60216444 Reflow Wave PWI

MKS Confidential 1

Process Improvement Team Project

Wave Soldering Thermal

Profiling Management Improvement

MKS Confidential 2

Problem Statement

PWI Introduction

Identify Performance Measures (Statistics)

Measurement Techniques for Performance Measuring

Setting Metric for Performance Measures

• Evaluating the current performance

• Data collection plan development

• Calculating sample size

• Collected data sets

• Analyzed data

Define Process Limits

Piloted to measure PWI

Define PWI Control Limits

Control plan

Benefits

MKS Confidential 3

Problem Statement

Questions:

• Making assumption we get the machine profiles as shown, how can we quantificational qualify the performance of the machine? Does the machine work stable and meet specified criteria?

• How can get profile #1 and profile #2 be compared, which one is better?

MKS Confidential 4

Problem Statement

There is no a quantifiable system of ranking equipment performance. Measuring and comparing the thermal profile to its process window is

a subjective judgment with no real uniformity or statistically reproducible results; from one engineer or technician to the next; from one product to the next…

Also, it is a time consuming process. Is there a quantifying approach to calibrate the performance of

machine?

This project will introduce a quantifying technique – PWI to measure the performance of wave soldering machine and reflow oven.

This presentation reported the implementation results of wave soldering only.

MKS Confidential 5

A Method for Quantifying Thermal Profile Performance - PWI

What is PWI

The Process Window IndexThe PWI is a quantifiable, reproducible, statistical measure of how well a profile

performs relative to critical process limits. Every thermal profile is ranked on the

basis of how it “fits” within the process window. The center of the process

window is defined as zero, and the extreme edge of the process window as

99%. A PWI of 100% or more indicates that the profile will not process product

within specification. A PWI of 99% indicates that the profile will process product

within spec, but it is running at the very edge of the process window. A PWI of

70% indicates a profile is using 70% of the process spec.

The PWI tells us exactly how much of our process window a given profile uses,

and thus how robust that profile is. The lower the PWI, the better the profile.

The thermal process can now be reliably measured, analyzed, compared and

tracked with the same level of SPC and Quality Control available to other

manufacturing processes.

MKS Confidential 6

A Method for Quantifying Thermal Profile Performance - PWI Calculating the PWI

The PWI for a complete set of profile statistics is

calculated as the worst case (highest number) in the

set of statistics. For example: if you run a profile with

three thermocouple, and four profile statistics are

logged for each thermocouple, then there will be a

set of twelve statistics for that profile. The PWI will be

the worst case (highest number expressed as

a percentage) in that set of profile statistics.

(Measured_value[i,j] - average_limits[I,j])

(range[I,j]/2PWI = 100 x MAX

I, j=1

N, M

MKS Confidential 7

Identifying Performance Measures Thermal profile specifications are ranges consisting of minimum or

maximum values. These ranges apply to numerous statistics such as soak time, slope, peak temperature and variety of others. Which statistics were determined to be a CTQ measures?

Project team selected below profile statistics as the performance measure that was being used to calibrate the wave machine.

1. Top Side Preheat Temperature Rising Slope

2. Bottom Side Preheat Temperature Rising Slope

3. Top Side Preheat Peak Temperature

4. Bottom Side Preheat Peak Temperature

5. Top Side Wave Peak Temperature

6. Bottom Side Wave Peak Temperature

MKS Confidential 8

Measurement Techniques for Performance Measuring

Run profiles using devices: Profile Checker SlimKIC 2000 Standard Profile Test board Thermocouples: K Type

Bonding Techniques Attaching the tip of the thermocouples to the

desired location with Aluminum Tape or high temperature solder.

Aluminum Tape Size; Kept solder joint as small as possible.

Thermocouples placements and KIC connections as shown.

Top thermo. measures - Preheat Slope; Peak Temp. & Top Wave

Peak Temp.Bot. thermo.

measures – Bot. Wave Peak

Temp.

Bot. thermo. measures – Bot. Preheat Peak Temp. & Slope

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Setting Target for Performance Measures

Following activities have been done prior to set the limits for the

above performance measures:

Evaluating the current performance of the machine.

Data Collection Plan Development

Calculating Sample Size

Collected data set

Analyzed data

Applied statistical tools to define the metric of the performance measure

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Based on previous data knew the standard deviation of measures. Refer to the appendix for the baseline data set

Variable StDev

• Top Max. Rising 0.0525

• Bot Max Rising 0.0540

• Top Preheat Temp. 0.725

• Bot Preheat Temp 0.793

• Top Wave Temp 2.37

• Bot Wave Temp 1.90

Evaluating the current performance of equipment

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N - Minimum Sample Size Calculation,

The minimum sample size was determined to 26 per below calculation, that means, 26 profiles required in order to meet the required precision.

