阅读说明：本技术 具有静电印制导电线路的电路板的制作 (Manufacture of circuit board with electrostatic printed conductive circuit ) 是由 林世智 于 2019-05-24 设计创作，主要内容包括：一种制作具有静电印制导电线路的电路板的方法,其包含二步骤阶段。首先,于一电性绝缘基材上,以静电印刷术将含有树酯及导电粉末的复合粉材印制形成电路板的该导电线路的复合粉胚。其次,对该导电线路的复合粉胚施加能量进行加温,以烧掉/气化该树酯,并烧结该导电线路的复合粉胚内的导电粉末,并将此烧结的导电粉末金属化而形成该导电线路,其中该树酯将已金属化的该导电线路粘附在该电性绝缘基材上,且其中该施加能量未对该电性绝缘基材产生“破坏性”实质加温。(A method for manufacturing a circuit board with electrostatic printed conductive circuits comprises two steps. Firstly, on an electric insulating base material, a composite powder material containing resin and conductive powder is printed by electrostatic printing to form a composite powder blank of the conductive circuit of the circuit board. Secondly, applying energy to the composite powder blank of the conductive circuit for heating so as to burn off/gasify the resin, sintering conductive powder in the composite powder blank of the conductive circuit, and metallizing the sintered conductive powder to form the conductive circuit, wherein the resin adheres the metallized conductive circuit on the electrically insulating substrate, and the applied energy does not generate destructive substantial heating on the electrically insulating substrate.)

1. a method for manufacturing a circuit board with electrostatic printed conductive circuit includes

(i) On an electrical insulating substrate, printing raw material powder containing resin and conductive powder by an electrostatic printing method to form a composite powder blank of the conductive circuit of the circuit board; and

(ii) Applying energy to the composite powder blank of the conductive circuit to heat so as to gasify/burn the resin, sintering the conductive powder in the composite powder blank of the conductive circuit, and forming the conductive circuit through sintering metallization, wherein the metallized conductive circuit is adhered to the resin of the unsintered composite powder blank below the metallized conductive circuit, and the resin is adhered to the electrically insulating substrate, and wherein the applying energy does not generate destructive substantial heating to the electrically insulating substrate.

2. The method of claim 1, wherein the heating of the composite powder blank of conductive traces is by a laser, and wherein

(i) The wavelength is 700 to 2000nm or 450 to 700nm or 250 to 450nm, preferably 700 to 2000 nm;

(ii) The laser is in the form of

(a) Can be a continuous wave or a pulse laser; or

(b) The beam profile of the laser can be Gaussian or high-top hat type; or

(c) The moving speed of the central point of the laser is more than 10 mm/sec; or

(d) The laser power of the composite powder blank used on the conducting circuit is more than 0.1W; or

(e) if the laser is a pulsed laser:

(e1) The pulse width is less than 1 ms; or

(e2) the maximum pulse energy is greater than 0.01 mj; or

(e3) Frequency: greater than 10 Hz;

(f) A plurality of laser beams are irradiated on the composite powder blank, and a line formed by connecting the central points of formed light spots and another parallel line with the same property has the line distance of not less than 0.03 mu m.

3. The method of claim 1, wherein the heating of the composite powder blank of the conductive circuit is by induction heating.

4. The method of claim 1, wherein the energy applied to heat the composite powder blank of the conductive trace is plasma.

5. The method of claim 1, wherein the energy applied to heat the composite powder blank of conductive traces is an ion beam.

6. The method of claim 1, wherein the photosensitive conductor has a surface roughness Rz value of not more than 10 μm.

7. The method as claimed in claim 1, wherein a cylindrical photosensitive conductor is used, which has a value of not more than 400 μm when measured as runout of a gear comprising a substrate bonded thereto.

8. The method as claimed in claim 1, wherein a cylindrical photosensitive conductor is used, which is measured to have a value of not more than 200 μm when the runout of the gear bonded to the substrate is not included.

9. The method as claimed in claim 1, wherein the gear not bonded to the substrate, a vertical cylindrical photosensitive conductor, whose upper and lower ends have a photosensitive layer thickness difference of not more than 15 μm at any two points within the photosensitive layer from 1.5 to 3mm from the edge of the photosensitive layer, are included.

10. The method as claimed in claim 1, wherein the amorphous film type photosensitive conductor has a difference of not more than 15 μm in film thickness at any two points of the photosensitive layer from the edge of the photosensitive layer by 1.5 to 3mm at upper and lower or left and right ends thereof.

