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Quantum Leap in Defect Reduction Six Sigma / DMAIC Application

Z.Mousavi SSBB, CQE, CRE (ASQ Certified) [email protected]

Agenda – Introduction – Applying DMAIC Steps in a MFG

Environment to Improve Quality – Review & Analyze a Case Study

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What Is Six Sigma? • First, What is Six Sigma? • Six Sigma is a highly disciplined process that helps us focus on

developing and delivering near-perfect products and services.

• Why "Sigma"? The word is a statistical term that measures how far a given process deviates from perfection. The central idea behind Six Sigma is that if you can measure how many "defects" you have in a process, you can systematically figure out how to eliminate them and get as close to "zero defects" as possible.

• To achieve Six Sigma Quality, a process must produce no more than 3.4 defects per million opportunities.

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Key Concepts of Six Sigma

At its core, Six Sigma revolves around a few key concepts. • Critical to Quality: Attributes most important to the

customer • Defect: Failing to deliver what the customer wants • Process Capability: What your process can deliver • Measure of variation is a measure that describes how

spread out or scattered a set of data • Stable Operations: Ensuring consistent, predictable

processes to improve what the customer sees and feels • Design for Six Sigma: Designing to meet customer needs

and process capability

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What is DMAIC ? • D…Define • M….Measure • A….Analyze • I…Improve • C…Control/check

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• Project History • Company X manufactures printed

circuit boards which are used in later stages of assembly lines as building blocks of microwave radios. Components are soldered on Printed Circuit Boards (PCB’s) with a wave soldering machine. Although this is considered the best method of soldering, a number of defective boards may be produced.

Case Study Review

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Project Goal • The original goal, was to find the root

cause of the problems, hence improving the efficiency of the wave soldering process and subsequently improving product quality

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Problem: Defective Boards

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Bridging defects

Apply DMIAC steps :

• D: Define problem: – Large number of defective boards are

produced in PCB manufacturing area of the company

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• Measure : – Data collection

• The first and the most important issue at the beginning was the correct definition of the problem and gathering of valid data, which were carried out during the first month.

• Analyze – Next, using some analytical tools the problem was defined

more precisely. Then by using quality tools such as a Pareto and root-cause diagram, the potential causes of the defects in the wave soldering process were noted.

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Process Flow

• Wave Soldering Flow Line

Wave .Soldering

Un populated

PCB populated

PCB

Inspection /Quality Control

In Put

Masking

Out Put

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Process Characteristics The following are characteristics of the wave soldering process:

•The solder connection is very reliable and also a clean connection

•The process is automated

•The process reuses the flux and solder that is left over

•It does require inspection, some touch ups, and also testing

•The productivity and efficiency is increased

Analysis Continue… • scientifically valid data were collected over 2-3

weeks. Pareto analysis was carried out and brainstorming sessions were held to find the possible causes of the problem. The solution to the problem (corrective action) was the main topic of all the meeting in the 2nd & 3rd months from the beginning of the project.

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• At this stage the problem board (the one with the highest number of defects) and the type of the defect were clearly identified.

Data Collection Defective PCB Data

P/N # of Joints/ Board

SAMPLE

SIZE(# BD)

SAMPLE

SIZE

# DEFECTIVE JOINTS/Bd

PROPOTION DEFECTIVE

021-11014-001 86 20 1720 9 0.00523256104-107407-016 1747 28 48916 123 0.00251451101-107662-101 1620 7 11340 30 0.0026455103-098770-024 2154 5 10770 71 0.00659239103-098750-001 1817 10 18170 38 0.00209136103-098770-028 2415 10 24150 102 0.0042236104-107407-012 1747 7 12229 33 0.0026985021-107445-001 1184 12 14208 124 0.00872748101-110282-002 290 20 5800 11 0.00189655

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The proportion defective solder joints for each board P/N were obtained:

Target, or no #1 problem identified

Route Cause Analysis Diagram /Fish Bone for the Wave Soldering Process • Parameters Affecting W.S process

W.S out put

Man Machine

Environment Material

Profile Training

PCB quality

Temperature

Shift

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• Analyze…. – A Design Of Experiment committee was formed in the company

in the following month. The objective of this committee was to investigate and find the prime reason for deficiency in the process regarding the number of defective boards produced by the wave soldering process.

