阅读说明：本技术 一种squid芯片与磁显微镜探头及其封装方法 (SQUID chip, magnetic microscope probe and packaging method thereof ) 是由 王海 朱浩波 李子豪 孔祥燕 于 2021-08-20 设计创作，主要内容包括：提供一种SQUID芯片与磁显微镜探头及其封装方法,SQUID芯片1衬底层2外表面设置焊盘5,衬底层2打孔,从磁通感应结区引出导电连接线6经衬底层2的孔与焊盘5电连接；磁显微镜探头包括杜瓦、冷指9与芯片1,冷指9顶端开设非贯穿槽12,铜引脚13以其导电面14朝上方式分别嵌入非贯穿槽12中,外端设置导电连接线6连接排插引脚11,焊盘5朝下分别对应铜引脚13的导电面14,由导电胶16电连接；导电胶16加热至近200度后粘贴在冷指9顶端,将芯片1压焊在冷指9顶端的对应位置,并达到设定的压力和时间；本发明能减少芯片到被测样品的距离,较大幅度提升磁显微镜的分辨率,并提升了效率,降低了维护难度。(A SQUID chip and magnetic microscope probe and its packaging method are provided, the external surface of the substrate layer 2 of the SQUID chip 1 is provided with a bonding pad 5, the substrate layer 2 is perforated, and a conductive connecting wire 6 is led out from a magnetic flux induction junction area and is electrically connected with the bonding pad 5 through the hole of the substrate layer 2; the magnetic microscope probe comprises a Dewar, a cold finger 9 and a chip 1, wherein the top end of the cold finger 9 is provided with a non-through groove 12, copper pins 13 are respectively embedded into the non-through grooves 12 in a mode that a conductive surface 14 faces upwards, the outer end of the cold finger is provided with a conductive connecting wire 6 connected with a socket pin 11, and a bonding pad 5 faces downwards and respectively corresponds to the conductive surface 14 of the copper pins 13 and is electrically connected by a conductive adhesive 16; heating the conductive adhesive 16 to nearly 200 ℃, then adhering the conductive adhesive to the top end of the cold finger 9, and pressure-welding the chip 1 at the corresponding position of the top end of the cold finger 9 to reach the set pressure and time; the invention can reduce the distance from the chip to the tested sample, greatly improve the resolution of the magnetic microscope, improve the efficiency and reduce the maintenance difficulty.)

1. The SQUID chip (1) comprises a substrate layer (2), an insulating layer (3) and a magnetic flux induction junction area clamped between the substrate layer (2) and the insulating layer (3), and is characterized in that a bonding pad (5) is arranged on the outer surface of the substrate layer (2), the substrate layer (2) is punched, and a conductive connecting line (6) is led out from the magnetic flux induction junction area and is electrically connected with the bonding pad (5) through a hole of the substrate layer (2).

2. A SQUID chip (1) according to claim 1, wherein said flux-inducing junction region is a single YBCO layer (4), and conductive connection lines (6) lead from said YBCO layer (4) and are electrically connected to said pads (5) through holes in the substrate layer (2).

3. A SQUID chip (1) according to claim 1, wherein said magnetic flux-inducing junction region is a niobium-aluminum oxide-niobium three-layer film structure comprising an upper small niobium sheet (20), a middle aluminum oxide sheet (21), and a lower large niobium sheet (22); the conductive connecting line (6) led out from the magnetic flux induction junction area is partially led out from the small niobium sheet (20), penetrates through the aluminum oxide sheet (21) and the substrate layer (2) and is electrically connected with the bonding pad (5); the other part is led out from the large niobium sheet (22) and electrically connected with the bonding pad (5) through the substrate layer (2).

4. A SQUID chip (1) according to claim 1, wherein said pads (5) are provided in 4 number, said substrate layer (2) is perforated with 4 holes, and said 4 conductive connection lines (6) led out from the magnetic flux induction junction region are electrically connected to said 4 pads (5), respectively; or, the number of the welding pads (5) is 6, 6 holes are formed in the substrate layer (2), and 6 conductive connecting lines (6) led out from the magnetic flux induction junction area are respectively and electrically connected with the 6 welding pads (5).

5. A magnetic microscope probe comprises a Dewar, a cold finger (9) and a SQUID chip (1), wherein the Dewar comprises a Dewar outer container (7) and a Dewar inner container (8), the cold finger (9) is connected with the Dewar inner container (8), the top end of the Dewar outer container (7) is provided with an opening, a sapphire glass window (10) is arranged on the opening, the Dewar outer container (7) and the sapphire glass window (10) form a sealed container, a row insertion pin (11) is arranged on the Dewar inner container (8), the magnetic microscope probe is characterized in that the SQUID chip (1) is the SQUID chip (1) according to the claim 1 or 2, the top end of the cold finger (9) is provided with non-through grooves (12) inwards from the side surface of the top end of the cold finger (9) according to the quantity of welding pads (5) of the SQUID chip (1), the non-through grooves (12) are not communicated with each other, 1 copper pin (13) is configured on each non-through groove (12), and the copper pin (13) comprises 1 flat conductive surface (14), the other is insulating face (15), copper pin (13) with its conducting surface (14) upwards the mode imbed respectively in non-through groove (12), the outer end of copper pin (13) sets up electrically conductive connecting wire (6) and connects row and insert pin (11), SQUID chip (1) is placed at cold finger (9) top with its pad (5) mode down, and every pad (5) of SQUID chip (1) correspond conducting surface (14) of 1 wherein copper pin (13) respectively, have between every pad (5) and its conducting surface (14) that corresponds copper pin (13) through heating pressure welding make it have the anisotropic conducting resin (16) of electric conductivity.