11. The method of claim 1, wherein the photosensitive conductor is in a printer and is operated at a minimum linear velocity of not less than 0.05 mm/sec.

Technical Field

The present invention relates generally to the fabrication of circuit boards (circuit boards) for electronic devices, and more particularly to the fabrication of circuit boards having electrostatic printing (electrostatic printing) conductive traces (conductor patterning).

Background

Most electronic devices today use Printed Circuit Boards (PCBs). Rigid pcbs (rigid pcbs) utilize a multi-layer stack configuration in order to support complex circuitry. In contrast, a flexible pcb (flexible pcb), which is relatively less well suited for application to complex circuitry, but which is adapted to impart mechanical flexibility to the circuit board system of flexible electronic devices (flexible electronics), may have only single-sided (single-layer) conductive traces.

Both rigid and flexible types use copper foil (foil) to make the conductive traces required on the circuit board. Currently, the mainstream manufacturing method of the PCB is to use a subtractive process (subtractive process) to form a conductive circuit by using a full-sheet complete copper foil. All copper material except the conductive lines has to be removed in the complete full-open area of the original raw copper foil. Currently, chemical etching (chemical etching) is the main means for removing these copper species.

However, the mainstream PCB subtraction process based on chemical etching is difficult to operate forever when environmental protection and product manufacturing carbon footprint are taken into consideration. First, the acidic or alkaline chemical etching waste liquid left by the etching process must be treated with chemical materials to recover the high-value copper or other precious metals. However, more waste liquid is thus generated for recycling.

secondly, the chemical waste liquid generated by the treatment of the etching liquid must be neutralized by a chemical method again, and water in the waste liquid and impurities (chemical sludge) in the water can be separated through a complicated waste liquid treatment process. Finally, the separated water must be subjected to another costly treatment if it is to be recycled. If it is to be discharged, it is also necessary to meet the legal discharge standards, which is also costly. In addition, the treatment of chemical sludge is costly.

In general, such "sub-processes" that are not directly associated with the manufacture of PCBs must account for the manufacturing costs of the PCBs in order to comply with the perpetual principles. However, many manufacturers have kicked them directly from the cost structure, and as a result, unfortunately, it is an environmental pollution.

In view of the above, there is a need in the art for a method of fabricating a circuit board with electrostatic printed conductive traces that substantially completely avoids the generation of chemical waste.

disclosure of Invention

Therefore, the present invention provides a method for manufacturing a circuit board with electrostatic printed conductive circuits, which is simple and easy to add, and can substantially and completely avoid the generation of chemical waste liquid.

To achieve the above object, the present invention provides a method for manufacturing a circuit board having electrostatic printed conductive traces, which comprises two steps. First, a composite powder (composite compact) for forming the conductive traces of the circuit board is printed on an electrically insulating substrate by electrostatic printing from a raw material powder (Toner) containing resin and conductive powder. And heating the composite powder blank of the conductive circuit by applying energy to burn off (Burning)/gasify (Sintering) the resin, Sintering (Sintering) the conductive powder in the composite powder blank of the conductive circuit, and metallizing (metallizing) the sintered conductive powder to form the conductive circuit, wherein the resin adheres the metallized conductive circuit to the electrically insulating substrate, and wherein the applying energy does not substantially heat the electrically insulating substrate in a destructive manner.

In order to achieve the above object, the present invention further provides a method for manufacturing a circuit board having an electrostatic printed conductive circuit, wherein the energy applied for heating the composite powder blank having a patterned protrusion structure of the conductive circuit is laser, and wherein (i) the wavelength is 700 to 2000nm, or 450 to 700nm, or 250 to 450nm, preferably 700 to 2000 nm; (ii) the laser is in the form of (a) Continuous Wave (CW) or pulsed (Pulse) laser; (b) the beam profile (beam profile) of the laser may be Gaussian or high top hat (Tophat); (c) the moving speed of the central point of the laser is more than 10 mm/sec; (d) the laser power of the composite powder blank used for the molded protrusion structure is more than 0.1 watt (W); (e) if the laser is a pulse laser: then (e1) Pulse width (Pulse duration, Pulse width): less than 1 millisecond (ms); (e2) maximum pulse energy: greater than 0.01 millijoules (mj); (e3) frequency: greater than 10 Hz; (f) a plurality of laser beams are irradiated on the composite powder blank, and a line formed by connecting the central points of formed light spots and another parallel line with the same property has the line distance of not less than 0.03 mu m.

