Process characterization
Note: For referrence only
1 TABLE OF CONTENTS
ITEM SECTION REVISION
1 TABLE OF CONTENTS 01
2 OVERVIEW 01
3 PROCEDURE 01
4 ROLES&RESPONSBILITY 01
5 ATTACHEMENTS 01
6 HISTORY PAGE 01
2 OVERVIEW
2.1 Purpose
To provide guidance for process characterization efforts. The intent of this process is to reduce variation, improve quality and reliability, and to reduce the cost of non-conformance.
2.2 Scope
This procedure applies to building 6.
2.3 Reference Documents
N/A
2.4 Definitions
2.4.1 CPK: Capability of Process
2.4.2 DOE: Design Of Experiment.
2.4.3 FMEA: Failure Modes and Effects Analysis
2.4.4 Gage R&R: Gage Repeatability and Reproducibility
2.4.5 MSA: Measurement System Analysis
2.4.6 OCAP: Out-of-Control Action Plan
2.4.7 PM: Preventative Maintenance
2.4.8 PRN: Resultant Priority Number
2.4.9 SPC: Statistic Process Control.
3 PROCEDURE
3.1 Formalize the team :
The team should be consist of
Team Leader
Product and Process “Experts”
Component Suppliers
Equipment Vendors
Operators and Technical Staff
Statistical Support
Measurement and Lab Personnel
Consultants
3.2 Process mapping:
Process mapping provides a tool for analyzing your current process and then re-engineer it to achieve breakthrough improvement. All the work consists of process and all process can be broken down into input, output and feedback loops.
3.3 Identify the critical process
FMEA is a useful tool to identify the critical process. FMEA is a structured problem solving technique that ranks possible failure modes by the severity of the failure, the occurrence of the cause, and the ease of detection of the cause. Each potential cause is ranked by these three categories, resulting in a summed RPN number. The larger the RPN, the higher a priority the reaction should be. High RPN’s may be verified to validate the FMEA findings.
Output of process FMEA:
List of potential process failure modes
List of confirmed critical characteristics and significant characteristics.
List of recommended actions for products with critical characteristics and with significant characteristics
List of process actions to eliminate the causes of product failure modes, or reduce their rate of occurrence, and to improve product detection if process capability can not be improved.
3.4 Assess the measurement system
The measurement system primary function is to ensure that the product is error-free or to determine equipment/process capability.
Measurement System Analysis: Is a statistical method to calculate the ratio of the amount of error/variation introduced by the measurement system to the total variation measured in a process (% R&R). The first step of any capability study, DOE, etc should be to validate the measurement system by completing an R&R study (unless already established).
 % R&R < 10%: measurement system is acceptable for use.
 % R&R 10% to 30%: measurement system may be acceptable for use, depending on the application. Caution should be exercised in making decisions based on the data from these measurement systems.
 % R&R > 30%: Data from these measurement systems is not acceptable for use in statistical analysis.
%R&R should be calculated for all measurements of critical parameters. For example, a 2D/3D paste inspection machine may require separate %R&R calculations for x, y, and theta offsets, % area coverage, and volume if those parameters are all identified as critical process outputs for screen print.
3.5 DOE:
DOE is part of a structured development strategy for product/process engineering in order to characterize, optimize and control the product with minimal waste. Experimentation allows the product/process engineer to adjust the settings of the machine in a systematic manner and to learn which factors have the greatest impact on the resultant quality. Using this information, the settings can be constantly improved until optimum quality is obtained.