The desired precision level was determined shown in below table.

2

△96.1

s

n=

KPIVs StdDev. △ n

Top Max. Rising 0.0525 0.05 5

Bot Max Rising 0.054 0.05 5

Top Preheat Temp. 0.725 0.5 8

Bot Preheat Temp 0.793 0.5 10

Top Wave Temp. 2.07 0.8 26

Bot Wave Temp 1.9 0.8 22

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Measurement/Metric

X or Y

Operational Definition

Type of Data

(Discrete/ Continuous

)

Data Source

and Location

Sample Size

Who Will Collect the

Data?

When Will Data

be Collected?

How Will Databe

Collected?

Is the Measureme

nt System

Capable?

Graphical and/or

Statistical Tools to be

Used

Top Max. Rising X　

Wave Soldering process　 Continuous

Wave Soldering Station 26

David Zhang

June, 2011　

Randomly selected Yes　 Excel form　

Bot Max Rising X　



David Zhang

June, 2011　


Top Preheat Temp. X　



David Zhang

June, 2011　


Bot Preheat Temp X　



David Zhang

June, 2011　


Top Wave Temp X　



David Zhang

June, 2011　


Bot Wave Temp X　



David Zhang

June, 2011　


Data Measurement Plan

MKS Confidential 13

Setting Pre-heat Zone 1 Temp. ( )℃

Pre-heat Zone 2 Temp.( )℃

Pre-heat Zone 3 Temp.( )℃

Wave Temp. ( )℃

Speed ( cm / min)

Top Side / 140 145

242 103Bottom Side 130 140 145

Run profile per below machine setting for data collection process.

Machine Settings

MKS Confidential 14

Date Top Max. Rising Bot Max Rising Top Preheat Temp. Bot Preheat Temp Top Wave Temp. Bot Wave Temp

1.67 1.73 119.1 120.2 157.6 238.71.64 1.7 119.73 120.3 163.1 238.71.61 1.69 119.2 120.2 160.3 238.91.65 1.68 119.1 120.17 159.7 236.91.59 1.56 119.1 119.7 166 2351.59 1.73 119.5 120.3 158.7 238.21.61 1.59 119.2 119.5 160.7 237.51.56 1.6 118.7 158.3 233.731.66 1.58 119.8 119.9 165 234.11.64 1.63 118.8 119.1 164 237.61.6 1.62 118.2 119.2 159.9 235.2

1.64 1.65 119 120 159.5 234.21.61 1.64 118.9 119.4 156.2 238.21.63 1.61 119.5 120.5 161.9 236.21.63 1.62 119.4 119.67 163.9 238.61.61 1.66 118.9 119.7 158.6 238.81.61 1.58 119.9 119.6 161.1 235.71.64 1.76 118.7 119.7 157.6 237.71.61 1.61 118.8 119.6 157.5 237.11.62 1.62 119 119.2 161.5 236.51.68 1.67 118.2 155.8 2351.62 1.61 119.3 119.4 160.6 235.91.64 1.66 119 118.8 156.1 237.71.65 1.67 119 119 158.4 240

2011/6/13 1.64 1.65 119.4 119.3 163.5 234.81.64 1.65 119.1 119.2 161 2351.64 1.67 119.1 119.1 157.6 237.1

2011/5/24

2011/5/26

2011/5/27

2011/5/30

2011/5/31

2011/6/1

2011/6/2

2011/6/3

2011/6/7

2011/6/8

2011/6/9

2011/6/10

2011/6/14

Collected Data Sets

MKS Confidential 15

1. 7001. 6751. 6501. 6251. 6001. 5751. 550

99

95

90

80

70

605040

30

20

10

5

1

Top Max. Ri si ng

Percent

Mean 1.627StDev 0.02628N 27AD 0.550P-Value 0.142

Probabi l i ty Pl ot of Top Max. Ri si ngNormal

121. 0120. 5120. 0119. 5119. 0118. 5118. 0

99

95

90

80

70

605040

30

20

10

5

1

Bot Preheat Temp

Percent


Probabi l i ty Pl ot of Bot Preheat TempNormal

167. 5165. 0162. 5160. 0157. 5155. 0

99

95

90

80

70

605040

30

20

10

5

1

Top Wave Temp.

Percent


Probabi l i ty Pl ot of Top Wave Temp.Normal

241240239238237236235234233232

99

95

90

80

70

605040

30

20

10

5

1

Bot Wave Temp

Percent


Probabi l i ty Pl ot of Bot Wave TempNormal

Data Analysis – Normality Test

120. 0119. 5119. 0118. 5118. 0

99

95

90

80

70

605040

30

20

10

5

1

Top Preheat Peak Temp.

