[labnetwork] Expired chemcials

[Bill Flounders]

Matthieu,
There are liability concerns with public response to
potential safety questions such as this. Regardless,
I will offer my personal suggestions on this topic.

For a safety issue such as a peroxide former, the
expiration date is strict. For a performance issue,
such as a photoresist, the expiration date is open to
judgement if the application is research and not ISO
certified production.
In general, I would encourage use of unopened
expired chemicals without issue.
I consider many expiration dates "release of liability"
dates for the manufacturer. There are some specific concerns.

Case by case review and your judgment is required.
Months past expiration or years past expiration?
Check condition of container, signs of discoloration,
leakage etc. Does the compound degrade upon reaction
with water vapor or O2 is an important consideration.
No sealing/bottling technique is perfect.

For resists - good temp control and light exclusion are key.
In dark cabinet or foil pouch - not just in an opaque bottle.
Higher performance, shorter wavelength resists are less forgiving.
Ebeam resists vary depending upond rxn mechanism.

- hydrogen peroxide (esp low concentrations) is likely to lose activity
* * Caution with any peroxide formers.**
Many published lists and guidelines are available - review them.
Dating peroxide formers upon receipt is best practice.

Bill Flounders
UC Berkeley




Matthieu Nannini, Dr. wrote:
> Dear colleagues,
>
> What is your take on expired chemicals like:
>
> - PMMA
> - acids
> - H2O2
> - BOE
> - TMAH
> - LOR
> - MIBK and solvents
>
> Thanks
>
> Matthieu
>
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