Date Visited: October 7, 1993
Report Author: J. Kukowski
Oki Electric, Japan's first telecommunications manufacturer, was founded in January 1881. It is developing its business globally, pursuing all aspects of research and development, production, marketing, and service from an international perspective. The company's business sectors are telecommunications systems, information processing systems, and electronic devices. The company produces a wide range of products that include switching systems, transmission systems, telecommunications terminals, data communications systems and peripherals, underwater acoustic systems, telemetry and telecontrol systems, automotive electronics systems, and electronic devices. The company's vision is to capitalize on the technical strength of the three business sectors to be successful in the coming multimedia age.
The Honjo manufacturing plant produces products for the telecommunications systems business sector. The products being produced at this site include asynchronous transfer mode (ATM) switching systems, modems, facsimiles, telephones, and other peripherals.
Detailed technical presentations were given on the following subjects:
Multichip Modules (MCM). The subject of MCM was presented by Mr. Iida. The topics covered were benefits, Oki development direction, MCM structures, design specifications for LTCC and copper polyimide thin film multilayer substrate, Oki's implementation schedule, and identified applications.
The benefits for creating a MCM are high speed, miniaturization, high reliability, and low cost. The driving forces are low cost and high speed. The key issues in achieving low cost and high speed have been identified as
- very fine pattern of substrate - flip chip bonding
Directions of MCM development at Oki
1993 MCM-C (multichip module-ceramic) - Substrate: Low-temperature co-fired ceramic (LTCC) - LSI: Wirebond / flip chip - I/O: Quad flat pack type (QFP).
1994 MCM-D/C (multichip module-deposited/ceramic) - Substrate: Modified Cu/Pl on LTCC - LSI: Flip chip - I/O: BGA/QFP type (ball grid array) - High power LSI and high reliability
1995 MCM-D/L (multichip module-deposited/laminate) - Substrate: Cu/BT resin on BT base - LSI: Flip chip - I/O: BGA/QFP type - Low power LSI
The ATM SW module, optical interface module, digital LSI tester module, clock recovery module, and super multi pins LSI package have been identified for potential applications to incorporate MCM technology. During the technical presentation on MCMs the key features of the LTCC substrate and the copper polyimide substrate were reviewed.
Figure Oki.1. MCM structures.
Design Specifications of MCM Substrates
(Low Temperature Co-Fired Multilayer Ceramic Substrate)
Design Specifications of MCM Substrates
(Copper Polyimide Thin Film Multilayer Substrate)
Note: Oki's LSI interconnection roadmap is shown in Table 4.12 .
Polyimide-Copper Thin-Film Multilayer Substrate
Oki's developments and research in polyimide-copper thin-film multilayer substrate were presented by Mr. Iguchi, who gave us technical details on the following topics:
Oki Development of a Single-PPM Soldering System. Mr. Takei presented Oki's challenges and accomplishments with respect to the goals of CFC elimination and single-PPM soldering.
CFC Elimination. Our hosts reviewed the utilization of CFC materials at the Honjo plant and the conventional reasons for CFC cleaning of PCBs. The presentation detailed the development process undertaken to meet the goal of CFC elimination. The process consisted of defining the development target/specifications, defining alternative approaches to eliminate CFCs, the development of experimental fluxes, and testing of the fluxes. Details of the reliability test specification, solderability test specification, contact resistance test specification, and final test results were reviewed. Oki has completed a successful development of a flux with RMA reliability, RA solderability, and ease of test pin contact. The Oki Honjo plant manufactured PCBs for 10 months using the new flux without any major problems reported, and it eliminated the use of CFCs in March 1992.
Nitrogen Flow Soldering System. The nitrogen flow soldering system required development of 3 major subsystems: swing spray fluxer for application of low solid flux; low-consumption nitrogen and flux fume chamber for management of nitrogen gas and flux fume flow; and cover plate over the solder bath to eliminate micro solder balls. Technical details and test results were reviewed. Results indicated a failure rate of .02% on a sample size of 21,002 PCBs assembled. The smallest component lead pitch on the PCBs tested was 0.5 mm.
