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ISSI Bare Die for Multi-Chip-Module and Hybrid circuits:


Why Use Bare Die?

Designers of space-constrained systems face the challenge of determining how to incorporate expanding functional needs into reduced spaces in a timely and cost-effective manner. For many handheld, portable and other small form factor products, silicon packaging has become the major size-limiting element of their design layout. The conversion from standard semiconductor packaging to unpackaged die provides the system designer with an opportunity to make more efficient use of limited space.

At the same time, bare die implementation affords improved electrical performance, better signal integrity, and higher levels of integration with reduced weight and height.

For memory the benefits of higher speeds can be realized at die level due to the reduced path lengths and helps designers keep up with ever increasing processor clock and bus performances. A classic application for this is the graphics card where both speed and integration are vital.

We provide products that can be used in two forms of die assemblies: Standard bare die for wire bond applications and Bare Die bumped for bumped flip-chip applications. Both assembly formats offer size improvements over traditional packaged product outlines.

As shown in the figure (below), the implementation in die form of a standard 18M Synchronous SRAM can reduce space consumption by greater than 50%.

Product Type Density
ASYNCHRONOUS SRAM 64K, 256K,512K, 1M, 2M, 3M, 4M, 8M
SDRAM 16M, 64M, 128M, 256M
EEPROM 1K, 2K, 4K, 8K, 16K, 32K, 64K, 128K, 256K

Why use ISSI?

Memory is one of the most rapidly developing technologies in the semiconductor industry today and is driven by demands for lower power, higher density, faster speeds, and lower cost for volume programs. At the leading edge, the memory market today can be cut-throat with a volatile spot market which is driven solely by supply & demand.

So what impact does this have for engineers wishing to use memory in die form?

Unlike packaged components which can usually be replaced on a pcb relatively easily die products are often unique to the design. When building a Multi-Chip-Module or Hybrid circuit which uses memory die all designers should look for the following support from their supplier:  

Commitment to support devices longer

Memory is one of the most rapidly developing technologies in the semiconductor industry today and is driven by demands for lower power, higher density, faster speeds, and lower cost for volume programs. At the leading edge, the memory market today can be cut-throat with a volatile spot market which is driven solely by supply & demand.

So what impact does this have for engineers wishing to use memory in die form?

Availability of die - Key point, die are not pin-for-pin replaceable like some packaged components and are often unique to the circuit they are designed into.

Because the memory market moves so rapidly demand for the older generations of package parts can quickly diminish. Often the decision is made by the vendor to stop producing those particular products in their wafer fabs very quickly so the actually production life-span of particular wafers may be very short. This means that after production has been stopped anyone who still needs to support their die based programs is faced with a complete re-design to continue manufacturing their finished product!

Solution, unlike many other memory vendors ISSI is committed to supporting both legacy and new memory products in die & wafer form.

E.g. 16Mb EDO DRAM, this ceased production several years ago with most other manufacturers but is still available via ISSI.

Working with ISSI, We are also able to offer a wafer / die banking scheme so that even when the parts are finally going obsolete we can offer the customer a total solution to support their program.

Notification of die changes

Notification of die shrinkages - Key point - At die level, every die mask becomes unique even if their electrical performance is identical.

From a circuit design perspective using the correct mask is vital. The size of the die and the pad location are critical to the designer whether the die are being flip-chipped or wire bonded. Working with ISSI.We are able to support designers with the most current die mask to provide the most consistent solution for their program.

If the mask is going to change we are able to notify the customer and pass on the option of a last time buy or wafer/die banking to protect the circuit design.

Long term commitment to SRAM

Commitment to SRAM - ISSI is 100% committed and now offers one of the widest SRAM portfolios on the market when many other vendors are moving focus away from SRAM products.

Support is offered from densities as small as 64K through to 36M.

Product Reliability

ISSI's wafer and die products are produced in mature wafer fabs and undergo a high level of testing to ensure reliability. Coupled with our processing capabilities we are able to offer a high quality product at die level.

For information on standard process flows please see process flows.

Note It is also possible to discuss custom process flows to develop specific KGD flows relevant to the customers application.

Automotive Commitment

ISSI has been supporting the Automotive Market since 1999 and offer a dedicated range of Automotive specific SRAM, DRAM & EEPROM

Working in partnership with ISSI, We can now offer die and wafer support for the Automotive Industry.

One of the primary problems what automotive customers face is the commitment from a manufacturer for long-term product support. This is not an issue with ISSI and us. The business model is built around the ability to work with our customers to deliver products that meet their needs for long periods of time. This is particularly crucial with regards to using die products where all designs are influenced not just by general product lifespan but also by the lifespan of the particular die size and mask which fits the circuit footprint.

Design cycles in the Automotive Market can be 3-4 years from inception to production. Then production will run another 5-6 years. The need for post-production support exists for several more years. ISSI is committed to provide customers with long-term support necessary for the automotive production-planning phase and offers die/wafer banking programs to ensure production can continue seamlessly.  

Automotive Products

Possible temp ranges available are -40°C to +85°C, -40°C to +105°C, and -40°C to +125°C.

We can setup the right wafer process and die testing flows to meet the appropriate level of reliability or "Known Good Die" required for the application.

We offer a through consultancy to establish what is required in order to meet reliability and cost parameters. To help you meet your quality and cost objective need, we aim to establish the following:

What is the target system yield? From the number of devices in the system, what is an acceptable yield for the individual device? What is the required operating temperature range of the device? What are the required test limits for each significant device parameter?

Please contact us to discuss your requirements.

Quality Management System ISSI recently obtained the IS09001:2000 certification and is in the process of obtaining TS16949 certification.

All ISSI new product entries meet or exceed the requirements set forth in the AEC-Q100 qualification standards.

Process Flow

Wafer manufacture and testing

ISSI is able to offer die products with the high level of quality and reliability needed to give confidence to multi-chip module & hybrid builders.

Wafers go through 2 rigorous sorting processes to ensure a high degree of reliability. The second wafer sort is performed to a higher specification by increasing test temperature by an additional 10°C.

We can add additional wafer process steps per customer's requirement.

Wafer processing and die supply

All die and wafers supplied are processed by Micross who have over 25 years experience in processing silicon wafers.

All product forms supplied undergo 100% visual inspection before packing and are accompanied by a Certificate of Conformance guaranteeing that the die meet the specification ordered.

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