surface metrology essay

7/23/2019 Surface Metrology Essay

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Omesh Kamat

Professor Brown

Final Paper Surface Metrology

October 21, 212

!hat " #earne$

!hat is surface metrology% Surface metrology is the measurement an$ analysis of

features of surfaces an$ its beha&iors' Surface form, wa&iness, an$ roughness are all parameters

that are most associate$ with surface metrology' !hy is surface metrology important% Surfaces

are chaotic, an$ so surface metrology helps with measurement an$ analysis of creation of the

surface an$ its beha&ior by using tools such as the Olympus #()* O#S+ Microscope'

*o better un$erstan$ surface metrology, it is important to comprehen$ roughness'

Surfaces co&er e&erything an$ so roughness is &ery important' oughness is either ma$e in

nature or man-ma$e' Manufacturing is the process use$ to ma.e surfaces with $esire$ properties'

"t is goo$ to .now that roughness is &aluable because it can be useful with lubrication, a$hesion,

an$ friction an$ roughness also influences performance' People usually belie&e that smoother is

better but that is not always the case' "n the beginning, smooth is better but then as roughness

increases later, performances increases as well' *he most commonly use$ roughness

measurement is / which is a&erage roughness' /lso there are cutoffs for specifying roughness

an$ this is usually gi&en by the $esigner' 0ifferent cutoffs ha&e a huge impact on roughness

&alues an$ so it is &ery important to get the cutoff beforehan$'

"t is not only necessary to .now what roughness is, but it is also important to .now how

to measure an$ calculate roughness' /s #or$ Kel&in sai$, !hen you measure, you ha&e to

epress it in numbers an$ then you .now something about it3' *here are many ways of $oing


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measurement of the surface but the two main ones are contact an$ optical measurement' 4ontact

is when there is a force hol$ing a stylus $own on a surface an$ it shows what the surface is li.e

on a &ertical graph' / $own-si$e of contact measurement is that sensiti&e surfaces can be

$amage$ because of the stylus an$ the force hol$ing $own on it' Optical is the use of an

instrument such as the Olympus #()* O#S+ to get a measurement an$ then analy5e it in

60' *his way, there is a great, sharp image an$ height information can be foun$ by changing it to

6 $imensional' *here are $ifferent measurements that can be foun$ using either techni7ue' 8ot

only there is the /but there is also 9 :stan$ar$ $e&iation of surface heights;, * :pea. to

&alley;, P :pea. height;, an$ < :&alley height;' /&erage roughness is sometimes useless

because it is in$epen$ent of what or$er the heights are obser&e$' *he / is also insensiti&e to the

fine scale topographic $etails'

"n surface metrology, correlating an$ $iscriminating are &ery important' 4orrelation helps

with the optimi5ation of the pro$uct an$ $esign while $iscrimination helps with 7uality

assurance' For correlation, it is important to ma.e a graph of performance &ersus roughness an$

manufacturing &ersus roughness' *his has to be $one with eperimentation' *here are many

approaches to multi-scale fractal analysis' One is scale $ecomposition where form is the largest

scale, then wa&iness, an$ finally roughness' *hen there is the $iscrimination test which is

comparing F- test to critical mean scale ratio an$ correlation test which is comparing the

$ifferent correlation coefficients of each scale'

/nother important topic is relati&e length :length scale fractal analysis;' "t is necessary to

notice that relati&e length $epen$s on the scale an$ as scale is $ecrease$, usually relati&e length

increases' *he formula for relati&e length is the sum of all :1=cos :angle in terms of ais; >

:pro?ecte$ length of step=total pro?ecte$ length;;' /rea scale fractal analysis is another techni7ue


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use$ in surface metrology' *riangular patches are use$ at $ifferent scales an$ this calculate$ the

apparent area' *hen the relati&e area is calculate$ area=nominal area' *he formula for relati&e

area is the sum of all :1=cos :angle in terms of ais;>:pro?ecte$ area of triangle=total pro?ecte$

area;;' /rea is &ery important as a teture characteri5ation parameter because it is in many

$ifferent processes such as in mass transfer, an$ 8ewton@s law of cooling' "t is necessary to .now

that the area of a surface is not uni7ue it $epen$s on the scale of obser&ation or calculation3'

For $iscrimination an$ correlation tests, the process is to first prepare the surfaces,

measure the tetures, analy5e the measurements an$ calculate characteri5ation parameters, an$

then finally run statistical tests' *o analy5e, it is goo$ to first select a metho$, then remo&e

artifacts, an$ use filtering' "n statistical tests, for $iscrimination $o F an$ * tests from statistics'

For correlation, $o the regression tests' "n the en$, $ecomposition by scale can impro&e the

ability to $iscriminate an$ fin$ correlations'

Finally, the last presentation was about aiomatic $esigns an$ how they are the best

$esigns' /n aiomatic $esign is base$ on two laws, maimi5e the in$epen$ence of the functional

elements, an$ minimi5e the information content' *his way the $esign can a&oi$ uninten$e$

conse7uences an$ maimi5e chance of success' "t is important to be able to tell a goo$ $esign

from a ba$ one' "n engineering $esign, one can either use the algorithmic approach or the

aiomatic approach' /lgorithmic approach assumes correct process results in goo$ result an$

re7uires trial an$ error' *his $oes not gi&e the guarantee of ha&ing the best solution' /iomatic

approach on the other han$, pro&i$es aioms an$ is a way of arri&ing at the best $esign solution

for the re7uirements gi&en'

*he three basic elements of engineering $esign are aioms :maimi5e in$epen$ence,

minimi5e information;, structures :hori5ontal $ecomposition, &ertical $ecomposition;, an$


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processes :5ig5agging $ecomposition, physical integration;' Some of the $omains in structures

are customer nee$s 48 what a$$s &alue, functional re7uirements F what it $oes, $esign

parameters 0P what it loo.s li.e, process &ariables P< how you ma.e it, an$ constraints

4O8 what nee$s to be a&oi$e$'

surface metrology essay

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