Laser activation direct chemical plating sensitized material and application thereof

Abstract

The invention relates to a laser activation direct chemical plating sensitized material and application thereof, and belongs to the field of PCB (Printed Circuit Board) manufacturing technology and chemical plating. The method comprises the following steps: firstly, providing a laser-sensitized material which is used as an activated bridging layer on the surface of an epoxy resin substrate; and then a metal catalytic source in the catalytic active agent can be reduced into metal particles with efficient catalytic activity in combination with a laser activation technology, so that the subsequent chemical copper plating reaction is catalyzed. The metal catalytic particles are effectively embedded into the middle modified layer after laser activation, so that the interface incompatibility between the activated bridging layer and the deposited copper layer is weakened, and the binding force between the epoxy resin substrate and the chemical plating layer is improved. The diazo photosensitizer can effectively enhance the utilization rate of laser energy by the substrate in the laser activation treatment process, so that the substrate achieves an excellent activation effect under proper laser power, and the catalytic efficiency in the chemical plating process is improved; and meanwhile, the machining precision of fine copper conductive pattern manufacturing can be obviously improved, and the uniformity of the surface of a chemical deposition copper layer is improved.

Description

Technical Field

[0001] The present invention belongs to the fields of PCB manufacturing technology and electroless plating, and particularly relates to a laser-activated direct electroless plating sensitizing material and its application. Background Art

[0002] In the field of PCB manufacturing, in order to achieve through-hole conduction inside the substrate and surface metallization, physical vapor deposition, chemical vapor deposition, metal spraying, surface lamination, etc. can usually be adopted. Electroless plating technology is also a common process for surface metallization of substrates. It mainly refers to the autocatalytic deposition of metal ions in a metal salt solution containing a reducing agent on the surface of a substrate that has been activated without an external power source. The traditional electroless copper plating process mainly includes the following steps: degreasing, roughening, sensitization activation, and electroless copper deposition; in recent years, with the development of electronic products towards high density and high reliability, electroless plating process technology has also been continuously innovating and progressing.

[0003] Compared with the "sensitization activation" two-step method in the traditional electroless copper plating process, people have continuously developed modified activation treatment processes such as colloidal palladium, nano silver, and ionic palladium, and used chemical reduction methods such as sodium hypophosphite, sodium borohydride, and polyol solutions to reduce metal ions to metal particles with high catalytic activity as active substances for catalyzing subsequent electroless copper plating reactions. However, the current laser-activated electroless plating process still faces many challenges and problems. For example, too high laser power will damage the physical structure of the substrate itself, and even cause overheating and carbonization on the surface of the substrate, while too low power may cause poor activation effect; the adaptability of the material itself to laser activation is poor, and its absorption ability to laser is weak, making it difficult to be effectively activated, thus unable to meet production requirements; in addition, the differences in laser scanning paths and energy distributions will lead to uneven activation degrees, resulting in poor surface uniformity of the subsequent electroless copper plating layer, as well as weak bonding force and easy detachment between the deposited copper layer and the substrate. Therefore, developing a laser-activated sensitizing material that can effectively improve the absorption rate of laser energy and activation effect has profound exploration value and research significance. Summary of the Invention

[0004] Aiming at the problems existing in the current laser-activated electroless plating technology, such as poor laser absorption rate, poor activation effect, difficulty in preparing high-resolution fine conductive copper circuits, and weak bonding force between the chemical deposition layer and the substrate, the present invention provides a laser-activated direct electroless plating sensitizing material and its application. The preparation method of this sensitizing material is simple to operate, has a high utilization rate of laser energy, excellent activation effect, and has potential application value in the field of manufacturing high-precision copper circuits.

[0005] The present invention provides a laser-activated sensitizing material added with a diazo photosensitizer. Combining with the laser activation technology, the metal catalytic source in the catalytic activator can be activated and reduced into metal particles with high catalytic activity, and effectively embedded in the intermediate bridging layer to catalyze the subsequent electroless copper plating reaction. The diazo photosensitizer can effectively enhance the absorption of laser energy by the substrate during the laser activation process, so that a good activation effect can be achieved under appropriate laser power, improving the catalytic efficiency in the electroless plating process; at the same time, it can effectively improve the processing accuracy of the production of fine copper conductive patterns and improve the uniformity of the surface of the electrolessly deposited copper layer.

