JP2003225790A - JOINING MATERIAL CONTAINING HIGH PURITY Sn PARTICLE, MOUNTED CIRCUIT BOARD, MOUNTED PACKAGE AND THEIR DISASSEMBLING METHOD - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of joining/disassembling a printed board and mounted components, a method that enables the disassembling without damaging the components and that makes the reutilization of the components possible. <P>SOLUTION: In areas for soldering a printed board and mounted components, the soldered zones are formed in a manner that they are dotted or layered with high purity Sn particles. The printed board having the soldered zones so formed is left under a low temperature for a certain period and then vibration or the like is applied thereto, thereby facilitating disassembling of the printed board and the mounted components. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bonding material for bonding an electronic component or a component to a circuit board or a package, a mounted circuit board or a package to which an electronic component or the like is bonded by the bonding material, and The present invention relates to a method for disassembling a mounted circuit board or a mounted package. More specifically, the present invention relates to a bonding material such as solder containing high-purity Sn particles, and also relates to a method for disassembling a mounting circuit board and a mounting package in which electronic components and components are bonded using the bonding material.

[0002]

2. Description of the Related Art Solder is often used for a mounting circuit board and a mounting package mounted on an electronic device in order to mount or seal electronic components and components. In the past, lead-containing eutectic solder was used to mount electronic components, but since lead is toxic, it has become a common practice in recent years to use conventional lead-containing solder as one of the mounting technologies that address global environmental issues. Therefore, the mounting technology using lead-free solder is drawing attention. Currently, as a candidate for lead-free solder alloy, S
n-Ag system, Sn-Ag-Cu system, Sn-Ag-Cu-
Bi type, Sn-Cu type, Sn-Zn type, Sn-Zn-B
There are i-types, etc., and approximately 90% by weight or more of the solder alloy is Sn
There are also solder alloys occupied by.

It is known that Sn undergoes a low temperature transformation from β-Sn (tetragonal system) to brittle α-Sn (cubic system) at about 13 ° C or lower, and is particularly promoted at -30 ° C or lower. ing. This phenomenon is commonly called tin plague. Recently, it has been reported that this phenomenon occurs in some lead-free solders (for example, Mate 2001 Proceedings P469-
474), it is beginning to be recognized as a risk factor for joint reliability due to lead-free solder, but it is considered that this is not a big problem because it is rarely used for a long time at -30 ° C or lower in a general product use environment. There is. It is also known that the tin plague generation is suppressed by a small amount or a small amount of metal contained as a solder component, an additive or an impurity, such as Ag, Bi, Pb or Sb.

In the above-mentioned mounted circuit board and mounted package, in addition to precious metals such as gold and silver, metals such as copper, tin, and zinc whose reserves are small compared to the used amount, or highly valuable resources Since many of them are used, the need to recycle mounted circuit boards and mounted packages is increasing due to the problem of resource depletion. In addition, some recent products have a shorter usage period year by year. For example, in products such as personal computers and mobile phones, many of the components on the printed circuit board that have not reached their end of life are included.
It is preferable to collect and reuse these from the viewpoint of the global environment.

As a method of collecting mounted components, solder, etc. from a mounted circuit board, for example, Japanese Patent Laid-Open No. 8-139446.
In the gazette, after heating a printed circuit board to melt an adhesive such as solder, an impact force is applied to the side surface of the board and a shearing force for peeling off the mounted component is applied to the printed circuit board. The disassembly method to remove from is described. Further, Japanese Patent Laid-Open No. 8-148823 discloses that
A printed circuit board is housed in a component removal drum formed of coarse mesh, the printed circuit board is heated to a temperature higher than the solder melting temperature, the components and solder are disassembled and separated from the printed circuit board, and the component removal drum It describes a disassembling method for separating and collecting components and solder with a finer solder removal drum.

[0006]

However, JP-A-8-1
The method of heating and disassembling the solder and the mounted component from the printed circuit board as shown in No. 39446 has a problem that thermal damage applied to the component is large and the component is likely to be broken. In particular, most lead-free solders have a melting temperature higher by about 10 to 30 ° C. than conventional eutectic solders, so that heat damage to components due to heating becomes a serious problem. Further, in the disassembling method in which an impact is applied with a drum, which is disclosed in JP-A-8-148823, there is a high possibility that mechanical damage will be given to parts. Even if you don't intend to reuse the parts,
It is necessary to sort by recycling material. However, according to the conventional method, there is a case where the joint is not fractured at a portion having weak thermal or mechanical strength, or is fractured from a portion to which an impact is applied. Therefore, it is difficult to separate the materials, and the recovery rate of the materials may be low. If it is crushed to the extent that it can be separated, much energy and time are required, and there is also the problem that a large amount of dust is generated at that time.