6. The magnetic microscope probe as claimed in claim 5, characterized in that the non-through groove (12) at the top end of the cold finger (9) is a square groove with a rectangular cross section, the copper pin (13) is a square copper pin (13) with a rectangular cross section, 1 of 4 surfaces in the length direction of the square copper pin (13) is a conductive surface (14), the surfaces of the square copper pin (13) contacting with the cold finger (9) are insulating surfaces (15), and the insulating surfaces (15) comprise the other 3 surfaces in the length direction and the end surface contacting with the cold finger (9).

7. A magnetic microscope probe according to claim 6, wherein each insulating surface (15) is coated with an insulating glue.

8. A magnetic microscope probe according to claim 5 wherein each copper pin (13) is largely embedded in a non-through slot (12) at the tip of the cold finger (9) and a small part is exposed.

9. A magnetic microscope probe according to claim 5, characterized in that the top of the cold finger (9) is square, the top of the cold finger (9) is provided with non-through grooves (12) from the near left side of 4 sides of the cold finger inwards, or the top of the cold finger (9) is provided with non-through grooves (12) from the near right side of 4 sides of the cold finger inwards.

10. A packaging method of a magnetic microscope comprises a Dewar, a cold finger (9) and a SQUID chip (1), wherein the Dewar comprises a Dewar outer container (7) and a Dewar inner container (8), the cold finger (9) and the Dewar are connected with the inner container, an opening is formed in the top end of the Dewar outer container (7), a sapphire glass window (10) is arranged on the opening, the Dewar outer container (7) and the sapphire glass window (10) form a sealed container, and a socket pin (11) is arranged on the Dewar inner container (8); characterized in that the SQUID chip (1) uses the SQUID chip (1) according to claim 1 or 2; the top end of the cold finger (9) is provided with non-through grooves (12) inwards from the side face of the top end of the cold finger (9) according to the quantity of the welding pads (5) of the SQUID chip (1), the non-through grooves (12) are not communicated with each other, each non-through groove (12) is provided with 1 copper pin (13), each copper pin (13) comprises 1 flat conductive surface (14), the other non-through grooves are insulating surfaces (15), the copper pins (13) are respectively embedded into the non-through grooves (12) in a mode that the conductive surfaces (14) of the copper pins are upward, and the outer ends of the copper pins (13) are provided with conductive connecting wires (6) connected with the extension pins (11); heating various anisotropic conductive adhesives (16) to 100-200 ℃ in advance, preserving heat for later use, and attaching the anisotropic conductive adhesives (16) which are heated, pressure-welded and made conductive to the top end of the cold finger (9); the method comprises the steps that the SQUID chip (1) faces the top end of a cold finger (9) through a bonding pad (5), the SQUID chip (1) is subjected to pressure welding at the corresponding position of the top end of the cold finger (9) in a mode that each bonding pad (5) of the SQUID chip (1) corresponds to a conductive surface (14) of one copper pin (13), a welding disc of the SQUID chip (1) and a conductive adhesive (16) between the conductive surfaces (14) of the copper pins (13) reach set pressure and pressure welding time, and the welding disc of the SQUID chip (1) is electrically communicated with the copper pins (13).

11. The packaging method of the magnetic microscope according to claim 10, wherein the SQUID chip (1) is pressure-welded at the corresponding position of the top end of the cold finger (9) by using a chip pressure welding device, the pressure welding device comprises a pushing rod which is driven by a driving device and can slide linearly, the pushing rod comprises a chip pushing head at the top part thereof, and the top end of the chip pushing head is provided with a chip accommodating groove corresponding to the SQUID chip (1); the SQUID chip (1) is placed in a chip accommodating groove of a pushing rod pushing head, and the pushing rod is driven by a driving device to press-weld the SQUID chip (1) to the corresponding position of the top end of the cold finger (9).

12. The packaging method of the magnetic microscope of claim 10, wherein the driving device of the bonding device has a sensor of the pressure exerted by the pushing rod and a pressure display thereof, when the pressure reaches a defined pressure value X, the driving device stops running, waits for a set time Y, and solidifies the conductive adhesive (16); and (5) after the waiting time is over, automatically and reversely running the driving device, returning to the original position, and finishing the pressure welding.

The technical field is as follows:

the invention belongs to the technical field of Magnetic detection, relates to a Superconducting Quantum Interference Device (SQUID chip for short), in particular to a SQUID chip used as a Magnetic Microscope (Magnetic Microscope) probe core element, and also relates to a Magnetic Microscope probe taking the SQUID chip as the core element, a packaging structure Device and a packaging method thereof.

Background art:

in recent years, due to the inherent advantages of the super-conducting quantum interference device such as excellent space, magnetic field resolution and passive nondestructive detection, and with the development of integrated circuit technology, the Magnetic Scanning SQUID Microscope (MSSM) technology for detecting the magnetism of a sample by using a SQUID chip attracts more and more researchers.