[0006] To achieve the above object of the present invention, the technical solutions adopted by the present invention are specifically as follows:

[0007] A laser-activated direct electroless plating sensitizing material, the sensitizing material comprising the following components: 20 - 40 g / L of epoxy resin, 0.2 - 0.8 g / L of catalytic activator, 0.06 - 0.15 mol / L of organic solvent, 0.4 - 0.8 g / L of photosensitizer, and 0.05 - 0.1 mol / L of resin curing agent.

[0008] As a preferred embodiment, the epoxy resin is a glycidyl ether epoxy resin, which has good adhesion and chemical stability, and the mass concentration is controlled at 20 - 40 g / L.

[0009] As a preferred embodiment, the catalytic activator includes one or more selected from: organic salts, organometallic carbonyl compounds, and acetylacetone complexes corresponding to rhodium, palladium, silver, copper, nickel, and cobalt that are soluble in organic solvents, and its mass concentration is controlled at 0.2 - 0.8 g / L.

[0010] As a preferred embodiment, the organic solvent is one or more of acetone, methyl ethyl ketone, chloroform, cyclohexane, and ethylene glycol, and its molar concentration is controlled at 0.06 - 0.15 mol / L.

[0011] As a preferred embodiment, the photosensitizer used is a diazo photosensitizer, and its components mainly include diazonium salts or diazo resins, and the mass concentration is controlled at 0.4 - 0.8 g / L.

[0012] As a preferred embodiment, the resin curing agent used is an ethylenediamine solution, and its molar concentration should be controlled at 0.05 - 0.1 mol / L.

[0013] The present invention also provides an application of a laser-activated direct electroless plating sensitizing material, including the following steps:

[0014] Step 1: Preparation of the laser sensitizing material

[0015] Weigh an appropriate amount of epoxy resin and place it in a beaker. While continuously stirring, successively add an organic solvent and a catalytic activator until a transparent solution is obtained after complete dissolution. Then, add a photosensitizer thereto, and maintain magnetic stirring to fully mix them. Finally, add a resin curing agent to obtain a laser-activated direct electroless plating sensitizing material;

[0016] Step 2: Surface pretreatment of the epoxy resin substrate

[0017] Immerse the epoxy resin substrate in an alkaline degreasing solution at 60 °C to remove organic stains such as surface grease, and then rinse off the remaining degreasing solution with deionized water; subsequently, place the substrate in absolute ethanol and ultrasonically clean it at room temperature for 15 min, and rinse off the excess ethanol with a large amount of deionized water; then, place the substrate in an oven to dry it, take it out and let it cool naturally to obtain a clean epoxy resin substrate for standby;

[0018] Step 3: Coating and curing of the laser sensitizing material

[0019] Coat the laser sensitizing material prepared in Step 1 on the surface of the clean epoxy resin substrate pretreated in Step 2, then place it in a constant-temperature drying oven and cure it for 1 - 2 h, and then take it out and let it cool naturally;

[0020] Step 4: Laser activation of the substrate surface

[0021] Use ultraviolet laser to perform activation treatment on the surface of the epoxy resin substrate cured in Step 3, aiming to reduce the metal particles in the catalytic activator and effectively deposit them on the substrate surface as the catalytic active source for the subsequent electroless copper plating reaction;

[0022] Step 5: Chemical copper deposition on the surface of the activated and modified epoxy resin substrate

[0023] Place the epoxy resin substrate after laser activation treatment in Step 4 in an electroless copper plating solution for chemical deposition. Continuously stir magnetically and introduce air into the electroless plating solution to improve the stability of the plating solution, and use a constant-temperature water bath to heat and maintain the temperature of the electroless copper plating solution at 40 - 50 °C; after the reaction is completed, repeatedly rinse with absolute ethanol and a large amount of deionized water, and let the substrate dry naturally at room temperature.

