Conductive polymer composite as plastic solder

Abstract

There is provided a method for soldering a first non-metallic component to one or more metallic or non-metallic component, the method comprising the step of removably securing the first non-metallic component to the one or more metallic component by using a conductive polymeric composite or removably securing the first non-metallic component to the one or more non-metallic component by using the conductive polymeric composite, wherein the conductive polymeric composite used in the method comprises a blend of at least one filler material and at least one thermoplastic polymer.

Claims

1. A method for soldering a first non-metallic component to one or more metallic or non-metallic components, the method comprising: removably securing the first non-metallic component to the one or more metallic component by using a conductive polymeric composite; or removably securing the first non-metallic component to the one or more non-metallic component by using the conductive polymeric composite, wherein the conductive polymeric composite used in the method comprises a blend of carbon black and polypropylene.

2. The method of claim 1, wherein the one or more metallic or non-metallic component is present on a porous or non-porous substrate.

3. The method of claim 2, wherein the porous or non-porous substrate is selected from the group consisting of plastic, glass and their combinations thereof.

4. The method of claim 1, wherein the one or more metallic or non-metallic component is a thermally sensitive assembly or component capable of being soldered by the conductive polymeric composite.

5. The method of claim 1, wherein the carbon black is about 20% to 40% weight percent based on the weight of the conductive polymeric composite.

6. The method of claim 5, wherein the carbon black is about 25% to 35% weight percent based on the weight of the conductive polymeric composite.

7. The method of claim 1, wherein the removably securing step occurs at a temperature of 165° C. to 185° C. when a soldering tip is used or a temperature of 220° C. to 230° C. when an extrusion pen with hot ends is used.

8. A method of using a conductive polymer composite for soldering a first non-metallic component to one or more metallic or non-metallic component, wherein the conductive polymer composite comprises a blend of carbon black and polypropylene.

9. The method of claim 8, wherein the conductive polymeric composite is capable of forming, repairing or enhancing electrical connections between one or more electronic component, wherein the electrical connections are removably formed between a metallic electronic component and a non-metallic electronic component or between two or more non-metallic electronic component.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) The accompanying drawings illustrate a disclosed embodiment and serves to explain the principles of the disclosed embodiment. It is to be understood, however, that the drawings are designed for purposes of illustration only, and not as a definition of the limits of the invention.

(2) FIG. 1 shows a simple circuitry setup having connections made from conductive polymers or metals. The black material (including the IMRE logo) is conductive polymer composite or conductive thermoplastic composite; the silver color parts attached with electrical wires are dried silver ink.

(3) FIG. 2 shows a closed functional 3D printed plastic circuit that connects a 9V battery to a blue light emitting diode (LED) with the LED on. The circuit is then cut with a penknife.

(4) FIG. 3 shows a follow-up from FIG. 2. After cutting, the circuit is open and unable to light up the embedded blue LED (LED off).

(5) FIG. 4 shows a follow-up from FIG. 3. After repair with plastic solder, the circuit recovers its function and lights up the embedded blue LED (LED on).

(6) FIG. 5 shows a summary of an iterative method for compounding conductive thermoplastics composite with conductive filler. Further details on this procedure can be found in the detailed description of drawings.

(7) FIG. 6 shows the volume resistivity of thermoplastic polypropylene (PP) composite containing various weight percentages of conductive carbon black (CB) filler.

(8) FIG. 7 shows the Differential Scanning calorimetric (DSC) thermograms (exo-up) of conductive thermoplastic polypropylene (PP) composites of containing 15% CB (solid line), 25% CB (short dash), 32% CB (long dash) by weight during heating cycle (0.fwdarw.250° C.).

(9) FIG. 8 Differential Scanning calorimetric (DSC) thermograms (exo-up) of conductive thermoplastic polypropylene (PP) composites containing 15% CB (solid line), 25% CB (short dash), 32% CB (long dash) by weight during cooling cycle (250.fwdarw.0° C.).

DETAILED DESCRIPTION OF DRAWINGS

(10) FIG. 1 describes a conductive circuit 2, which is displayed on a non-conductive plastic substrate (ABS) 4. The conductive circuit 2 has ports 6 for connecting to a battery and ports 8 for connecting to an LED light bulb.

(11) FIG. 5 describes the process of preparing the composite. In a first step, the thermoplastics are being mixed and compounded with conductive filler to extrude filament with lower weight percentage of filler, for example 25% by wt (14). Then, in a subsequent compounding step, the mixture is cut into cylindrical pellets (<1 cm long) and the pellets are mixed and compounded with more conductive filler to extrude filament with higher percentage of filler (16). After a first compounding step (16), the percentage of the filler is gradually increased (e.g. increment of 5-7%) until the desired percentage of the filler is obtained (20) and step (16) is repeated. Upon reaching the desired percentage of the filler, a homogenization step (18) is required. In this process step, the mixture is cut into cylindrical pellets (<1 cm long) and this is followed up by a further mixing and re-extruding step to homogenize the filler content of a filament further (18). This step may be optionally repeated to improve homogeneity of conductive-filler distribution within the filament (22).

EXAMPLES

(12) Non-limiting examples of the invention and a comparative example will be further described in greater detail by reference to specific examples, which should not be construed as in any way limiting the scope of the invention.