Drawings

The above and other features and advantages of the present invention will be more readily understood from the following description taken in conjunction with the accompanying drawings. In the drawings:

fig. 1 is a schematic diagram illustrating a stage I and a stage II process for manufacturing a circuit board having electrostatic printed conductive traces according to an embodiment of the invention.

FIG. 2 shows a schematic diagram of a Carlson Cycle (Carlson Cycle) for printing conductive traces of a circuit board by xerography using photosensitive conductors, in accordance with one embodiment of the invention.

fig. 3 and 4 are a comparison of the properties exhibited by the sintered and unsintered surfaces of the composite powder compact, respectively.

Description of reference numerals:

102 electrostatic printing apparatus

104 sintering device

110 non-conductive blank substrate of circuit board

112 circuit board substrate printed with composite powder blank of conductive circuit

122 composite powder blank for electrostatically printing conductive circuit by using raw material powder

125 sintered conductive line

124 composite powder blank of conducting wire

130 circuit board with complete conducting circuit

201 cloth electricity

202 Exposure

203 developing

204 transcription

205 scraping residual powder

206 cleaning residual static electricity

211 fixation

Detailed Description

Fig. 1 is a schematic diagram illustrating a stage I and a stage II process for manufacturing a circuit board having electrostatic printed conductive traces according to an embodiment of the invention. The process illustrated in this example can be divided into two main process stages, namely, stage I for electrostatic printing and stage II for sintering the green powder. Referring to the schematic of fig. 1, the electrostatic printing stage I uses an electrostatic printing apparatus 102, and the powder blank sintering stage II uses a sintering apparatus 104.

It should be noted that in the present invention, xerography is an automated process similar to the modern automated lithography technique widely used in photocopying, laser printing applications, as disclosed in U.S. Pat. No. 2,297,691 to Chester Carlson and related technologies hereafter. Compared with the prior art of electrostatic printing. The present invention is different in the technique of manufacturing a circuit board having an electrostatic printed conductive circuit, in that the two kinds of raw material powder are different, and the printing method of the setting is different. These various features of the present invention are illustrated in FIG. 2.

According to the present invention, in the electrostatic printing stage I, the electrostatic printing apparatus 102 prints the conductive traces required by the target circuit board on a blank substrate 110 having electrical insulation properties by using the raw material powder supply source 122. The result of the printing process is the stage circuit board 112 printed with the composite powder blank 124 of the conductive traces.

According to the present invention, the raw powder or the original powder refers to a mixed powder containing two or more powders of conductive materials, such as metal materials, and resins, and the composite powder blank can be used for electrostatic printing to form conductive circuits.

In addition, the composite powder blank of the present invention refers to a conductive circuit blank which is printed on a substrate of a circuit board by using the raw material powder of the present invention and has a conductive circuit shape structure of the circuit board and is not completely shaped and cured by using an electrostatic printing technique. Before the composite blank is shaped and cured by a sintering process, the blank is a flexible but stable stage structure due to the resin contained therein.

Note that the composite powder 124 of the conductive traces printed on the circuit board 112 at this stage of the process of fig. 1 does not yet have the good conductive properties that the conductive traces of the target circuit board should have. This is because the composite powder compact 124 has a structure in which powder of a conductive material, such as metal powder, is present, but not only gaps are formed between particles thereof, but resin particles are mixed.

Thus, following stage I, the circuit board substrate 112 printed with the composite powder blank 124 may be sent to the sintering device 104 for performing the powder blank sintering process of stage II to sinter and metallize the conductive powder, such as copper powder particles, in the composite powder blank 124 to form a continuous conductor. After the sintering process is completed, the circuit board 130 with the complete conductive traces 125 can be obtained, and the conductive traces 125 on the insulating substrate have good conductivity.

According to the present invention, in the sintering process of the powder blank in the process stage II, the energy source for sintering may be laser, and the wavelength thereof may be 700 to 2000nm, or 450 to 700nm, or 250 to 450nm, and 700 to 2000nm is the most preferable. The laser form can be continuous wave type or pulse type laser, and the beam profile of laser can be gaussian or high-top hat type, and the translation speed of laser central point is then greater than 10 mm/sec. The laser power of the composite powder blank used for the conductive circuit is more than 0.1W.