Thus, the object of the present invention is (1) ease of disassembly when disassembling a mounting circuit board or a mounting package,
(2) Possibility of disassembling without damaging mounted parts or components, mounted package, mounted circuit board, etc. (3) Disassembled at intended parts such as joints, dismantled separation The possibility of separating and more efficiently disassembling the separated parts, (4) more efficient separation of recycled materials, (5) improved recovery rate of recycled materials, (6) generation of dust Mounting circuit board and mounting package that can realize reduction, (7) reduction of various energy required for recycling, and (8) reduction of recycling cost.
It is to provide a joining structure of mounted components and various components, a disassembling method, materials used therefor, and the like.

[0008]

The present inventors pay attention to the Sn crystal system transition phenomenon (low temperature transformation phenomenon) promoted at low temperature, and positively enhance the joint portion of a mounting circuit board or a mounting package. By using the purity Sn, under normal use conditions, the joint portion was weakened by low-temperature storage without lowering the reliability of the joint strength, and the mounted circuit board and the like were easily disassembled. Further, it has been clarified that by providing the coating barrier layer on the surface of the high-purity Sn region made of high-purity Sn, it is possible to prevent the Sn purity of the high-purity Sn region from being lowered even in the solder.

That is, the present invention is a coated high-purity Sn particle comprising high-purity Sn particles and a coating barrier layer coating the surface of the high-purity Sn particles, the coating barrier layer being composed of one or a plurality of layers. At least one layer constituting the coating barrier layer is formed of a metal or an alloy having a function of preventing diffusion of components other than Sn in the high-purity Sn particles, and the outermost shell layer of the coating barrier layer is The coated high-purity Sn particles are provided which are formed of a metal or an alloy that is wettable by solder. Preferably, the coated high-purity Sn particles of the present invention have a Sn purity of 4N (9).
9.99%) or more.

In the coated high-purity Sn particles of the present invention, the coating barrier layer may be composed of one layer or multiple layers. In any structure, the coating high purity S
On the outermost surface of the n-particle, a solder-wetting layer made of a metal or an alloy having high solder-wettability, and on the inner layer, high-purity Sn particles and, for example, a component other than Sn such as a solder component are melt-mixed. A barrier layer having a barrier function for preventing the above is formed. When the covering barrier layer is composed of one layer, a metal or an alloy having a high solder wettability and a barrier function is used as a metal to be used. When it is composed of one layer, Ni and Ni alloy are preferable as the material used for the coating barrier layer. The Ni alloy includes, for example, NiPd and NiCu. Two
When the coating barrier layer is composed of three, three or four or more layers, for example, in the case of two layers, Au / Pt or Cr is used.
A combination such as / Cu is used. In addition, as described above, if a layer having a barrier function is formed on either the inner layer or the layer formed of a metal or alloy having high solder wettability on the outermost shell, Cr, Cu, Co, Ti, Pt, Mo, Ta,
W, Fe, Nb, In, Zn, Cd, Ag, P, Mn,
Ru and Re can also be used as appropriate. In particular,
The coated high-purity Sn particles of the present invention are characterized in that the metal or alloy that wets the solder is Ni or a Ni alloy.

Furthermore, the coated high-purity Sn particles of the present invention are
The coating barrier layer has a thickness of 1 to 5 μm. The thickness of the coating barrier layer depends on the particle size of the high-purity Sn particles, the solder component used, the type of metal or the like used for the coating barrier layer, the operating conditions, etc., but the solder component or the like melts in the high-purity Sn particles. Any thickness may be used as long as it exhibits a barrier function so as not to mix. The thickness of the coating barrier layer is 1 μm
It is preferable if it is at least 5 μm so that the barrier function can be exhibited, and if it is 5 μm or less, for example, the coating barrier layer can be easily formed by electroless plating or the like.

The present invention provides a solder ball containing one or a plurality of the above-mentioned coated high-purity Sn particles contained in a solder component and one solder of the above-mentioned coated high-purity Sn particles on the coating barrier layer. A solder ball having a layer is provided. The present invention also provides one or more coatings of high purity Sn.
A solder paste or thread solder containing particles is also provided.

Further, according to the present invention, there is provided a mounted circuit board or a package in which electronic components are bonded, and a high purity Sn region made of high purity Sn is present in a part of a bonded portion of the electronic components. Provided is a mounting circuit board or a mounting package that is characteristic. More specifically, the mounted circuit board or mounted package of the present invention is characterized in that the high-purity Sn region is present in a part of the joint in any of a dot shape, a block shape, or a layer shape. . That is, in the mounted circuit board or the mounted package of the present invention, since the high-purity Sn region exists at the joint portion of the electronic component, low-temperature storage causes Sn low-temperature transformation in the high-purity Sn region. As a result, it is possible to reduce the strength of the desired joint, and it is possible to separate and disassemble the mounting circuit board or the mounting package. The high-purity Sn region is
For example, as shown in FIG. 5 and FIG. 7, they may be present as dots in the joint portion, or may be present as lumps as shown in FIG. Further, the high-purity Sn region can be made to exist in layers as shown in FIG.

