Most dies are small, say less than 4 mm. Micro-centrifuging tubes work well and can be put into racks.

You can probably get away with storing multiple dies together but it is not recommended for any valuable samples since they can scratch each other up.

Do not store dies wet with water as it has the potential to corrode them. This is less of an issue for static analysis but is still a best practice.

Above: (first row) 8“ Entegris wafer carrier, 6” SEP wafer carrier, (second row) blue tape diced wafer w/ top film cover, simple plastic case for metal mask, red plastic case for mask, wafer held in simple plastic case, green test tube rack for dies in micro-centrifuge tubes, (third row) Fluoroware mask holder, Fluoroware 4“ wafer holder, wafers in plastic case, vacuum sealed wafer.

General notes

Store in moisture free environment. Residual acids will cause corrosion, so make sure to wash well. It is unknown how much scratching storing multiple dies in the same container will cause.

Small dies

Centrifuging tubes in the several mL range as used in the biotech industry seem to work well. Permanent marker labels can rub or be washed off with acetone, so consider using a labeler. Above: the ones that a lot of my specimens are stored in. Finally, note that 0.5 mL look the same as the 1.5 mL tubes but have less volume inside, don't buy them. I'm not sure how the 2.0 mL tubes compare.

Tubes I've had:

  • Above picture: VWR 20170-213 1.5mL SCREW CAP TOP WITH SKIRT
    • Retail: looks to be about $144/1000 (includes cap)
    • Paid about 30 for a mostly full bag
  • Liberated from noisebridge: believe to be “AGILENT TECHNOLOGIES 5188-5251 MICRO TUBE, SCREW TOP, 1.5ml”
    • Retail: $37/100 (includes cap)
    • Not skirted. I tend to prefer skirted

Large dies

Larger centrifuging tubes, such as 50 mL.

Open large packages

VHS cases are a low cost solution. Circular locking petri dish type containers also work well but I'm not sure what they are called.


Wafers should be stored in standard wafer cassettes. Polypropylene units can be found fairly inexpensive on eBay (ie don't go nuts and buy a PFA cassette since it may cost $200).

Cassette / carrier

Most common form for holding bulk wafers for transport. Entegris/Fluoroware seems to be a popular brand.

Above: 6” simple polypropylene Entegris ULTRAPAK 150mm carrier with wafers. Three pieces: box top, box bottom, and wafer carrier. Also if you look closely you'll notice that I have more than one wafer per slot…don't do that for wafers you care about. I have extra blank wafers that I was either going to throw away or stack up.

Above: Shin-Etsu Polymer Co., Ltd. MW200-N 200mm with wafers, a more complex device for holding 8“ wafers. Same basic parts as previous but wafers are now spring loaded instead of held in place by the box itself and there is a gasket ring to keep it sealed better. Looks like a few different materials were used as well instead of being uniform PP.

Fabs use special robotic types depending on the technology. 6” typically use Smif interface while 8“ uses FOUP.


Used for temporary storage. Fused silica boats are used to anneal wafers.

Twist lock

Most common form for holding small quantities of wafers for transport. Above: Fluroware H22-30 4” single wafer twist lock carrier.

Blue tape

Diced wafers are usually on blue tape. Thin plastic films should stick easily to seal it up.

Vacuum pack

I've seen some wafers vacuum packed but presumably only when used for display. A good example are the “Intel: Journey inside the computer” kit wafers.


Above: Fluoroware H92-500IPW mask holder with mask. Note the nub in each corner so that only the side of the mask is touched.


This section was added to try to learn why some black conductive foams degrade into powder and others degrade into a (mildly corrosive?) sticky mess

Terms [Foam vs]:

  • Conductive: surface resistance < 1 x 10 5 ohms/square
  • Dissipative: 1 x 10 5 ohms/square < surface resistance < 1 x10 11 ohms/square
  • Insulative: surface resistance > 1 x 10 12 ohms/square
  • Anti-static: inhibits triboelectric charging, “the buildup of an electric charge by the rubbing or contact with another material”


Vendors talk about low and high density foams. There doesn't seem to be any agreement whatsoever as to what these mean, even within the same vendors. Look at the kg/m3 ratings I guess if you care about density

Blowing agent

In order to turn a liquid into a foam, you need a way to aerate it. Looks like traditionally this was done with CFCs but looks like it may now typically be done with nitrogen.

Pink foam

Also seen in the form of bags and packing bubbles.

Alternatives are available, but seems to typically contain amines either coated on the surface or injected into the material to make them static dissipative. In either case that means that it forms a sort of oily coat that can degrade over time as well as coat the product. For example, you should never use pink foam for optical assemblies. Over time this builds up (“blooms”) which makes affixing labels to the surface difficult. A sample product has one year shelf life. [Anti-Static Poly Bags]

Seems that EPE (Expanded Polyethylene) is most common material

Types [Foam materials]:

  • EPS (Expanded Polystyrene)
    • “most resistant to moisture absorption”
    • “acceptable for cold storage applications”
    • “resistant to virtually all aqueous media including dilute acids and alkalis, as well as water-soluble alcohols and silicones”
    • “limited resistance to paraffin oil, vegetable oils, diesel fuel, and Vaseline”
  • EPP (Expanded Polypropylene)
    • “excellent energy absorption”
    • “excellent recoverability from repeated shocks and deformations”
    • “retain their high degree of dimensional stability when exposed to temperature extremes”
  • EPE (Expanded Polyethylene)
    • “can withstand repetitive deformations and still maintain its dimensions and cushioning ability”

Blue foam

Like above, but less sensitive to moisture [Why pink]. Unclear if it has any disadvantages (cost, lifetime, etc)

Black foam

From private communication (speculative but may be good lead):

  • Crosslinked type
    • probably lasts longer but it decays into goo
  • Non-crosslinked
    • lasts shorter and decays into powder
  • how long each one lasts depends on manufacturer, amount of ozone/uv exposure, etc

Some foam is firm and is probably the type that decays into powder. Other is squishy and is possibly the type that decays into goo. This is density of the same foam type or a way to tell the crosslinking? In either case unclear what it means

Maybe could UV irradiate foam to simulate aging


equipment/storage.txt · Last modified: 2016/01/19 14:31 by azonenberg
Except where otherwise noted, content on this wiki is licensed under the following license: CC Attribution 4.0 International
Recent changes RSS feed Donate Powered by PHP Valid XHTML 1.0 Valid CSS Driven by DokuWiki