Waxless Fixturing
NTA's and IPTAs are a waxless fixturing system for mounting wafers, or other suitable material,
for polishing. Instead of wax, these fixtures or templates, use the capillary effects
from water in the pores of the mounting material, coupled with surface tension of the water
flim under the wafer, to hold the wafer, or any other suitable material, in place: no
chemical adhesive is required. Compared to wax mounting, template assemblies are cost
efficient and easy to use:
- Easy application - pressure sensitive adhesive on template
assemblies allows easy application to carrier plates.
- Easy removal - wafers are easily removed with a water pick
or in a bath after polishing.
- No de-waxing clean step is required - no chemicals are used
to hold the wafers.
- No CFC's - template assemblies are environmentally friendly
and non-hazardous.
- Costs - very inexpensive as compared to wax.
Eminess produces two types of waxless fixturing; the NTA and the IPTA.
NTA
NTA's are the standard template assembly. They offer a smaller initial investment than the
IPTA's. They are ideal for polishing a number of different-sized or unusually shaped
wafers. Also, polishing wafers of a variety of thicknesses. They are composed of the
backing material, which holds the wafer by capillary effect, and a structure of FR4 material
that gives additional support to the wafers (see NTA diagram). The possible shapes of the
recess are the standard circular or square shapes (we can look into doing other shapes for you).
The limits of the depth of the recesses are 0.004" to 0.040". This means that you can use these
templates to polish materials with a thickness of 0.006" to 0.060".
For the NTAs there are two choices of backing
material; DF200 and WB20.
DF200 - The DF200 material is a buffed material which provides a tubelike pore structure
(nap) that absorbs particles and cushions their effect. This nap allows water tension to hold
the wafer in place but still allows the wafer to rotate in the pocket, producing a flater surface. The compressibility of this material is 15%.
WB20 - The WB20 material is a unbuffed material which offers an extremely
strong wafer-to-mounting material bond. It has a smooth top layer that will hold the wafer when the wafer is pressed into the template. The wafer will not rotate in the
pocket and the backside of the wafer is sealed against slurry, so if wafer back side
stainning due to slurry is an issue, WB20 would be the way to go. The compressibility of this material is less than 5%.
IPTA
Insert Process Template Assemblies, IPTAs,
are composed of the urethane support structure with recesses that holds disposable inserts
(see IPTA diagram). They are ideal when a lot of wafers with the same dimensions are needed to be polished.
Unlike the standard template assembly, the two parts (backing material or inserts and the
support structure) are physically separate
entities (they are sold separately). The support structure consists of urethane base with
recesses cut into the base. Inserts of mounting material are precision die-cut
to fit in the recesses before the wafers are put into place. They are made out of
DF245 material (DF200 material slightly buffed to a 0.0245 inch thickness). The assemblies
are cost effective because the inserts - the surface the wafer contacts - are easily
renewable while the support structure can remain on the carrier for numerous changes.
Insert process template assemblies offer the following advantages over standard
template assemblies:
- Improved flatness - over many runs, the inserted mounting material can easily be changed.
- Greater economy - the more durable portion of the fixture, the template itself, need not
be replaced when the mounting material is worn or fatigued.
- Greater efficiency - less operator time and effort are needed to replace an insert than to
change standard template assemblies.
To receive a template quotation, please fill out the Template Quotation Request Form (click here)
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