Output of DOE:
List of optimized parameter
List the response of the parameter change
Designed the tolerance
3.6 Process capability study
Cpk is a measure of the ability of a process to operate within predetermined specification limits. The higher the Cpk, the lower the probability that the measured process output will fall beyond the specifications. Once a process output has been identified (i.e. placement x offset), the measurement system identified and found to have an acceptable gage R&R (View Basic, %R&R of 4.5%), the Cpk can be measured. There are several ways to conduct a Cpk study and methods to limit variation introduced into the process (i.e. use of a glass plate or dummy components instead of a FR4 PCB or real components). While these methods are valid and can help to more accurately identify machine issues, they can significantly affect the resulting Cpk. Therefore, the experiment methodology, along with the associated measurement system R&R (R&R will likely change between measuring placement offset on glass/tape vs. real PCB in paste) should be included with any Cpk report, so that meaningful comparisons can be made between equipment types, facilities, or over time. The specification limits used in the Cpk calculation should match that on the control plan and also be published in Cpk reports. The GR&R of the measurement system & test methodology (glass plate on tape vs. real PCB in paste) should also be included for reference. For example, a Cpk report should include all the information below somewhere accessable to the reader:
“MV2_cell1: Cpk x offset = 2.26; Cpk y offset = 1.89; spec of +/-.001” on a glass plate using 0805 components on double-sided tape”. Measurement system MVT JS-10; R&R 9.2%
3.7 Continue monitor and improvement
SPC is a useful tool to monitor the process. The following is the SPC control gauideline:
4 Roles&Responsibility
4.1 Management
 Provide the mandate for universal participation
 Assure all new processes are introduced with process controls in place
 Assure all employees are SPC trained
 Review SPC performance weekly for improvement opportunities
 Determine root-cause for any out-of-control conditions and take action to add or modify any missing factory controls
4.2 Process engineer
 Characterize the process
 Select process control factors
 Assure SPC is in place for your area
 Develop corrective action plan for each process area
 Assure process is capable
 Review process performance for improvement opportunities
 Compute control limits
 Sustain SPC activities
 Develop OCAP and adjustment matrices
 Assure all documentation is complete for process control
4.3 QA engineer
 Work with process engineer to develop SPC methods for each process
 Develop blanket studies to characterize the variation patterns in the process
 Conduct analysis to determine proper subgroup formation
 Select the subgroup formation method and associated control chart
 Assure corrective action procedures are in place for out-of-control conditions
 Assist in process characterization
 Design and deploy automated SPC systems
4.4 Supervisor
 Assure all operators are trained on the proper use of all floor process controls
 Coordinate floor concerns with responsible engineers and managers
 Review SPC performance data in a weekly meeting with area personnel
 Audit operator SPC performance to assure operators are following correct procedures
4.5 Operator
 Collect data per the process control plan
 Enter data in real time
 Chart the data and follow control rules for process adjustment
 Use the process control action plan for any out of control conditions
 Log all process adjustments and any observations concerning machines, materials or process conditions
 Ask questions if unsure of the proper action to take
4.6 Maintenance
 Conduct PMs on schedule
 Respond to out of control conditions as requested by process engineers and line operators
 Review weekly reports to determine opportunities for improvement
5 Attachment
ATTACHEMENT 1: Process Characterization Flow Chart
6 HISTORY PAGE
DCO. # DATE REV. ORIGINATOR REMARKS
- 03/21/02 01 David Xiong Initial Release
1 TABLE OF CONTENTS
ITEM SECTION REVISION
1 TABLE OF CONTENTS 01
2 OVERVIEW 01
3 PROCEDURE 01
4 ROLES&RESPONSBILITY 01
5 ATTACHEMENTS 01
6 HISTORY PAGE 01
2 OVERVIEW
2.1 Purpose
To provide guidance for process characterization efforts. The intent of this process is to reduce variation, improve quality and reliability, and to reduce the cost of non-conformance.
2.2 Scope
This procedure applies to building 6.
2.3 Reference Documents
N/A
2.4 Definitions
2.4.1 CPK: Capability of Process
2.4.2 DOE: Design Of Experiment.
2.4.3 FMEA: Failure Modes and Effects Analysis
2.4.4 Gage R&R: Gage Repeatability and Reproducibility
2.4.5 MSA: Measurement System Analysis
2.4.6 OCAP: Out-of-Control Action Plan
2.4.7 PM: Preventative Maintenance
2.4.8 PRN: Resultant Priority Number
2.4.9 SPC: Statistic Process Control.
3 PROCEDURE
3.1 Formalize the team :
The team should be consist of
Team Leader
Product and Process “Experts”
Component Suppliers
Equipment Vendors
Operators and Technical Staff
Statistical Support
Measurement and Lab Personnel
Consultants
3.2 Process mapping:
Process mapping provides a tool for analyzing your current process and then re-engineer it to achieve breakthrough improvement. All the work consists of process and all process can be broken down into input, output and feedback loops.
3.3 Identify the critical process
FMEA is a useful tool to identify the critical process. FMEA is a structured problem solving technique that ranks possible failure modes by the severity of the failure, the occurrence of the cause, and the ease of detection of the cause. Each potential cause is ranked by these three categories, resulting in a summed RPN number. The larger the RPN, the higher a priority the reaction should be. High RPN’s may be verified to validate the FMEA findings.
Output of process FMEA:
List of potential process failure modes
List of confirmed critical characteristics and significant characteristics.
List of recommended actions for products with critical characteristics and with significant characteristics
List of process actions to eliminate the causes of product failure modes, or reduce their rate of occurrence, and to improve product detection if process capability can not be improved.
3.4 Assess the measurement system
The measurement system primary function is to ensure that the product is error-free or to determine equipment/process capability.
Measurement System Analysis: Is a statistical method to calculate the ratio of the amount of error/variation introduced by the measurement system to the total variation measured in a process (% R&R). The first step of any capability study, DOE, etc should be to validate the measurement system by completing an R&R study (unless already established).
 % R&R < 10%: measurement system is acceptable for use.
 % R&R 10% to 30%: measurement system may be acceptable for use, depending on the application. Caution should be exercised in making decisions based on the data from these measurement systems.