Among the current magnetic microscopes, the scanning SQUID microscope is the most sensitive due to its higher spatial resolution and magnetic field resolution; the design accuracy requirements of the probe are extremely high. The SQUID chip comprises a substrate layer, an insulating layer and a magnetic flux induction junction area sandwiched between the substrate layer and the insulating layer, wherein the magnetic flux induction junction area of the SQUID chip is a sensitive source of a magnetic microscope. During detection, the distance between the magnetic flux induction junction of the SQUID chip and a sample to be detected has obvious influence on the spatial resolution and the magnetic field resolution of the magnetic microscope, so that the spatial resolution and the magnetic field resolution of the magnetic microscope depend on the distance H between the magnetic flux induction junction of the SQUID chip and the sample to be detected to a great extent, and the closer the distance between the magnetic microscope spatial resolution and the magnetic field resolution, the higher the magnetic microscope spatial resolution and the magnetic field resolution.

The prior SQUID chip is divided into a high-temperature SQUID chip and a low-temperature SQUID chip according to the applicable environmental temperature requirement interval. The applicable environment temperature requirement of the high-temperature SQUID chip is 77K, which is about 196 ℃ below zero. The applicable environment temperature requirement of the low-temperature SQUID chip is 4.2K, which is about 269 ℃ below zero. Both of which comprise a substrate layer 2, an insulating layer 3 and a flux-inducing junction area sandwiched between the substrate layer 2 and the insulating layer 3. Both of them have no difference in appearance, as shown in fig. 2 and 3, a pad 5 is provided on the outer surface of the insulating layer 3, the insulating layer 3 is perforated, and the conductive connection line 6 is led from the magnetic flux induction junction region and electrically connected to the pad 5 through the hole of the insulating layer 3. Generally, the number of the pads 5 is set to 4 to 6. But the structures of the magnetic flux induction junction areas of the two parts are greatly different.

The basic structure of the existing magnetic microscope probe is shown in fig. 5 and 6, and comprises a Dewar, a cold finger 9 and a SQUID chip 1, wherein the cold finger 9 is made of red copper and has excellent conductivity. The Dewar includes that Dewar outer container 7 and Dewar inner container 8, and cold finger 9 is connected with Dewar inner container 8, and Dewar outer container 7 top sets up the opening, is provided with sapphire glass window 10 on the opening, and Dewar outer container 7 and sapphire glass window 10 form sealed container, are provided with on the Dewar inner container 8 and arrange pin 11, and SQUID chip 1 pastes on cold finger 9 top with low temperature glue 19, and SQUID chip 1's pad 5 is connected with electrically conductive connecting wire 6 between the pin 11 with arranging. Since the pad 5 is thin and can only be wired from its upper surface, the conductive connection line 6 between the pad 5 and the pin 11 must have a certain bending height, and the total distance H from the chip to the sample 18 is Ha + Hb + Hc + Hd. Ha is the distance from the highest point of the conductive connecting line 6 between the SQUID chip 1 and the extension pin 11 to the chip sensitive source, Hb is the distance from the conductive connecting line to the sapphire glass window 10, Hc is the thickness of the sapphire glass window 10, and Hd is the distance from the sample 18 to the sapphire glass window 10. Hd can be reduced as much as possible by adjusting the position of the sample 18. When the dewar is in operation, the interior is in vacuum, and the sapphire glass window 10 can be bent by atmospheric pressure, so Hc and Hb have minimum values, and the magnitude is more than hundred um. For a scanning SQUID microscope, even a distance of several tens of um is shortened, there is a significant influence on the spatial resolution and the magnetic field resolution.

In order to reduce the bending degree of the conductive connecting wire 6 between the bonding pad 5 of the SQUID chip 1 and the extension pin 11 and shorten Ha, the prior art adopts a mode of leading wires on the side surface of the cold finger, as shown in figure 7, the specific implementation mode is that after the lead wire binding of the conductive connecting wire 6 is led out between the SQUID chip 1 and the extension pin 11, the lead wire is pulled to the side surface of the cold finger in a manual mode, and then the lead wire is fixed on the cold finger by low-temperature glue. In this way, the bending degree of the lead wire can be reduced by a small amplitude, so that the distance from the lead wire to the chip magnetic flux induction area is reduced. However, this approach has the following disadvantages: 1. the operation difficulty is high, only a manual mode can be used, and the operation cannot be completed by a mechanical device until now; 2. the later maintenance degree of difficulty is big, and the dismouting is inconvenient.