If the laser is a pulse laser, the pulse width should be less than 1ms, the maximum pulse energy should be greater than 0.01mj, and the frequency should be greater than 10Hz. If a plurality of laser beams are irradiated on the composite powder blank, the line formed by connecting the central points of the formed light spots and another parallel line with the same property has the line distance not less than 0.03 mu m.

According to the present invention, in the sintering process of the powder blank in the process stage II, the energy source for sintering may also be induction heating (induction heating), which can excite eddy current in the composite powder blank metal conductive material to generate heat for sintering.

According to the present invention, the energy source for sintering the powder blank in the process stage II can also be Plasma (Plasma beam).

According to the present invention, the energy source for sintering the powder blank in the process stage II can also be Ion beam (Ion beam).

FIG. 2 is a schematic diagram of a Carlson cycle for xerographically printing a composite powder blank of conductive traces of a circuit board using photosensitive conductors (photoconductors), in accordance with one embodiment of the present invention.

Referring also to fig. 1, according to this embodiment, the pattern of the conductive traces (final sintered conductive traces 125 in fig. 1) of the target circuit board is electrically applied to the photosensitive conductor 200 via the optical system of the electrostatic printing apparatus 102 to form an electrical application area in the first area 201 of the cycle. As understood by those skilled in xerography, the charge distribution region 201 of the photosensitive conductor 200 is then rotated clockwise as shown and irradiated by the beam 202 which forms a latent image of the line, and the surface of the photosensitive layer is generated at 203 in a charge region corresponding to the line of the composite soot.

Then, the photosensitive conductor 200 continuously rotates, so that the powder supplied by the raw material powder 122 is adsorbed on the photosensitive conductor due to static electricity, and a charge area corresponding to the shape of the conductive circuit is generated on the surface of the photosensitive material layer. When the composite powder blank adsorbed on the photosensitive conductor advances to the transfer area position of 204, the powder adsorbed on the photosensitive conductor is transferred and attached to the non-conductive substrate 110 due to the voltage opposite to the photosensitive conductor provided by the transfer area, and the circuit board substrate 112 of the composite powder blank 124 printed with the conductive circuit is formed.

Thereafter, the circuit board substrate 112 is continuously moved forward in the opposite direction of the substrate moving direction as shown in fig. 2, and the conductive circuit composite powder blank 124 printed thereon is fixed at the position 211. The composite powder 124 can be firmly attached to the surface of the substrate 112 by using a roller of the fixing system and applying heat and pressure appropriately.

Then, the composite powder blank 124 printed with the conductive circuit is processed by additional energy or heat to gasify or burn off the resin contained in the composite powder blank, and the remained conductive material is metallized by sintering to form a conductive circuit (125), thereby completing the manufacture of the circuit board 130 with complete conductive circuit.

note that in the embodiments of the foregoing illustrative nature, the manufacturing process can be used to manufacture, for example, a flexible circuit board (flex circuit board). Although the circuit board fabricated in this example has only single-sided conductive traces, it will be understood by those skilled in the art that the embodiment can also be adapted to fabricate a circuit board with double-sided conductive traces by repeating substantially the same procedure.

in addition, similar to the principle of four toner cartridges in the existing color printer, the original powder materials of conductive materials with different electrical conductivities (electrical conductivity) are placed in different toner cartridges, and the circuit board with local circuits with different electrical conductivities can be manufactured on the same film substrate through printing and sintering/metallization procedures.

According to the invention, the photosensitive conductor (fig. 2, 200) has the following characteristics in its structure:

(i) The substrate of the photosensitive conductor used can be rigid column type or non-rigid soft film type.

(ii) The photosensitive conductor used may be an inorganic or organic photosensitive conductor.

(iii) If an inorganic photosensitive conductor is used, it may be an amorphous silicon photosensitive conductor, or if an organic photosensitive conductor is used, it may be a single layer or more than a single layer of organic photosensitive conductor.

(iv) The base material used for the photosensitive conductor may be a metal or a polymer.

(v) The surface roughness Rz value of the photosensitive conductor is not more than 10 μm.

(vi) The rigid cylindrical photosensitive conductor is cylindrical

(vi-1) the deflection of the gear comprising the gear bonded to the substrate is measured to be not more than 400 μm.

(vi-2) when it is measured that the runout of the gear bonded to the base material is not more than 200. mu.m.