 % R&R > 30%: Data from these measurement systems is not acceptable for use in statistical analysis.
%R&R should be calculated for all measurements of critical parameters. For example, a 2D/3D paste inspection machine may require separate %R&R calculations for x, y, and theta offsets, % area coverage, and volume if those parameters are all identified as critical process outputs for screen print.
3.5 DOE:
DOE is part of a structured development strategy for product/process engineering in order to characterize, optimize and control the product with minimal waste. Experimentation allows the product/process engineer to adjust the settings of the machine in a systematic manner and to learn which factors have the greatest impact on the resultant quality. Using this information, the settings can be constantly improved until optimum quality is obtained.
Output of DOE:
List of optimized parameter
List the response of the parameter change
Designed the tolerance
3.6 Process capability study
Cpk is a measure of the ability of a process to operate within predetermined specification limits. The higher the Cpk, the lower the probability that the measured process output will fall beyond the specifications. Once a process output has been identified (i.e. placement x offset), the measurement system identified and found to have an acceptable gage R&R (View Basic, %R&R of 4.5%), the Cpk can be measured. There are several ways to conduct a Cpk study and methods to limit variation introduced into the process (i.e. use of a glass plate or dummy components instead of a FR4 PCB or real components). While these methods are valid and can help to more accurately identify machine issues, they can significantly affect the resulting Cpk. Therefore, the experiment methodology, along with the associated measurement system R&R (R&R will likely change between measuring placement offset on glass/tape vs. real PCB in paste) should be included with any Cpk report, so that meaningful comparisons can be made between equipment types, facilities, or over time. The specification limits used in the Cpk calculation should match that on the control plan and also be published in Cpk reports. The GR&R of the measurement system & test methodology (glass plate on tape vs. real PCB in paste) should also be included for reference. For example, a Cpk report should include all the information below somewhere accessable to the reader:
“MV2_cell1: Cpk x offset = 2.26; Cpk y offset = 1.89; spec of +/-.001” on a glass plate using 0805 components on double-sided tape”. Measurement system MVT JS-10; R&R 9.2%
3.7 Continue monitor and improvement
SPC is a useful tool to monitor the process. The following is the SPC control gauideline:
- []Define the purpose[/][]Assure specifications are understood and used[/][]Determine control factors [/][]Study the variation in the process (blanket studies, POV, and correlation studies)[/][]Determine the drift rate and then select the sample frequency and subgroup size[/][]Select the proper control chart (x&R, X&MR or x&s) [/][]Using the sampling plan collect data and determine control limits[/][]Determine corrective action plan for out of control conditions (applying predetermined control factors). Set up the associated process logs.[/][]Validate and deploy the process control system[/][]Document, train, standardize and automate[/][]Routine line audits[/]
4 Roles&Responsibility
4.1 Management
 Provide the mandate for universal participation
 Assure all new processes are introduced with process controls in place
 Assure all employees are SPC trained
 Review SPC performance weekly for improvement opportunities
 Determine root-cause for any out-of-control conditions and take action to add or modify any missing factory controls
4.2 Process engineer
 Characterize the process
 Select process control factors
 Assure SPC is in place for your area
 Develop corrective action plan for each process area
 Assure process is capable
 Review process performance for improvement opportunities
 Compute control limits
 Sustain SPC activities
 Develop OCAP and adjustment matrices
 Assure all documentation is complete for process control
4.3 QA engineer
 Work with process engineer to develop SPC methods for each process
 Develop blanket studies to characterize the variation patterns in the process
 Conduct analysis to determine proper subgroup formation
 Select the subgroup formation method and associated control chart
 Assure corrective action procedures are in place for out-of-control conditions
 Assist in process characterization
 Design and deploy automated SPC systems
4.4 Supervisor
 Assure all operators are trained on the proper use of all floor process controls
 Coordinate floor concerns with responsible engineers and managers
 Review SPC performance data in a weekly meeting with area personnel
 Audit operator SPC performance to assure operators are following correct procedures
4.5 Operator
 Collect data per the process control plan
 Enter data in real time
 Chart the data and follow control rules for process adjustment
 Use the process control action plan for any out of control conditions
 Log all process adjustments and any observations concerning machines, materials or process conditions
 Ask questions if unsure of the proper action to take
4.6 Maintenance
 Conduct PMs on schedule
 Respond to out of control conditions as requested by process engineers and line operators
 Review weekly reports to determine opportunities for improvement
5 Attachment
ATTACHEMENT 1: Process Characterization Flow Chart
6 HISTORY PAGE
DCO. # DATE REV. ORIGINATOR REMARKS
- 03/21/02 01 David Xiong Initial Release
没有找到相关结果
已邀请:
RSS Feed
11 个回复
steventec (威望:38) (广东 深圳) 咨询业 咨询顾问 - 你来自云南元谋，我来自北京周口，握着你毛绒绒的手...
赞同来自: