CN114211068A - Method for forming full IMCs structure welding spot by prefabricating IMCs welding pad - Google Patents
Method for forming full IMCs structure welding spot by prefabricating IMCs welding pad Download PDFInfo
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- CN114211068A CN114211068A CN202111660949.0A CN202111660949A CN114211068A CN 114211068 A CN114211068 A CN 114211068A CN 202111660949 A CN202111660949 A CN 202111660949A CN 114211068 A CN114211068 A CN 114211068A
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K1/00—Soldering, e.g. brazing, or unsoldering
- B23K1/0008—Soldering, e.g. brazing, or unsoldering specially adapted for particular articles or work
- B23K1/0016—Brazing of electronic components
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K1/00—Soldering, e.g. brazing, or unsoldering
- B23K1/20—Preliminary treatment of work or areas to be soldered, e.g. in respect of a galvanic coating
- B23K1/203—Fluxing, i.e. applying flux onto surfaces
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K1/00—Soldering, e.g. brazing, or unsoldering
- B23K1/20—Preliminary treatment of work or areas to be soldered, e.g. in respect of a galvanic coating
- B23K1/206—Cleaning
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K3/00—Tools, devices, or special appurtenances for soldering, e.g. brazing, or unsoldering, not specially adapted for particular methods
- B23K3/08—Auxiliary devices therefor
- B23K3/085—Cooling, heat sink or heat shielding means
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K35/00—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting
- B23K35/02—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by mechanical features, e.g. shape
- B23K35/0222—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by mechanical features, e.g. shape for use in soldering, brazing
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K35/00—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting
- B23K35/22—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by the composition or nature of the material
- B23K35/24—Selection of soldering or welding materials proper
- B23K35/28—Selection of soldering or welding materials proper with the principal constituent melting at less than 950 degrees C
- B23K35/282—Zn as the principal constituent
Abstract
The invention discloses a method for forming full IMCs structure welding spots by prefabricating IMCs welding pads, which belongs to the field of material preparation and connection, is suitable for preparing micro braze welding butt joints of full IMCs, is applied to the reliability research of mechanics, thermal and electricity of microelectronic connection, and is realized by the following steps: solder skip printing; heating and remelting the solder to form a solder ball; selecting solder balls according to size requirements; placing the solder balls on the copper sheet on the surface of the printed circuit board, heating and remelting the solder balls for combination and forming a bump structure; corroding the salient point structure; manufacturing two IMCs bonding pads; heating and remelting to bond the IMCs pads; and grinding and fine polishing the welding points of the IMCs welding pads to finally obtain the full IMCs welding points. The invention can avoid the condition that the anisotropy of Sn in the Sn-based solder reduces the reliability of the welding spot; simple process and low cost. The key steps of the invention are that the solder is coated on the prefabricated IMCs pads for remelting and cooling, and the components of the welding spots are determined to be IMCs by EDS technology.
Description
Technical Field
The invention relates to the field of material preparation and connection, in particular to a method for forming a full IMCs structure welding spot by prefabricating an IMCs welding disc.
Background
The welding spots play a role in mechanical connection and electric signal transmission in microelectronic interconnection, the microelectronic packaging space is reduced, the number of components is increased, and the heat generation of the components is intensified; moreover, the current density borne by the solder joint is increased, and under the drive of thermodynamic and kinetic factors, IMCs formed in the solder can grow or dissolve, so that the failure of the solder joint is caused, and the service life and the reliability of an electronic product are influenced.
At present, the solder used in microelectronic interconnection is mainly Sn-based solder (containing more than 80% of Sn), and research shows that the Sn-based lead-free interconnection welding spot prepared by melting often has a single crystal or twin crystal structure, the BCT crystal structure of β -Sn has anisotropy (a is 0.5832, c is 0.3182, and c/a is 0.546), and diffusion of atoms such as Cu in the solder joint exhibits strong anisotropy due to different crystal grain orientations of β -Sn, for example, the diffusion rate of Cu along the c axis of a beta-Sn crystal lattice is 2 multiplied by 10 < -6 > cm2/s at 25 ℃, which is 500 times of the diffusion rate along the a and b axes, the directional diffusion behavior can seriously affect the electromigration behavior of welding spots, the Sn-based solder single crystal welding spots with c axes parallel to the current direction are easy to generate early failure, the growth rate of the interfacial IMCs is about 10 times that of a single crystal welding point or a twin crystal welding point with the c axis vertical to the current direction. Therefore, it is a difficult problem to avoid the influence of the anisotropy of β -Sn in the solder joint. After the interconnection is completed, each welding spot has a unique crystal orientation, so that some welding spots inevitably fail in advance in the use process of the electronic product due to the unfavorable orientation of beta-Sn crystal grains, and the service life of the electronic product is further reduced. It can be seen that the grain orientation of the solder joint can seriously affect the service reliability.