In the existing probe scheme of the scanning SQUID microscope magnetic microscope, the existing SQUID chip is used. For this scheme, the distance from the magnetic flux induction junction of the SQUID chip to the sample 18 is mainly composed of the following four parts: the bending height (about tens of um) of the conductive connecting line 6 between the SQUID chip 1 and the pin 11, the linear distance (more than hundred um) from the conductive connecting line to the sapphire window, the thickness (about hundred um) of the sapphire glass window 10 and the distance from the sapphire glass window 10 to the sample 18. Wherein the sapphire glass window 10 to sample 18 distance can be reduced as much as possible by mechanically moving the platform. The thickness of the sapphire glass window 10 is limited by the dewar vacuum and material properties, making reduction difficult. And because the dewar is vacuumized and the sapphire glass window 10 is bent under the influence of pressure when the dewar works, the linear distance from the conductive connecting wire to the sapphire window has a minimum value and is difficult to completely eliminate. Although the lead wire of the positive-hole SQUID chip can be completed only by simple welding, the conductive connecting wire is necessarily bent during welding. The bending of the conductive connection lines directly pulls the distance from the SQUID chip to the sapphire glass window 10, which limits the spatial resolution and magnetic field resolution of the scanning SQUID microscope.

The conventional SQUID chip can be divided into a single-layer SQUID chip and a three-layer SQUID chip according to the film structure of the magnetic flux induction junction region of the SQUID chip.

The cross section of single-layer film SQUID chip is shown in figure 1, the common film layer of magnetic flux induction junction of single-layer film SQUID chip is single-layer YBCO layer 4, YBCO is called Yttrium Barium Copper Oxide, which is a crystal with chemical formula YBa 2 Cu 3O 7-x. YBCO is a high temperature superconductor material which can maintain superconducting characteristics at a temperature higher than the boiling point of liquid nitrogen (77K), and YBCO needs to work below 93K. Ha using the chip is the distance from the highest point of the lead to the single-layer film.

The cross section of the three-layer membrane SQUID chip is shown in fig. 4, the josephson junction region of the three-layer membrane SQUID chip is a niobium-aluminum oxide-niobium three-layer membrane structure, which comprises a small niobium sheet 20 positioned on the upper part, an aluminum oxide sheet 21 positioned in the middle part and a large niobium sheet 22 positioned on the lower part. The conductive connection line 6 led out from the Josephson junction of the three-layer film SQUID chip is partially led out from the small niobium sheet 20 and is electrically connected with the bonding pad through the insulating layer. The other part is led out from the large niobium sheet 22 and upwards passes through the insulating layer 3 to be electrically connected with the bonding pad 5. Referring to fig. 12, a top view of the josephson junction region, Ha using the chip is the distance from the highest point of the conductive connection line 6 to the aluminum oxide wafer 21.

The conventional welding method of the SQUID chip is to bond a conductive connecting wire (an aluminum wire or a gold wire) to a SQUID chip bonding pad by using a bonding machine through ultrasonic vibration or hot pressing. And the conductive connecting wire is led out from the SQUID chip bonding pad 5 for external connection. The conductive connecting line is very thin and has high operation difficulty, so that a line outlet is easy to block when a hard material is bound; the binding machine is manually operated to carry out binding operation, so that the requirement on the proficiency of an operator is high; the bonding machine can only complete bonding of one bonding pad in one operation.

The invention content is as follows:

the invention aims to solve the technical problem of providing an SQUID chip, a magnetic microscope probe and a packaging method thereof.

In order to solve the technical problems, the technical scheme of the SQUID chip provided by the invention is as follows:

the SQUID chip comprises a substrate layer, an insulating layer and a magnetic flux induction junction area clamped between the substrate layer and the insulating layer, and is characterized in that a bonding pad is arranged on the outer surface of the substrate layer, the substrate layer is punched, and a conductive connecting wire is led out from the magnetic flux induction junction area and is electrically connected with the bonding pad through a hole of the substrate layer.

The SQUID chip further adopts the technical scheme that:

the magnetic flux induction junction area is a single-layer YBCO layer, and a conductive connecting wire is led out from the YBCO layer and is electrically connected with the bonding pad through a hole of the substrate layer.

The magnetic flux induction junction area is of a niobium-aluminum oxide-niobium three-layer film structure and comprises an upper small niobium sheet, a middle aluminum oxide sheet and a lower large niobium sheet; one part of the conductive connecting wire led out from the magnetic flux induction junction area is led out from the small niobium sheet, penetrates through the aluminum oxide sheet and the substrate layer and is electrically connected with the bonding pad; the other part is led out from the large niobium sheet and penetrates through the substrate layer to be electrically connected with the bonding pad.

4 bonding pads are arranged, 4 holes are punched in the substrate layer, and 4 conductive connecting wires are led out from the magnetic flux induction junction area and are respectively and electrically connected with the 4 bonding pads; or, the number of the welding pads is 6, 6 holes are punched in the substrate layer, and 6 conductive connecting lines led out from the magnetic flux induction junction area are respectively and electrically connected with the 6 welding pads.

Because the bonding pad is arranged on the outer surface of the substrate layer of the SQUID chip, and the substrate layer punching lead is connected with the bonding pad, compared with the traditional SQUID chip punching lead from an insulating layer, the SQUID chip belongs to a back side punching lead, and can be called as a back hole SQUID chip for short.

