WILSON CHAN WEE HOCK (SG)
| US5229575A | 1993-07-20 | |||
| US4871899A | 1989-10-03 | |||
| US4412123A | 1983-10-25 | |||
| US3991297A | 1976-11-09 | |||
| US4942282A | 1990-07-17 | |||
| US1816115A | 1931-07-28 |
| Long Thermode assembly Claim: 1. A thermode assembly having heating strip of geometry, length, width, thickness and material defined by application as the heating element. 2. A thermode assembly according to claim 1 having a thermally stable rigid electrical insulator pressure pad that spans the entire length of the thermode; holds the heating element at both ends. 3. A thermode assembly having at least two thermocouple welded on the heating strip for temperature control and safety interlock requirements. 4. A thermode assembly according to claim 1 have a tensioning mount at both ends of the tension bar to keep the heating element in position. 5. A thermode assembly according to claim 1 have a air nozzle along the thermode length for cooling and maintain of the thermode. |
Conventional precision pulse heat thermode consists of a heating element usually in the form of a folded blade, support and mount structure in one piece, that is cut out from a material usually from a single block of metal for the purpose of bonding for example, fine pitch flex printed circuit to a glass substrate with similar connection points. The thin folded section forms the heating element part and the thick block section forms the support structure and the mount. This type of design serves the purpose well for medium to short bar applications, and for applications that do not require high precision levels. The draw back of this design is that warping comes into effect the longer the thermode is for the application, causing different bonding force along the length of the thermode as the thermode is press down onto the flex to the glass. This is due to the expansion characteristic and different expansion rates caused by vast differences in temperature within the thermode. This problem is inherent in the design and materials used for the thermode.
In precision bonding where planar integrity is in the region of a few microns. The long thermode assembly solves the problem by physically separating the heating element from the support structure, Since the expanding part which is the heating element does not stress the thermally stable support block which has a low expansion coefficient, there is no warping. The heating element expands on its own and does not affect the other structures.
Figure 1 shows the front view of the long thermode assembly Figure 2 shows the side view of the long thermode assembly.
The thermode assembly consist of the tension bar 10, heating element 2, thermally stable rigid electrical insulator pressure pad 3, tensioning mount 7, air nozzle 9, electrical power connection 6 and rigid bar 4 . The thermode assembly is mounted to the press head heat sink 5,6 where during operation the thermode assembly is moved down by means of the press head heat sink affixed to a linear actuator device. The rigid bar 4 holds the thermally stable rigid electrical insulator pressure pad 3 to the tension bar 10 The rigid electrical insulator pressure pad is of a thermally stable material and has a flat surface for support of the heating element during the process of bonding to achieve even bond pressure along the line of the heating element. The tensioning mount holds the heating element straight and taut to the insulator pressure pad. Electrical power connection is applied to the two electrical terminal block during the bonding process to attain the required bonding temperature. Air vent cools the thermode assembly after the bonding process and minimize temperature transfer to rest of thermode assembly and also prevents over heating of the thermode. Two or more thermocouples 8 are welded to the heating element for temperature control, monitoring and for safety interlocking purposes.