Example 1

Example 1: Preparation of Thermoplastic Solders

(13) Thermoplastic solders can be prepared by compounding of thermoplastic with non-metal fillers. One example is the compounding of carbon black (Enasco 260P, TIMCAL) with polypropylene (homo PP, SCG) using single- or twin-screw extruder. To ensure high uniformity and even distribution of filler present inside the resulting thermoplastic composite, there was performed an iterative compounding carbon black (CB) filler into polypropylene (PP) according to the steps described in FIG. 5. Typical weight percentages of carbon black in polypropylene are 5%, 10%, 15%, 20%, 25%, 30%, 35%, and 40 wt % (FIG. 6). FIG. 6 shows the volume resistivity of thermoplastic polypropylene (PP) composite containing various weight percentages of conductive carbon black (CB) filler. It can be seen from FIG. 6, that the volume resistivity is very high (>1000 m.Math.Ohm) when a small amount of carbon black is embedded in the polypropylene and drops below 0.01 m.Math.Ohm at percentages higher 30%.

(14) Characterization of the THERMOPLASTIC COMPOSITES

(15) Electrical resistivity of conductive composite filaments containing 5% to 40% of carbon black by weight is summarized in FIG. 6. When the amount of carbon black in the composite exceeds 30% by weight, the electrical resistance of the composite drops below 10.sup.−2 Ωm. Differential scanning calorimetry (DSC) analyses of the composites are summarized in FIGS. 7 and 8.

(16) FIG. 7 shows the Differential Scanning calorimetric (DSC) thermograms (exo-up) of conductive thermoplastic polypropylene (PP) composites of containing 15% CB (long dash), 25% CB (solid line), 32% CB (short and long dash) by weight during heating cycle (0.fwdarw.250° C.). It can be seen that the transition temperature various mixtures of carbon black in polypropylene is at about between 160-180° C.

(17) FIG. 8 Differential Scanning calorimetric (DSC) thermograms (exo-up) of conductive thermoplastic polypropylene (PP) composites containing 15% CB (long dash), 25% CB (solid line), 32% CB (short and long dash) by weight during cooling cycle (250.fwdarw.0° C.). It can be seen that the transition temperature various mixtures of carbon black in polypropylene is at about between 110-125° C.

Example 2

Soldering Process

(18) FIG. 1 is a diagram of a simple circuitry setup having connections made from conductive polymers or metals. For further clarification, it is a closed functional 3D printed plastic circuit that connects a 9V battery to a blue light emitting diode (LED). In the initial setting in FIG. 2, the LED light is on (10). The circuit is then cut with a penknife (FIG. 2). After cutting into the circuit, the circuit is open (resulting in cut 12, FIG. 3) and the embedded blue LED does not light up (10′, FIG. 3).

(19) A soldering step is then performed to repair the circuit. The plastic solder used in this example is a thermoplastic composite >25 weight % carbon black in polypropylene and its preparation is described in Example 1. Two soldering methods have been tested on the plastic solder for repairing the circuit. In one method, the plastic solder is brought into contact with the hot end of a soldering iron pre-heated to 200-230° C. The region of the plastic solder in direct physical contact with the hot end of a soldering iron is softened and partially melted into viscous liquid. The liquefied form of plastic solder is then deposited at the site of the circuit that has been damaged with penknife. Once the gap of the damaged circuit is filled with liquefied plastic solder and the soldering iron is removed from the plastic solder deposited at the previously damaged site, the liquefied plastic solder solidified rapidly (in less than 10 seconds).

(20) In another method, a filament of plastic solder of appropriate diameter is inserted into the top of a 3D-printing pen, which has an open nozzle at bottom heated to 230° C. The inserted filament is then guided and driven mechanically to the interior of the printing pen when the user switches on the gear system of the printing pen. When the inserted plastic solder comes into contact with the heated nozzle, the region of the plastic solder in immediate physical contact with the heated nozzle is softened and partially melted into viscous liquid. The liquefied form of plastic solder is then deposited at the site of the circuit that has been previously damaged with penknife. Once the gap of the damaged circuit is filled with liquefied plastic solder and the 3D printing pen is removed from the plastic solder deposited at the damage site, the liquefied plastic solder solidified rapidly (in less than 10 seconds) and bridges the open ends.

(21) After a soldering step according to any one of the two methods described immediately above, the circuit is repaired with plastic solder (12′, FIG. 4) and recovers its function. The embedded LED light bulb lights up (10′″, FIG. 4).

INDUSTRIAL APPLICABILITY

(22) The developed method and conductive polymeric composite may be used for soldering electrical components to electrical circuits or for repairing damaged circuits. These circuits may be derived from thermoplastics.

(23) The method may be further used for soldering a non-metallic electronic component to a metallic electronic component or another non-metallic electronic component. The soldering method may be used to repair broken connections in a circuit, to enhance contact between printed layers of exposed wires or to solder circuit components to printed circuits. The method may comprise the step of joining respective ends of the electronic components together using the conductive polymeric composite as defined above. This method can also be used for soldering components onto a substrate. Conversely, the present method may also be used to solder a metallic component to one or more non-metallic component.

(24) The developed method and conductive polymeric composite may serve to provide a conductive solder for making joints between metallic leads of electrical components and conductive polymer or for making joints between conductive polymers and conductive polymers. Particularly, the conductive polymeric composite can be used as conductive solder for repairing 3D-printed electrically conductive circuit.

(25) The presently developed method and conductive polymeric composite can also be used for soldering electronic components to 3D printed parts, repairing 3D printed polymer circuits. They can be used in the toy industry for low cost integrated wiring in toys so as to provide electrical functionalities such as, but not limited to, forming joints or for self-repairs.

(26) Advantageously, the developed method and conductive polymeric composite addresses the above limitations and disadvantages while providing improved wettability.

(27) It will be apparent that various other modifications and adaptations of the invention will be apparent to the person skilled in the art after reading the foregoing disclosure without departing from the spirit and scope of the invention and it is intended that all such modifications and adaptations come within the scope of the appended claims.