Stacked electrical resistor pad for optical fiber attachment
View Patent ↗An electrical resistor structure overlies a substrate and comprises a composite resistor having a first resistor of relatively low resistance and a second resistor of relatively high resistance overlying the first resistor. First and second electrodes make contact with the composite resistor at spaced locations, and a bond pad overlies the second resistor at a position between the electrodes. A metallized fiber is soldered a to a metal bond pad by providing a stacked resistor structure beneath the bond pad, disposing a solder preform over the bond pad, disposing the metallized fiber over the bond pad, and flowing a current through the stacked resistor structure. The stacked resistor structure, when subjected to a current flowing generally along a first axis, is characterized by a temperature profile that has first and second peaks on either side of the bond pad. The fiber is disposed along a second axis in the region of the bond pad where the second axis is at a non-zero angle (possibly, but not necessarily a right angle) with respect to the first axis.
1. A method of soldering a metallized fiber to a metal bond pad, the method comprising:
providing a stacked resistor structure having first and second layers beneath the bond pad with the first layer lying directly beneath the bond pad having a higher relative resistance than the second layer, the stacked resistor structure, when subjected to a current flowing generally along a first axis, being characterized by a temperature profile that has first and second peaks on either side of the bond pad where the first and second peaks are disposed relatively closer to the bond pad than to a source of the current;
disposing a solder perform over the bond pad;
disposing the metallized fiber over the bond pad with the fiber extending along a second axis in the region of the bond pad, the second axis being as a non-zero angle with respect to the first axis; and
flowing a current through the stacked resistor structure.
2. The method of claim 1 wherein the first and second axes are approximately 90.degree. from each other.
3. The method of claim 1 wherein the stacked resistor structure comprises:
a composite resistor comprising first and second resistors, each having nominally upper and lower surfaces, wherein
the first resistor's lower surface faces a substrate,
the second resistor's lower surface faces at least a portion of the first resistor's upper surface, and
the first and second resistors have respective first and second resistance values with the second resistance value being higher than the first resistance value; and
first and second electrodes contacting the composite resistor at spaced first and second locations;
the metal bond pad being bonded to the second resistor's upper surface at a location between the first and second electrodes.
4. The method of claim 1 wherein the current is applied in a pulse for a duration on the order of 0.5-5 seconds.
5. The method of claim 1 wherein the non-zero angle is a right angle.