BACKGROUND 0001 The present invention relates generally to electronic test instruments and more particularly to a test probe assembly for electrically connecting a ball grid array surface mount package to an electronic measurement device. 0002 Ball grid array (BGA) has become the package of choice in the surface mount technology arena. BGA's offer many advantages over standard fine-pitch surface mount and pin grid array technologies. These advantages include reduced placement problems since BGAs are self-centering, reduced handling issues because there are no leads to damage, lower profile and higher interconnect density. There is, however, a significant drawback with BGA technology: the lack of established BGA test accessories and procedures. 0003 Electronic test instruments (e.g., oscilloscope, logic analyzer, emulator) are used to analyze various electrical aspects of the IC including voltage and current waveforms. Typically, a loaded printed circuit board is crowded with various electrical components, including multiple IC packages. Due to the close spacing of components on the board (i.e., high board density) it is often difficult to electrically connect the ICs to the test instrument. BGAs tend to exacerbate this problem since there are no leads to access for testing purposes. 0004 As processor packages become more dense due to electrical requirements, it has become increasingly difficult to probe these packages. With pin counts in the 600-700 range, and pin to pin spacing now at 0.050 inches or less, it has become necessary for motherboard sockets to go to BGA style packages vs. the former pin grid array (PGA) packages. This trend has increased the difficulty in reliably dividing and attenuating signals within the interstitial array of pins. 0005 Also, increasing pin counts and pin densities increases the insertion force required to insert the processor into a conventional low insertion force socket. Typically, the collective insertion force required to insert a 603 pin processor is approximately 55-60 lbs. of force.

SUMMARY 0006 The present invention provides a BGA-PGA-Flex probing system. Advantageously, the invention allows use of a user's pre-existing BGA socket while continuing to use a method of egressing signals from a PGA using flexible circuit material. The invention also allows replacement of a Low-Insertion Force (LIF) socket with an adaptation of a user's BGA Zero-Insertion Force (ZIF) socket. 0007 Accordingly, a user can easily insert a processor package into a probe according to the invention without damage to the silicon. The BGA-PGA-Flex probing system of the invention offers an electrically and mechanically superior interface to existing interposing probes for high-density processor packages. Advantageously, the current invention allows a user to utilize existing ZIF sockets. Implementation of a user's socket into the probing system of the invention makes processor bus simulations easier due to fact that a user will already have simulated the socket by itself. The invention also offers the advantage of a ZIF socket versus a LIF socket. 0008 In a preferred embodiment, the present invention comprises an unsealed BGA socket, nail head pins which can be inserted flush into a pin carrier to produce a PGA header, a Flex circuit assembly comprising a piece of flexible circuit with various passive resistors and connectors attached and solder preforms used to solder the flex assembly to the pin grid array.

DESCRIPTION OF THE DRAWINGS 0009 FIG. 1 is an exploded partial side view of a BGA-PGA-Flex probe in accordance with the invention. 0010 FIG. 2 is a partial view of a BGA-PGA-Flex probe in accordance with the invention.

DETAILED DESCRIPTION 0011 FIG. 1 shows an exploded partial side view of of a BGA-PGA-Flex probe in accordance with the invention. Generally, the probe is interposed between an integrated circuit device and a printed circuit board. The probe assembly allows a user to access signals from the processor. 0012 Referring now to FIG. 1, an exploded partial side view of a preferred embodiment of a BGA-PGA-Flex probe is shown. A microprocessor 101 that plugs into the top of the probe 100. The probe 100 comprises a BGA socket 102, a PGA header 103, a flexible circuit assembly 104, a matched impedance connector 105 soldered to the flexible circuit 104 and a motherboard ZIF socket 106 that is suited to plug into a motherboard (not shown). 0013 The BGA socket 102 is a ZIF socket allowing a user to easily insert the processor 101 into the probe 100 without damaging the processor's 101 silicon. The PGA header 103 comprises a plurality of nail head pins 107 inserted flush into a pin carrier 108. Preferably, the plurality of nail head pins 107 comprise brass nails with gold over nickel plating. The gold over nickel plating is preferably 0.000010 inches gold over 0.000050 inches nickel. The flexible circuit assembly 104 comprises a flexible circuit 109 with a variety of passive resistors and connectors attached (not shown). 0014 Referring now to FIG. 2, a partial side view of a BGA-PGA-Flex probe is shown. The probe 200 comprises a BGA socket 202, a PGA header 203, a flexible circuit assembly 204, a matched impedance connector (not shown) soldered to the flex circuit 204 and a probe assembly plug (not shown). This is the same probe 200 as the probe 100 shown in FIG. 1 from a different angle. 0015 Also shown in FIG. 2 are a plurality of socket plugs 210 in the top of the BGA socket 202, a plurality of BGA solder balls 211 attached to the plurality of nail head pins 207, an SMT resistor 212 and a plurality of solder preforms 213 which have been soldered to one side of the flexible circuit assembly 204. Not shown in FIG. 2 are the processor and the matched impedance connector soldered to the flexible circuit. 0016 A processor (not shown) plugs into the top of the BGA socket 202. The BGA socket 202 is soldered to the PGA header 203 utilizing a soldering method called reflow. The plurality of nail head pins 207 extend through the pin carrier 208 to produce the PGA header 203. Preferably, the pin carrier 208 is an FR4 pin carrier. The flexible circuit assembly 204 is inserted over the plurality of nail head pins 207 and soldered thereto using solder preforms placed over each nail head pin 207. The flexible circuit is soldered to the PGA pins to produce a resistive divider for the signals coming out of the processor. The solder preforms are preferably a 63-37 solder material, which has a reflow temperature of 183 C. 0017 The BGA socket 201 is preferably a ZIF socket allowing easy insertion of a processor (not shown) into the insertion holes 210 in the top of the socket 201. Also preferably, the plurality of nail head pins 207 are 0.012 inch diameter pins with 0.020 inch pin heads allowing proper reflow of the plurality of solder balls 211. The preferred composition of the plurality of nail head pins 207 is brass C3600, ASTM-B-16 with a 0.000010 inch gold over 0.000050 inch nickel plating. Also preferably, the flexible circuit 204 is a 0.017 inch thick multi-layer flexible circuit. Also preferably, the resistor 212 is a 0201 resistor. A person skilled in the art will appreciate that the material, size, thickness and other characteristics of the components can vary in accordance with the method of the invention to achieve proper reflow and soldering of components. 0018 In operation, referring still to FIG. 2, a processor (not shown in FIG. 2) is inserted into the BGA ZIF socket 202 on the interposing probe 200. The BGA socket 202 is actuated by depressing locking levers (not shown) which locks the processor into place. Matched impedance cables are attached to the matched impedance connectors (not shown in FIG. 2) which are soldered on the end of the flexible circuit assembly 204. The BGA-PGA-Flex probe 200 is inserted into the target system socket (not shown). The target system is preferably a motherboard ZIF socket. The target socket is actuated to lock the probe 200 into place. The probe 200 is connected to an electronic test instrument and the capturing of front side bus traces is enabled. The matched impedance connectors soldered to the flexible circuit enables connectivity of signals by matched impedance cables. 0019 The BGA-PGA-Flex probing system provided by the invention enables a more flexible and efficient method of probing a BGA socket. As component density increases on users' target systems; it becomes increasingly important to make interposing probes smaller and more flexible. 0020 While the method of the present invention has been illustrated and described in connection with the preferred embodiment, it is not to be limited to the particular structure shown.