阅读说明：本技术 清洁方法 (Cleaning method ) 是由 吴清吉 陈裕丰 于 2019-06-03 设计创作，主要内容包括：一种清洁方法,包含提供已焊上IC的电路基板；提供大气电浆产生装置；导入气体至大气电浆产生装置中,并利用大气电浆产生装置活化气体以形成电浆,且让大气电浆产生装置以约100至约300米/秒(m/s)的风速喷出电浆；以及利用喷出的电浆清洁已焊上IC的电路基板的表面,以达成具有极佳移除污染物的能力。(A cleaning method comprises providing a circuit substrate having IC soldered thereon; providing an atmospheric plasma generating device; introducing a gas into the atmospheric plasma generating device, activating the gas by the atmospheric plasma generating device to form a plasma, and ejecting the plasma from the atmospheric plasma generating device at a wind speed of about 100 to about 300 meters per second (m/s); and cleaning the surface of the circuit substrate on which the IC has been soldered by using the plasma sprayed out, thereby achieving an excellent ability to remove contaminants.)

1. A method of cleaning, comprising:

providing a circuit substrate on which an IC is welded;

providing an atmospheric plasma generating device;

introducing a gas into the atmospheric plasma generating device, activating the gas by the atmospheric plasma generating device to form plasma, and making the atmospheric plasma generating device eject the plasma at a wind speed of 100 to 300 m/s; and

cleaning a surface of the IC-bonded circuit substrate by the plasma sprayed.

2. The method of claim 1, wherein introducing the gas into the atmospheric plasma generation device comprises: providing 20 to 40 standard liters/minute of the gas to the atmospheric plasma generating apparatus.

3. The cleaning method of claim 1, wherein activating the gas to form the plasma using the atmospheric plasma generating device comprises forming the plasma with a plasma potential of 60 to 80 volts.

4. The cleaning method as claimed in claim 3, wherein cleaning the surface of the IC-bonded circuit substrate by ejecting the plasma comprises contacting the plasma with the surface of the IC-bonded circuit substrate, and the atmospheric plasma generating device is moved at a scanning linear velocity of 50 to 200 mm/sec.

5. The method of claim 4, wherein cleaning the surface of the IC-bonded circuit substrate with the plasma comprises cleaning the surface of the IC-bonded circuit substrate with the plasma 10 to 50 times.

6. The method of claim 1, wherein activating the gas to form the plasma using the atmospheric plasma generating device comprises providing 500 to 700 watts of RF power to the atmospheric plasma generating device to activate the gas.

7. The method of claim 1, wherein activating the gas to form the plasma using the atmospheric plasma generating device comprises providing a multi-frequency power of 500 to 700 watts to the atmospheric plasma generating device to activate the gas.

8. The cleaning method as claimed in claim 1, wherein in the step of cleaning the surface of the IC-bonded circuit substrate by spraying the plasma, a first working distance exists between the atmospheric plasma generating means and the IC-bonded circuit substrate, and the first working distance is 5 to 8 mm.

9. The method of claim 1, wherein the gas is air, oxygen, nitrogen, carbon dioxide, argon, helium, or a combination thereof.

10. The method of claim 1, wherein cleaning the surface of the IC-bonded circuit substrate with the ejected plasma comprises removing at least one organic contaminant from the surface with the ejected plasma.

11. The method of claim 1, wherein cleaning the surface of the IC-bonded circuit substrate with the ejected plasma comprises removing at least one metal salt contaminant from the surface with the ejected plasma.

12. The method of claim 11, wherein removing the metal salt contaminants from the surface using the ejected plasma comprises:

oxidizing the metal salt contaminant into a metal oxide by the ejected plasma; and

removing the metal oxide by a lateral gas flow generated after the plasma impacts the surface.

13. The method of claim 1, wherein cleaning the surface of the IC-bonded circuit substrate with the ejected plasma comprises removing at least one inorganic contaminant from the surface with the ejected plasma.

Technical Field

Embodiments of the present invention relate to a cleaning method, and more particularly, to a method for cleaning contaminants on a circuit substrate having an IC bonded thereto by using atmospheric plasma.