The mounting circuit board or mounting package of the present invention is characterized in that a coating barrier layer made of a metal or an alloy wettable by solder is present in a part of the joint portion, adjacent to the high-purity Sn region. . Preferably, the mounted circuit board or the mounted package of the present invention is characterized in that a coating barrier layer made of a metal or an alloy adjacent to the high-purity Sn region and wettable with a solder is Ni or a Ni alloy.

The mounting circuit board or mounting package of the present invention is characterized in that the thickness of the coating barrier layer made of a metal or an alloy adjacent to the high-purity Sn region and wettable by the solder is 1 to 5 μm. The thickness of the coating barrier layer depends on the particle size of the high-purity Sn particles, the type of solder used, the type of metal or the like used for the coating barrier layer, the operating conditions, etc. Any thickness may be used as long as it exhibits a barrier function so as not to be melt-mixed. When the thickness of the coating barrier layer is 1 μm or more, the barrier function is exhibited, and when it is 5 μm or less, the coating barrier layer can be easily formed by, for example, electroless plating, which is preferable.

Further, in the mounting circuit board or mounting package of the present invention, the Sn purity of the high-purity Sn region is 4N (9).
9.99%) or more. If the Sn purity is 4N or more, the Sn low temperature transformation phenomenon occurs efficiently,
This is preferable because the high-purity Sn region is likely to collapse.

Furthermore, the present invention further includes a step of leaving it at a low temperature for a predetermined period of time or longer, and a step of disassembling it by applying an external force, to dismantle the mounted circuit board or the mounted package according to any one of claims 8 to 14. Also provide. The external force applied when disassembling includes, for example, vibration, wind force, gravity, electromagnetic force, or mechanical force using a brush, a manipulator, etc., so as not to damage electronic parts during dismantling. Any external force can be used as long as it is a simple method.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION 1. High-Purity Sn Particles A schematic cross-sectional view of the coated high-purity Sn particles 1 of the present invention is shown in FIG. The coated high-purity Sn particles 1 are composed of high-purity Sn particles 101 made of high-purity Sn and a coating barrier layer 102 formed on the surface thereof. The Sn purity of Sn particles is
In order to efficiently generate the low temperature transformation phenomenon, 99.9
It is preferably 9% (4N) or more, but may have a purity lower than 4N, such as 99.9% (3N), depending on factors such as the diameter of Sn particles, which is appropriately determined according to the use conditions. . Further, the coating barrier layer is formed by using a metal having a melting temperature higher than that of the solder used, having solder wettability, and capable of preventing the diffusion of the solder. As such a metal capable of preventing solder diffusion, for example, Ni metal having a melting point of 1455 ° C. can be used. Also, Ni alloys such as NiPd and NiCu can be used.

The thickness of the coating barrier layer depends on the conditions of use, such as the type of solder used with the coated high-purity Sn particles of the present invention, the melting temperature, etc., so as to maintain the purity of the Sn particles. Can be determined, but 1-5 μm
Is preferred. For example, in FIG.
Coated high-purity Sn particles 1 in which a coating barrier layer 102 having a thickness of about 1 to 5 μm is formed by electrolessly plating Ni or Ni alloy on the surface of 4 μm (99.99%) high-purity Sn particles 101 of μm. Indicates.

2. Solder Paste As the first embodiment of the present invention, a solder paste 2 containing the above-mentioned coated high-purity Sn particles can be produced. The solder paste 2 shown in FIG. 2 includes the coated high-purity Sn particles 1 and the solder particles 201 in a weight ratio of, for example, 2 to 8.
Then, the mixture of the coated high-purity Sn particles 1 and the solder particles 201 and the flux component 202 such as rosin are kneaded at a weight ratio of, for example, 9: 1 to prepare the mixture. As the solder component of the solder particles, for example,
Sn-8Zn-3Bi-based solder and Sn-3Ag-
0.5 Cu solder can be used.

3. Solder Ball As a second embodiment of the present invention, a solder ball 3 containing one or more coated high-purity Sn particles in the solder component.
Can be produced. Particles using a solder material used in a configuration in which one or a specific number of electrodes for one electrode are arranged in a gap between opposing electrodes are often referred to as "solder balls".
Although described as "solder ball", the shape of the solder ball is not limited to a true sphere, and may be a disk shape, a column shape, a drum shape, an elliptical sphere, a cube or the like depending on the application. From the viewpoint of surface coverage and handling, the more preferable shape of the solder ball is a true sphere.

For example, as shown in FIG. 3A, the solder ball 3 has a plurality of coated high-purity Sn particles 1 in the solder region 30.
1 may be included. Also, FIG. 3B
The solder ball 3 shown in FIG.
Approximately 5 μm on the surface of high purity Sn particles 101.
Coating barrier layer 1 by electroless plating of thick Ni
02, and a solder layer 302 of about 10 μm is formed on the outside by electrolytic plating. The higher the purity of Sn particles, the more efficiently the collapse of Sn particles due to the low-temperature transformation phenomenon of the Sn crystal system occurs. However, as the size of high-purity Sn particles increases, the degree of influence of the crack growth to the surroundings due to the volume change. Tends to be large. Therefore, the purity of the high-purity Sn particles 101 contained in the solder ball is 4N in this embodiment, but may be lower than this.