Semiaqueous cleaning. The presentation on the development of semi-aqueous cleaning technology was given in two parts. Part one discussed the development of alternative solvents, and part two discussed the development of a cleaning machine.
Solvent development. Mr. Takei defined the basic criteria for selecting an alternative solvent:
A detailed matrix for three alternative semiaqueous solvents was reviewed. The review covered the topics of solvent properties, damage to other materials, bubble height and elimination time, and drying ability.
Cleaning Machine Development. There are several basic development criteria for a cleaning machine:
- pure water to be used for rinse - lower ionic contamination than CFCs - immersed water of PCB to be dried up
Detailed technical matrices were reviewed, covering cleaning methods, waste water process, influence of liquid quantity taken out by passing PCB concentration, cleanliness of PCBs, machine stability, and reliability and quality of post-CFC cleaning methods.
LSI Packing Technology
Mr. Kohara covered the following topics on the subject of LSI packaging technology:
- logic LSI package roadmaps - high pin count future direction - wire bond technology improvement - comparison of high-power package cross-sections - thermal resistance - high-speed packages
- technology roadmap for memory-SOJ - technology roadmap for memory-TSOP - heat resistance in reflow soldering - concerns of thin plastic package TSOP - package outlines
- technology roadmap for TAB
Packaging Technology for Fiber-Optic Devices
Mr. Ishii presented a technical overview on packaging for fiber-optic devices and reviewed the specifications and block diagram for the optical parallel transmission module. Also included were the topics of coupling efficiency for photo diode and laser diode array modules and bit error rates.
The first area we toured was a pilot production area to produce LTCC. The manufacturing process is enclosed in a class-10,000 clean room. This process was in the technology development stage at the time of our visit. The equipment being evaluated for this process consisted of screen printers, inspection stations, NC hole punch, lamination, ovens, laser trim, laser solder for outer lead bond, and thermode bonding for inner and outer lead bonding. The process included screen printing of resistors and capacitors.
Memory Package (TSOP) Technology Roadmap
Note: See Table 4.5 for Oki's memory package (TSOP) roadmap and Table 4.13 for its TAB package roadmap.
The second area the JTEC team toured was a production facility for the assembly of printed circuit boards and end products. Our tour was focused in the area of the printed circuit board assembly. The manufacturing facility was organized into islands of automation; their manufacturing operations are controlled by a central host computer. The operation begins with an automated storage and retrieval system. The management information system (MIS) defines whether or not incoming material, received from a vendor, requires inspection before being placed into the storage area. Components are automatically identified and retrieved by the use of computer control in combination with a bar code system. An automated guided vehicle is used to deliver material to the process lines; this includes magazines of printed circuit boards and prekited component feeders for the placement machines. The standard screen, place, and reflow manufacturing process is being used for surface mount assembly. Bar code labels are applied to bare printed circuit boards, and automated in-line inspection is performed immediately after screen printing of solder paste, component placement, and solder reflow. Automated inspection and test of individual components is performed within the placement machines. Solder reflow profiles are downloaded from the host system. Presently Oki is using vision for solder reflow inspection but is developing a 3-D laser inspection station. A warp prevention robot was developed for processing of large printed circuit boards through the reflow oven. Design rules have been established to obtain optimum yields within the manufacturing process. The rules define the placement location of components onto the printed circuit boards
Oki is organized into three business divisions that are highly integrated. The company possesses the technological capabilities required for success in the coming multimedia age. The organization is involved in development and production of products, systems, materials, automated equipment, and manufacturing processes. Oki gives credit to automation as the key in obtaining product yield improvement with high quality and reliability. The driving forces for its development of new products are cost, weight, and miniaturization.
During the JTEC visit our hosts were open in technical discussions and extremely hospitable.