[0024] As a preferred method, the epoxy resin substrate described in Step 2 is a composite substrate with epoxy resin as the matrix and glass fiber cloth as the reinforcing material, with a thickness of 1 mm, and is cut into a square or rectangle according to requirements by an automatic cutting machine

[0025] As a preferred method, the coating method described in Step 3 is one of dip coating, casting, and spin coating.

[0026] As a preferred method, the wavelength used in the laser activation in Step 4 is 355 nm, and the set parameters are as follows: the scanning speed is 400 mm / s, the power is 2 W, the frequency is 32.5 kHz, the pulse width is 20 μs, the line width is 0.1 cm, and the number of processing times is 1.

[0027] As a preferred method, the components of the electroless copper plating solution in Step 5 are as follows: potassium sodium tartrate tetrahydrate 32 g / L, disodium ethylenediaminetetraacetate dihydrate 2.5 g / L, copper sulfate pentahydrate 12.5 g / L, nickel sulfate hexahydrate 3.5 g / L, 2,2'-bipyridine 10 mg / L, potassium ferrocyanide trihydrate 20 mg / L, sodium hydroxide 10 g / L, formaldehyde solution 12 ml / L. The main function of nickel sulfate hexahydrate is to accelerate the reaction of copper ions and simultaneously inhibit the generation of hydrogen evolution phenomenon.

[0028] As a preferred method, the air flow rate into the electroless copper plating solution in Step 5 is 2.5 - 4 cm 3 / min, and the electroless plating time is 40 - 60 min.

[0029] The principle involved in the present invention is specifically as follows:

[0030] The catalytic activator and the diazo photosensitizer are physically dispersed in the glycidyl ether type epoxy resin to form an activation bridging layer for catalyzing the electroless copper plating reaction. A catalytic active source with high catalytic activity and excellent selectivity is selected. Through laser activation treatment, it can be reduced to catalytic metal particles and embedded in the intermediate bridging layer, thereby weakening the interfacial incompatibility between the activation bridging layer and the deposited copper layer, and thus improving the bonding force between them. At the same time, the thermal effect generated by the laser can rapidly increase the local temperature on the surface of the epoxy resin substrate, causing physical changes, generating a large number of micropores and nanoscale particle protrusions, increasing the specific surface area, and being conducive to adsorbing more metal catalyst particles. In addition, the energy of the laser radiation can break some chemical bonds on the surface of the substrate, further improving the surface chemical activity and promoting the deposition of subsequent electroless copper plating. Under the irradiation of ultraviolet light, the diazo photosensitizer will undergo photolysis, cleavage or corresponding other chemical reactions of the diazo group, resulting in local chemical property changes on the surface of the substrate, promoting the absorption of laser energy and transferring energy, so that excellent activation effects can be achieved at appropriate laser wavelengths and powers, improving the utilization rate of laser radiation and reducing energy loss.

[0031] Through the preparation and application of the above-mentioned laser-activated direct electroless plating sensitized material, the present invention has the following beneficial effects:

[0032] The metal catalytic particles in the catalytic activator are effectively deposited and fixed in the activation bridging layer by laser-activated reduction to promote the subsequent electroless copper plating reaction, while increasing the surface roughness and specific surface area of the substrate, thereby ensuring good adhesion between the epoxy resin substrate and the electroless copper plating layer. With the addition and use of photosensitizers, laser activation treatment can achieve higher-precision activation of micro-areas, further meeting the processing requirements of fine circuits, while improving the utilization rate of laser energy and the activation effect. Compared with the traditional electroless copper plating process, the application method of this laser-activated sensitizing material can avoid the use of a large amount of chemical reagents, effectively reduce environmental pollution, and conform to the current development concept of green environmental protection. In summary, the present invention has the characteristics of simple operation process, high laser energy utilization rate, excellent activation effect, etc. The prepared fine copper conductive circuit has high resolution and good uniformity of the copper plating layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 FIG. is a schematic flow chart of a laser-activated direct electroless plating sensitizing material and its application provided by the present invention.

[0034] Figure 2 FIG. is a metallographic microscope image of the copper layer chemically deposited on the surface of the epoxy resin substrate after laser activation of the present invention.

