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JPCA Show 2000 Japan is keeping the pace
August 2, 2000 |Estimated reading time: 5 minutes
JPCA Show 2000: Japan is keeping the pace
Japanese electronic equipment manufacturers are directing their innovations toward Build-Up PCBs and chip carriers. As for testing, currently a bridge is being built between optical inspection and electrical testing. In the field of advanced imaging, we note the announcement of a positive dry film for LDI.
The Japanese PCB industry is keeping pace in the field of HDI PCB manufacturing, and, in particular, Build-Up PCBs and chip carriers. Miniaturization is, more than ever, the industrys byword. In Europe and North America, the lightest cellular phones weigh just 70 to 100 grams. In Japan, everybody in the street (teenagers, in particular) uses even lighter cellular phones. They must be light, because almost every person uses a special strap to carry the phone--which is, most of the time, heavier than the phone itself !
The trend is the same with micro-computersPCs that can fit easily in your pocket, with special features such as CCD cameras. On display for the first time, roadmaps referring to direct chip attached (bare chip) were shown with short-term application, as is the case for the Panasonic (see below), announcing up to 3000-pin-count per bare chip, for the years 20022004. The result will be even higher densities on boards. In addition, Panasonic presented the roadmap for its ALIVH build-up technology (Any Layer Inner Via Hole).
With ALIVH-B and ALIVH Ver.4, L/S of 50/50 µm are becoming common in Japan (ALIVH Ver.2 enabled 60/90 µm, and ALIVH ver.3 enabled 60/70 µm L/S).
When talking about imaging or patterning, resolution (and L/S) is an important point. Another very important factor is layer-to-layer accuracy. Intel requested 20 µm for this parameter during a presentation in the conference portion of the show. Shinko has tried to target this spec, using conventional equipment: yields were less than 20%.
Electrical test: improvements but no revolution, TDR, TDR, TDR . . . and a bridge under construction between inspection and electrical test
In the world where automation has actual meaning, nothing brand new was observed in the field of pure electrical testing during the show. The first thing that caught ones attention was that TDR Flying Probes were everywhere, under the pressure of the Japan Build-Up PCB industry (cell phones, RAMBUS, and other RF using nomad applications). This is something we may see soon in Western countries. The second observation that can be made is the real progression of AOI and, more generally speaking, inspection technologies aiming at competing with actually complementing conventional electrical test equipment for cheaper testing. Whatever the solution (more inspection and/or non-contact electrical test), it seems that electrical testing is on the move from parametric test (actual resistance measurement) to non-parametric test (go/no-go test), obviously because of significant limitations (mainly economical) of conventional electrical test technologies when testing HDI PCBs. I do not mean that the future belongs to non-parametric electrical testing. But, because of an increasing range of requirements (continuity test, isolation test, embedded passives (R, C, and sometimes L) test, Z0 (TDR), and, very soon, cross-talk test), its very difficult to imagine that a single piece of equipment will perform the whole range of tests. Therefore, there will be on one side the good old horses for performing rather conventional electrical tests (continuity and isolation) for mainstream applications, and more and more niche markets for specific test requirements. If only one thing drastically new popped up in this JPCA show in the field of Electrical and Inspection, it would be (for me) OHTs new Flash Shock: a new link between Inspection and Electrical Test. OHT (known for its Flash Probe 50% non-contact technology) has indeed introduced a universal sensor, a mesh, requiring no specific fixture for the top side of chip carriers. It still requires a fixture or spring-loaded probes for the bottom side, which can be reused because the bottom side pitch of chip carriers, typically an array, is rather standard (1.5 mm, 1.0 mm, 0.8 mm, etc.). As with the Flash Probe method, an AC signal is injected by the probe on the bottom side of the chip carrier. Then the top side sensor, a mesh, gathers the signal and converts it into an image, which is displayed on a screen and also software processed:
Mouse-bites, dish-downs, opens and shorts appear to be detected by this method, which is not a true 100% electrical test method (non-parametric test), though the name given by OHT of ET+V obviously refers to such. Its actually an electromagnetic visual inspection. But the distance between 100% electrical test and inspection is not very far anymore. OHT claims resolution is 5 µm, and claimed throughput is about 333 nets/second (roughly 1000 TP/s based on 3 TP per net on average). The sensor has auto-alignment capability.
Advanced imaging: a revolution, maybe?
The most important outcome fromof this JPCA show in the field of advanced imaging may be summarized as follows:
- Just right a breakthrough in Laser Direct Imaging Technologies, with the announcement of a new positive dry film by the Japanese firm Kansai Paint, for UV-LDI.
- The announcement of a High Power Solid State laser for Dainippon Screens LDI (532 nm)
- The progression of step and repeat projection lithography systems, for testing high volume, high end production
Once again, if only one thing had to be highlighted, I would mention the announcement of the new Kansai Paint Positive dry film for UV-LDI: Kansai Paint has announced the availability, within 6six months, of a new positive dry film and a liquid resist dedicated to UV (356 nm) - LDI. The main expectedanticipated characteristics of the dry film are :
- Positive type (so far, most of the dry films for UV-LDI are negative type): this characteristic, according to Kansai Paint, will allow users to peel the protective Mylar before exposure (the film is not sensitive to oxygen), reducing diffraction due to the cover sheet on conventional negative dry films, and therefore allowing higher resolution (typically 25/25 µm instead of 40/40 µm).
- L/S min: 25/25 µm
- Thickness: 10 µm
- Sensitivity:
2 to 3 mJ/cm2. Another very interesting feature: while conventional negative
dry film does have a sensitivity of 9 to -10 mJ/cm2, the Kansai Paint positive
dry film will allow users to increase throughput , considering the point
that throughput is limited by three main factors:
- Laser Useful Power available (typically 4 W for Coherent lasers)
- Data rate
- Resist or dry film sensitivity (a lower sensitivity will require less power from laser or less exposure time per pixel, whichat will speed up the imaging process, at a givening resolution).
Conclusion Along with other breakthroughs, such as the new 3 µm copper RCC (direct CO2 laser drilling compatible), this show has confirmed the very fast progression of the PCB processes, in the field of high-densities PCBs, in particular for nomad applications and chip carriers.
Its not by chance that 75% of the chip carrier orders are produced in Japan. The good point is that one starts to see the real facts of progress in Europe and in North America, showing that absolute leadership of Japan in the field of HDI PCBs should not last forever. Christophe VAUCHER, T4 Bare Board Test Work Group and Advanced Imaging & Patterning Reference Group ChairmanChristophe.Vaucher@bare-board-test.com