Background

Plasma is a form of matter consisting primarily of charged ions and free electrons. In addition to solid, liquid and gaseous states, the plasma is often considered to be a fourth state of matter. The characteristic of plasma is utilized to induce many specific chemical and physical reactions, and is widely used in various fields, such as dry etching in semiconductor manufacturing, cleaning of circuit boards, and surface property modification of materials.

In the conventional printed circuit board manufacturing process, a wet etching process is used to clean the contaminants in the manufacturing process or on the workpiece. The wet etching process uses a large amount of water and solvent, not only forThe dry etching process is widely used because it is not environmentally friendly and wastes water. In the conventional dry etching process, organic contaminants are cleaned by oxygen or oxidizing gas, and inorganic contaminants are cleaned by using special gas (such as SF)₆、Cl₂Or the like). However, the special gas is expensive, has safety concerns and is not environment-friendly, so that the development of a new cleaning method is a problem to be solved.

Disclosure of Invention

One aspect of the invention is a cleaning method comprising providing a circuit substrate having an IC soldered thereon; providing an atmospheric plasma generating device; introducing a gas into the atmospheric plasma generating device, activating the gas by the atmospheric plasma generating device to form a plasma, and ejecting the plasma from the atmospheric plasma generating device at a wind speed of about 100 to about 300 meters per second (m/s); and cleaning the surface of the circuit substrate on which the IC is soldered by using the plasma sprayed out.

According to some embodiments of the invention, wherein introducing the gas into the atmospheric plasma generation device comprises providing about 20 to about 40 standard liters per minute (SLM) of the gas into the atmospheric plasma generation device.

According to some embodiments of the invention, wherein activating the gas to form the plasma using the atmospheric plasma generating device comprises forming the plasma with a plasma potential of about 60 to about 80 volts (V).

According to some embodiments of the present invention, wherein cleaning the surface of the IC-mounted circuit substrate with the ejected plasma comprises contacting the plasma with the surface of the IC-mounted circuit substrate, and the atmospheric plasma generating device is moved over the surface of the workpiece with a scanning linear velocity of about 50 to about 200 millimeters per second (mm/s).

According to some embodiments of the present invention, wherein cleaning the surface of the IC-mounted circuit substrate with the atmospheric plasma comprises cleaning the surface of the IC-mounted circuit substrate with the plasma about 10 to about 50 times.

According to some embodiments of the present invention, wherein activating the gas to form the plasma using the atmospheric plasma generating device comprises providing about 500 to about 700 watts (watt) of radio frequency power to the atmospheric plasma generating device to activate the gas.

According to some embodiments of the present invention, wherein activating the gas to form the plasma using the atmospheric plasma generating device comprises providing a multi-frequency power of about 500 to about 700 watts (watt) to the atmospheric plasma generating device to activate the gas.

According to some embodiments of the present invention, in the step of cleaning the surface of the circuit substrate on which the IC is soldered by using the jetted plasma, there is a first working distance between the atmospheric plasma generating device and the circuit substrate on which the IC is soldered, and the first working distance is about 5 to about 8 millimeters (mm).

According to some embodiments of the invention, wherein the gas is air, oxygen, nitrogen, carbon dioxide, argon, helium, or a combination thereof.

According to some embodiments of the present invention, wherein cleaning the surface of the circuit substrate to which the IC has been soldered using the ejected plasma comprises removing at least one organic contaminant from the surface using the ejected plasma.

According to some embodiments of the present invention, wherein cleaning the surface of the circuit substrate to which the IC has been soldered with the ejected plasma comprises removing at least one metal salt contaminant from the surface with the ejected plasma.

According to some embodiments of the present invention, wherein removing metal salt contaminants from the surface using the ejected plasma comprises oxidizing the metal salt contaminants to metal oxides using the ejected plasma; and removing the metal oxide by using a lateral gas flow generated after the high-speed plasma gas flow impacts the surface.

According to some embodiments of the present invention, wherein cleaning the surface of the circuit substrate to which the IC has been bonded with the ejected plasma comprises removing at least one inorganic contaminant from the surface with the ejected plasma.

Drawings

Aspects of the present disclosure will be better understood when the following detailed description is read in conjunction with the accompanying drawings. It is noted, however, that in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion.