[0035] Figure 3 FIG. is a metallographic comparison diagram of the influence of laser activation treatment with / without photosensitizer on the catalytic electroless copper plating circuit. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0036] The present invention will be further described in detail below in conjunction with specific embodiments and the accompanying drawings of the specification. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0037] Example 1:

[0038] As Figure 1 shown, this embodiment provides an application method of a laser sensitizing material for the electroless copper plating process of an epoxy resin substrate. The specific steps are as follows:

[0039] Step 1: Preparation of the laser sensitizing material

[0040] Weigh 2 g of bisphenol A epoxy resin and place it in a dry and clean glass beaker. Then slowly add 4 mL of methyl ethyl ketone solution and stir evenly with a glass rod to fully mix them. Then add 0.02 g of pale yellow powder of tris(triphenylphosphine)rhodium(I) carbonylacetylacetonate and 2 mL of chloroform, and stir magnetically (400 rpm) at 25 °C for 20 min to form a pale yellow transparent solution; continue to add 0.05 g of diazo photosensitizer, keep magnetic stirring for 10 min, and mix evenly to enhance the absorption of laser energy and reaction activity of the substrate during the subsequent laser activation process; finally, add 3 mL of ethylenediamine as a curing agent to finally prepare a laser-activated direct electroless plating sensitization material;

[0041] Step 2: Pretreatment of the surface of the epoxy resin substrate

[0042] Cut the epoxy resin substrate into a square with a side length of 4×4 cm, then immerse it in an alkaline degreasing solution at 60 °C and stir and clean it with a glass rod for 10 min to remove organic stains such as grease on the surface, and then rinse off the residual degreasing solution with deionized water; then place the substrate in a beaker filled with anhydrous ethanol and clean it with an ultrasonic cleaner (110 W, 40 kHz) at room temperature for 15 min to remove other contaminating impurities on the surface of the substrate, and then rinse off the ethanol solution on the surface with a large amount of deionized water; then place the substrate in an oven with a temperature set at 80 °C and dry it for 20 min, and take it out and let it cool naturally to obtain a clean epoxy resin substrate for standby;

[0043] Step 3: Coating and curing of the laser sensitization material

[0044] Coat the laser sensitization material prepared in Step 1 on the surface of the clean epoxy resin substrate pretreated in Step 2 by spin coating method, place it in a constant temperature drying oven at 60 °C and cure it for 1 h, and then take it out and let it cool naturally;

[0045] Step 4: Laser activation of the substrate surface

[0046] Use ultraviolet laser to activate the surface of the epoxy resin substrate cured in Step 3. The laser wavelength used is 355 nm, and the set parameters are: scanning speed is 400 mm / s, power is 2 W, frequency is 32.5 kHz, pulse width is 20 μs, line width is 0.1 cm, and the number of processing times is 1. The purpose of this step is to reduce rhodium in the organometallic carbonyl compound and effectively deposit it on the surface of the substrate as a catalytic active source for the subsequent electroless copper plating reaction;

[0047] Step 5: Chemical copper deposition on the surface of the activated and modified epoxy resin substrate

[0048] Place the epoxy resin substrate after the laser activation treatment in step four in an electroless copper plating solution for chemical deposition. The specific composition of the electroless copper plating solution is as follows: potassium sodium tartrate tetrahydrate 32 g / L, disodium ethylenediaminetetraacetate dihydrate 2.5 g / L, copper sulfate pentahydrate 12.5 g / L, nickel sulfate hexahydrate 3.5 g / L, 2,2'-bipyridine 10 mg / L, potassium ferrocyanide trihydrate 20 mg / L, sodium hydroxide 10 g / L, formaldehyde solution 12 ml / L. By continuously stirring magnetically and introducing air into the electroless plating solution at 2.5 cm 3 / min to improve the stability of the plating solution, use a constant temperature water bath to heat and maintain the temperature of the electroless copper plating solution at 50 °C, and the electroless plating time is 60 min; repeatedly rinse the surface of the epoxy resin substrate deposited with copper circuits with anhydrous ethanol and a large amount of deionized water, and wait for the substrate to dry naturally at room temperature to obtain an epoxy resin substrate with copper circuits deposited on its surface.