In order to solve the technical problems, the technical scheme of the magnetic microscope probe provided by the invention is as follows:

a magnetic microscope probe comprises a Dewar, a cold finger and a SQUID chip, wherein the Dewar comprises a Dewar outer container and a Dewar inner container, the cold finger is connected with the Dewar inner container, the top end of the Dewar outer container is provided with an opening, a sapphire glass window is arranged on the opening, the Dewar outer container and the sapphire glass window form a sealed container, and the Dewar inner container is provided with a row-inserting pin, the SQUID chip is the back hole SQUID chip, the top end of the cold finger is provided with non-penetrating grooves inwards from the side surface of the top end of the cold finger according to the quantity of bonding pads of the SQUID chip, the non-penetrating grooves are not communicated with each other, each non-penetrating groove is provided with 1 copper pin, the copper pins comprise 1 flat conductive surfaces, the other conductive surfaces are insulating surfaces, the copper pins are respectively embedded into the non-penetrating grooves in a mode that the conductive surfaces of the copper pins face upwards, conductive connecting wires are arranged on the copper pins to be connected with the row-inserting pin, the SQUID chip is arranged on the top end of the cold finger in a mode that the bonding pads of the SQUID chip face downwards, each bonding pad of the SQUID chip corresponds to the conductive surface of 1 copper pin, and anisotropic conductive adhesive which is heated, pressure-welded and made to have conductivity is arranged between each bonding pad and the conductive surface of the corresponding copper pin.

The invention discloses a magnetic microscope probe, which comprises the following steps:

the non-through groove at the top end of the cold finger is a square groove with a rectangular cross section, the copper pin is a square copper pin with a rectangular cross section, 1 of 4 surfaces of the square copper pin in the length direction is a conductive surface, the surfaces of the square copper pin, which are in contact with the cold finger, are insulating surfaces, and each insulating surface comprises 3 other surfaces in the length direction and an end surface in contact with the cold finger.

And each insulating surface is coated with insulating glue.

Most of each copper pin is embedded into the non-through groove at the top end of the cold finger, and a small part of each copper pin is exposed outside.

The top of the cold finger is square, and the top ends of the cold fingers are internally provided with non-penetrating grooves from the positions close to the left sides of the 4 side surfaces of the cold finger, or the top ends of the cold fingers are internally provided with non-penetrating grooves from the positions close to the right sides of the 4 side surfaces of the cold finger.

In order to solve the technical problems, the technical scheme of the packaging method of the magnetic microscope is as follows:

a packaging method of a magnetic microscope comprises a Dewar, a cold finger and a SQUID chip, wherein the Dewar comprises a Dewar outer liner and a Dewar inner liner, the cold finger is connected with the Dewar inner liner, an opening is formed in the top end of the Dewar outer liner, a sapphire glass window is arranged on the opening, the Dewar outer liner and the sapphire glass window form a sealed container, and a row-inserting pin is arranged on the Dewar inner liner; the SQUID chip is characterized in that the back hole SQUID chip is used; the cold finger top end is internally provided with non-penetrating grooves from the side surface of the cold finger top end according to the quantity of SQUID chip bonding pads, the non-penetrating grooves are not communicated with each other, each non-penetrating groove is provided with 1 copper pin, each copper pin comprises 1 flat conductive surface, the other copper pins are insulating surfaces, the copper pins are respectively embedded into the non-penetrating grooves in a mode that the conductive surfaces of the copper pins face upwards, and the outer ends of the copper pins are provided with conductive connecting wires to be connected with extension pins; heating various anisotropic conductive adhesives to 100-200 ℃ in advance, preserving heat for later use, and attaching anisotropic conductive adhesives with conductivity by heating and pressure welding to the top ends of the cold fingers; and (3) pressing and welding the SQUID chip at the corresponding position of the cold finger top end in a mode that each bonding pad of the SQUID chip corresponds to the conductive surface of 1 copper pin respectively by the bonding pad of the SQUID chip towards the cold finger top end, so that the bonding pad of the SQUID chip and the conductive adhesive between the conductive surfaces of the copper pins reach the set pressure and the set pressing and welding time, and the bonding pad of the SQUID chip is electrically communicated with the copper pins.

The invention further adopts the technical scheme that the packaging method of the magnetic microscope comprises the following steps:

the SQUID chip is pressure-welded at the corresponding position of the top end of the cold finger by using a chip pressure welding device, the pressure welding device comprises a pushing rod which is driven by a driving device and can slide linearly, the pushing rod comprises a chip pushing head positioned at the top of the pushing rod, and the top end of the chip pushing head is provided with a chip accommodating groove corresponding to the SQUID chip; and the SQUID chip is placed in a chip accommodating groove of the pushing rod pushing head, and the pushing rod is driven by the driving device to press-weld the SQUID chip to the corresponding position of the top end of the cold finger.

The driving device of the pressure welding device is provided with a sensor for applying pressure by the pushing rod and a pressure display thereof, and stops running when the pressure reaches a limited pressure value X, waits for a set time Y, and solidifies the conductive adhesive; and (5) after the waiting time is over, automatically and reversely running the driving device, returning to the original position, and finishing the pressure welding.

The invention provides a novel back hole SQUID chip, a magnetic microscope probe and a packaging method thereof. Compared with the design mode of the conventional SQUID chip, the back-hole SQUID chip with the lead-out bonding pad punched on the substrate is developed, and the back-hole SQUID chip packaging mode does not need to use a lead for bonding the SQUID chip bonding pad, so that the distance from a lead bending part to a SQUID chip sensitive source is completely eliminated, and the distance from the SQUID chip to a Dewar sapphire glass window is shortened. The shortened distance is about several tens of um, and is about 10% shorter than the distance (several hundreds of um) from the SQUID chip to the sample 18. This also gives a lifting rate of about 10% for spatial resolution. Therefore, the spatial resolution and the magnetic field resolution of the magnetic microscope can be greatly improved, and the detection sensitivity of the magnetic microscope can be further greatly improved.