– The members of the committee were the quality engineer, the manufacturing engineer, the project lead, the quality specialist, and the operator. Two brainstorming sessions were held every week for one month.

Continue analyze phase…..

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Process Parameters of the wave soldering machine changed Various Design Of Experiments used, but not much improvements were obtained in the process. Research on alternative ways on defective joints prevention in the wave soldering process started

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Analysis continued…

After weeks of research, Dynamic Solder Management was introduced and presented by the Project lead. During this month the preliminary experiment and the actual experiment were carried out and the final results were recorded on the last day of the 3rd month.

Improvement Phase

alternative approach, using other process changes in the PCB assembly line

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Reduction of defective joints on the same board shown on SPC chart after process improvement

SPC charts before and after implementation of Process Improvement

Results Sample n

Number

Defective

# DEFECTIVE AFTER

Implementation of DSM

1184 14 0

1184 8 1

1184 10 1

1184 10 1

1184 18 0

1184 2 1

1184 2 1

1184 12 0

1184 11 0

1184 9 1

1184 11 2

1184 22 11184 20SUM 149 9

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Results Recommendation

• Defective Joints decreased to 11%

• An improvement of ~ 90%

• Reduced process time

• Reduced Cost

• Implementing the method by means of robotics will improve it even further

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Final Result Perfect Quality

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Cost Savings

Company X had a cost savings of nearly $40,000 on the specific board discussed after the first month of the implementation of the project. This method can be used for different geometries of the PCB consequently improving product quality and efficiency of the component integration process on Printed Circuit Boards using wave soldering machines.

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Back Up References

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References • https://www.youtube.com/watch?v=in

HzaJIE7-4 • WWW.ASQ.ORG

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Defn: • An "opportunity" is defined as a chance for

nonconformance, or not meeting the required specifications. This means we need to be nearly flawless in executing our key processes.

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Definition of Defect • By definition, a “defect” is an individual non-

conformity on a product that causes it to fail to meet a quality specification. A “zero defect” product refers to a product which meets all technical or engineering specifications, and hence has no defects. An item or article is “defective” if it fails to conform to specifications to some respect.

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Yield to Sigma Conversion Table

Yield % Sigma Defects Per Million Opportunities

99.9997 6.00 3.4

99.9995 5.92 5

99.9992 5.81 8

99.9990 5.76 10

99.9980 5.61 20

99.9970 5.51 30

99.9960 5.44 40

99.9930 5.31 70

99.9900 5.22 100

99.9850 5.12 150

99.9770 5.00 230

99.9670 4.91 330

99.9520 4.80 480

99.9320 4.70 680

99.9040 4.60 960

99.8650 4.50 1350

99.8140 4.40 1860

99.7450 4.30 2550

99.6540 4.20 3460

99.5340 4.10 4660

99.3790 4.00 6210

99.1810 3.90 8190

98.9300 3.80 10700

98.6100 3.70 13900

98.2200 3.60 17800

97.7300 3.50 22700

97.1300 3.40 28700

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97.1300 3.40 28700

96.4100 3.30 35900

95.5400 3.20 44600

94.5200 3.10 54800

93.3200 3.00 66800

91.9200 2.90 80800

90.3200 2.80 96800

88.5000 2.70 115000

86.5000 2.60 135000

84.2000 2.50 158000

81.6000 2.40 184000

78.8000 2.30 212000

75.8000 2.20 242000

72.6000 2.10 274000

69.2000 2.00 308000

65.6000 1.90 344000

61.8000 1.80 382000

58.0000 1.70 420000

54.0000 1.60 460000

50.0000 1.50 500000

46.0000 1.40 540000

43.0000 1.32 570000

39.0000 1.22 610000

35.0000 1.11 650000

31.0000 1.00 690000

28.0000 0.92 720000

25.0000 0.83 750000

22.0000 0.73 780000

19.0000 0.62 810000

16.0000 0.51 840000 34 ZMTECHNICAL