Ribbon bonding tool and process
An ultrasonic bond is formed using a bond tool foot having a waffle shape of thin protrusions and gaps between the protrusions. The tool is brought in contact with the ribbon to a depth to create depressions in a ribbon approximately 150 μm or less from the underlying bonding surface. The tool is then brought down further into the ribbon to contact the portions of the ribbon between the depressions, such as an additional 25 to 50 μm. The result is lightly bonded regions underneath the groove portions and highly bonded regions underneath the protrusions and around the perimeter of the bond. In another embodiment, an ultrasonic bond is formed along a partial width of a ribbon.
1. A flexible conductive ribbon material bonded to an underlying surface, the flexible conductive ribbon material comprising:
an upper surface of the flexible conductive ribbon material including a first portion, a second portion, and a third portion, the third portion being defined by a plurality of indentations extending below the second portion; and
a lower surface contacting the underlying surface,
wherein the flexible conductive ribbon material has a first thickness between the first portion of the upper surface and the lower surface, a second thickness between the second portion of the upper surface and the lower surface, and a third thickness between the third portion of the upper surface and the lower surface, the first thickness being greater than the second thickness, and the second thickness being greater than the third thickness,
wherein a first area of the flexible conductive ribbon material below the first portion is unbonded with respect to the underlying surface, a second area of the flexible conductive ribbon material approximately below the second portion is bonded to the underlying surface at a first strength, and a third area of the flexible conductive ribbon material approximately below the third portion is bonded to the underlying surface at a second strength, the second strength being greater than the first bond strength.
2. The flexible conductive ribbon material of claim 1 , further comprising a perimeter bonded area surrounding the second area and the third area, the perimeter bonded area having a third strength greater than the second strength.
3. The flexible conductive ribbon material of claim 1 , wherein the second area and the third area do not extend along a complete width of the flexible conductive ribbon material.
4. The flexible conductive ribbon material of claim 1 wherein a difference between the first thickness and the second thickness is between 25-50 μm.
5. The flexible conductive ribbon material of claim 3 , wherein a bonded portion of the ribbon including the second area and the third area is approximately circular shaped.
6. The flexible conductive ribbon material of claim 3 , wherein a bonded portion of the ribbon including the second area and the third area is approximately square shaped.
7. The flexible conductive ribbon material of claim 1 wherein the third thickness is approximately 100 μm or less.
8. The flexible conductive ribbon material of claim 1 wherein the plurality of indentations include tapered side wall portions formed using a bonding tool having tapered teeth.
9. The flexible conductive ribbon material of claim 1 wherein the plurality of indentations include substantially vertical side wall portions formed using a bonding tool having teeth with a uniform cross section along a length of each of the teeth.
10. The flexible conductive ribbon material of claim 1 wherein the flexible conductive ribbon material has a width greater than 2 mm.
11. The flexible conductive ribbon material of claim 1 wherein the flexible conductive ribbon material has a width of approximately 3 mm.
12. The flexible conductive ribbon material of claim 1 wherein the plurality of indentations have a depth of greater than 100 μm with respect to the second portion of the upper surface.