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Development of Printed Circuit Board Technology Embedding Active and Passive Devices for E-Function Module

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Development of Printed Circuit Board Technology Embedding Active and Passive Devices for E-Function Module Development of Printed Circuit Board Technology Embedding Active and Passive Devices for e-Function Module Noboru Fujimaki Kiyoshi Koike Kazuhiro Takami Sigeyuki Ogata Hiroshi Iinaga Background shortening of signal wirings between circuits, reduction of damping resistors and elimination of characteristic Higher functionality of today’s portable devices impedance controls. Embedded component module demands smaller, lighter and thinner electronic boards have been adopted for higher functionality of components. Looking at the evolution of package video cameras and miniaturizing wireless communication miniaturization from the flat structure (System in Package: devices. It is expected the use will spread to a wider SiP) -> silicon chip stack structure (Chip on Chip: CoC) -> range of areas including automotive, consumer products, package stack structure (Package on Package: PoP) -> Si industrial equipment and infrastructure equipment. To through chip contact structure, the technology has gone meet these needs, a technology to package and embed from two-dimensional to three-dimensional packaging the various components and LSI will be required. This achieving high density packages. The trends in printed article discusses the method of embedding components, circuit boards and their packaging are shown in Figure 1. soldering technology, production method, reliability and Among the printed circuit boards, the three-dimensional case examples of the embedded component module integrated printed circuit board (hereafter referred to as board. “embedded component module board”) is attracting great attention. Integrating components into embedded component module boards Component embedding enables passive components (1) Embedding active components to be positioned directly beneath the LSI mounted There are two methods of embedding active on the surface providing electrical benefits such as components. One is to embed the components in bear Packaging Micro packages trends Fine pitch BGA packages High density Bare chips surface packages W-CSP packages Function modules Flip-chip Embedded passive AD/ CR CR packages components CPU DAC CR CR e-Function modules CR CR ASIC RAM Embedded XTAL Flex-rigid boards ISB boards components MID Automotive modules Buildup boards (3D Molded Interconnect Circuit-board Devices) RF modules trends Analog mixed SiP ZigBee Modules Hiper VIA boards Embedded component module board AD/ CPU DAC Image sensor modules ASIC RAM Digital SiP ASIC ASIC CPU Flash ASIC CPU SD CPU ASIC CPU SiP Trends RAM SiP (CoC) PoP SiP SiP (flat) (Silicon chip stack) (Package stack) (Si through chip contact) 3-dimentional LSI 2003 2004 2005 2006 2007 2010 Figure 1. Trends in Printed circuit Boards and Packaging Oki Technical Review April 200/Issue 26 Vol.77 No. R08fig01 Special Edition on Component Technologies Supporting Innovative Design chip form, and the other is to process components Component thickness is an obstacle when it comes into a package prior to embedding. Considering the achieving thinner devices. Manufacturers are working to stability of quality and yield, we have decided on the develop components that are both large capacity and low latter method utilizing W-CSP (Wafer-Level Chip Size profile. Currently it is possible to manufacture 1005-sized Package). Inspection guarantees the quality of W-CSP, components comparable in thickness with 0603-sized and achieving KGD (Known Good Die) will not be an components. issue. Soldering technology for embedded (2) Embedding passive components Passive components (C, R, L) can be embedded component module boards either by building them in during the manufacturing In order to simultaneously mount W-CSP and chip process of the board or embedding commercially available components, reflow soldering using lead-free solder was chip components. Guaranteeing the properties with the employed. The benefits of this soldering method are given former method is difficult. Additionally, required properties below. cannot be obtained due to manufacturing constraints. It is an extension of an existing process and does not For example, a required capacitance can be achieved by require a new facility. expanding the area of the layered stack or increasing the It can utilize exiting components. number of stacked layers, however that would stray from LSI and passive components can be mounted the purpose of miniaturizing and thinning. In comparison, simultaneously. the latter method ensures reliability using general-purpose Our component mounting technology was acquired components that have guaranteed properties and are with the cooperation of Nagano OKI. An integrated line available commercially. We have chosen to use the latter consisting of solder printing machine, mounter, reflow method. oven and inspection machine was built and a production (3) Sizes of embedded components Basic Processing of Embedded Component Module