WIRE BONDING METHOD FOR FLEXIBLE SUBSTRATES
A wire bonded electrical interconnection includes a first electrical contact, a second electrical contact, and a bond wire having a first end bonded to the first electrical contact, a second end bonded to the second electrical contact, and a central portion connecting the first and second ends. The central portion includes notches formed during a wire bonding process, with each notch having at least two corners.
1 . A wire bonded electrical interconnection comprising:
a first electrical contact;
a second electrical contact; and
a bond wire having a first portion bonded to the first electrical contact, a second portion bonded to the second electrical contact, and a third portion connecting the first and second portions, wherein a plurality of notches are formed by the third portion of the bond wire, each of the plurality of notches being defined by at least two corners
2 . The wire bonded electrical interconnection of claim 1 , wherein each notch has a generally rectangular shape.
3 . The wire bonded electrical interconnection of claim 1 , wherein the first and second electrical contacts and the bond wire are covered by an elastomeric material.
4 . The wire bonded electrical interconnection of claim 1 , wherein an angle of each corner is about 90 degrees.
5 . The wire bonded electrical interconnection of claim 1 , wherein the second portion of the wire is bonded to the second contact by a stitch bond with a security bond.
6 . The wire bonded electrical interconnection of claim 1 , wherein at least one of the first and second electrical contacts is formed on a flexible substrate.
7 . A method of making an electrical interconnection between a first electrical contact and a second electrical contact, the method comprising:
passing a bond wire through a wire bonding system;
identifying a first portion of the bond wire to be bonded to the first electrical contact, a second portion of the bond wire to be bonded to the second electrical contact, and a third portion of the bond wire connecting the first and second portions;
forming a plurality of notches with the third portion of the bond wire using a wire shaping tool to form corners defining the notches, each notch being defined by at least two corners;
bonding the first portion of the bond wire to the first electrical contact; and
bonding the second portion of the bond wire to the second electrical contact.
8 . The method of claim 7 , wherein the wire bonding system includes a capillary through which the wire bond passes, and wherein the step of forming the notches occurs before the wire bond passes through the capillary
9 . The method of claim 7 , wherein the wire bonding system includes a capillary through which the wire bond passes, and wherein the step of forming the notches occurs after the wire bond passes through the capillary.
10 . The method of claim 7 , wherein each of the plurality of notches is formed to have a generally rectangular shape.
11 . The method of claim 7 , wherein the corners are formed to have angles of about 90 degrees.
12 . The method of claim 7 , wherein the bonding of the first portion of the bond wire to the first electrical contact includes forming a ball bond.
13 . The method of claim 7 , wherein the bonding of the second portion of the bond wire to the second electrical contact includes forming a security bond over a stitch bond.
14 . A wire bonding system comprising:
a bond wire feed supplying a bond wire;
a capillary that receives the bond wire for application to a bonding site; and
a wire shaping tool disposed between the bond wire feed and the bonding site and configured to form notches within a portion of the bond wire by forming corners in the portion of the bond wire, each notch being defined by at least two corners.
15 . The system of claim 14 , wherein the wire shaping tool includes a first die and a second die, the first and second dies being spaced apart from each other along a feed direction of the bond wire and being disposed on opposing sides of the bond wire.
16 . The system of claim 15 , wherein at least one of the first and second dies is in the form of a plate having an edge facing the bond wire and an opening formed in the edge facing the bond wire.
17 . The system of claim 15 , wherein the wire shaping tool further includes a third die spaced apart from the first and second dies along the feed direction of the bond wire and disposed on an opposing side of the bond wire from the second die.
18 . The system of claim 14 , wherein the wire shaping tool is disposed between the bond wire feed and the capillary.
19 . The system of claim 14 , wherein the wire shaping tool is disposed between the capillary and the bonding site.