In this case, when the solder material printed in the circuit board or the solder material in the solder balls is melted in the solder joining process of the mounted circuit board and the mounted components, the melting point or reflow condition of the solder paste or the solder material. Thus, the coating barrier layer 102 serves as a diffusion barrier regardless of whether the high-purity Sn particles 101 are melted or not, so that the high-purity Sn particles 101 are kept in high purity. Examples of the solder component in the solder region include Sn-Bi solder and the like.

4. Thread Solder As a third embodiment of the present invention, the coated high-purity S of the present invention
The thread solder 4 containing the n particles 1 can be produced. A cross section of the thread solder 4 is shown in FIG. As shown in FIG. 4, the solder wire 4 has a coating barrier layer 102 such as NiCu.
The coated high-purity Sn particles 1 composed of the high-purity Sn particles 101 having a diameter of 80 μm coated with the flux component (not shown)
Can be dispersed in the solder region 301 containing

5. Laminated Structure of High-Purity Sn Layer / Coating Barrier Layer As a fourth embodiment of the present invention, as shown in FIG. 8, a laminated structure of a high-purity Sn layer and a covering barrier layer such as a NiPd alloy is formed at a joint portion of a mounting circuit board. It can also be formed.
In this configuration as well, as in the first to third embodiments, the coating barrier layer functions as a diffusion barrier, so that the high-purity Sn layer is kept in high purity. The high-purity Sn layer and the coating barrier layer can be formed by a conventional technique such as sputtering.

6. Coated high-purity Sn particle-containing resin As shown in FIG. 9, various mounting components 91 are mounted on the MID.
(Molded Interconnected Device, three-dimensional injection molded circuit component) Package 9 has a form in which several MID component parts 92 on which mounting component 91 is mounted are combined and sealed and bonded with resin to form a housing. In the MID package 9, there are component parts that have a high recovery utility value because they are expensive.

The various mounting parts are disassembled by utilizing the Sn low-temperature transformation phenomenon by joining the MID constituent parts with the solder paste 2 containing the coated high-purity Sn particles according to the first embodiment of the present invention. Can be separated. Further, in the present invention, as the resin used for joining the MID component parts, a thermosetting resin such as an epoxy resin is allowed to contain the coated high-purity Sn particles of the present invention to prepare a coated high-purity Sn particle-containing resin 93. The MID component parts are joined together using this, and the MID package is formed. As a result, the joining portion between the MID component parts can be separated at the intended place. As the resin used for the coated high-purity Sn particle-containing resin, a resin whose brittleness is weakened at a low temperature or a resin residue which is easily removed from the MID material by another method may be used.

7. Dismantling / Recovery System FIG. 10 shows a processing flow of disassembling a printed circuit board and mounted components according to the present invention. When dismantling and recycling waste electrical products such as home appliances and information devices, collect printed circuit boards and sort by product and model. Store the collected printed circuit boards in a cold storage. When storing, the information such as the number of the original product or model, the name of the part / resource with valuable collection value, the storage start time, etc. is stored in the mounted circuit board or the container that stores the mounted circuit board so that it can be used later. It is desirable to mark symbols, attach information labels, enclose IC cards on which information and control symbols are recorded, and manage the information with a computer so that it can be utilized in the disassembly process of the mounted circuit board. For example, after about 6 months, these substrates are taken out from the storage and placed in the mounted circuit board disassembly device.

FIG. 11 shows an example of the mounting circuit board disassembling apparatus 11. The mounted component 1101 is the printed circuit board 1102.
Part 1103 mounted on the mesh belt 110
Place on 4 and convey while applying vibration. The vibration is applied to the part 1103 by the vibration generator 1105 via the mesh belt 1104. At this point, the mounted component 1101 and the printed circuit board 1102 are stored by low temperature storage.
Since the joint with and is fragile, the mounted component 1101
Are disassembled and separated from the printed circuit board 1102. At this time, unlike the conventional example, it is possible to easily and efficiently disengage at the intended joint portion without requiring heating or strong impact force.
Since no impact force is applied, unintended destruction does not occur, no damage is caused by heating, and a component that has a market value as a used product in a mounted state is disassembled and separated while maintaining its value.

The disassembled and separated mounting component 1101 drops through the mesh belt 1104, is collected in the component collection tray 1106, and the printed circuit board 1102 is conveyed and collected in the circuit board collection tray 1107. The component recovery tray 1106 has a cushion or cushioning property so that the component is not damaged even if it is dropped from the mesh belt 1104. Although the collected mounted components 1101 are separated, they are separated at the intended joint portion, so that the separation efficiency is good and the separation rate is improved. Parts with market value as second-hand goods are reused. It is dismantled while maintaining its value when dismantled, and it is not damaged even when dropped, so the recovery rate and reuse rate of parts are improved. Parts that have no value as used but include precious metals
After further dismantling or shredder crushing, the precious metal resources are sent to a metal smelter or the like to be recovered. Other parts and crushed waste will be disposed of at managed landfills. By improving the separation rate, the recycling rate can be improved and the generation of dust can be reduced. The energy used in the process of dismantling is much lower than in the past, and not only the cost required for it, but also the recycling cost can be reduced by improving the efficiency of dismantling and separation, the separation rate, the recovery rate, and the reuse rate.

