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Process planning for manual PWB assembly
Computers ind. E.gng VoL 31, No. If)-, pp. 181 - 184,1996 Copyright© 1996 ElsevierSdu~.¢ Ltd Printed in Great Britain. All riglm m ~ e d
Pergamon
S0360-8352(96) 00106-4
0360- s 3 5 2 ~ $t5.oo + 0.0o
PROCESS PLANNING FOR MANUAL PWB ASSEMBLY
ARNOLD KtY, K. SRIHARI, Ph.lT and JUDE DILELLA++ +Department of Systems Science and Industrial Engineering ++Director of Engineering State University Of New York Dovatron Manufacturing East Binghamton, New York 13902-6000. Binghamton, New York 13902-5212. ABSTRACT This paper discusses a Computer Aided Process Planning (CAPP) system which was developed for use in a microelectronics Printed Wiring Board (PWB) assembly facility which specializes in contract manufacumng This CAPP system focuses on the manual PWB assembly process. It is implemented on a centralprocessor within a star tcVciogyLocal Area Network (LAN) system. The CAPP system is described, and itsinputs and outputs are delineated.
KEYWORDS Computer aided process planning; printed wiring board assembly; through hole technology; manual assembly.
INTRODUCTION The complexity of manufacturing seen in the elecu'onics assembly arena has increased tremendously over the past two decades (Hwang, 1995). This increase in process complexity has further enhaced the importance of process planning in electronics assembly. In order to achieve effective process planning, it is essential to collect and analyze relevant information. Also, an efficient management system is essential to store and retrieve the collected information as and when necessary.
In a microelectronics Printed Wiring Board (PWB) assembly facilitywhich specializes in contract rr~a-f._~ng, the information received by the process planner from the customer includes one or more of the following:assembly drawing, cornlxment descriptions,a sample assembly, etc. The process planner has to work with this input informaZion and use his/her knowledge of the capabilities of the facility in determining an acceptable process plan that meets both process and scheduling needs (Masood & Srihari, 1993). In performing these functions, the human is inhibited by the increasing complexities and the escalating demands of the manufacturing environment. Proper information collection and analysis are important for process planning. Data storage and retrieval are the essential functions of information communication and organization. They are the key to effective decision making.
PWB ASSEMBLY AND MANUAL ASSEMBLY PROCESSES During the PWB assembly process, electrical components are first mounted on to a substrate prior to being solderedin place (Coombs, 1995). A PWB assembly is composed of organic and inorganic materials with 181
182
19th International Conference on Computers and Industrial Engineering
internaland external wiring, k is an integralpart of the electronic packaging hierarchy, and allows electronic components to be mechanicallyjoined and electricallyconnected. In the PWB assembly process, components are either inserted or surface mounted on the PWB. Inserted components or Through Hole Mounted Components (THMCs) are mounted on the PWB by feeding the leads of the components into holes in the PWB. Surface Mount Components (SMCs) are attached directly to the surface of the PWB. A PWB assembly can include pure insertion, pure surface mount, or a combination of both. SMT addresses some of the bottlenecks of through hole technology through its smaller size, more functions per part, higher I/Os, and better electronic device performance. The manual assembly of through-hole components involves the following steps: Component PREP(preparation): Consists of all the components that require special forming or prepar~on prior to insertion into the PWB. This may include standoffs, cutting leads, forming leads or any other special configuration. OFFLINE Hand assembly: Consists of operations where special equipment or processes are required that are not within the normal flow line. This includes, but is not limited to, a tab router (de-panelization), pinning, masking, arbor press, final boxing, etc. PRE-SOLDER hand assembly: Consists of all hand assembled components that require clinching and cutting of leads, swaging offor attachment using hardware, and taping or masking of areas that need to remain solder free. DROP-IN / WAVE / CLEAN: Consists of all the operations related to the insertion of components that do not require clinching or cutting. These components must be able to be inserted into the board with little or no additional mechanical bonding to the PCB. This assembly line flows directly into the wave soldering equipment and, if required, on to the cleaning equipment. TOUCH-UP: All the solderjoints formed through wave soldering process are inspected for defects. Those joints which do not meet the applicable workmanship specifications are reworked. Those boards which cannot be reworked are scrapped. The rework operation is performed using soldering irons and core solder. POST SOLDER hand assembly: Consists of all hand assembled components that cannot be subjected the wave soldering process and/or machine cleaning. For further information on PWB assembly (both surface mount and through hole), please refer to Coombs (1995).
