re ic packages in article apr sol ctr columbia edu seema madvlsi columbia edu seema varma writes hi i am looking for some help in choosing a package for a high speed silicon adc mhz currently being fabricated this is a phd research project and i have to test the chip at speed on a pcb i expect to have roughly packaged circuits and will do dc low speed and high speed testing using different set ups for the test chip i know for sure that a dip will not work the long lead lines have too high an inductance getting a custom made package is too expensive so i am trying to choose between a flatpak and a leadless chip carrier the flatpack would be hard to test since it has to be soldered on to the test setup and i would spend loads of time soldering as i kept changing the test chip the leadless chip carrier sockets also have long lead lines and may not work at high speeds does anyone out there have experience knowledge of this field i would greatly appreciate help any ideas names of companies manufacturing holders sockets packages would help p s the multi layer fancy gaas packages seem like a bit of overkill seema varma you didn t mention whether or not cost is an issue where exactly are you running mhz the digital side ttl ecl we run mhz and mhz all over our ic test equipment all day long in the ecl domain and we use dip s along with plcc s mil and mil pitch pin qfp s to name a few i don t see a problem in packaging as long as you adhere to sound engineering practices a good source of information is motorola s mecl system design handbook the latest ed is dated that is considered to be one of the bibles in high speed design the very fact that you need to build a test fixture means you re most likely going to need a socket it in itself has far more inductance per pin than the package you are testing not to mention any impedance discontinuities i don t see the big concern over the packaging because it probably isn t going to make that much difference if you re trying to get ttl to run at mhz have fun ttl was never designed to run in a mhz environment aaron p s my opinions have nothing to do with my company the standard disclaimer applies