(vi-3) a gear not bonded to the substrate, a vertical cylindrical photosensitive conductor, and photosensitive layer thicknesses of any two points whose upper and lower ends are 1.5-3mm away from the edge of the photosensitive layer in the photosensitive layer, the difference between the two film thicknesses being not more than 15 μm.

(vi-4) the amorphous film type photosensitive conductor has the upper and lower ends or the left and right ends thereof in the photosensitive layer at any two points 1.5-3mm away from the edge of the photosensitive layer, and the difference between the film thickness of the photosensitive layer and the film thickness of the photosensitive layer is not more than 15 μm.

(vii) If an organic photosensitive conductor is used, then

(vii-1) the Charge generating agent (CGM) used therein is a Charge generating agent of an organic or organometallic pigment or dye, such as phthalocyanine pigment.

(vii-2) the positive-type carrier transportable material (HTM) used in the present invention may be a hydrazone compound, a styrene compound, a diamine compound, a butadiene compound, an indole compound, or the like, alone or in combination.

(vii-3) the Electron Transport Material (ETM) used may be a benzoquinone derivative, a phenanthrenequinone derivative, a stilbenquinone derivative, a diazoquinone derivative, which may be used alone or in combination of 2 or more.

(vii-4) the Binder (Binder) used may be a styrenic polymer or a copolymer of styrene with other series of monomers. Acrylic polymers, copolymers of polyethylene or ethylene with other series of monomers, polyvinyl chloride, copolymers of vinyl chloride with other series of monomers, copolymers of polypropylene or propylene with other series of monomers, copolymers of polyester or polyester with other series of monomers, copolymers of a polyol resin, polyamide, polyurethane, polycarbonate resin or carbonic acid with other series of monomers, thermoplastic resins such as polyarylate, polysulfone, diallyl phthalate resin, polyketone resin, polyvinyl butyral resin, acrylonitrile-containing resin and polyether resin; or silicone, epoxy, phenolic, urea, melamine and other cross-linking thermosetting resins; or photocurable resins such as epoxy acrylate and urethane acrylate. These binders may be used alone or in combination of two or more.

In accordance with the present invention, the operation of the photosensitive conductor (fig. 2, 200) can have the following characteristics:

(viii) The photosensitive conductor is in the printer and the operation process thereof

(viii-1) minimum linear velocity (line speed) of operation of not less than 0.05 mm/sec.

(viii-2) following the six steps of the Chester Carlson cycle of FIG. 2, the charging voltage (charge) applied to the surface of the photosensitive conductor is preferably within a range of + -150-990V, more preferably + -200-750V; preferably + -200-650V.

(viii-3) the photosensitive conductor is electrified and then exposed by a light source (exposure), and the surface voltage of the photosensitive conductor before development is more than +2V or less than-2V.

(viii-4) the printer's electrical distribution system to the photosensitive conductor can be a charging roller or a charging wire system.

(viii-5) the light source of the exposure system of the printer to the photosensitive conductor may be a laser or a Light Emitting Diode (LED).

(viii-6) if the raw material powder must be charged, the charging voltage is-500 to-100V or +500 to + 100V.

(viii-7) in the fixing stage, the printer heats the resin of the composite powder blank to a molten state, and presses the molten resin on the substrate, at the same time, the composite powder blank and the non-conductive blank substrate will be adsorbed to each other due to Van Waals force and form a circuit.

According to the present invention, the raw material powder (fig. 1, 122) used in combination with the photosensitive conductor (fig. 2, 200) can have the following characteristics:

(i) The particle size is 0.05 to 100 μm, preferably 1 to 50 μm, more preferably 10 to 35 μm

(ii) Resistivity (Resistivity) of more than 1.0X 10-4 omega m

(iii) the appearance is irregular, sheet-like or spherical.

(iv) at least contains one or more than one adhesive.

according to the invention, the conductive powder component in the raw material powder may have the following characteristics:

(i) particle size: 0.05 to 30 μm, preferably 5 to 15 μm.

(ii) Resistivity: less than 1.0X 10-4 omega m

(iii) The appearance is irregular, sheet-like or spherical.

According to the invention, the Binder (Binder) component of the raw meal may have the following characteristics:

(i) Softening point (softening point): greater than 70 c,

(ii) A Glass Transition Temperature (Tg) of greater than 40 DEG C

(iii) It may be a thermoplastic resin such as polyester resin, acryl resin or a copolymer of acryl and styrene.

(iv) it may be a thermosetting resin such as a phenolic resin.