As a method other than applying vibration, a mounting component whose joint is weakened may be blown off by weak wind force if it is a small component, or the mounting circuit board may be slid in an inclined state or the mounting surface may be turned upside down. It is also possible to use a method of using gravity such as dropping in a closed state, a method of sweeping off with a soft brush that does not scratch, a method of picking up with a manipulator for heavy parts.

Instead of storing in a low temperature storage, it may be stored in a warehouse in cold regions such as high latitude regions and high mountains. Electric energy is required to use the cold storage, but natural energy can be used for cold storage to promote weakening of the joint. For this reason, cold area storage is environmentally friendly, and energy costs for low temperature preservation in the above-mentioned low temperature storage storage and a site for establishing a low temperature storage facility in an area generally higher in land price than the cold area are required. Is superior to.

[0033]

Examples Example 1: Reliability evaluation test of bonding strength of mounting parts bonded using the solder paste of the present invention (1) Preparation of sample Sample A 4N (99.99%) high purity with a particle size of about 40 μm The coating barrier layer 102 is formed by electrolessly plating the surface of the Sn particles 101 with Ni having a thickness of about 1 μm.
n-particle 1a was produced. The coated high-purity Sn particles 1a and the Sn-8Zn-3Bi solder particles 201a were mixed at a weight ratio of 2 to 8, and then the coated high-purity Sn particles 1a were mixed.
The mixture of the particles 1a and the solder particles 201a and the rosin flux component 202 are kneaded in a ratio of 9: 1, and
A solder paste 2a as shown in 1 was prepared.

FIG. 5 shows QF using solder paste 2a.
The schematic sectional drawing of the joining part 5 at the time of joining the P lead 51 to the circuit board terminal 53 which consists of Cu of the printed circuit board 52 is shown. First, the solder paste 2a was transferred onto the printed circuit board 52 using a screen printing method. A mounting device such as QFP is mounted on the printed circuit board 52 using a mounter device or the like, and is heated to a peak temperature of about 220 ° C. by a reflow device to melt the solder paste 2a to mount the mounting component on the printed circuit board 52. Solder bonded. A dispenser or the like may be used to supply the solder paste to the circuit board.

The melting temperature of Sn-8Zn-3Bi is about 19
Since the melting temperature of 7 ° C. and Sn is about 232 ° C., the high-purity Sn particles do not melt at the time of heating, and the joint portion 5 has unmelted coated high-purity Sn particles 1 a scattered in the solder region 301. It is in a solidified state. Since the surface of the high-purity Sn particles 101 is covered with the Ni coating barrier layer 102,
The coating barrier layer 102 serves as a diffusion barrier, and the high-purity S
The n particles 101 are kept in high purity.

Sample A was prepared by mounting a 144-pin 42 alloy lead QFP package on a FR4 glass epoxy substrate using the solder paste 2a.

Sample B A coating barrier layer 102 was formed by electrolessly plating a Ni layer having a thickness of about 5 μm on the surface of 4N (99.99%) high-purity Sn particles 101 having a particle size of about 40 μm. Sn particles 1b were produced. This coated high-purity Sn particle 1b
And Sn-3Ag-0.5Cu solder particles 201b in a weight ratio of 2 to 8, and then a mixture of the coated high-purity Sn particles 1b and solder particles 201b and a rosin flux component 202 in a ratio of 9: 1. The mixture was kneaded at a ratio to prepare a solder paste 2b as shown in FIG.

This solder paste 2b was transferred onto a printed circuit board using a screen marking method. Mounted components such as QFP on the printed circuit board using a mounter, etc.
The solder paste 2b was melted by heating at 40 ° C., and the printed circuit board and the mounting component were soldered and joined.

The melting temperature of Sn-3Ag-0.5Cu is about 220 ° C., the melting temperature of Sn is about 232 ° C., and the high-purity Sn particles 101 melt when heated, but the surface of the high-purity Sn particles 101 is Ni. Since it is covered with the coating barrier layer 102 of 1., it prevents the solder components from being melted and mixed in Sn, and the solidification is completed in a state where the high-purity Sn particles 101 are scattered in the solder region. Since the surface of the high-purity Sn particles 101 is covered with the Ni coating barrier layer 102,
The coating barrier layer 102 serves as a diffusion barrier and has a high purity of Sn.
The particles 101 are kept in high purity.

Sample B was prepared by mounting a 144-pin 42 alloy lead QFP package on a FR4 glass epoxy substrate using the solder paste 2b.

Control Sample C As a comparative example, a control sample C was prepared in the same manner as the sample A using the Sn-8Zn-3Bi solder paste 2c containing no coated high-purity Sn particles of the present invention.

