Memory madness in the telecommunications industry
05/01/2000
Digital wireless content is everywhere. Cellular phones, internet applications, pagers and other personal communications devices are capable of receiving and storing a wide variety of message types, including e-mail, voice, fax and executable code. Digital handsets, which are selling at twice the rate of personal computers (PCs), will soon be equipped to handle just about everything a PC does today, yet on a smaller scale.
These new applications and the growth of portable communications integrated circuits (ICs) are driving the need for reliable and secure data storage in smaller, faster flash memory and SRAM semiconductors. You might say that the revolution in telecom is paying dividends in memory technology.
Hot Memory Market
Memory is growing quickly, as is the rest of the $149 billion semiconductor market. Where's the growth? According to the Semiconductor Industry Association (SIA), flash memory increased 83 percent to $4.6 billion in 1999, primarily driven by wireless communications. Direct random access memory (DRAM) grew by 48 percent, due to strong PC and server demand, to $20.7 billion. Also growing fast were digital signal processors, expanding 25.7 percent to $4.4 billion. Microprocessors grew 9.8 percent to $27.2 billion.
The market doesn't seem to be slowing down, either. The SIA forecasts 20 percent growth in 2000 and 2001. Leading the way are memory-heavy devices, such as cellular phone sales, which are projected to grow from 200+ million units in 1999 to over one billion by 2003 - a quintupling of the market. Devices connected to the Internet (PCs, information appliances and Internet-enabled cell phones) are a close second, forecasted to grow from 200 million units in 1999 to more than 700 million in 2003. Contributing to both trends is e-commerce - a market projected to expand from 1998 figures of $50 billion to $1.3 trillion in 2003.
Recent Developments
To keep up this pace, memory chips are undergoing a revolution in design, manufacturing and test. Here's a look at the latest developments:
New Standards: The industry trade group Joint Electronic Devices Engineering Council (JEDEC) has completed work on a standard packaging and pinout for multichip modules that includes both SRAM (for working memory) and flash memory (for program storage). The booming cellular phone market views this as good news because it can move from proprietary pinouts to standardized pinouts, which should translate into increased sales.
Single Memory Subsystem: Wireless systems will benefit from combining flash and SRAM on one chip because it promises to lower the expense and power needed to achieve high performance code execution. This pioneering technology is already in volume production for 2000 in two versions - as a stacked chip-scale package (CSP) or a stacked multichip package (MCP).
Flash-memory Cards: Designed for smart phones, digital cameras, PDAs and even wristwatches, flash-memory cards address the demanding memory needs of digital consumer products. Six compact flash card formats, each specifying a card that's smaller than a PCMCIA PC card storage-card, have been proposed.
Higher Speeds: Clock speeds are up for all memory chips, just to keep pace with the range and amount of wireless content they carry. Rambus recently announced plans to double the speed of its high-bandwidth memory technology to data transfer rates of 1.6 GHz, while (DDR) SDRAM is purported to offer a 3.2 Gbyte/s bandwidth, the same rate achieved by dual-channel direct RDRAM shipping in a RIMM module.
Redesigned Flash: Like other semiconductor technologies, flash-memory is undergoing a transformation. Flash-memory interfaces have been simplified, leading to shorter programming time and improved manufacturing throughput. Like other microchips, flash-memory now features a wider range of pin-count densities - from 8Mb to 32Mb - facilitating upgrade to more end-product features and capabilities.
Miniaturization
As digital wireless devices continue to shrink, so do the electronics inside. Of all the form factors available to help meet these size requirements, few can match the power of the chip-scale package when considering size, cost and manufacturability. In the case of one memory manufacturer, the flash packages shrank 80 percent with the CSP technology as compared to older packages.
Memory is also taking a well-worn path toward integration. The first integration phase in semiconductors was to process discrete digital functions onto one chip and group together analog functions. Now, digital and analog functions are being integrated on the same chip.
Since the cost for memory (e.g., DRAM, SRAM and Flash) is largely determined by the amount of silicon area that it takes to store a bit of information, the memory chip's future is clearly toward system-on-chip (SOC). Semiconductor process equipment is improving, allowing smaller device features to be drawn on the silicon wafer, resulting in a smaller, more cost-effective memory cell. The old rule still holds: more bits per silicon area provide for higher-density memories and a lower cost per bit.
Impact to Testing
As chips get smaller, the challenge to those of us who supply burn-in test sockets to the IC makers is formidable. CSPs are being adopted faster than any previous package, creating a lack of industry standardization. This presents a unique challenge to socket designers, as each package/application has a slightly different size.
How do we make reliable contact to a CSP package that has a 0.5mm pitch? 0.5mm is the thickness of your basic mechanical pencil lead. How do we transition from product development to high-volume manufacturing to meet the explosive demand for wireless products?
The most significant design issue for testing memory CSP is a reliable contact system with limited space. This, in turn, must meet customer requirements, such as automation, easy load/unload and minimized damage to the package. Global make-teams are also necessary to support worldwide customer burst capacity on short notice.
In today's semiconductor market, it seems that there is no longer a controlled product introduction, but rather a steep ramp and sharp decline with the total product life-cycles getting shorter and shorter. As a socket supplier, the ability to transition seamlessly from product development to high-volume manufacturing is a must. If you miss the initial ramp, you cannot make a return on your investment.
Fortunately, companies that are committed to the vision of a networked society are meeting these challenges and the chipscale burn-in test socket infrastructure is well on its way to being implemented throughout the world.
 |
ED CRAIG, sales and marketing manager, can be contacted at Texas Instruments Inc., 111 Forbes Boulevard, M/S 14-08, Mansfield, MA 02048; 508-236-5202; Fax: 508 236-5339; E-mail: [email protected].