(v) It may be a photocurable resin such as epoxy acrylate.

According to the invention, the ratio of the conductive powder to the adhesive in the raw material powder is as follows:

1/9-9/1 of conductive powder/adhesive,

Preferably: 1/4-4/1.

Optimally: 1/2-2/1.

That is, the weight of the conductive powder is 10% to 90% of the weight of the whole powder.

Preferably: 20-80%.

Optimally: 35-65%.

[ experiment I ]

I. Process stage I: electrostatic printing

1. Non-conductive powder (non-conductive powder) for image formation:

(i) A resin solution obtained by dissolving a resin (Polyester resin, Polyester resin DIACRONL FC-1565) with Methyl Ethyl Ketone (MEK) had a solid content of 25%.

(ii) The conductive powder (copper powder used here) was poured into a 500ml beaker containing the MEK solution described above. Copper powder was used twice the weight of the resin content in the MEK solution. After the copper powder is poured into the MEK solution, the copper powder is dispersed by a homogenizer, and at the moment, the temperature of the outside of the beaker is reduced by using water with low temperature of 4-10 ℃.

(iii) After the homogenizer dispersed for 30 minutes, the dispersed copper powder-containing solution was continuously stirred and dispersed by a stirrer, and MEK was volatilized until the solid content of the entire solution became more than 60%, and then the stirring was stopped.

(iv) the solution of (iii) was poured into a stainless steel dish having an area of about 20cm x30cm and a height of about 3-5cm and dried in an oven at 45-50 ℃ for 6 hours. Then, continuously drying at 70-75 ℃ for more than 20 hours, taking out and cooling.

(v) And (iv) crushing the cooled solid by using a crusher to obtain fine powder, namely the non-conductive raw material powder for imaging.

2. Printing a composite powder blank of a conductive circuit by using an electrostatic imaging method:

(i) The raw powder is poured into a toner cartridge of an AM30 printer (manufactured by Avision), and the charging voltage of a photosensitive conductor (an organic photosensitive drum manufactured by Green Rich Technology Co.) is +600 to +650V when printing.

(ii) The surface voltage of the photosensitive conductor after the electricity distribution of the printer is +70 to +150V after the exposure by laser irradiation.

(iii) A Polyimide Film (PI Film) with a thickness of 50 μm is used as a non-conductive blank substrate for printing, and the non-conductive raw material powder is imaged on the Film to form a circuit board substrate with a conductive circuit printed by the composite powder blank.

Process stage II: sintering of powder blank

And (3) carrying out high-temperature sintering treatment on the composite powder blank by utilizing laser on the PI film which is obtained in the process stage I and has the surface provided with the composite powder blank which is printed and formed by utilizing the raw material powder and has no conductivity. In the experiment, resin in the powder blank is instantaneously gasified or burnt by utilizing the high temperature of laser, and the conductive copper powder is sintered and metalized into a structural body with whole body conductivity. The moving speed and energy of the laser are changed in the program, so that the vertical sintering depth can be controlled:

(i) Using pulsed laser with the wavelength of 1064nm as a light source;

(ii) The moving speed of the central point of the laser is more than 50 mm/sec;

(iii) The laser power used is more than 0.5W;

(iv) The pulse width is less than 0.5ms, and the maximum pulse energy is more than 0.05 mj;

(v) The line formed by connecting the central points of the light spots formed by the pulse laser sintering and the other parallel line with the same property are not less than 0.03 μm.

(vi) The frequency is greater than 10Hz.

Results of the experiment

(i) Fig. 3 and 4 are a comparison of the properties exhibited by the sintered and unsintered surfaces of the composite powder compact, respectively. It can be seen that the conductive powder apparently has agglomerated on the surface on the right side of the figure after sintering. And the left unsintered part, the conductive powder of which is still in a dispersed state.

(ii) a simple test method is to use a multimeter to measure whether sintering is successful. The resistance value of the left part was measured and found to be in an insulating state, while the sintered part of the right part was turned on and had a resistance value of 6-35 Ω. It can therefore be judged that after sintering at a high temperature, the conductive powder has been sintered into a lump and metallized into a conductor that is entirely conductive.

The present invention is disclosed in the preferred embodiments and described above with reference to the accompanying drawings, which are not intended to limit the present invention. Various changes and modifications can be made by one skilled in the art without departing from the spirit and scope of the invention, and the scope of the invention is therefore defined by the appended claims.