FIG. 1 is a schematic diagram of a system utilizing a plasma cleaning method, according to some embodiments of the present invention;

FIGS. 2A-2C are enlarged partial schematic views of the area 300 of FIG. 1 according to some embodiments of the present invention;

fig. 3A-3C are enlarged partial views of the region 300 of fig. 1 according to some embodiments of the invention.

Detailed Description

The present disclosure now provides many different embodiments, or examples, for implementing different features of the disclosure. The components and arrangements of specific embodiments are described below to simplify the present disclosure. These are merely exemplary and are not intended to limit the present disclosure. For example, a first element formed "on" or "over" a second element can include the first element in direct contact with the second element in embodiments, or can include additional elements between the first element and the second element such that the first element and the second element are not in direct contact. Moreover, in various examples of the present disclosure, reference numerals and/or letters may be used repeatedly. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations. In addition, various features may be drawn to different scales for simplicity and clarity.

Further, terms such as "under," "below," "lower," "above," "higher," and other similar relative spatial relationships may be used herein to describe one element or feature's relationship to another element or feature in the drawings. The relative spatial relationships are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as "below" or "beneath" other elements or features would then be oriented "above" the other elements or features. Thus, the exemplary term "lower" can encompass both an orientation of upper and lower. The device may have other guiding ways (rotating 90 degrees or towards other directions), and the relative spatial relationship can be interpreted according to the above ways.

In this document, unless the context requires otherwise, the word "a" and "an" may mean "one" or "more".

FIG. 1 is a schematic diagram of a system for cleaning using an atmospheric plasma generation device, according to some embodiments. The system 100 includes an atmospheric plasma generator 110, an atmospheric plasma generator controller 120, a stage 130, a pumping port 140, a gas inlet tube 160, and a circuit substrate 210 on which ICs are bonded.

According to some embodiments, the system 100 provides a cleaning method comprising providing a circuit substrate 210 with an IC bonded thereon; providing an atmospheric plasma generating device 110; introducing a gas 10 into the atmospheric plasma generating device 110, activating the gas 10 by the atmospheric plasma generating device 110 to form a plasma 180, and letting the atmospheric plasma generating device 110 eject the plasma 180 at a wind speed of about 100 to about 300 meters per second (m/s); and cleaning the surface 212 of the IC-bonded circuit substrate 210 by the plasma 180.

The gas 10 may be continuously supplied by a gas supply (not shown) and introduced into the atmospheric plasma generating device 110 through the gas inlet pipe 160. In some embodiments, the step of introducing the gas 10 into the atmosphere plasma generating device 110 comprises providing about 20 to about 40 standard liters per minute (SLM) of the gas 10 into the atmosphere plasma generating device 110. In addition, the present embodiment uses low cost and environmentally friendly gases for cost and safety considerations. Thus, in some embodiments, the gas 10 may be air, oxygen, nitrogen, carbon dioxide, argon, helium, or a combination thereof.

The atmospheric plasma generator 110 is electrically connected to the atmospheric plasma generator controller 120 through a wire 150. The atmospheric plasma generator controller 120 provides the power required by the atmospheric plasma generator 110, so that the atmospheric plasma generator 110 can activate the gas 10 to generate the plasma 180. In another embodiment, the atmospheric plasma generation device controller 120 may also include, but is not limited to, various external components, such as a computer, to regulate various process parameters in the system 100. The atmospheric plasma generator controller 120 may be a radio frequency power system or a multi-frequency power system. Therefore, in some embodiments, the step of activating the gas 10 to form the plasma 180 using the atmospheric plasma generating device 110 includes providing about 500 to about 700 watts (watt) of RF power to the atmospheric plasma generating device 110 to activate the gas 10. In some other embodiments, the step of activating the gas 10 to form the plasma 180 using the atmospheric plasma generating device 110 comprises providing a multi-frequency power of about 500 to about 700 watts (watt) to the atmospheric plasma generating device 110 to activate the gas 10.

Any point in the plasma 180 has the same potential. That is, the plasma 180 may be considered as a plasma body having an equipotential (equilibrium potential), and the plasma potential (Vp) is the potential that appears when the potential is measured relative to ground (ground line 170). In some embodiments, activating the gas 10 to form the plasma 180 using the atmospheric plasma generating device 110 includes forming the plasma 180 with a plasma potential of about 60 to about 80 volts (V). If the plasma potential is below 60 volts, it may not be possible to provide sufficient ion bombardment energy to clean contaminants from the surface 212 of the circuit substrate 210 to which the IC has been bonded.

