Hello Kay,

Here is one take on the terms...

1. a homogeneous material?

The Oxford dictionary definition is fine one for a broad overview but in this
industry it can also be a mixture.  e.g. encapsulants are mixtures of filler
and resin but are homogeneous from the users perspective, alloys are mixtures
of metals, etc.

2. a unit?

A unit varies from where one is in the manufacturing chain.  An IC is a unit,
a packaged IC is a unit but so also is a complete computer a unit.

3. mechanical separation?

This is arguable but the term might generally lead one to conclude that it is
one or more items can be separated by only mechanical means by hand and/or
with common tools, e.g. nuts & bolts, snaps, pressure fit connections.

Desoldering is also possibly on the boarder mechanical separation but with
the use of heat as the "tool" of choice (e.g one can buy a heat gun in a tool
store) and this might be where definitions get fuzzy.

On the extreme end of this is incineration which will cause mechanical
separation so long as one does not care what the items separated look like when
done. ;-)

4. a single material?

Sounds like a homogenous material but could also be a composite (e.g.,
laminates) the properties of which can vary more widely.

I suspect you are going to have a wide range of responses

Good luck,
Joe

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