The invention is a technology worth popularizing in the technical field of chip detection. In addition, the novel back hole SQUID chip, the magnetic microscope probe and the packaging method thereof provided by the invention can be widely applied to magnetic detection systems based on SQUID, including but not limited to cardiac magnetism, brain magnetism, lung magnetism, muscle magnetism, geophysical, low-field nuclear magnetic resonance and nondestructive detection systems, and are particularly suitable for scanning SQUID microscope systems for detecting semiconductor chip current magnetic anomaly.

In addition, the SQUID chip with the back hole can adopt a chip pressure welding device to weld bonding pads, and a plurality of bonding pads can be pressure welded at one time, so that the welding efficiency is greatly improved, and the welding cost is reduced. And (3) heating the conductive adhesive to nearly 200 ℃, then performing pressure welding, and setting the pressure threshold of the film pressure sensor to be 35 newtons and the pressure welding time to be 30 seconds, wherein the chip and the copper pin have good conductivity.

Drawings

FIG. 1 is a schematic cross-sectional view of a prior art single-layer film SQUID chip;

FIG. 2 is a schematic top view of a prior art SQUID chip;

FIG. 3 is a schematic bottom view of a prior SQUID chip;

FIG. 4 is a schematic cross-sectional view of a prior art three-layer SQUID chip;

FIG. 5 is a schematic diagram of a basic structure of a conventional magnetic microscope probe;

figure 6 is a schematic top view of a prior art SQUID chip package;

FIG. 7 is a schematic diagram of a conventional magnetic microscope probe with a cold finger side lead;

figure 8 is a schematic cross-sectional view of a single layer membrane SQUID chip of the present invention;

FIG. 9 is a schematic top view of a SQUID chip of the present invention;

FIG. 10 is a schematic bottom view of a SQUID chip of the present invention;

figure 11 is a schematic cross-sectional view of a three-layer membrane SQUID chip of the present invention;

figure 12 is a schematic top view of a three-layer film SQUID chip flux-inducing junction region of the present invention;

FIG. 13 is a schematic diagram of the basic structure of a magnetic microscope probe according to the present invention;

figure 14 is a schematic top view of a SQUID chip package of the present invention;

FIG. 15 is a schematic view of the tip structure of the cold finger of the present invention;

FIG. 16 is a schematic view of a copper pin;

FIG. 17 is a schematic view showing a state where a square copper pin is embedded in a non-through groove of a cold finger;

FIG. 18 is a schematic view of the application of conductive gel to the tip of a cold finger;

FIG. 19 is a perspective view of the SQUID chip pressure welded to the tip of the cold finger;

FIG. 20 is a schematic top view of a SQUID chip press-bonded to the cold finger tip;

figure 21 is a side view schematic diagram of the SQUID chip pressure bonded on the cold finger tip.

The figures are schematic and do not correspond to actual proportions. For example: the components Ha, Hb, Hc and Hd of the total distance H from the chip to the sample are shown in an exaggerated manner in FIGS. 5 and 10.

The parts indicated by the reference numerals in the figures are: 1. a SQUID chip; 2. a substrate layer; 3. an insulating layer; 4. a YBCO layer; 5. a pad; 6. a conductive connection line; 7. a Dewar outer container; 8. a Dewar liner; 9. cold fingers; 10. a sapphire glass window; 11. a pin of the extension socket; 12. a non-through groove; 13. a copper pin; 14. a conductive surface; 15. an insulating surface; 16. a conductive adhesive; 17. conductive particles; 18. a sample; 19. low-temperature glue; 20. small niobium flakes; 21. aluminum oxide sheet; 22. a large niobium sheet; 23. and (4) a notch.

Detailed Description

The present invention is described in further detail below with reference to the attached drawings.

The SQUID chip 1 comprises a substrate layer 2, an insulating layer 3 and a magnetic flux induction junction area sandwiched between the substrate layer 2 and the insulating layer 3, wherein a bonding pad 5 is arranged on the outer surface of the substrate layer 2, the substrate layer 2 is perforated, and a conductive connecting wire 6 is led out from the magnetic flux induction junction area and is electrically connected with the bonding pad 5 through the hole of the substrate layer 2. The SQUID chip 1 can be divided into a single-layer film SQUID chip 1 and a three-layer film SQUID chip 1 according to the film layer structure of the magnetic flux induction junction area of the SQUID chip. Both of which comprise a substrate layer 2, an insulating layer 3 and a flux-inducing junction area sandwiched between the substrate layer 2 and the insulating layer 3. Both of them are not different in appearance, and as shown in fig. 9 and 10, a pad 5 is provided on the outer surface of the insulating layer 3, the insulating layer 3 is perforated, and the conductive connection line 6 is led from the magnetic flux induction junction region and electrically connected to the pad 5 through the hole of the insulating layer 3. Generally, the number of the pads 5 is set to 4 to 6. But the film layer structure of the magnetic flux induction junction area of the two is greatly different.