PROBLEM STATEMENT AND RESEARCH OBJECTIVE In a manual process planmng mode, domain experts initially obtain information about the PWB assembly under consider~on from the customer. They typically use manual processing methods to store and organize information, and to subsequently make decisions on scheduling, line balancing, and process planning for the overall PWB assembly scheme. In order to effectively cope with complex data collection and organizational needs, the domain expert has to spend significant amounts of time to handle and analyze the information needed prior to arriving at a viable and efficient process plan. A Computer-Aided Process Plato-ring(CAPP) system was designed to assist the domain expert in analyzing and planning the through-hole hand mount technology process. Detailed process reports were generated to help the process engineers and the managers in decision making. Tools are provided to help deal with system update and to ensure soitware flexibility. This research considers a batch type PWB assembly environment. The size of the batch and the arrival rata are variables. The assembly sequence adopted for the PWB batches that amve at the facility is limited to the First Come First Served (FCFS) rule. This process planning system focuses on the manual assembly of through hole components only. These components could be inserted on to boards that contain surface mount and/or through hole components.
19th International Conference on Computers and Industrial Engineering
183
SYSTEM DESIGN The CAPP system for this research is primarily composed of an information processor and three databases (the main a~ahase, the standard operating time database, and the data changed history database) as shown in Figure 1. The process planning system designed and developed in this research uses three distinct databases for different functions and a central information processor. The main d~t_abase provides for the functions of data storage and retrieval for most of the information used in the overall system. The database that contains the component hand assembly operational standard times is used to analyze the work station balancing conditions while the d~hase that records the history of data changes provides the domain experts with easy access to past records. The information processor facilitates data communication and processing. It includes functions such as data manipulation, computation and process balancing, and the output generator. The dat~ manipulation function helps with unporfing data, data communication, and data retrieval. The overall calculation and process balancing function assists with data organization and line balancing. The output generator provides the function of generating the processing document or the output dam files. A user friendly interface is provided in this process planning tool. In addition to these databases, the CAPP system also needs to provide the function of CAD data file transformation.
Iorma~n roeeuor
\\
l r i l .
!
Prseessl~ ~] Dscuma¢ |
The Local Area Network (LAN) system provides the function of information communication. In this research, a star topology LAN was used as the implementation environment of the CAPP systeat The core computer software used in this research was Microsof~ Access (Version 2.0). The Microsot~ Access (Version 2.0) package provides the fi'amework of the soflxvare design. The CorelDraw package (Version 4.0) provides the function of CAD data file transformation. Object Linking and Embedding (OLE) was used as the bridge between the Microsoft Access (Version 2.0) and the CoreIDraw CAD data files. The CAPP system was built on the Microsoit Access Version 2.0 running on Noveil NetWare Version 3.11.
]WlL~re1. Areblteetur¢Of Tie Computer Aided lSreees8PbsnnlmiSystem
After the assembly information is received, the domain expert formats the d~n and then channels it into the developed CAPP system. The overall flow of the system can be described as follows: 1. 2. 3. 4. 5. 6. 7. 8.
Data preparation. Checking of the import file; import the data file (if any) and then go to the next step. Manual data entry or edit. Check the assembly drawing file (if any) and then modify the drawing (if necessary). Finally, link with the system and go to the next step. Enter the parameter of the report. Preview the output report. Check the d~a and the results. If the data is correct, then go to the next step (If the data is wrong, then go back to step 3). Print out the process sheet.
