since the customer will have to pay lab costs. Another alternative is to conduct a solderability test at your site.
This entails a little more than just adding flux and solder to the terminations. I always try to solder the component to the PCB under normal conditions in order to get a better picture of the soldering characteristics.
Senior Manufacturing Engineer
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