Retractable Pen Style
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Pencil Style
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Diamond is the hardest material known to mankind and since nothing is harder,
when coming in contact with some other surface, it is always that some other
surface that gets abraded away first and the diamond, relatively speaking,
remains unworn. Hence diamond is the material of choice for use in scribing
instruments, and therefore the name "diamond scribe".
Only natural diamonds are used in the production of the SPI Supplies brand
of diamond scribes. Each diamond is cut and shaped to the desired profile
and then polished (with
fine diamond paste) to a mirror finish.
The exact hardness of the diamond is anisotropic, meaning that from a
crystallographic standpoint, the hardness varies by unit call dimensions.
Then the effective hardness of a particular diamond scribe depends on the
crystallographic relationship of the diamond relative to the writing
direction and each crystal therefore must be set with plane associated with
the highest hardness in the "right" direction". Hence great care must be
taken to ensure that the correct orientation is in fact the one used for the
writing tip. If one did not pay attention to the orientation (and lower
cost makers of diamond scribing tools often times don't track the
orientation) there would be a distribution of hardness from tool to tool,
some having the harder faces and some having the softer faces. This could
result in a substantial population of a new batch of diamond scribes have a
much shorter useful lifetime. When the SPI Supplies diamond scribes are
manufactured, great care is taken to ensure that the right orientation of
the diamond is used in order to ensure the longest possible lifetime.
Another important consideration is the degree of polish given to the diamond.
The diamond on the SPI diamond scribes are polished to a mirror finish
and this what is imperative for the perfect scribing tool. Some lower cost
scribing tools are just rough diamonds and are not polished at all, which
results in higher friction and far less smooth scribed lines which in some
cases,results in less even breaking of silicon, glass, quartz or other
substrate materials. An unpolished diamond also results in more
particulates being generated with an average larger size.
Like with all fine diamond tools, the diamond found in the SPI Supplies
Brand family of diamond scribes will eventually wear out. Continued
scribing with a worn out diamond results in uneven scribe lines and the
generation of more and larger debris particles, both of which are quite
undesirable characteristics.
Like with a new set of automobile tires, one can not predict the useful
lifetime of a diamond scribe since this will be determined by frequency of
use, composition (actually hardness) of the substrate being scribed, and
other factors, such as the bending stress placed on the diamond itself. And
since the wear is so gradual, and again like an automobile tire, it is not
always obvious, without close inspection, when it is indeed time to replace
the scribing tool with a new one.
We recommend the regular inspection of the diamond with some type of convenient to use inspection tool such as
one of our pocket magnifiers.
It does not matter which one is used, but the important thing is to be able to
image the diamond. If when using the scribe, the scribe line loses "sharpness" relative
to when it was new, starting all over again with a new scribe will probably bring
back the original sharpness to the scribed line. We always recommend keeping hand
an exemplar scribed substrate made with a brand new scribe. Hence when trying to make
the decision about replacement, compare the present result with the result
obtained with a new scribe. The cross-sectional view of the scribed "line"
should have a shape resembling a "V". An old and worn out diamond will
exhibit a cross-sectional profile more like a "U". Since more
force/pressure is always required with a worn out diamond and the excess
particulates that are generated are pushed up along the sides of the groove.
In the case of a silicon wafer, and other single crystal substrates, this
added pressure can create dislocations and create other forms of damage.
There is also the possibility that research results quality will be enhanced
when always scribing with a "good" diamond.
Our various diamond scribes are described in terms of their "included angle". The tip of the
diamond is a cone, and the included angle is the angle of the tip of the cone. For many years,
we offered only a 90° included angle. 90° is a compromise between
scribing a finer line with a smaller included angle and longer tip life with a larger included
angle. A smaller included angle also allows one to locate the scribed line more precisely, which
is particularly important in certain types of failure analysis work.
We offer basically two different types:
A) "Retractable pen" and
B)
"Pencil". There is a preference for the retractable pen style since it can
be carried in a shirt pocket much like a ball point pen. It is always with
you when needed. And since the element containing the diamond can be
removed, inexpensive "refills" are also available.
But the ability to make a somewhat more precise line is possible with the
"pencil" style. And with the pencil style, it is also possible to create
angled styles for catering to the different preferences of different people.
With the retractable pen style, one can only offer straight style designs.
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