184
19th International Conferenceon Computers and Industrial Engineering SYSTEM INPUTS AND OUTPUTS
The system's inputs can be categorized as follows. They are essential to generate the output information. The CUSTOMER d~a entry screen requests the following information : the customer name, the 'request for quote numbeg, the assembly number, the date, the engineering factor, the revision number, and the name of the person preparing the process plan. There are six work center screens that require data input under the CUSTOMER data entry screen. They are the OFFLINE data entry screen, PREP data entry screen, PRESOLDER HAND ASSEMBLY data entry screen, DROP-IN/WAVE/CLEAN data entry screen, POST SOLDER HAND ASSEMBLY data entry screen, and the OFFLINE (Other) data entry screen. The information requested at these screens includes the name of the customer, the assembly number, the code, the method, the rate, the step, the find location, the component part number, the description of the component, and its orientation. Information can also be imported from other databases. Data can be imported from a d~base using the d_at__a_basefile format (*.MDB); data can be imported from a text file using the text file format ( *.TXT ); and data can be imported from an Excel file format (*.XLS) spreadsheet. The output reports can be presented in either a landscape or portrait format. These reports will provide the description of components, crew size at the workstations, processing instructions, and information on the hand assembly method. This output information can be categorized into the following reports: oItline report, prep report, pre-solder report, drop-in/wave/clean report, and the post solder report. Each report would include the current date, total number of hours, sequence number, revision level and date, name of the customer, the assembly number, the station, the step, the find location, the part number of the components, the description of the component, the methods to be used, the orientation of the component, the rate of assembly, etc. The touch-up report would specify the current date, the sequence number, the revision level and date, the name of the customer, the assembly number, the rate of touch-up, etc.
VALIDATION ANDTESTING
This CAPP system was rigorously tested by the domain experts. The information processor of the CAPP system was tested and verified along with its the overall functions. The process planning procedure was also validlY. The CAD file transformation function was tested and its link to the CAPP system was verified. A case study was created and executed to verify the process pi~amingprocedure that provides the appropriate process plans associated with the real time status of the shopfloor. The outputs generated include the CAD data file that has been reviewed and evaluated by experts in manual PWB assembly.
CONCLUSION The CAPP system developed in this research employed the relational database management concept to deal with the complicated data mampulation problems seen in the decision making associated with the manual PWB assembly process. This system helps in crucial decision making, a need felt in most PWB assembly environments. The managernent's decision making is supported by this CAPP system through the provision of integrated and summarized reports tailored to the needs of the various levels of management. The manufacturing tasks associated with manual PWB assembly operations considered in this research include job sequencing, process plan generation, operation time analysis, and production line balancing. REFERENCES Coombs, C.F. (1995), Printed Circuits Handbook, McGraw Hill, New York. Hwang, J.S., (1995), Ball Grid Array & Fine Pitch Peripheral lnterconnections, Electrochemical Publications, Ayr, Scotland. Masood, A., Srihari, K. (1993), RDCAPP - A Realtime Dynamic CAPP System For An FMS, International Journal Of Advanced Manufacturing Technology, Vol.8, No.6, pp.358-370.
Pergamon
S0360-8352(96) 00106-4
0360- s 3 5 2 ~ $t5.oo + 0.0o
PROCESS PLANNING FOR MANUAL PWB ASSEMBLY
ARNOLD KtY, K. SRIHARI, Ph.lT and JUDE DILELLA++ +Department of Systems Science and Industrial Engineering ++Director of Engineering State University Of New York Dovatron Manufacturing East Binghamton, New York 13902-6000. Binghamton, New York 13902-5212. ABSTRACT This paper discusses a Computer Aided Process Planning (CAPP) system which was developed for use in a microelectronics Printed Wiring Board (PWB) assembly facility which specializes in contract manufacumng This CAPP system focuses on the manual PWB assembly process. It is implemented on a centralprocessor within a star tcVciogyLocal Area Network (LAN) system. The CAPP system is described, and itsinputs and outputs are delineated.
KEYWORDS Computer aided process planning; printed wiring board assembly; through hole technology; manual assembly.
INTRODUCTION The complexity of manufacturing seen in the elecu'onics assembly arena has increased tremendously over the past two decades (Hwang, 1995). This increase in process complexity has further enhaced the importance of process planning in electronics assembly. In order to achieve effective process planning, it is essential to collect and analyze relevant information. Also, an efficient management system is essential to store and retrieve the collected information as and when necessary.
In a microelectronics Printed Wiring Board (PWB) assembly facilitywhich specializes in contract rr~a-f._~ng, the information received by the process planner from the customer includes one or more of the following:assembly drawing, cornlxment descriptions,a sample assembly, etc. The process planner has to work with this input informaZion and use his/her knowledge of the capabilities of the facility in determining an acceptable process plan that meets both process and scheduling needs (Masood & Srihari, 1993). In performing these functions, the human is inhibited by the increasing complexities and the escalating demands of the manufacturing environment. Proper information collection and analysis are important for process planning. Data storage and retrieval are the essential functions of information communication and organization. They are the key to effective decision making.