[0049] Figure 2 It is the metallographic microscope image of the copper layer chemically deposited on the surface of the epoxy resin substrate after laser activation. It can be seen from the figure that the surface of the deposited copper circuit is flat and uniform, with good metallic luster.

[0050] Example 2:

[0051] Step 1: Preparation of laser sensitizing material

[0052] Weigh 1 g of bisphenol A glycidyl ether and mix it with 0.8 g of 4-methylhexahydrophthalic anhydride, place them in a dry and clean glass beaker, stir mechanically for 10 min to form a glycidyl ether epoxy resin solution, then add 0.1 g of copper acetate and 0.1 g of acetylacetone as catalytic activators, as well as 5 mL of butanone solution, stir magnetically (400 rpm) at 25 °C for 10 min to make them evenly mixed; continue to add 0.06 g of diazo photosensitizer, and keep magnetic stirring for 10 min to facilitate the absorption of laser energy and reaction activity of the substrate during the subsequent laser activation process; finally, add 2 mL of ethylenediamine as a curing agent to finally prepare a laser-activated direct electroless plating sensitizing material;

[0053] Step 2: Pretreatment of the surface of the epoxy resin substrate

[0054] Cut the epoxy resin substrate into a square with a side length of 4×4 cm, then immerse it in an alkaline degreasing solution at 60°C and stir it with a glass rod for 10 minutes to remove organic stains such as grease on the surface, and then rinse off the residual degreasing solution with deionized water; then place the substrate in a beaker filled with anhydrous ethanol and clean it with an ultrasonic cleaner (110W, 40kHz) at room temperature for 15 minutes to remove other contaminating impurities on the surface of the substrate, and then rinse off the ethanol solution on the surface with a large amount of deionized water; then place the substrate in an oven with a temperature set at 80°C and dry it for 20 minutes, and take it out to cool naturally to obtain a clean epoxy resin substrate for standby;

[0055] Step 3: Coating and curing of the laser sensitizing material

[0056] Coat the laser sensitizing material prepared in Step 1 on the surface of the clean epoxy resin substrate pretreated in Step 2 by the casting method, place it in a constant temperature drying oven at 100°C and cure it for 1 hour, and then take it out to cool naturally;

[0057] Step 4: Laser activation of the substrate surface

[0058] Use ultraviolet laser to perform activation treatment on the surface of the cured epoxy resin substrate in Step 3. The laser wavelength used is 355nm, and the set parameters are: scanning speed is 400mm / s, power is 2W, frequency is 32.5kHz, pulse width is 20μs, line width is 0.1cm, and the number of processing times is 1. The purpose of this step is to reduce the copper ions in copper acetylacetonate and effectively deposit them on the surface of the substrate as the catalytic active source for the subsequent electroless copper plating reaction;

[0059] Step 5: Electroless copper deposition on the surface of the activated and modified epoxy resin substrate

[0060] Place the epoxy resin substrate after laser activation treatment in Step 4 in an electroless copper plating solution for electroless deposition. The specific composition of the electroless copper plating solution is as follows: potassium sodium tartrate tetrahydrate 32g / L, disodium ethylenediaminetetraacetate dihydrate 2.5g / L, copper sulfate pentahydrate 12.5g / L, nickel sulfate hexahydrate 3.5g / L, 2,2'-bipyridine 10mg / L, potassium ferrocyanide trihydrate 20mg / L, sodium hydroxide 10g / L, formaldehyde solution 12ml / L. Improve the stability of the plating solution by continuous magnetic stirring and introducing air into the electroless plating solution at 3cm 3 / min, and use a constant temperature water bath to heat and maintain the temperature of the electroless copper plating solution at 50°C. The electroless plating time is 50 minutes; repeatedly rinse the surface of the epoxy resin substrate deposited with copper lines with anhydrous ethanol and a large amount of deionized water, and wait for the substrate to dry naturally at room temperature to prepare an epoxy resin substrate with copper lines deposited on the surface.

[0061] Figure 3 Au phase contrast diagram of the effect of laser activation treatment with / without photosensitizer on catalytic electroless copper plating circuit. Through observation and analysis, it is found that the introduction of photosensitizer effectively improves the selectivity and uniformity of copper deposition. The prepared copper circuit has better surface morphology continuity and structural integrity, while the copper circuit prepared without photosensitizer has problems such as lateral deposition defects and uneven copper plating.

