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Pareto Principle

• Alfredo Pareto (1848-1923) Italian Economist:– Conducted studies of the distribution of wealth in

Europe.– 20% of the population has 80% of the wealth

• Joseph Juran used the term “vital few & trivial many or useful many”. He noted that 20% of the quality problems caused 80% of the dollar loss.

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Pareto diagram

Perc

ent f

rom

eac

h ca

use

Causes of poor quality

Machine c

alibrati

ons

Defecti

ve part

s

Wrong d

imen

sions

Poor D

esign

Operator e

rrors

Defecti

ve m

ateria

ls

Surfa

ce ab

rasions

0

10

20

30

40

50

60

70(64)

(13)(10)

(6)(3) (2) (2)

A pareto diagram is a graph that ranks data classifications in descending order from left to right.

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Pareto diagram%

Com

plai

nts

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Pareto diagram

• Sometimes a pareto diagram has a cumulative line.

• This line represents the sum of the data as they are added together from left to right.

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Pareto diagram

• Sometimes a pareto diagram has a cumulative line.

• This line represents the sum of the data as they are added together from left to right.

Above the bars, using the 2nd Y-axis representing the cumulative data, plot the cumulative percentage values in the form of a line.

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Pareto diagram• The cumulative percentage can be computed (dotted line).

• On the right, add a vertical percent scale equal in length to the scale on the left.

• Label this from 0% to 100% .

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Pareto diagramTable 1. Example of a Tabulation of Causes of Ball Bond Lifting for use in a Pareto Chart

Ball Lifting Cause Frequency Percent (%) Cum Percent (%)

Bonder Set-up Issues 19 38% 38%Unetched Glass on Bond Pad 11 22% 60%Foreign Contam on Bond Pad 9 18% 78%Excessive Probe Damage 3 6% 84%Silicon Dust on Bond Pad 2 4% 88%Corrosion 1 2% 90%Bond Pad Peel-off 1 2% 92%Cratering 1 2% 94%Resin Bleed-out 1 2% 96%Others 2 4% 100%Total 50 100% -

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Pareto diagramTable 1. Example of a Tabulation of Causes of Ball Bond Lifting for use in a Pareto Chart

Ball Lifting Cause Frequency Percent (%) Cum Percent (%)

Bonder Set-up Issues 19 38% 38%Unetched Glass on Bond Pad 11 22% 60%Foreign Contam on Bond Pad 9 18% 78%Excessive Probe Damage 3 6% 84%Silicon Dust on Bond Pad 2 4% 88%Corrosion 1 2% 90%Bond Pad Peel-off 1 2% 92%Cratering 1 2% 94%Resin Bleed-out 1 2% 96%Others 2 4% 100%Total 50 100% -