BARE CHIP ASSEMBLY

Market demands today require products to be smaller and lighter, less power consuming, more intelligent and user friendly and cost-effective. For the design engineer, this implies miniaturization and specialized assembly techniques such as chip-on-board (COB), TAB, flip-chip, multi-chip modules (MCM) and others. Indeed, these assembly technologies can bring very significant size and cost reductions to electronic modules and can make the difference between having a competitive, state-of-the-art product or just one from last year.

UNTHINKABLE BECOMES THINKABLE

Bare chip assembly, in fact, is at the core of many of today's advanced products, for example, mobile telephones and pagers, ultra-thin LCD displays, chip cards and intelligent sensors. All are unthinkable without these technologies.

Bare Chip Basics

In bare chip assembly, the silicon IC chip is attached directly to the substrate (e.g., PCB, flex, etc.) in unhoused form. The most common method is COB. The IC is first glued face-up on the substrate, after which thin micron-sized wires are soldered to the chip pads and the corresponding substrate contacts to provide the electrical interconnects. An encapsulating resin is then applied over the ensemble to provide stability against thermal and mechanical stresses as well as to protect the assembly.

In flip-chip assembly, the chip to substrate interconnections are made directly through soldering bumps mounted on the chip pads. The chip is flipped over and the bumps aligned over a corresponding metal pad pattern on the substrate. It is then pressed down and soldered in place. The soldering operation may be performed in a number of ways depending on requirements. Finally, an underfill resin is allowed to flow under the chip to provide mechanical and thermal stability.

With TAB, the chip is mounted in a similar way, but onto thin polyimide film on which corresponding metal leads have been etched. This package is then connected to the substrate via the outer film leads.

These methods can provide savings of 5 to 25 times in volume over the traditional DIL package.

OTHER ADVANTAGES

As well, bare chip assembly can be advantageous in other ways:

  • Decreased materials requirements, e.g., smaller PCB and thus smaller module housing, which can lead to overall cost reduction.
  • Improved electrical performance due to shorter interconnects.
  • Cost-effective alternative to ASIC creation especially for small/medium volume production. Bare chip assembly may also be used in conjunction with ASIC's.

To apply bare chip technologies requires specific know-how, experience and a substantial material investment. At CFG, we specialize in miniaturization techniques and it is our goal to help product designers and manufacturers access and apply these advanced technologies to new and wide-ranging applications. Indeed, we have done this already for well over 200 different products from automobile and helicopter electronics to medical instrumentation to mobile communication devices to chip cards, RF/ID tags and more.

Some of the specific modules which CFG has designed and manufactured include:

  • Complete LCD module with less than 2 mm overall thickness for use in cellular telephones - made possible through chip-on-flex technology.
  • Complete control electronics for a pager consisting of 7 IC chips mounted chip-on-board along with SMD passive components, all on a 2.5 x 6.5 cm² PCB.
  • 4Mbit memory chip card made possible through COB and TAB technology.
  • Tactile alarm watch for the auditorily-impaired, comprised of clockwork, RF receiver, low power-consumption micro-controller, micro-motor vibrator and batteries, all in one wrist-watch housing.

Assembly Services

At CFG, we will take your project in hand, advise you as to the best strategy and the most cost-effective technologies to use. We will develop the necessary electronics and mechanics, if needed, and procure the required materials. We then test the manufacturing processes for the product, qualify them, and produce prototypes for testing and approval before entering into full scale production.

True to our art, we constantly improve our technologies and processes. All products are fully ISO 9001 quality assured. We select only the highest quality materials and we pre-age all products and fully test for defects before final shipment.

We think you’ll agree that we have the ability to help you find and implement a truly competitive solution to answer your manufacturing and market requirements.