Disclosure of Invention
The invention aims to provide a method for forming a welding spot with a full IMCs structure by prefabricating an IMCs welding disc, which aims to solve the problems in the prior art, obtain the welding spot with the full IMCs structure, avoid the influence of beta-Sn anisotropy, and simultaneously ensure the realization of lower temperature combination and higher temperature service in microelectronic interconnection.
In order to achieve the purpose, the invention provides the following scheme: the invention provides a method for forming a welding spot with a full IMCs structure by prefabricating an IMCs welding disc, which is realized by the following steps:
step S1: solder skip printing;
step S2: heating and remelting the solder after the printing leakage to form a solder ball, and cooling;
step S3: carrying out ultrasonic cleaning treatment on the solder balls;
step S4: selecting the solder balls according to size requirements;
step S5: ultrasonically cleaning and processing the printed circuit board;
step S6: placing the solder balls on the copper sheet on the surface of the printed circuit board, heating, remelting and combining to form a bump structure, and cooling;
step S7: corroding the bump structure to enable only IMCs pads to be left on the copper sheet of the printed circuit board;
step S8: making two pads of the IMCs by the steps S1 to S7;
step S9: heating and remelting to combine the two IMCs pads, and cooling;
step S10: grinding welding spots of the two IMCs welding pads, and finely polishing a specified interface to finally obtain full IMCs welding spots;
step S11: and acquiring EDS data of the fine polishing section, and determining whether the welding spot is a welding spot consisting of IMCs.
Preferably, the solder is Sn-Ag-Bi-In series lead-free solder.
Preferably, in the step S2, the step S6, and the step S9, a hot air welding device is used to perform a heating remelting process, wherein the remelting temperature is 220 ℃ to 280 ℃.
Preferably, in the step S2, the step S6, and the step S9, the cooling process is performed by any one of furnace cooling, air cooling, and water cooling.
Preferably, in step S3, the solder balls are cleaned in an ultrasonic cleaning machine by using acetone and ethanol sequentially.
Preferably, in step S5, the surface of the printed circuit board is cleaned with ethanol in an ultrasonic cleaning machine.
Preferably, in step S7, the soldered bump structure is etched with a nitric acid-ethanol-water solution, and observed through a metallographic microscope, so as to ensure that all Sn is etched, and the IMCs at the Cu-Sn interface are retained.
Preferably, between the step S5 and the step S6, a layer of flux is coated on the printed circuit board.
Preferably, in step S9, any one of the pads of the IMCs is inverted, placed in parallel and perfectly aligned with another one of the pads of the IMCs, and reflowed by heating to bond the two pads of the IMCs.
Preferably, in step S8, an oxidizer and a solder are sequentially coated on the surfaces of the two manufactured IMCs pads, respectively.
The invention discloses the following technical effects: the method can obtain the welding spots with the full IMCs structure and avoid the influence of the anisotropy of the beta-Sn. Besides, because the melting point of the IMCs is higher than that of the Sn-based solder, the realization of lower-temperature combination and higher-temperature service in microelectronic interconnection can be ensured, and the situation that the reliability of the welding spot is reduced due to the anisotropy of Sn in the welding spot of the Sn-based solder can be avoided by predicting the welding spot with the full IMCs structure. The method has the advantages of low cost and low technological process.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without inventive exercise.
FIG. 1 is a photograph of a screen with different apertures during a screen printing process according to the present invention;
FIG. 2 is an SEM photograph of a solder joint of the present invention;
FIG. 3 is an EDS analysis photograph of a solder joint of a full IMCs structure of the present invention;
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below.