As shown in fig. 8, the single-layer film SQUID chip 1 has a single-layer YBCO layer 4 as a magnetic flux induction junction region, and a conductive connection line 6 led out from the YBCO layer 4 is electrically connected with a bonding pad 5 through a hole of the substrate layer 2.

The three-layer SQUID chip 1 is shown in fig. 11 and 12, and the magnetic flux induction junction region is a niobium-aluminum oxide-niobium three-layer film structure, which comprises an upper small niobium sheet 20, a middle aluminum oxide sheet 21 and a lower large niobium sheet 22; a conductive connecting line 6 led out from the magnetic flux induction junction area, wherein one part of the conductive connecting line is led out from the small niobium sheet 20, penetrates through the aluminum oxide sheet 21 and the substrate layer 2 and is electrically connected with the bonding pad 5; the other part is led out from the large niobium sheet 22 and penetrates through the substrate layer 2 to be electrically connected with the bonding pad 5.

In the SQUID chip 1, no matter the single-layer film SQUID chip 1 or the three-layer film SQUID chip 1, as shown in figures 9 and 10, 4 bonding pads 5 are arranged, 4 holes are formed in a substrate layer 2, and 4 conductive connecting wires 6 led out from a magnetic flux induction junction area are respectively electrically connected with the 4 bonding pads 5; or, the number of the bonding pads 5 is 6, 6 holes are formed in the substrate layer 2, and 6 conductive connecting lines 6 are led out from the magnetic flux induction junction area and are respectively electrically connected with the 6 bonding pads 5.

Because the bonding pad 5 is arranged on the outer surface of the substrate layer of the SQUID chip, and the substrate layer 2 is provided with the punched lead wire to be connected with the bonding pad 5, compared with the traditional SQUID chip which is punched from the insulating layer, the SQUID chip belongs to the lead wire with the punched hole on the back surface, and can be called as a back hole SQUID chip for short.

The magnetic microscope probe of the invention is shown in figures 13 and 14, and comprises a Dewar, a cold finger 9 and a SQUID chip 1, wherein the Dewar comprises a Dewar outer container 7 and a Dewar inner container 8, the cold finger 9 is connected with the Dewar inner container 8, the top end of the Dewar outer container 7 is provided with an opening, a sapphire glass window 10 is arranged on the opening, the Dewar outer container 7 and the sapphire glass window 10 form a sealed container, the Dewar inner container 8 is provided with a row pin 11, the SQUID chip 1 is the back hole SQUID chip 1, the top end of the cold finger 9 is provided with non-through grooves 12 from the side surface of the top end of the cold finger 9 according to the quantity of welding pads 5 of the SQUID chip 1, the non-through grooves 12 are not communicated with each other, each non-through groove 12 is provided with 1 copper pin 13, the copper pins 13 comprise 1 flat conductive surfaces 14, the other are insulating surfaces 15, the copper pins 13 are respectively embedded into the non-through grooves 12 in a mode that the conductive surfaces 14 face upwards, the outer ends of the copper pins 13 are provided with conductive connecting wires 6 connected with the row pin 11, the SQUID chip 1 is placed on the top end of the cold finger 9 in a mode that the bonding pads 5 face downwards, each bonding pad 5 of the SQUID chip 1 corresponds to a conductive surface 14 of 1 copper pin 13, and an anisotropic conductive adhesive 16 which is heated and pressed to enable the bonding pads 5 to be conductive is arranged between each bonding pad 5 and the conductive surface 14 of the corresponding copper pin 13.

As shown in fig. 15, the top of the cold finger 9 is square, and the top ends of the cold fingers 9 are provided with non-penetrating grooves 12 from the left side of the 4 side faces inwards, or the top ends of the cold fingers 9 are provided with non-penetrating grooves 12 from the right side of the 4 side faces inwards. The non-through groove 12 at the top end of the cold finger 9 is a square groove with a rectangular cross section. As shown in fig. 16, the copper pin 13 is a square copper pin 13 with a rectangular cross section, 1 of 4 surfaces of the square copper pin 13 in the length direction is a conductive surface 14, the surfaces of the square copper pin 13 contacting the cold finger 9 are all insulating surfaces 15, the insulating surfaces 15 include the other 3 surfaces in the length direction and end surfaces contacting the cold finger 9, and each insulating surface 15 is coated with insulating glue. As shown in fig. 17, each copper pin 13 is mostly embedded in the non-through slot 12 at the top end of the cold finger 9, and a small part is exposed.