(2) Evaluation of Bonding Strength Reliability After Thermal Shock Test FIG. 12A shows the results of evaluating the bonding strength after the thermal shock test for Samples A, B and C. The thermal shock test is performed by -40 ° C. for 30 minutes and 125 ° C. for 30 minutes as one cycle, up to 1000 cycles, and evaluated by measuring the bonding strength (45 ° peel strength) of the sample QFP lead every 250 cycles. did. The samples A and B prepared using the solder paste containing the coated high-purity Sn particles have the same bonding strength reliability against the thermal shock test as the control sample C prepared using the solder paste not containing the coated high-purity Sn particles. It was confirmed to have.

(3) Evaluation of Bonding Strength Reliability After Low Temperature Storage Test FIG. 12B shows the results of bonding strength evaluation of the sample A and the control sample C by the low temperature storage test at -15 ° C. In sample A, the bonding strength begins to decrease after 2500 hours, and the bonding strength becomes almost 0 after 3500 hours. On the other hand, in the control sample C, there was no change in the bonding strength even after 5000 hours. This is because, in sample A, in the high-purity Sn particles kept in the high-purity state in the bonded portion, low-temperature transformation into α-Sn occurs, and this portion becomes brittle, and at the same time, the high-purity Sn particles are changed due to volume change. This is because cracks propagate around the circumference. Moreover, in FIG.
The results of joint strength evaluation by a low temperature storage test at 5 ° C are also shown. In sample B, the bonding strength begins to decrease after 2000 hours, and after 3000 hours, the bonding strength is almost zero. This is high purity Sn
Even if the particles 101 were melted, the high-purity Sn particles 101 were kept in high purity because of the coating barrier layer 102.
This is because the high-purity Sn particles in the joint undergo low-temperature transformation into α-Sn, and this portion becomes brittle, and at the same time, cracks develop around the high-purity Sn particles due to volume change.

(4) Conclusion From the above two reliability test results of the bonding strength, the components mounted on the printed circuit board by using the solder paste containing the coated high-purity Sn particles of the present invention can be used under normal operating conditions. By keeping the printed circuit board at a low temperature without lowering the reliability of the bonding strength below, the printed circuit board and the mounted components can be easily disassembled and separated.

Example 2 A mounting barrier layer 10 of about 5 μm thick on the surface of 4N (99.99%) high-purity Sn particles 101 with a mounting particle size of about 200 μm using solder balls.
2 is formed by electroless plating, and about 10 μm on the outside
The solder layer 302 was formed by electrolytic plating using Sn-Bi solder of No. 3 to produce the solder ball 3 shown in FIG. 3B.

In FIG. 6, using this solder ball 3, C
The schematic sectional drawing of the joining part 6 at the time of joining SP61 to the ceramic circuit board 63 is shown. First, the flux is transferred to the land 62 of the CSP 61, the solder balls 3 are transferred onto the land 62 by a ball mounting machine, and fixed by collective reflow. Next, Sn-8Zn-3Bi solder paste is printed on the circuit pattern of the ceramic circuit board 63, and the CSP 61 and other components to which the solder balls 3 are fixed are mounted on the ceramic circuit board 63 using a mounter or the like.
It is mounted on the terminal 64 of. This ceramic circuit board 63
Is heated to a peak temperature of about 220 ° C. by using a reflow device to melt the solder paste, and the ceramic circuit board and the mounted component are soldered. At this time, Sn-8Zn-3
Since the melting temperature of Bi solder is about 197 ° C. and the melting temperature of Sn is about 232 ° C., the high-purity Sn particles 101 that are the cores of the solder balls 3 do not melt, and the Ni coating barrier layer 102 serves as a diffusion barrier. Therefore, high-purity Sn particles 101
Is kept in high purity.

As in the first embodiment, the ceramic circuit board of the present embodiment is stored at a low temperature, so that the solder balls 3 having high-purity Sn particles as cores from the ceramic circuit board 63.
It is possible to easily disassemble and separate only the CSP 61 joined by the above, and the other components can be kept joined to the ceramic circuit board 63. Therefore, the ceramic circuit board can be easily upgraded by replacing the CSP or BGA.

Example 3 Mounting Using Thread Solder FIG. 7 is a schematic view of the joint portion 7 when the lead portion 72 of the insertion component 71 is inserted into the insertion hole provided in the metal core circuit board 73 and soldered. A sectional view is shown. Insert part lead part 7
In the soldering of No. 2, a thread solder having a cross section as shown in FIG. 4, that is, a coated high-purity Sn particle 1 having a diameter of 80 μm and coated with a coating barrier layer 102 of NiCu in a solder region 301 containing a flux component. The thread solder 4 prepared by dispersing is used. At the joint portion 7, the coated high-purity Sn particles 1 contained in the thread solder 4 are solidified in a state of being uniformly dispersed, and the coating barrier layer 102 serves as a diffusion barrier. It is kept in high purity. In disassembling a mounted circuit board having such a joint, if the storage is performed at a predetermined temperature or lower for a predetermined period of time or longer, the coated high-purity Sn particles become brittle and the joint strength decreases, so that the insertion part can be easily recovered. .