The invention provides a method for forming full IMCs structure welding spots by prefabricating IMCs welding pads, belongs to the field of material preparation and connection, is suitable for welding spots with low-temperature combination with high-temperature service characteristics in microelectronic interconnection, and is applied to reliability research of mechanics, thermal and electricity of microelectronic connection. The invention aims to avoid the influence of the anisotropy of Sn on the reliability and the service life of a welding spot in the microelectronic interconnection, and manufacture the welding spot with a full IMCs structure. Meanwhile, the full IMCs welding spot mechanical, thermal and electrical tests are expected to be used for characterization, the understanding level of how the full IMCs structure influences the reliability of the welding spot and the service life is improved, and the purpose of evaluating the reliability of the welding spot is achieved. Referring to fig. 1 to 3, in order to achieve the above object, the present invention provides a method for forming a solder joint of a full IMCs structure by prefabricating an IMCs pad, which is specifically implemented by the following steps:
step S1: solder printing, namely printing Sn-Ag-Bi-In series solder on the glass plate through a screen;
step S2: heating and remelting the solder after the screen printing by hot air welding equipment to form a solder ball, and cooling;
step S3: ultrasonic cleaning treatment is carried out on the solder balls, and acetone and ethanol are sequentially used for cleaning the solder balls in an ultrasonic cleaning machine;
step S4: selecting solder balls according to the size requirement, and selecting the solder balls meeting the size requirement under a stereoscopic microscope for later use;
step S5: ultrasonic cleaning Printed Circuit Board (PCB) with ethanol, and coating a layer of flux on the PCB;
step S6: placing the prefabricated Sn-Ag-Bi-In solder balls on a copper sheet on the surface of the printed circuit board, heating the solder balls by hot air welding equipment to enable the solder balls to be remelted and combined with the copper sheet on the printed circuit board, and cooling;
step S7: corroding the bump structure, corroding the welded bump structure by using a nitric acid-ethanol-water solution (the volume ratio is 1:1:8), observing by using a metallographic microscope to ensure that all Sn is corroded, and reserving an Intermetallic compound (IMC) at a Cu-Sn interface;
step S8: two IMCs pads are made by steps S1 through S7;
step S9: heating and remelting to combine the two IMCs pads, and cooling;
step S10: grinding welding spots of the two IMCs welding pads, and finely polishing an appointed interface to finally obtain full IMCs welding spots;
step S11: and acquiring EDS data of the fine polishing section, and determining whether the welding spot is a welding spot consisting of IMCs.
The method has the advantage that the situation that the reliability of the welding spot is reduced due to the anisotropy of Sn in the welding spot of the Sn-based brazing filler metal can be avoided by predicting the welding spot with the full IMCs structure. Simple process and low cost.
In a further optimized scheme, the solder is Sn-Ag-Bi-In series lead-free solder.
In the further optimization scheme, in the step S2, the step S6 and the step S9, hot air welding equipment is adopted for heating remelting treatment, and the remelting temperature is 220-280 ℃.
In a further preferred embodiment, in steps S2, S6, and S9, the cooling process is performed by any one of furnace cooling, air cooling, and water cooling.
And further optimizing the scheme, in the step S7, corroding the welded bump structure by using a nitric acid-ethanol-water solution, observing by using a metallographic microscope, ensuring that all Sn is corroded, and keeping IMCs at the Cu-Sn interface.
In a further optimization scheme, In step S8, the surfaces of two prepared IMCs pads are respectively coated with a combustion improver and solder In sequence, before the solder is coated, Sn-Ag-Bi-In solder is printed on a glass plate through a screen, and the solder on the glass plate is scraped and coated on the IMCs pads by using a flat-head toothpick.
In a further optimization scheme, in step S9, any one of the IMCs pads is inverted, placed in parallel with another one of the IMCs pads and completely aligned with the another one of the IMCs pads, heated by a hot air welding device to reflow the solder between the IMCs pads on the two sides and ensure that the IMCs pads on the two sides are bonded with the solder, and cooled.
The method can obtain the welding spots with the full IMCs structure and can avoid the influence of the anisotropy of the beta-Sn. In addition, the melting point of the IMCs is higher than that of the Sn-based solder, so that low-temperature combination and high-temperature service in microelectronic interconnection can be guaranteed.