The packaging method of the magnetic microscope comprises a Dewar, a cold finger 9 and a SQUID chip 1, wherein the Dewar comprises a Dewar outer container 7 and a Dewar inner container 8, the cold finger 9 is connected with the Dewar inner container, an opening is formed in the top end of the Dewar outer container 7, a sapphire glass window 10 is arranged on the opening, the Dewar outer container 7 and the sapphire glass window 10 form a sealed container, and a row-inserting pin 11 is arranged on the Dewar inner container 8. The SQUID chip 1 uses the above back-hole SQUID chip 1. The top end of the cold finger 9 is inwards provided with non-through grooves 12 from the side surface of the top end of the cold finger 9 according to the quantity of the SQUID chip 1 bonding pads 5, the non-through grooves 12 are not communicated with each other, each non-through groove 12 is provided with 1 copper pin 13, each copper pin 13 comprises 1 flat conductive surface 14, the rest are insulating surfaces 15, the copper pins 13 are respectively embedded into the non-through grooves 12 in a mode that the conductive surfaces 14 face upwards, and the outer ends of the copper pins 13 are provided with conductive connecting wires 6 which are connected with the extension pins 11. The anisotropic conductive adhesive 16 is selected in advance and heated to 100 to 200 ℃ for standby. As shown in fig. 18, an anisotropic conductive paste 16 having conductivity by heating and pressure welding is applied to the tip of the cold finger 9. The SQUID chip 1 is pressure-welded at the corresponding position of the top end of the cold finger 9 in a mode that the welding pads 5 of the SQUID chip 1 face the top end of the cold finger 9, so that each welding pad 5 of the SQUID chip 1 corresponds to the conductive surface 14 of one copper pin 13, the conductive adhesive 16 between the welding pad of the SQUID chip 1 and the conductive surface 14 of the copper pin 13 reaches the set pressure and the pressure-welding time, and the welding pad of the SQUID chip 1 is electrically communicated with the copper pin 13.

The anisotropic conductive adhesive 16, which is a special bonding consumable for the bonding apparatus of the present invention, is commercially available. The anisotropic conductive adhesive contains discrete conductive particles 17 inside, is not compressed and has no conductivity; the conductive particles 17 are electrically conductive only when the conductive particles 17 are brought into contact with each other in the compression direction by gathering the conductive particles 17 in a discrete state at the pressed portion through a certain degree of heat compression. The conductive principle of the conductive adhesive is as follows: the contact of the conductive particles 17 can be improved by compressing the heated conductive paste by pressure, thereby forming a conductive path. Anisotropic conductive adhesives are adhesives that are only conductive in one direction, such as the Z direction, and only non-conductive in the X and Y directions.

Pressing and welding the SQUID chip 1 at the position corresponding to the top end of the cold finger 9 by using a chip pressing and welding device, wherein the pressing and welding device comprises a pushing rod which is driven by a driving device and can slide linearly, the pushing rod comprises a chip pushing head positioned at the top of the pushing rod, and the top end of the chip pushing head is provided with a chip accommodating groove corresponding to the SQUID chip 1; the SQUID chip 1 is placed in a chip accommodating groove of a pushing rod pushing head, and the pushing rod is driven by a driving device to press-weld the SQUID chip 1 to the corresponding position of the top end of the cold finger 9. The driving device of the pressure welding device is provided with a sensor for applying pressure by the pushing rod and a pressure display thereof, when the pressure reaches a limited pressure value X, the driving device stops running, and waits for a set time Y to solidify the conductive adhesive 16; and (5) after the waiting time is over, automatically and reversely running the driving device, returning to the original position, and finishing the pressure welding. The specific embodiments of the chip bonding apparatus and the bonding method can be found in the patent application specification and the accompanying drawings of the applicant filed on the same date as the present application and entitled "SQUID chip bonding apparatus and bonding method".

After the bonding is completed, as shown in fig. 19, 20, and 21. After the bonding process is completed, as shown in fig. 21, the conductive paste 16 still remaining between the bonding pad 5 of the SQUID chip 1 and the conductive surface of the copper lead 13 reaches a set degree of compression, the discrete conductive particles 17 are gathered at the compressed position, and the conductive particles 17 are in contact with each other in the compression direction to have conductivity, so that the electrical connection is formed between the bonding pad 5 of the SQUID chip 1 and the conductive surface of the copper lead 13. And the conductive adhesive 16 which is not positioned between the bonding pad 5 of the SQUID chip 1 and the conductive surface of the copper pin 13 is not enough in compression degree and is not conductive. The SQUID chip 1 after the pressure welding is placed at the top end of the cold finger 9 in a mode that the bonding pad 5 faces downwards, and no conductive connecting wire 6 which is led out from the bonding pad 5 and is used for external connection is arranged on the bonding pad 5 of the SQUID chip 1.

After the packaging is completed, as shown in fig. 13, the total distance H from the SQUID chip 1 to the sample 18 is Ha + Hb + Hc + Hd. Ha is the distance from the highest point of the conductive connecting line to the chip sensitive source, Hb is the distance from the conductive connecting line to the sapphire glass window 10, Hc is the thickness of the sapphire glass window 10, and Hd is the distance from the sample 18 to the sapphire glass window 10. Hd can be reduced as much as possible by adjusting the position of the sample 18. When the dewar is in operation, the interior is in vacuum, and the sapphire glass window 10 can be bent by atmospheric pressure, so Hc and Hb have minimum values, and the magnitude is more than hundred um. Therefore, only Ha is reduced in order to reduce H. After the back-hole SQUID chip 1 packaging mode is used, the total distance H from the chip to a sample is Ha + Hb + Hc + Hd. Wherein Ha can be reduced by dozens of um, other parameters are not changed, namely H can be reduced by dozens of um. The invention can improve the spatial resolution and the magnetic field resolution of the magnetic microscope to a large extent, and further improve the detection sensitivity of the magnetic microscope to a large extent.