The atmospheric plasma generating device 110 may be coupled to a flexible mechanism so that it can be moved linearly and clean different areas of the circuit substrate 210 where ICs are soldered. In some embodiments, the step of cleaning the surface 212 of the IC-bonded circuit substrate 210 with the ejected plasma 180 includes contacting the plasma 180 with the surface 212 of the IC-bonded circuit substrate 210, and the atmospheric plasma generating device 110 is moved at a scanning linear velocity of about 50 to about 200 millimeters per second (mm/s). In one embodiment, the scanning linear velocity of the atmospheric plasma generating device 110 is lower than 50 mm/s, so that the circuit substrate 210 with the soldered IC is excessively heated, causing warpage of the circuit substrate or damage to the components on the workpiece. In another embodiment, the scanning line speed of the atmospheric plasma generating device 110 is higher than 200 mm/s, which may cause the plasma 180 to stay on the circuit substrate 210 with the IC bonded thereon too short for thorough cleaning. In addition, a first working distance H exists between the atmospheric plasma generating device 110 and the circuit substrate 210 on which the IC is soldered. In some embodiments, the first working distance H between the atmospheric plasma generating device 110 and the IC-bonded circuit substrate 210 is about 5 to about 8 millimeters (mm).

When organic contaminants are present on the surface 212 of the IC-bonded circuit substrate 210, the plasma 180 may chemically react with the organic contaminants, causing the organic contaminants to react into gaseous reaction products. This gaseous reaction product may then be exhausted via the extraction port 140. For example, in one embodiment, when the gas source of the plasma 180 is oxygen, the chemical reaction between the plasma 180 and the organic contaminants is as follows: o is^* _(g)+C_xH_y(s)→xCO_2(g)+1/2yH₂O_(g). Thus, in some embodiments, cleaning the surface 212 of the IC-bonded circuit substrate 210 with the ejected plasma 180 includes removing at least one organic contaminant from the surface 212 with the ejected plasma 180.

Next, please refer to fig. 2A to 2C, which are schematic partial enlarged views of the area 300 in fig. 1 according to some embodiments. In some embodiments, the surface 212 of the IC-bonded circuit substrate 210 has metal salt contaminants 220, and the step of cleaning the surface 212 of the IC-bonded circuit substrate 210 with the sprayed plasma 180 may include removing at least one of the metal salt contaminants 220 from the surface 212 with the sprayed plasma 180.

More specifically, in fig. 2A, the plasma 180 is sprayed downward to contact the metal salt contaminants 220 and chemically react with the metal salt contaminants, thereby oxidizing the metal salt contaminants 220 into metal oxides 220' in fig. 2B. In addition, the downward ejection of the plasma 180 continues to impact the surface 212 of the IC-bonded circuit substrate 210 and generates a lateral flow 190. Finally, in fig. 2C, the metal oxide 220' is removed from the surface 212 of the circuit substrate 210 along with the lateral gas flow 190. In some embodiments, the velocity of the plasma 180 is about 100 to about 300 m/s. When the velocity of the plasma 180 is less than 100 m/s, the lateral flow 190 of the gas generated by the plasma 180 striking the surface 212 is not strong enough to remove the metal oxide 220' attached to the surface 212. When the speed of the plasma 180 is higher than 300 m/s, the impact force of the plasma 180 on the circuit substrate 210 to which the IC is soldered may be too strong to cause damage to the circuit substrate 210 to which the IC is soldered.

