Tuesday, June 10, 2003
The next generation DDR memory modules like the DDR2 DIMM will all be running at higher frequency starting at 533Mhz and up to 1Ghz in operating frequency. The high operating frequencies render existing DDR chip packaging technology to naturally migrate from the conventional TSOP chip packaging to micro-BGA package in order to attain its performance characteristics, which in return manifest a new set of testing and handling problems for memory module manufacturers.
Figure 1 shows- DDR-1SODIMM build with BGA chips
One of the main downside of using micro-BGA versus TSOP package is the high cost of packaging which adds to the higher cost on the DDR2- DIMM module. Secondly the BGA chips assemble on the DIMM module requires extremely delicate handling during mass production testing, any shock, dropping or hard impact on the BGA chips may caused the package surface to be crack, scratch or cosmetic damages to the body of the chip.
The only method to safely handle BGA assemble modules with extreme care are by far using expensive " Pick and Place" automated handler system which can cost from $100K to a million dollars. A "Pick and Place" system basically uses a Robotic arm to load and unload module into each test site and eventually move the tested modules into anti-static trays for final packaging.
Figure 2 shows a typical 'Pick and Place" Handler system
With the current slow economy and a tight squeezed for profit margin in this competitive memory module sector medium to large sized OEM manufacturers can no longer afford to spend million of dollars to upgrade their handlers and all are in need for a fast ROI on any new equipment investment.
CST have recognized there is an urgent need immediately for an affordable low cost and reliable memory module handler that will handle the next generation high frequency DDR memory module, without using any "Pick and Place" concept.
CST conducted a survey with several major OEM memory module manufacturers in the United States and several key manufacturing managers were asked to list the importance of features on an alternative handler which does not used the Pick and Place concept:
- Scratch-Free, and no mechanical stress on the module under test are the highest concerns on their list.
- Module should not fall into each other in the sorting bin after testing
- Module should not be dragged on any surface during transfer from point to point.
- Handler must have minimal adjustment features and must be easy to operate.
- Change over from one type of module to another should be simple and straight forward
- Manufacturers also want the fastest handler for efficiency when compared with the Pick and Place handler
RESEARCHING AND TESTING OF A NEW IDEA
In order to offer an alternative to the "Pick and Place" handling concept, CST engineers studied various Pick and Place system and found one thing in common, the DIMM module insertion into the test socket were pretty much similar to CST RoboFlex-1 solution , with the exception of tested module being neatly stacked into anti-static tray after testing. CST also found out that not many companies stack module into plastic trays after testing - final packaging methods differs from company to company - therefore redesigning the sorting after testing is alot easier.
In order to prevent inflicting module from possible mechanical stress and scratches after testing CST engineers had to discard the conveyor belt concept completely and came up with the following idea :
- Soft-landing platform under the Pusher system to buffer module from dropping after testing.
- Pneumatic control Scratched-Free "Transfer carrier" to piggyback DIMM module to stacking system
Figure 3 shows the DIMM resting on Roboflex-2 Beltless Transfer Carrier System , right under the carrier is the "Soft-landing mechanism"
- Introduce a Stacking assembly to re-stacked tested module into vertical trays.
Figure 4 shows the Roboflex-2 Stacking system ( Modules are stacked upwards- by a special Elevator Platform)
Finally the conclusion was that CST do have a winning concept which will satisfy all the "Pick and Place" condition and yet provide a "scratched-free transfer system" and "output stacking system". The new handling concept can also out perform any "Pick and Place System" as an alternative. With the above improvement the handler would provide all the features found in a expensive Pick and Place system at a fraction of a cost.
INTRODUCING the ROBOFLEX-II AUTOMATIC DIMM HANDLER
The RoboFlex-II Handler has a vertical input tray hosting the modules to be tested. The modules are then dropped one by one onto holding rails. A pusher-system grabbed hold of the memory module by the notches on its two sides and slides the module horizontally into the test socket.
Figure 5 shows the untested DIMM on the left vertical trays and finished tested DIMM on the right stacker
The test socket is an integral part of the memory module tester that mounts on the back of the handler. At the completion of the test, the module is pulled back out of the socket and soft-landing platform buffer the module into a Carrier system. The "good" modules are then transported to the right hand side for re-stacking into a vertical tray. For the "bad" modules, a trapped-door activates and channels the bad module through the left-hand side of the handler into collecting bins.
UPGRADES AND OPTIONS
Since users want minimum setup time when changing from one size module to the other, the new RoboFlex-2 handler is built with tolerance and flexibility and will fit all Roboflex-1 Pusher system. The only difference between the RoboFlex-1 and RoboFlex-2 base is the output stacker offered as a standard option on the RoboFlex-2 base handler.
The standard output stacker will support all 184pin/168pin single side and double-sided modules without any adjustment. It can also work with any module height from 0.8 inches to 1.75 inches.
Figure 6 shows the RoboFlex-2 base Handler with standard 184pin output stacker
If user need to change for 144pin / 200pin SODIMM , a simple fixture at the Output stacker location will have to be swopped in order for the RoboFlex-II handler to stack SODIMM memory.Changing the setup to test the smaller SODIMM modules are made easy through the easily swap "pusher module". The "pusher module" includes the input tray, the sliding rail, and the singulator all preset to the small size module. The entire change over can be done in less than a minute
Figure 7 shows a completely assemble RoboFlex-2
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