PWB ASSEMBLY AND MANUAL ASSEMBLY PROCESSES During the PWB assembly process, electrical components are first mounted on to a substrate prior to being solderedin place (Coombs, 1995). A PWB assembly is composed of organic and inorganic materials with 181
182
19th International Conference on Computers and Industrial Engineering
internaland external wiring, k is an integralpart of the electronic packaging hierarchy, and allows electronic components to be mechanicallyjoined and electricallyconnected. In the PWB assembly process, components are either inserted or surface mounted on the PWB. Inserted components or Through Hole Mounted Components (THMCs) are mounted on the PWB by feeding the leads of the components into holes in the PWB. Surface Mount Components (SMCs) are attached directly to the surface of the PWB. A PWB assembly can include pure insertion, pure surface mount, or a combination of both. SMT addresses some of the bottlenecks of through hole technology through its smaller size, more functions per part, higher I/Os, and better electronic device performance. The manual assembly of through-hole components involves the following steps: Component PREP(preparation): Consists of all the components that require special forming or prepar~on prior to insertion into the PWB. This may include standoffs, cutting leads, forming leads or any other special configuration. OFFLINE Hand assembly: Consists of operations where special equipment or processes are required that are not within the normal flow line. This includes, but is not limited to, a tab router (de-panelization), pinning, masking, arbor press, final boxing, etc. PRE-SOLDER hand assembly: Consists of all hand assembled components that require clinching and cutting of leads, swaging offor attachment using hardware, and taping or masking of areas that need to remain solder free. DROP-IN / WAVE / CLEAN: Consists of all the operations related to the insertion of components that do not require clinching or cutting. These components must be able to be inserted into the board with little or no additional mechanical bonding to the PCB. This assembly line flows directly into the wave soldering equipment and, if required, on to the cleaning equipment. TOUCH-UP: All the solderjoints formed through wave soldering process are inspected for defects. Those joints which do not meet the applicable workmanship specifications are reworked. Those boards which cannot be reworked are scrapped. The rework operation is performed using soldering irons and core solder. POST SOLDER hand assembly: Consists of all hand assembled components that cannot be subjected the wave soldering process and/or machine cleaning. For further information on PWB assembly (both surface mount and through hole), please refer to Coombs (1995).
PROBLEM STATEMENT AND RESEARCH OBJECTIVE In a manual process planmng mode, domain experts initially obtain information about the PWB assembly under consider~on from the customer. They typically use manual processing methods to store and organize information, and to subsequently make decisions on scheduling, line balancing, and process planning for the overall PWB assembly scheme. In order to effectively cope with complex data collection and organizational needs, the domain expert has to spend significant amounts of time to handle and analyze the information needed prior to arriving at a viable and efficient process plan. A Computer-Aided Process Plato-ring(CAPP) system was designed to assist the domain expert in analyzing and planning the through-hole hand mount technology process. Detailed process reports were generated to help the process engineers and the managers in decision making. Tools are provided to help deal with system update and to ensure soitware flexibility. This research considers a batch type PWB assembly environment. The size of the batch and the arrival rata are variables. The assembly sequence adopted for the PWB batches that amve at the facility is limited to the First Come First Served (FCFS) rule. This process planning system focuses on the manual assembly of through hole components only. These components could be inserted on to boards that contain surface mount and/or through hole components.
19th International Conference on Computers and Industrial Engineering
183
SYSTEM DESIGN The CAPP system for this research is primarily composed of an information processor and three databases (the main a~ahase, the standard operating time database, and the data changed history database) as shown in Figure 1. The process planning system designed and developed in this research uses three distinct databases for different functions and a central information processor. The main d~t_abase provides for the functions of data storage and retrieval for most of the information used in the overall system. The database that contains the component hand assembly operational standard times is used to analyze the work station balancing conditions while the d~hase that records the history of data changes provides the domain experts with easy access to past records. The information processor facilitates data communication and processing. It includes functions such as data manipulation, computation and process balancing, and the output generator. The dat~ manipulation function helps with unporfing data, data communication, and data retrieval. The overall calculation and process balancing function assists with data organization and line balancing. The output generator provides the function of generating the processing document or the output dam files. A user friendly interface is provided in this process planning tool. In addition to these databases, the CAPP system also needs to provide the function of CAD data file transformation.
Iorma~n roeeuor
\\
l r i l .
!
