SCALABLE INTERCONNECT TECHNOLOGY THAT ENABLES HIGH DENSITY, HIGH PERFORMANCE AND LOW PROFILE CONNECTIVITY FOR BOARD TO BOARD, PACKAGE TO BOARD AND BOARD TO FLEX APPLICATIONS

摘要

As chip scale packages migrate to finer pitch, high density interconnect substrate technology co-evolves to provide the higher interconnect needs. But the load board, with its large area, thick substrate and many layers cannot keep up. While integrating a few high density interconnect layers on top of a conventional load board to do the geometry transformation is being done, it is very expensive in direct cost and in yielded cost. An alternative solution is to adopt the approach for testing a single die or whole wafer: add a space transformer from the fine pitch pads of the device to the coarse pitch pads of the circuit board. After all, needle probe cards have been doing this for many years. Other technologies have evolved for wafer probing that use a ceramic substrate as the space transformer. In many probe cards, for example, MEMs compliant tips are fabricated on the top of the ceramic substrate on pitches as fine as 2 mils [4]. The pads on the bottom of the ceramic substrate interface to the load board with another compliant one to one interposer but on pitches of 50 to 100 mils [4]. This same approach can be implemented for final test of packaged devices. A daughter board acts as the space transformer from the finer pads pitch of the CSP to the coarser pad pitch of the load board. A fine pitch socket technology is used on the top surface and a board to board interposer is used between the daughter card and the conventional load board. Highlighted in this article is such a board-to-board interposer from HCD Inc. High Connection Density's interconnect technology enables high speed, high current & low profile connectivity reducing the cost of test for board to board, package to board and flex to board connections and in today's world of increasing pin count and high performance applications, it is the technology of choice with excellent electrical performance and reliable contact.