It should be noted that the coating high-purity Sn particles are not uniformly dispersed as shown in FIG. 7 depending on the selection of the solder component of the thread solder, the soldering conditions, the selection of the lead thickness of the insertion part and the size of the insertion hole. Alternatively, it may be intentionally localized to some extent on the thread solder supply side, below the circuit board, or around the fillet. Localization is performed by coating the coating with high-purity Sn when the solder component is molten.
This can be performed by utilizing the particle size of the particles or the difference in specific gravity between the coated high-purity Sn particles and the solder component. In the case where the coated high-purity Sn particles are localized in this way, the coated high-purity Sn particles are compared with the case of the soldering portion in which the coated high-purity Sn particles are relatively evenly dispersed as described above. However, if there is a portion where the coated high-purity Sn particles are gathered in the soldered portion even if the amount is the same as the whole, cracking from that portion occurs quickly, so that the destruction of the joint portion is likely to proceed. Therefore, similar dismantling property can be obtained even under mild low temperature storage and dismantling conditions. In addition, the coating high purity S contained in the solder wire
Even if the amount of n-particles is small, by collecting the coated high-purity Sn particles to some extent, the same dismantling property can be obtained under the same low-temperature storage and dismantling conditions.

Example 4: Lamination formation of high-purity Sn layer / covering barrier layer In order to disassemble and separate mounted parts by utilizing the low-temperature transformation phenomenon of high-purity Sn, as described above, high-purity Sn particles were used. Even if it is not contained in the solder component, it can be achieved by providing a high-purity Sn layer at the joint portion of the mounted circuit board. FIG. 8 shows the protruding electrode 82 of the BGA 81.
7 is a schematic cross-sectional view of the joint portion 8 when the is joined to the circuit board terminal 84 of the printed circuit board 83. The protruding electrode 82 of BGA is made of Au by electrolytic plating. Circuit board terminal 8
A high-purity Sn layer 85 and a NiPd alloy coating barrier layer 86 are sequentially formed on the upper surface of the No. 4 by a sputtering method.
A laminated structure of a coating barrier layer of / NiPd was formed. Further, an Au layer 87 was formed on it. These layers can be easily formed using a conventional film forming technique other than the sputtering method. An insulating layer 88 is formed other than the terminals and on the edges of the terminals. The bump electrode 82 and the circuit board terminal 84 are joined with Ag paste 89.
Since the coating barrier layer 86 serves as a diffusion barrier as in the above-described embodiments, the high-purity Sn layer 85 is kept in high purity.

In disassembling the mounted circuit board having such a joint, if the low-temperature storage is performed at a predetermined temperature or lower for a predetermined period or longer, the high-purity Sn layer 85 becomes brittle and cracks or delamination occurs in the Sn layer 85. As a result, the bonded portion 8 can be disassembled, the BGA and the printed circuit board can be easily recovered, and the recovery rate of precious metals and the like is improved.

Example 5: Application to coated high-purity Sn particle-containing resin FIG. 9 shows a MID (Molded I) on which various mounting parts 91 are mounted.
The schematic cross-sectional view of the nterconnected Device, three-dimensional injection molded circuit component) package 9 is shown. Some of these MID packages 9 are expensive and therefore have a component value that can be recovered and utilized. In this embodiment, the MID package 9 is
Several MID component parts 9 with mounting parts 91 mounted
The two are combined and sealed and joined together to form a housing. The various mounting parts 91 are coated high purity S with a diameter of 30 μm.
The solder paste 2 containing n particles is used for bonding, and MI
30 μm at the joint where D component parts 92 are combined
The resin 93 containing the coated high-purity Sn particles 1 having a diameter is used. Since the melting temperature of the solder paste 2 that joins the mounting components 91 is higher than the curing temperature of the resin 93 that joins the MID component parts 92, the solder of the mounting components does not melt during sealing and joining of the mounting components does not occur. Stays good. In the high-purity Sn particles 101 of the coated high-purity Sn particles 1 contained in the solder paste 2, the coating barrier layer 102 serves as a diffusion barrier, so that the high-purity Sn particles 101 are kept in high purity.

When disassembling a package having such a joint, if the storage is carried out at a predetermined temperature or lower for a predetermined period of time or longer, the coated high-purity Sn particles become brittle, and cracks develop in the solder at the joints of various mounting parts and MID component parts. Since the cracks in the resin at the joints of the parts are further developed, the mounted parts and MID constituent parts can be easily disassembled and separated, and various mounted parts and MID constituent parts can be easily collected.

In addition to the components shown in the above embodiments, the components to be mounted may be TCP, chip components, semiconductor chips, etc., and the circuit board to be mounted may be a glass substrate, an organic substrate, a fluororesin substrate or the like. The mounting package may be a WCSP or a ceramic package. Further, the solder material is not limited to lead-free solder, but may be applied to lead-containing solder, or may be applied to a bonding method other than solder, for example, wire bond, ribbon bond, or the like.