Percent

Mean 119.1StDev 0.4081

N 26

AD 0.504

P-Value 0.186

Probabi l i ty Pl ot of Top Preheat Peak Temp.Normal

• P-value > 0.05

• All data are normally distributed

1. 751. 701. 651. 601. 551. 50

99

95

90

80

70

605040

30

20

10

5

1

Bot Preheat Max. Ri si ng Sl ope

Percent

Mean 1.646StDev 0.04917

N 27

AD 0.258

P-Value 0.692

Probabi l i ty Pl ot of Bot Preheat Max. Ri si ng Sl opeNormal

MKS Confidential 16

Data Analysis - Hypothesis Test

Verified the two data sets – Top Preheat Max. Rising Slope and Bot. Preheat Max. Rising, if both without a statistical significant difference, than two measures could be combined and defined with an identical process limits.

Paired T-Test and CI: Top Max. Rising, Bot Max Rising

N Mean StDev SE Mean

Top Preheat Max. Rising 27 1.62704 0.02628 0.00506

Bot Preheat Max. Rising 27 1.64593 0.04917 0.00946

Difference 27 -0.01889 0.04627 0.00890

95% CI for mean difference: (-0.03719, -0.00058)

T-Test of mean difference = 0 (vs not = 0): T-Value = -2.12 P-Value = 0.044

Since P-value is < 0.05, rejected the Null Hypothesis. That is the two measures

– Top Max. Rising and the Bottom Max. Rising with statistical significant

difference.

MKS Confidential 17

Verified the two data sets – Top Preheat Max. Peak Temp. and Bot. Preheat Peak Temp. if both measures without a statistical significant difference, then these two measures could be combined and defined with an identical process limit.

Paired T-Test and CI: Top Preheat Temp., Bot Preheat Temp

N Mean StDev SE Mean

Top Preheat Temp. 27 119.052 0.421 0.092

Bot Preheat Temp 27 119.511 0.535 0.117

Difference 27 -0.459 0.493 0.108

95% CI for mean difference: (-0.683, -0.235)

T-Test of mean difference = 0 (vs not = 0): T-Value = -4.27 P-Value = 0.000

Since P-value is < 0.05, Reject the Null Hypothesis. That mean the two measures –

Top Max. Preheat Temp. and the Bottom Max. Preheat Temp. with statistical

significant difference.

Data Analysis - Hypothesis Test

MKS Confidential 18

28252219161310741

1. 8

1. 7

1. 6

1. 5

Obser vat i on

Individual Value

_X=1.6464

UCL=1.7815

LCL=1.5114

28252219161310741

0. 20

0. 15

0. 10

0. 05

0. 00

Obser vat i on

Moving Range

__MR=0.0508

UCL=0.1659

LCL=0

6

1

2

1

I-MR Chart of Bot Preheat Max. Rising Slope

Define Process Limits - In-control/Out of Control and Stability Verification• Test the six statistical using rules as shown.

• With exception of the statistical listed below others are in control and stable.

− Bot. Preheat Max. Rising Slope

− Bot. Preheat Peak Temp.252219161310741

1. 70

1. 65

1. 60

1. 55

Observation

Indiv

idual V

alu

e

_X=1.6259

UCL=1.6965

LCL=1.5553

252219161310741

0. 08

0. 06

0. 04

0. 02

0. 00

Observation

Movi

ng R

ange

__MR=0.02654

UCL=0.08671

LCL=0

I-MR Chart of Top Preheat Max. Rising Slope

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252219161310741

120. 5

120. 0

119. 5

119. 0

118. 5

Observation

Ind

ivid

ua

l Va

lue

UCL=120.827

LCL=118.257

_X=119.542

252219161310741

1. 6

1. 2

0. 8

0. 4

0. 0

Observation

Mo

vin

g R

an

ge

__MR=0.483

UCL=1.578

LCL=0

1

66

I-MR Chart of Bot Preheat Peak Temp

252219161310741

170

165

160

155

150

Observation

Ind

ivid

ua

l Va

lue

UCL=169.75

LCL=150.56

_X=160.15

252219161310741

12

9

6

3

0

Observation

Mo

vin

g R

an

ge

__MR=3.61

UCL=11.79

LCL=0

I-MR Chart of Top Wave Temp.

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243

240

237

234

231

Observation

Ind

ivid

ua

l Va

lue

_X=236.78

UCL=241.68

LCL=231.88

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6. 0

4. 5

3. 0

1. 5

0. 0

Observation

Mo

vin

g R

an

ge

__MR=1.844

UCL=6.024

LCL=0

I-MR Chart of Bot Wave Temp

Define Process Limits -

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120

119

118

Observation

Ind

ivid

ua

l Va

lue

_X=119.153

UCL=120.428

LCL=117.878

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1. 6

1. 2

0. 8

0. 4

0. 0

Observation

Mo

vin

g R

an

ge

__MR=0.479

UCL=1.566

LCL=0

I-MR Chart of Top Preheat Peak Temp.