[0062] In summary, the above embodiments are only used to illustrate the principle and its efficacy of the present invention, rather than to limit the present invention. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes completed by those with ordinary knowledge in the technical field without departing from the spirit and technical idea disclosed by the present invention should still be covered by the claims of the present invention.

Claims

1. A laser activated direct chemical plating sensitized material, characterized in that: The sensitizing material comprises the following components: 20-40 g / L of epoxy resin, 0.2-0.8 g / L of catalytic activator, 0.06-0.15 mol / L of organic solvent, 0.4-0.8 g / L of photosensitizer, and 0.05-0.1 mol / L of resin curing agent.

2. The laser activated direct chemical plating sensitized material according to claim 1, characterized in that: The epoxy resin is a glycidyl ether epoxy resin.

3. The laser activated direct chemical plating sensitized material according to claim 1, characterized in that: The catalytic activator includes one or more organic acid salts, organic metal carbonyl compounds, and acetylacetone complexes corresponding to rhodium, palladium, silver, copper, nickel, and cobalt that are soluble in organic solvents.

4. The laser activated direct chemical plating sensitized material according to claim 1, characterized in that: The photosensitizer is a diazo-type photosensitizer, specifically a diazonium salt or a diazo resin.

5. The laser activated direct chemical plating sensitized material according to claim 1, characterized in that: The organic solvent is one or more of acetone, butanone, chloroform, cyclohexane and ethylene glycol; the resin curing agent is ethylenediamine solution.

6. An application of laser activated direct chemical plating sensitized material, characterized in that: The following steps are involved: Step 1: preparing the laser activated direct chemical plating sensitized material as described in any one of claims 1 to 5; Step 2: Surface pretreatment of epoxy resin substrate: immerse the epoxy resin substrate in alkaline degreasing liquid at 60°C, then rinse it with deionized water and anhydrous ethanol repeatedly, then put the substrate into an oven to dry, take it out and cool it naturally to obtain a clean epoxy resin substrate for use; Step 3: coating and curing of laser sensitized material: coating the sensitized material on a clean epoxy resin substrate, placing it in a constant temperature drying oven for curing, and then taking it out for natural cooling; Step 4: Laser activation of the substrate surface: using ultraviolet laser to activate the surface of the epoxy resin substrate cured in step 3; Step 5: Place the epoxy resin substrate after the laser activation treatment in step 4 in a chemical copper plating solution for chemical deposition, continue magnetic stirring and introduce air into the chemical plating solution, and heat the chemical copper plating solution in a constant temperature water bath to maintain the temperature of the solution at 40-50°C; after the reaction is completed, rinse repeatedly with anhydrous ethanol and deionized water, and allow the substrate to dry naturally at room temperature.

7. The use of a laser activated direct chemical plating sensitized material according to claim 6, characterized in that: The coating method in step 3 is one of dip coating, casting and spin coating.

8. The use of a laser activated direct chemical plating sensitized material according to claim 6, characterized in that: The wavelength used for the laser activation is 355 nm, and the setting parameters are: scanning speed is 400 mm / s, power is 2 W, frequency is 32.5 kHz, pulse width is 20 μs, line width is 0.1 cm, and processing times is 1.

9. The use of a laser activated direct chemical plating sensitized material according to claim 6, characterized in that: The chemical copper plating solution has the following ingredients: 32 g / L potassium sodium tartrate tetrahydrate, 2.5 g / L disodium ethylenediaminetetraacetic acid dihydrate, 12.5 g / L copper sulfate pentahydrate, 3.5 g / L nickel sulfate hexahydrate, 10 mg / L 2,2'-bipyridine, 20 mg / L potassium ferrocyanide trihydrate, 10 g / L sodium hydroxide, and 12 ml / L formaldehyde solution.

10. The use of a laser activated direct chemical plating sensitized material according to claim 6, characterized in that: The air flow rate of the air introduced into the chemical plating solution is 2.5 to 4 cm 3 / min, the chemical plating time is 40 to 60min.

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