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The Challenges of testing DDR2 chips

Thursday, July 28, 2005

Intel has been releasing more and more newer chipsets to support DDR2 Memory. The new generation memory, DDR2 DIMM, is already officially on the market, but mass adoption are still at a snail pace.However, this new DDR2 memory has stirred up a lot of questions about how to test it effectively and at the lowest cost at the chip level.

Most memory module manufacturer receives the DDR2 chip and assemble them straight into memory modules without verifying if the chips are conforming to the dram manufacturer specification. This is a risky effort since defective DDR2 chips are not easily reworkable as compared with TSOP chips.

One of the dilemmas of DDR2 BGA device is the wide variety of packaging size offer for each group of memory size such as the 256Mbit, 512Mbit and the 1Gbit devices. For example, Samsung makes a 256Mbit DDR BGA device in a 60 Ball (11x13mm size) while for the same memory size, Elpida offers the 256Mbit BGA device in an 84Ball (11x13mm size).

Why are there different ball matrix package offered by manufacturers (60 ball Vs 84 Ball) for a 256Mbit device?

The answer is simple, each company uses different semiconductor process and equipment to fabricate wafers and the final die-size is dependent on the wafer process technology. Secondly, the die sized is also dependent on the memory density of the device. For example in the figure above ,the 256 Mbit device are often found in a 60 Ball with a package size of 11x13mm . A 1 Gbit device will be larger usually offer in a 92 Ball with 11x21.7mm. 

Example of a Samsung 256Mbit with 11x13mm package

Since the early 90s, we have heard of semiconductor Buzzwords such as 0.13,.0.15, 0.18 micron and 90nm. The 90nm point represents a milestone in the size of circuits in LSI semiconductor manufacturing and fabrication. The industrial standard before was the 0.18 micrometer (180nm) process, and the next milestone is the 65nm process. Smaller sizes in fabrication lead to increased circuit 'real estate' and speed, through smaller processor gates. The narrower a gate is, the faster the gate can be switched from an "on" position to an "off" position, increasing the maximum clock speed of the chip.

The following are the different package size  and Ball Matrix offered for a common 256Mbit device developed by 0.13 micron and 90nm process.

  • Samsung 256Mbit 60 Ball Size : 11x13mm
  • Micron 256Mbit 60 Ball Size : 8x12mm
  • Elpida 256Mbit 84 Ball Size : 11x13mm
  • Infineon 256Mbit 60 Ball Size : 10x10.5mm
  • Hynix 256Mbit 60 Ball Size : 12x14mm

Types of Common BGA Ball FootPrint

Most DDR2 chip will be offer in the following Ball Matrix , the most common package for 256Mbit and 512mbit are offered in the 60 & 84 Ball, while the larger 1Gbit Density device usually comes in a 92 Ball package

In order to test DDR2 device cost effectively, an affordable memory chip tester must be capable of supporting the different type of device with a universal test adapter and socket to fit the different array of BGA package. CST have the solution for all the different packages.

CST, Inc. has been delivering the DDR2 memory module tester for over a year now, and have recently cooperated with major system manufacturers, module manufacturers as well as memory chip manufacturers to resolve production test issues for this new type of memory chip.

CST’s DDR2 chip testers offers an innovative universal Chip test socket practically eliminates the need for multiple socket and allows you to test all different size chips with basically two test socket. The Low cost mechanical socket "inserts" are used to accommodate the different sizes and shapes. At the present moment, there are about 29 different types of DDR2 chip offer by the major dram manufacturer, and CST have all the inserts and test sockets available to support all the DDR2 chips.

CST DDR2 solution for testing DDR2 Chips

Lets imagine you have a bunch of DDR2 chip samples  ,and you need to test the chips and verify that the chips density,frequency and latency accurately. Usually that can be achieve very easily by decoding the part numbers etched on the device. What if the DDR2 chips have no form of markings , it would be almost impossible to identify the chips without a tester.

1) Using a CST tester, first check and measure the "package size" and ball grid configuration. In the example - the chip test is a Samsung 32Mx16 - 512Mbit device offer in an 11x13mm package. 

2) Next step, select the correct CST ‘s INSERTs,  mount the inserts into the appropriate tests sockets provided on the Chip adapter.

- In this example , a "11x13mm" inserts will be use with 84 Ball BGA  test socket. All socket and inserts are available from CST.

- Power Up the chip tester , Load chips by pushing down on the Inserts to open the test sockets.

 3) Use a handheld Vaccum device to pick up the BGA chips ( See illustration)

 4) Insert the DDR2 chip carefully ensuring the orientation of the chips are lined up in the test socket-Once Chips are in placed, - release the inserts and allow the test socket mechanism to latch the chip firmly in the test socket.

5) Select the Tester 's "Auto" identification feature to detect the chip configuration,frequency,latency....etc .

- View sample of the Sp3000 tester software detecting the chip configuration.

- After verifying the chip configuration , you are ready to start testing the chips

( View sample Pass results from tester)

( 6) View sample Failed results from tester.

From the above examples , you will see how easy it is to use CST tester to test and sort chips

:-find the correct inserts and test sockets

- insert the chip into the Sp3000 tester ,

- press a push button and wait afew seconds

- Test result will indicate if chip have passed or failed

- Remove tester chips and insert new chips for testing

Other features of the CST Sp3000 tester

The “SP3000 DDR2 Chip Adapter” is built to work with the CST SP3000 base tester, which allows user to swap inter-changeable DDR2, DDR, SDRAM & DRAM test adapters. With a simple push-button the SP3000-DDR2-Chip tester quickly auto-identify and displays the memory size, clock frequency, and speed of the memory chip. Unlike DIMM shape chip converters that can give uncertain test result, the SP3000-DDR2 Chip Adapter test sockets are fully buffered and isolated for “no confuse” fault detection.

The new “SP3000 DDR2 Chip” tester provides added troubleshoot capability for the present and future DDR2 memories at affordable prices. It is targeted for the manufacturers, computer integrators, memory distributors, and service depots. It is indeed the fastest tester and the easiest to use in its class. An advanced PC software is available for interfacing to a PC. The SP3000-DDR2 Chip tester can also be interfaced to different chip handler for mass volume testing.  


Benefit of Testing DDR2 Chips with CST Memory Testers

  • Most affordable DDR2 chip tester in the industry
  • Support all major brands of DDR2 Chips ( Samsung,Micron,Infineon,Hynix, Nanya & Elpida)
  • Support all different packages and density of DDR2 chip on one test platform
  • Can test up to 4 device in a single test
  • Real-Time testing ( can detect functional failures before chips are assemble on DIMM PCB)
  • Fast test time - 4 device ==> 512Mbit in under 20 seconds
  • Easy to replace worned out sockets
  • Easy and simple to operate

The SP3000-DDR2 CHIP tester is available now and is priced at only U$6800. For more information you can log on www.simmtester.com for details. A copy of the chip tester specification can be downloaded from http://www.simmtester.com/page/products/sp3000/sp3brochure.asp


By: DocMemory
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