Board Sizes of components that can be embedded are 4-layer board example 0402, 0603 and 005. However, if 0402, 0603 and 005 Material are mixed in the same layer, internal board thickness will be the same as when 1005 is implemented. The cross- Exposure Etching sectional view of a embedded component module board Mid-layer with 0603 and 005-sized chips mixed in the same layer inspection is shown in Figure 2. Component Due to recent increase in product applications, 005- mounting sized components capable of handling capacitance greater than 1μF are increasingly being implemented. Clean Copper foil Prepreg Configure 0603 0603 1005 0603 Prepreg Copper foil 0603-sized 1005-sized 0603-sized resistor capacitor capacitor Laminate 0603 1005 To surface processing Figure 2. Mixing Chip Components with Different Sizes Figure 3. Embedded Component Module Board Manufacturing Oki Technical Review April 200/Issue 26 Vol.77 No. 2 R08fig02 R08fig03 system was established (line is capable of processing the same work size as circuit board manufacturing). Mounting Surface-mounted board (312 mounted chips) 24000 400000 density is at the same level as surface mounting. Strain Over-range 22000 380000 20000 Strain Resistance 360000 18000 Manufacturing embedded 16000 340000 ) 14000 320000 component module boards ) 12000 -6 300000 10000 (×10 Resistance ( The manufacturing process of embedded component 8000 280000 module boards (4-layer board example) is shown in Strain 6000 260000 4000 240000 Figure 3. Using a photographic method, copper circuits are 2000 220000 formed on both sides of a 2-layer board. After solder paste 0 -2000 200000 printing, reflow soldering is used to mount components, 2 4 6 8 10 Number of bends which is followed by flux residue cleaning. The mounted Embedded component board (312 mounted chips) board is sandwiched and laminated between the prepregs 24000 400000 Strain Over-range 22000 and copper foils then heat bonded. To avoid stress on the 380000 20000 Strain Resistance 360000 components during pressure bonding, the height of the 18000 components are taken into consideration when selecting 16000 340000 ) 14000 320000 ) the prepreg thickness. Thereafter, the surface processing -6 12000 300000 (×10 10000 is the same as the manufacturing process of a normal Resistance ( 8000 280000 Strain printed circuit board. 6000 260000 4000 We offer one-stop service including miniaturization 240000 2000 220000 suggestions, circuit board design, board fabrication, 0 -2000 200000 component assembly and product inspection based 2 4 6 8 10 12 14 16 18 20 on specification and other information provided by the Number of bends customer. Figure 4. Bending Reliability of Surface-Mounted and Embedded Component Boards Reliability of embedded component module boards Table 1. Reliability Test Results of Embedded (1) Comparing reliability of surface-mounted and Component Module Board embedded component boards Result of the temperature cycle test has revealed the Test Test Condition and Result Remarks Drop test Board dropped on its X, Y and Z-axis. No embedded W-CSP has more than twice the lifespan of a resistance change after 50 drops. surface-mounted board 1). The following describes the Repeated reflow After moisture absorption, reflow profile Cross-section R08fig04 test repeated 20 times. observed with result of the evaluation. No change in resistance. S A T , a n d n o Using an exclusive TEG (Test Element Group), a No blistering or peeling. problems found. T e m p e r a t u r e -65°C (30min) 25°C (30min) board with embedded W-CSP and chip component was cycle test No resistance change after 3,000 cycles. manufactured. The embedded W-CSP was 6mm square, HAST test 0°C, 85%RH, DC25V bias Passed 500 hour test 0.5mm pitch and had 2 terminals. The chip component Static electricity Discharged ten times for max. 8KV at 5s. N o p e e l i n g was a 0603-sized resistor. Temperature was cycled test Resistance and capacitance measured observed with -25°C/9min room temperature 125°C/9min for the IEC-6000-4-2 before and after were found to be within SAT normal values. evaluation. As a result, the time for the 50% failure rate to Vibration test 0 ~ 2000Hz applied for 20 cycles each occur from W-CSP breakdown was more than twice the JIS C 60068-2-6 in X, Y, Z directions. Resistance and (IEC60068-2-6) capacitance measured before and after surface-mounted board. were found to be within normal values. Next, a board with surface-mounted chip resistors and Repair tolerance After mounting BGA to the surface, N o p e e l i n g post-rework connection was verified. observed with another with embedded components were prepared. They Resistance and capacitance measured SAT before and after were found to be within were subjected to a push-bending test along 18% of their normal values. length. Number of 0603 chip resistors connected in series Bending test Amount of bending changed (5, 10, 20% Reference test of length) and breakage was observed. on each board was 312. Changes in resistance were Breakage occurred after 14 bends at 10%, observed and the result is shown in Figure 4. after 4 bends at 20%. Oki Technical Review 3 April 200/Issue 26 Vol.77 No.
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