The present invention relates generally to probe adapters for measurement probes and more particularly to a variable spacing probe tip adapter usable with very high frequency differential measurement probes.
Probe tip adapters are accessories developed for measurement probes to allow probing to various type of electrical components. The adapters allow connections to square pins mounted on a circuit board, ground points on the circuit board, leads of surface mounted integrated circuit devices, and the like. The P6246 Active Differential Measurement Probe 10, manufactured and sold by Tektronix, Inc., Beaverton, Oreg. and assignee of the instant invention, has a measurement probe head 12 and first and second socket type probe tips 14 and 16 as shown in FIG. 1. The socket tips 14 and 16 have an overall length of 0.255 inches and a diameter of 0.065 inches. The socket bores have a diameter of 0.038 inches and a length of 0.255 inches. Various types of probe tip adapters are inserted into the socket to allow various types of probing.
One type of probe tip adapter for the above described differential measurement probe 10 is a dual probing tip variable spacing adapter 18. The adapter 18 has first and second probing tips 18 and 20 that are formed from a wire having a diameter that allows rotational movement of the probing tips within the socket type probe tips 14 and 16 of the measurement probe head 12. The probing tips 18 and 20 have first and second straight portions 24 and 26 that are offset by respective lateral transition portions 28 and 30. The probing tips 18 and 20 are ganged together using a non-conductive spacer 32. The non-conductive spacer 32 has first and second bores formed therein that have the same pitch geometry or center to center spacing as the socket type probe tips 14 and 16 in the measurement probe head 12. The probing tips 20 and 22 are secured in the spacer 32 by either an outwardly extending rib formed on the first straight portion 24 that engages the bore of the spacer 32 or by a non-conductive retainer inserted on the first straight portion 24 and positioned to engage the probe side of the spacer 32. Either retaining means allow rotational movement of the probing tips within the bore. The probing tips are rotatable within the socket type probe tips 14 and 16 and the spacer 32 to allow the pitch geometry of the probing tips to be changed to match the pitch geometry of the leads on integrated circuit devices.
Probe tip capacitance and inductance are major drawback to using socket type probe tip or tips in measurement probes. Tip capacitance and inductance limits the input bandwidth of the probe. With the electronic industry continuing to develop integrated and hybrid circuits operating at higher and higher gigahertz frequencies, a new type of measurement probe design is required that has substantially reduced probe tip capacitance and inductance. This requires reducing the probe tip length and diameter. Likewise, probe tip adapters are required for these low capacitance probes that have reduced length and diameter.
What is needed is a probe tip adapter that is compatible with a low capacitance measurement probe having a reduced size probing tip. The adapter should be adaptable to various integrated circuit lead pitch geometries while minimizing as much as possible additional probe tip capacitance and inductance by reducing the length and diameter of the adapters.
Accordingly, the present invention is to a variable spacing probe tip adapter for a differential measurement probe having a measurement probe head with first and second probe tips extending from the probe head. Ribs and grooves formed in the probe head that extend radially from each of the probe tips. Each of first and second offset probing tips have an electrically conductive shaft that has a bore formed in one end for engaging the respective probe tips of the measurement probe. Each shaft has a surface normal to the bore with ribs and grooves formed therein that extend radially from the bore for engaging the corresponding grooves and ribs in the probe head. The other end of the conductive shaft tapers to a probing point with a portion of the shaft toward the tapered end of the shaft being angled to offset the probing tip. The conductive shafts are rotatable on measurement probe tips and locked into position by the engagement of the ribs and grooves in the probe head and the probing tips. The grooves and ribs formed around the respective conductive shaft bores and the probe tips of the measurement probe provide selected probing point separation. Preferably the probing point separation matches standard integrated circuit lead pitch geometries of 0.025 inches, 0.050 inches, and 010 inches. The variable spacing probe tip adapter may also include a probing tip holder having first and second bores formed therein for receiving the first and second probing tips.
The objects, advantages and novel features of the present invention are apparent from the following detailed description when read in conjunction with appended claims and attached drawings.