Example 1
Referring to fig. 1-3, the present embodiment provides a method for forming solder joints of full IMCs structures by prefabricating IMCs pads, which is implemented by the following steps:
step S1: printing Sn-Ag-Bi-In solder on a glass plate through a drain screen, wherein the size of the drain screen is 700 mu m;
step S2: heating the solder after the screen printing by hot air welding equipment (PACE ST325 in USA, the same below) to form a solder ball with the size of 700 mu m, remelting at 245 ℃ for 30s, and furnace-cooling for 30 s;
step S3: cleaning the solder balls in an ultrasonic cleaning machine by using acetone and ethanol in sequence;
step S4: selecting the solder balls meeting the size requirement under a stereoscopic microscope for later use;
step S5: cleaning the surface of a printed circuit board by using ethanol in an ultrasonic cleaning machine, and coating a layer of soldering flux on the printed circuit board;
step S6: placing the prefabricated Sn-Ag-Bi-In solder balls on a copper sheet on the surface of a printed circuit board, heating by hot air welding equipment to re-melt the solder balls and combine the solder balls with the copper sheet on the printed circuit board, wherein the re-melting temperature is 245 ℃, the re-melting time is 30s, and the solder balls are cooled for 30s along with a furnace;
step S7: corroding the welded bump structure by using a nitric acid-ethanol-water solution (volume ratio is 1:1:8), observing by using a metallographic microscope, ensuring that all Sn is corroded, and keeping IMCs at a Cu-Sn interface;
step S8: coating soldering flux on the surface of a bonding pad of the IMC (hereinafter referred to as an IMC bonding pad);
step S9: printing Sn-Ag-Bi-In solder on a glass plate through a drain screen, wherein the size of the drain screen is 250 mu m;
step S10: scraping the solder on the glass plate by using a flat-head toothpick, and coating the solder on the IMC bonding pad;
step S11: inverting any IMC pad structure to be parallel to another IMCs pad and completely aligning the IMC pad structure;
step S12: and (4) heating the structure completed in the step S11 by using hot air welding equipment to enable the solder between the IMCs pads on the two sides to be remelted and ensure that the IMCs pads on the two sides are combined with the solder, and cooling. The remelting temperature is 245 ℃, the remelting time is 30s, and the equipment is cooled for 30 s;
step S13: grinding the welding spots, and finely polishing the specified interface to finally obtain full IMCs welding spots;
step S14: and acquiring EDS data of the fine polishing section, and determining that the welding spot is a micro-interconnection welding spot consisting of IMCs with preferred orientation.
Example 2
Referring to fig. 1-3, the present embodiment provides a method for forming solder joints of full IMCs structures by prefabricating IMCs pads, which is implemented by the following steps:
step S1: printing Sn-Ag-Bi-In solder on the glass plate through a drain screen, wherein the size of the drain screen is 650 mu m;
step S2: heating the solder after the screen printing by hot air welding equipment (PACE ST325 in USA, the same below) to form a solder ball with the size of 650 mu m, remelting at 245 ℃ for 30s, and furnace-cooling for 30 s;
step S3: cleaning the solder balls in an ultrasonic cleaning machine by using acetone and ethanol in sequence;
step S4: selecting the solder balls meeting the size requirement under a stereoscopic microscope for later use;
step S5: cleaning the surface of a printed circuit board by using ethanol in an ultrasonic cleaning machine, and coating a layer of soldering flux on the printed circuit board;
step S6: placing the prefabricated Sn-Ag-Bi-In solder balls on a copper sheet on the surface of a printed circuit board, heating by hot air welding equipment to re-melt the solder balls and combine the solder balls with the copper sheet on the printed circuit board, wherein the re-melting temperature is 245 ℃, the re-melting time is 30s, and the solder balls are cooled for 30s along with a furnace;
step S7: corroding the welded bump structure by using a nitric acid-ethanol-water solution (volume ratio is 1:1:8), observing by using a metallographic microscope, ensuring that all Sn is corroded, and keeping IMCs at a Cu-Sn interface;
step S8: coating soldering flux on the surface of a bonding pad of the IMC (hereinafter referred to as an IMC bonding pad);
step S9: printing Sn-Ag-Bi-In solder on a glass plate through a drain screen, wherein the size of the drain screen is 200 mu m;
step S10: scraping the solder on the glass plate by using a flat-head toothpick, and coating the solder on the IMC bonding pad;
step S11: inverting any IMC pad structure to be parallel to another IMCs pad and completely aligning the IMC pad structure;
step S12: and (4) heating the structure completed in the step S11 by using hot air welding equipment to enable the solder between the IMCs pads on the two sides to be remelted and ensure that the IMCs pads on the two sides are combined with the solder, and cooling. The remelting temperature is 245 ℃, the remelting time is 30s, and the equipment is cooled for 30 s;
step S13: grinding the welding spots, and finely polishing the specified interface to finally obtain full IMCs welding spots;
step S14: and acquiring EDS data of the fine polishing section, and determining that the welding spot is a micro-interconnection welding spot consisting of IMCs with preferred orientation.