MKS Confidential 20

Define Process Limits -

The team performed a cause & effect analysis and determined the most possible root cause as following.

Actions have been taken to eliminate the special cause variations so that the process could be drawn back under control and stable.

• The frequency of changing the aluminum tape has been specified at 1 test / 1 times

• Tape dimension required: 6mm x 6mm

• Run test until setting temp. being reached

Defined the Process Limits for the six statistical per the table as shown below.

Spec. Top Max. Rising Bot Max Rising Top Preheat Temp. Bot Preheat Temp Top Wave Temp. Bot Wave Temp

UCL= x' + 3s 1.71 1.79 120.4 120.8 169.9 241.8

x' 1.63 1.65 119.1 119.6 160.2 236.8

LCL= x' - 3s 1.55 1.51 117.8 118.4 150.5 231.8

MKS Confidential 21

Piloted to Measure PWI The profile checker, machine

setting and sample size (26) used to collect the PWI was identical to the baseline data collection. The pilot was run for 13 days starting on Jun 13, run two profiles per each day.

The collected 26 PWIs were less than 100%, which reveals that the pre-defined Process Limits are robust being used to measure the performance of the wave soldering machine.

2321191715131197531

100. 00%

75. 00%

50. 00%

25. 00%

0. 00%

Observati on

Individual Value

_X=51.70%

UCL=97.75%

LCL=5.64%

2321191715131197531

60. 00%

45. 00%

30. 00%

15. 00%

0. 00%

Observati on

Moving Range

__MR=17.32%

UCL=56.58%

LCL=0.00%

I - MR Chart of PWI - Pol i ted

MKS Confidential 22

Define Control Limits for PWI The control limits of PWI is specified as following based on the

piloted measurements. Targeted PWI: ≤75% No need to take action Process Indicator: >75% Keep close monitor the next data Out of Spec: >97% Root cause analysis & take corrective action

Wave Soldering PWI Daily Performance

PWI (%)

0

15

30

45

60

75

90

105

120

26May

26May

27May

27May

30May

30May

31May

31May

01Jun

01Jun

02Jun

02Jun

03Jun

03Jun

07Jun

07Jun

08Jun

08Jun

09Jun

09Jun

10Jun

10Jun

13Jun

13Jun

14Jun

14Jun

GoodPWI

WarningPWI

OutOfSpec

MKS Confidential 23

Process Control Plan

PWI is indentified as the indicator to measure the performance of the wave soldering machine.

PIE technician must to measure the PWI by the mean of running thermal profile every day.

Profile daily record should be reviewed by engineer. Any out of control limits data should be analyzed by

PCBA PIE engineer.

MKS Confidential 24

Process Control Plan

Project Name:

Introduction of PWI methodology for monitoring the performance of Wave Soldering Machine

Process Step Key Indicator

X (control)

or

Y (monitor

)

Product/Process

Specifications/Target

Evaluation/

Measurement Technique

%P/Total (R&R)

%P/Tolerance

Sample

Size

Sample Frequenc

yRespons

ibilityControl Method

Contingency Action Plan

Set wave soldering machine 　　　　　　

Conveyor Speed 　 x　1.03m/min　

Speedometer 　　 1 Day David

Profile Program

Calibrate machine

Bot. Pre-heat Zone #1 Temp.　 x　 130℃　

Th

erm

om

ete

r

　 1 Day　 DavidProfile Program

Top Pre-heat Zone #2 Temp. x　 130℃ 　 1　 Day 　

David 　

Profile Program

Bot. Pre-heat Zone #2 Temp. x　 140℃ 　　 1　 Day 　 David　

Profile Program

Top Pre-heat Zone #3 Temp. x　 140℃ 　　 1　 Day 　

David 　

Profile Program

Bot Pre-heat Zone #3 Temp. x　 145℃ 　　 1　 Day 　

David 　

Profile Program

Wave Temp. x　 145℃　　 1　 Day 　David 　

Profile Program

Profiling

PWI Y 0% - 99% 1 Day David

Profile Record & I-MR Control Chart

Calibrate machine

& Check Profile

Test Board

MKS Confidential 25

Control Plan – Machine Profile Daily Records Print the Machine Profile out and send it to the engineer for approval.

PWI Result

Accept Criteria

Signoff

MKS Confidential 26

Benefits of Ranking with PWI

Greatly simplifies the profiling process. Confidence in thermal process capability Profiles can be easily compared Improved Quality Control Significant production savings

Documents

60216444 Reflow Wave PWI