1.      Embedded Component Boards: Makers Place Volume Orders

April 2006 Issue
Nikkei Electronics Asia

At InterNepcon Japan, the largest mounting technology exhibition in Asia, 
held January 18-20, 2006, high-density mounting technologies were in the 
spotlight again, including system-in-package (SiP), multi-layer thin 
boards and flexible boards.
One of the items that attracted the most attention was embedded component 
boards. While overseas manufacturers have been in the lead until now, 
major Japanese printed circuit board (PCB) manufacturers have finally 
announced plans to launch volume production in 2006.
?Serious? Prototypes
Hoping to demonstrate the maturity of their products, Japanese board 
manufacturers showed prototype boards with embedded components obviously 
designed with an eye toward the end product.
Dai Nippon Printing Co Ltd of Japan chose a fingerprint verification 
module (Fig 1a) for portable equipment, while CMK Corp of Japan exhibited 
a digital TV tuner module (Fig 2a) supporting one-segment reception. Both 
used boards with embedded components to slash the mounting footprint of 
modules for portable gear by 20 to 50%.
New Functionality
The main reason that major board manufacturers are ramping up for volume 
production of boards with embedded components is the rapid addition of new 
functionality to portable equipment. Until now module manufacturers have 
been able to shrink wiring pattern line width and spacing, and components, 
to handle the new functions.
The rising pixel counts in cameras and view functions for digital TV, 
however, along with other new functions, ?have caused the functionality of 
portable equipment to grow at a much faster speed than mounting density, 
making it impossible to squeeze any more components onto small module 
boards,? explained Kenji Sasaoka, assistant manager, Electronic Systems 
Laboratory, Research & Development Center, Dai Nippon Printing.
Beyond the Conventional
At last the time has come for boards with embedded components, now that 
mounting density must be raised beyond the level possible with 
conventional technology.
Board manufacturers like Dai Nippon Printing and CMK are working to reduce 
barriers to adopting the new technology, determined not to lose out on the 
opportunity. In particular, they stress the high post-assembly yield, as 
compared to conventional technologies.
The major reason that module and equipment manufacturers have been less 
than enthusiastic to adopt boards with embedded components is the poor 
downstream yield. If a defect is detected after placing a component into a 
board, both component and board would have to be scrapped.
Board manufacturers are innovating new structures and manufacturing 
methods to avoid this type of situation. The actual method of 
implementation varies with whether the component involved is a passive 
device like a resistor or capacitor, or an integrated circuit (IC).
Dai Nippon Printing will begin volume production of multi-layer boards 
capable of holding embedded passive components in April 2006. The boards 
will be able to use passive devices from the merchant market with assured 
characteristics, boosting the precision of the components after being 
embedded.
New Assembly Method
Dai Nippon Printing developed a new board assembly method to achieve this. 
 For an 8-layer board, for example, first a 2-layer board with wiring 
patterns is fabricated (Fig 1b). This w-layer board is then used as the 
base to mount merchant-market passive components on, using standard 
surface-mount technology (SMT). A 4-layer board with cutouts to sit around 
the passive components is then mounted on top, and the whole thing is 
topped off with another 2-layer wiring board like the one at the bottom of 
the stack. The firm?s board can embed components up to 1005 (1.0 x 0.5mm) 
size, the firm claims.
The Dai Nippon Printing board also has an advantage in that vias running 
through all layers can be placed anywhere. This not only significantly 
improves layout freedom, but also makes it possible to connect embedded 
components to patterns with the shortest possible lead length, which is 
expected to contribute to improvements in high-frequency response.  Dai 
Nippon Printing says it will handle component positioning, pattern design 
and operational testing for the products, assuring stable operation.
Embedded ICs
When ICs are embedded in the board, the key to boosting post-assembly 
yield is making sure that only good semiconductors are used. This is why 
CMK and others have decided to embed semiconductors using wafer-level 
packages (WLP), as shown in Fig 2b.
Good WLP can be selected in the same way as for standard packages, making 
it easier to ensure that only good semiconductors are embedded.
The firm plans to begin volume production of boards with embedded 
components, called embedded wafer-level packages (EWLP), by June 2006. A 
source at the firm commented, ?We have completed reliability evaluation 
and user certification. We can launch volume production and begin shipment 
to match customer product release.?
At InterNepcon, Oki Electric Industry Co Ltd of Japan also exhibited a 
board with embedded passive components and semiconductors in wafer-level 
chip-scale packages (CSP). Adapted into a ZigBee module, the module 
mounting footprint was half that of the standard design. The firm will 
begin shipping engineering samples to clients in April 2006. It is 
currently evaluating reliability, and volume production plans are pending.