Example 3
Referring to fig. 1-3, the present embodiment provides a method for forming solder joints of full IMCs structures by prefabricating IMCs pads, which is implemented by the following steps:
step S1: printing Sn-Ag-Bi-In solder on a glass plate through a drain screen, wherein the size of the drain screen is 700 mu m;
step S2: heating the solder after the screen printing by hot air welding equipment (PACE ST325 in USA, the same below) to form a solder ball with the size of 700 mu m, remelting at 220 ℃ for 40s, and furnace-cooling for 40 s;
step S3: cleaning the solder balls in an ultrasonic cleaning machine by using acetone and ethanol in sequence;
step S4: selecting the solder balls meeting the size requirement under a stereoscopic microscope for later use;
step S5: cleaning the surface of a printed circuit board by using ethanol in an ultrasonic cleaning machine, and coating a layer of soldering flux on the printed circuit board;
step S6: placing the prefabricated Sn-Ag-Bi-In solder balls on a copper sheet on the surface of a printed circuit board, heating the solder balls by hot air welding equipment to re-melt the solder balls and combine the solder balls with the copper sheet on the printed circuit board, wherein the re-melting temperature is 220 ℃, the re-melting time is 40s, and cooling the solder balls for 40s along with a furnace;
step S7: corroding the welded bump structure by using a nitric acid-ethanol-water solution (volume ratio is 1:1:8), observing by using a metallographic microscope, ensuring that all Sn is corroded, and keeping IMCs at a Cu-Sn interface;
step S8: coating soldering flux on the surface of a bonding pad of the IMC (hereinafter referred to as an IMC bonding pad);
step S9: printing Sn-Ag-Bi-In solder on a glass plate through a drain screen, wherein the size of the drain screen is 250 mu m;
step S10: scraping the solder on the glass plate by using a flat-head toothpick, and coating the solder on the IMC bonding pad;
step S11: inverting any IMC pad structure to be parallel to another IMCs pad and completely aligning the IMC pad structure;
step S12: and (4) heating the structure completed in the step S11 by using hot air welding equipment to enable the solder between the IMCs pads on the two sides to be remelted and ensure that the IMCs pads on the two sides are combined with the solder, and cooling. Remelting at 220 deg.C for 40s, and cooling for 40 s;
step S13: grinding the welding spots, and finely polishing the specified interface to finally obtain full IMCs welding spots;
step S14: and acquiring EDS data of the fine polishing section, and determining that the welding spot is a micro-interconnection welding spot consisting of IMCs with preferred orientation.
Example 4
Referring to fig. 1-3, the present embodiment provides a method for forming solder joints of full IMCs structures by prefabricating IMCs pads, which is implemented by the following steps:
step S1: printing Sn-Ag-Bi-In solder on a glass plate through a drain screen, wherein the size of the drain screen is 700 mu m;
step S2: heating the solder after the screen printing by hot air welding equipment (PACE ST325 in USA, the same below) to form a solder ball with the size of 700 mu m, remelting at 280 ℃ for 20s, and cooling for 20s with a furnace;
step S3: cleaning the solder balls in an ultrasonic cleaning machine by using acetone and ethanol in sequence;
step S4: selecting the solder balls meeting the size requirement under a stereoscopic microscope for later use;
step S5: cleaning the surface of a printed circuit board by using ethanol in an ultrasonic cleaning machine, and coating a layer of soldering flux on the printed circuit board;
step S6: placing the prefabricated Sn-Ag-Bi-In solder balls on a copper sheet on the surface of a printed circuit board, heating by hot air welding equipment to ensure that the solder balls are remelted and combined with the copper sheet on the printed circuit board, wherein the remelting temperature is 280 ℃, the remelting time is 20s, and the solder balls are cooled for 20s along with a furnace;
step S7: corroding the welded bump structure by using a nitric acid-ethanol-water solution (volume ratio is 1:1:8), observing by using a metallographic microscope, ensuring that all Sn is corroded, and keeping IMCs at a Cu-Sn interface;
step S8: coating soldering flux on the surface of a bonding pad of the IMC (hereinafter referred to as an IMC bonding pad);
step S9: printing Sn-Ag-Bi-In solder on a glass plate through a drain screen, wherein the size of the drain screen is 250 mu m;
step S10: scraping the solder on the glass plate by using a flat-head toothpick, and coating the solder on the IMC bonding pad;
step S11: inverting any IMC pad structure to be parallel to another IMCs pad and completely aligning the IMC pad structure;
step S12: and (4) heating the structure completed in the step S11 by using hot air welding equipment to enable the solder between the IMCs pads on the two sides to be remelted and ensure that the IMCs pads on the two sides are combined with the solder, and cooling. Remelting at 280 deg.c for 20s, and cooling for 20 s;
step S13: grinding the welding spots, and finely polishing the specified interface to finally obtain full IMCs welding spots;
step S14: and acquiring EDS data of the fine polishing section, and determining that the welding spot is a micro-interconnection welding spot consisting of IMCs with preferred orientation.