The number of processes to be performed on the same area of the circuit substrate 210 on which the IC is soldered can be adjusted as required by the plasma 180 ejected from the atmospheric plasma generator 110. If the number of cleaning passes is less than 10, excessive contaminants may remain on the surface 212 of the IC-bonded circuit substrate 210. However, excessive cleaning times (e.g., more than 50 times) may increase the risk of damaging the surface 212 of the circuit substrate 210 to which the IC has been soldered. Thus, in some embodiments, the step of cleaning the surface 212 of the IC-mounted circuit substrate 210 with the plasma 180 comprises cleaning the surface 212 of the IC-mounted circuit substrate 210 with the plasma 180 from about 10 to about 50 times. In some embodiments, after the step of contacting the plasma 180 to the surface 212 of the IC-bonded circuit substrate 210, the surface 212 has a residual concentration of acid ions of less than 4 milligrams per square inch (μ g/in)²). The conventional chemical reaction of plasma and metal salt pollutants generates solid metal oxide and volatile gaseous products. The gaseous products can be removed from the surface of the circuit substrate with the IC soldered thereon by the air-pumping system, and the solid metal oxide will remain on the surface of the circuit substrate with the IC soldered thereon, and cannot be removed by air-pumping. However, according to some embodiments of the present disclosure, the high-speed plasma gas flow may be used to generate a lateral gas flow after impacting the surface of the circuit substrate to which the IC is bonded to remove the metal salt contaminants attached to the surface of the circuit substrate to which the IC is bonded.

Continuing to refer to fig. 3A-3C, an enlarged partial schematic view of region 300 of fig. 1 is shown, according to some embodiments. In some embodiments, the surface 212 of the IC-bonded circuit substrate 210 has contaminants 220, wherein the contaminants 220 may include inorganic contaminants 215A and etchable contaminants 215B, and the step of cleaning the surface 212 of the IC-bonded circuit substrate 210 with the ejected plasma 180 may include removing at least one of the inorganic contaminants 215A from the surface 212 with the ejected plasma 180.

More specifically, in FIG. 3A, the plasma 180 is ejected downward to contact the contaminant 220, and the lateral gas flow 190 generated when the plasma 180 impacts the surface 212 also drives the plasma 180 to etch the contaminant 220 in the lateral direction. As shown in fig. 3B, the etchable contaminant 215B of the contaminant 220 is removed by the plasma 180. After the etchable contaminants 215B are removed, the inorganic contaminants 215A lose their attachment points and are thus removed. With continued reference to fig. 3C, the lateral gas flow 190 removes the inorganic contaminants 215A from the surface 212 of the IC-mounted circuit substrate 210 while the inorganic contaminants 215A are not yet secured to the surface 212 of the IC-mounted circuit substrate 210. Conventional inorganic contaminants cannot be removed from the surface of the circuit substrate to which the IC has been bonded by dry etching (e.g., using plasma). However, according to some embodiments of the present disclosure, when the plasma cleaning is performed on the surface of the circuit substrate on which the IC is soldered, the etchable contaminants on the surface of the circuit substrate on which the IC is soldered are removed, and the inorganic contaminants are carried away by the lateral gas flow while the etchable contaminants are removed.

Finally, in order to confirm that the cleaning method of the present embodiment has an excellent ability to remove contaminants, the following experiment was performed.

Analysis of residual quantity of acid radical ion before and after plasma treatment

The sample used for the test was a commercially available Circuit board with Integrated Circuit (IC). The residual amount of acid ions on the circuit board before and after the plasma treatment in this embodiment was analyzed. As shown in the table one below, SPEC is an industry standard specification, which is a tolerable standard residue on a circuit board, and examples 1 to 3 differ in the number of plasma cleans. Specifically, the number of plasma cleanings in example 1 was 0, i.e., samples that had not been plasma treated. The number of plasma cleanings in example 2 was 10. The number of plasma cleanings in example 3 was 20.

Watch 1

Example 1 residual sulfate ion (SO) before plasma treatment₄ ^2-) ComprisesThe amount was 436.120636. mu.g/in²Clearly exceeding the allowable value of 4. mu.g/in²Many. Example 2 residual sulfate ion (SO) after 10 cleanings with plasma treatment₄ ^2-) The content is 4.926163 mug/in²Still slightly larger than 4 mu g/in defined by standard specification². Example 3 residual sulfate ion (SO) after 20 plasma cleaning₄ ^2-) The content is 1.18875 mug/in²Much less than 4 μ g/in as defined by the standard specification². Therefore, the plasma processing of the surface of the circuit board using the embodiment of the present invention can have an excellent cleaning effect.

The foregoing outlines features of several embodiments so that those skilled in the art may better understand the aspects of the present disclosure. Those skilled in the art should appreciate that the present disclosure may be readily utilized as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions, and alterations herein without departing from the spirit and scope of the present disclosure.