Prseessl~ ~] Dscuma¢ |
The Local Area Network (LAN) system provides the function of information communication. In this research, a star topology LAN was used as the implementation environment of the CAPP systeat The core computer software used in this research was Microsof~ Access (Version 2.0). The Microsot~ Access (Version 2.0) package provides the fi'amework of the soflxvare design. The CorelDraw package (Version 4.0) provides the function of CAD data file transformation. Object Linking and Embedding (OLE) was used as the bridge between the Microsoft Access (Version 2.0) and the CoreIDraw CAD data files. The CAPP system was built on the Microsoit Access Version 2.0 running on Noveil NetWare Version 3.11.
]WlL~re1. Areblteetur¢Of Tie Computer Aided lSreees8PbsnnlmiSystem
After the assembly information is received, the domain expert formats the d~n and then channels it into the developed CAPP system. The overall flow of the system can be described as follows: 1. 2. 3. 4. 5. 6. 7. 8.
Data preparation. Checking of the import file; import the data file (if any) and then go to the next step. Manual data entry or edit. Check the assembly drawing file (if any) and then modify the drawing (if necessary). Finally, link with the system and go to the next step. Enter the parameter of the report. Preview the output report. Check the d~a and the results. If the data is correct, then go to the next step (If the data is wrong, then go back to step 3). Print out the process sheet.
184
19th International Conferenceon Computers and Industrial Engineering SYSTEM INPUTS AND OUTPUTS
The system's inputs can be categorized as follows. They are essential to generate the output information. The CUSTOMER d~a entry screen requests the following information : the customer name, the 'request for quote numbeg, the assembly number, the date, the engineering factor, the revision number, and the name of the person preparing the process plan. There are six work center screens that require data input under the CUSTOMER data entry screen. They are the OFFLINE data entry screen, PREP data entry screen, PRESOLDER HAND ASSEMBLY data entry screen, DROP-IN/WAVE/CLEAN data entry screen, POST SOLDER HAND ASSEMBLY data entry screen, and the OFFLINE (Other) data entry screen. The information requested at these screens includes the name of the customer, the assembly number, the code, the method, the rate, the step, the find location, the component part number, the description of the component, and its orientation. Information can also be imported from other databases. Data can be imported from a d~base using the d_at__a_basefile format (*.MDB); data can be imported from a text file using the text file format ( *.TXT ); and data can be imported from an Excel file format (*.XLS) spreadsheet. The output reports can be presented in either a landscape or portrait format. These reports will provide the description of components, crew size at the workstations, processing instructions, and information on the hand assembly method. This output information can be categorized into the following reports: oItline report, prep report, pre-solder report, drop-in/wave/clean report, and the post solder report. Each report would include the current date, total number of hours, sequence number, revision level and date, name of the customer, the assembly number, the station, the step, the find location, the part number of the components, the description of the component, the methods to be used, the orientation of the component, the rate of assembly, etc. The touch-up report would specify the current date, the sequence number, the revision level and date, the name of the customer, the assembly number, the rate of touch-up, etc.
VALIDATION ANDTESTING
This CAPP system was rigorously tested by the domain experts. The information processor of the CAPP system was tested and verified along with its the overall functions. The process planning procedure was also validlY. The CAD file transformation function was tested and its link to the CAPP system was verified. A case study was created and executed to verify the process pi~amingprocedure that provides the appropriate process plans associated with the real time status of the shopfloor. The outputs generated include the CAD data file that has been reviewed and evaluated by experts in manual PWB assembly.
CONCLUSION The CAPP system developed in this research employed the relational database management concept to deal with the complicated data mampulation problems seen in the decision making associated with the manual PWB assembly process. This system helps in crucial decision making, a need felt in most PWB assembly environments. The managernent's decision making is supported by this CAPP system through the provision of integrated and summarized reports tailored to the needs of the various levels of management. The manufacturing tasks associated with manual PWB assembly operations considered in this research include job sequencing, process plan generation, operation time analysis, and production line balancing. REFERENCES Coombs, C.F. (1995), Printed Circuits Handbook, McGraw Hill, New York. Hwang, J.S., (1995), Ball Grid Array & Fine Pitch Peripheral lnterconnections, Electrochemical Publications, Ayr, Scotland. Masood, A., Srihari, K. (1993), RDCAPP - A Realtime Dynamic CAPP System For An FMS, International Journal Of Advanced Manufacturing Technology, Vol.8, No.6, pp.358-370.