Example 5
The difference from the above embodiment 1 is only that the air cooling method is selected for cooling for 20 s.
Example 6
The difference from the above embodiment 1 is only that the water cooling method is selected for cooling for 20 s.
In the description of the present invention, it is to be understood that the terms "longitudinal", "lateral", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like, indicate orientations or positional relationships based on those shown in the drawings, are merely for convenience of description of the present invention, and do not indicate or imply that the referenced devices or elements must have a particular orientation, be constructed and operated in a particular orientation, and thus, are not to be construed as limiting the present invention.
The above-described embodiments are merely illustrative of the preferred embodiments of the present invention, and do not limit the scope of the present invention, and various modifications and improvements of the technical solutions of the present invention can be made by those skilled in the art without departing from the spirit of the present invention, and the technical solutions of the present invention are within the scope of the present invention defined by the claims.
Claims (10)
1. A method for forming full IMCs structure welding spots by prefabricating IMCs welding pads is characterized by comprising the following steps:
step S1: solder skip printing;
step S2: heating and remelting the solder after the printing leakage to form a solder ball, and cooling;
step S3: carrying out ultrasonic cleaning treatment on the solder balls;
step S4: selecting the solder balls according to size requirements;
step S5: ultrasonically cleaning and processing the printed circuit board;
step S6: placing the solder balls on the copper sheet on the surface of the printed circuit board, heating, remelting and combining to form a bump structure, and cooling;
step S7: corroding the bump structure to enable only IMCs pads to be left on the copper sheet of the printed circuit board;
step S8: making two pads of the IMCs by the steps S1 to S7;
step S9: heating and remelting to combine the two IMCs pads, and cooling;
step S10: grinding welding spots of the two IMCs welding pads, and finely polishing a specified interface to finally obtain full IMCs welding spots;
step S11: and acquiring EDS data of the fine polishing section, and determining whether the welding spot is a welding spot consisting of IMCs.
2. The method of claim 1 for forming solder joints of full IMCs structures by prefabricating pads of IMCs, wherein: the solder is Sn-Ag-Bi-In series lead-free solder.
3. The method of claim 1 for forming solder joints of full IMCs structures by prefabricating pads of IMCs, wherein: in the step S2, the step S6, and the step S9, a hot air welding device is used to perform heating remelting treatment, wherein the remelting temperature is 220 ℃ to 280 ℃.
4. The method of claim 1 for forming solder joints of full IMCs structures by prefabricating pads of IMCs, wherein: in the steps S2, S6, and S9, the cooling process is performed by any one of furnace cooling, air cooling, and water cooling.
5. The method of claim 1 for forming solder joints of full IMCs structures by prefabricating pads of IMCs, wherein: in the step S3, the solder balls are cleaned in an ultrasonic cleaning machine by using acetone and ethanol in sequence.
6. The method of claim 1 for forming solder joints of full IMCs structures by prefabricating pads of IMCs, wherein: in step S5, the surface of the printed circuit board is cleaned with ethanol in an ultrasonic cleaning machine.
7. The method of claim 1 for forming solder joints of full IMCs structures by prefabricating pads of IMCs, wherein: and in the step S7, corroding the welded bump structure by using a nitric acid-ethanol-water solution, observing by using a metallographic microscope, ensuring that all Sn is corroded, and keeping IMCs at a Cu-Sn interface.
8. The method of claim 1 for forming solder joints of full IMCs structures by prefabricating pads of IMCs, wherein: between the step S5 and the step S6, a layer of flux is applied on the printed circuit board.
9. The method of claim 1 for forming solder joints of full IMCs structures by prefabricating pads of IMCs, wherein: in step S9, any one of the pads of the IMCs is inverted, placed parallel to and in perfect alignment with another one of the pads of the IMCs, and reflowed by heating to bond the two pads of the IMCs.
10. The method of claim 1 for forming solder joints of full IMCs structures by prefabricating pads of IMCs, wherein: in step S8, a combustion improver and a solder are sequentially coated on the surfaces of the two manufactured IMCs pads, respectively.
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