[0055]

According to the present invention, since the low temperature transformation phenomenon of Sn is used when disassembling the mounted circuit board and the mounted parts or the mounted package, the dismantling is facilitated, and the mounted parts, constituent parts and mounted parts are mounted. It can be disassembled without damaging the package or mounted circuit board, etc., and can be disassembled at the intended part such as the joint part, so sorting according to the disassembled parts and further efficient disassembly are possible, and dust While reducing various kinds of energy required for generation and recycling and recycling cost, it is possible to improve efficiency of separation of recycled materials, improvement of recovery rate of recycled materials and reuse rate of parts. In addition, CSP and BGA using the solder balls of the present invention,
It can be selectively dismantled, facilitating the upgrade of the printed circuit board by replacing these parts.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a coated high-purity Sn particle of the present invention.

FIG. 2 is a schematic cross-sectional view of a solder paste containing coated high-purity Sn particles of the present invention.

FIG. 3 is a schematic sectional view of a solder ball containing the coated high-purity Sn particles of the present invention.

FIG. 4 is a schematic cross-sectional view of a thread solder containing coated high-purity Sn particles of the present invention.

FIG. 5 is a conceptual diagram of a solder joint portion when the solder paste of the present invention is used.

FIG. 6 is a conceptual diagram of a solder joint portion when the solder ball of the present invention is used.

FIG. 7 is a conceptual diagram of a solder joint portion when the thread solder of the present invention is used.

FIG. 8 is a conceptual diagram of a solder joint portion when the high-purity Sn layer / covering barrier layer of the present invention is used.

FIG. 9 is a conceptual diagram of a mounting package assembled using a resin containing coated high-purity Sn particles of the present invention.

FIG. 10 is a flowchart showing a disassembly procedure of a mounted circuit board.

FIG. 11 is a schematic view of a mounting circuit board disassembly device for disassembling a mounting circuit board or a mounting package.

FIG. 12 is a graph showing reliability evaluation results of connection strength of parts joined by using a solder paste containing coated high-purity Sn particles of the present invention.

[Explanation of symbols]

1 ... Coated high-purity Sn particles, 101 ... High-purity Sn particles, 102 ... Covering barrier layer 2 ... Solder paste, 201 ... Solder particles, 202 ... Flux component, 3 ... Solder balls, 301 ... solder area, 302 ... solder layer, 4 ... Thread solder, 5 ... joint, 51 ... QFP lead, 52 ... Printed circuit board, 53 ... Circuit board terminal, 6 ... joint, 61 ... CSP, 62 ... land of CSP, 63 ... Ceramic circuit board, 64 ... Circuit board terminal, 7 ... joint, 71 ... Inserted parts, 72 ... Lead part, 73 ... Metal core circuit board, 8 ... joint, 81 ... BGA, 82 ... protruding electrode, 83 ... Printed circuit board, 84 ... Circuit board terminal, 85: high-purity Sn layer, 86 ... Covering barrier layer, 87 ... Au layer, 88 ... Insulating layer, 89 ... Ag paste, 9 ... MID package, 91 ... Mounted parts, 92 ... MID component parts, 93 ... Resin, 11 ... Mounted circuit board dismantling device, 1101 ... Mounted parts, 1102 ... Printed circuit board, 1103 ... parts, 1104 ... Mesh belt, 1105 ... Vibration generator, 1106 ... a parts collection tray, 1107 ... Circuit board recovery tray.

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Claims (14)

[Claims] 1. A coated high-purity Sn particle comprising high-purity Sn particles and a coating barrier layer coating the surface of the high-purity Sn particles, wherein the coating barrier layer is composed of one or a plurality of layers. At least one layer constituting the barrier layer is formed of a metal or alloy having a function of preventing diffusion of components other than Sn in the high-purity Sn particles, and the outermost shell layer of the coating barrier layer is a metal wettable with solder. Alternatively, the coated high-purity Sn particles formed of an alloy. 2. The Sn purity of the high-purity Sn particles is 4N (9
9.99%) or more, The coated high-purity Sn particles according to claim 1, wherein 3. The solder wettable metal or alloy is Ni.
Or a Ni alloy.
The coated high-purity Sn particles described. 4. The coated high-purity Sn particles according to claim 1, wherein the coating barrier layer has a thickness of 1 to 5 μm. 5. A solder ball containing one or a plurality of coated high-purity Sn particles according to any one of claims 1 to 4 in a solder component. 6. A solder ball having a solder layer on the coating barrier layer of one coated high-purity Sn particle according to any one of claims 1 to 4. 7. A solder paste or a thread solder containing one or a plurality of coated high-purity Sn particles according to any one of claims 1 to 4. 8. A mounted circuit board or a mounted package to which electronic components are bonded, wherein a high-purity Sn region made of high-purity Sn is present in a part of the bonded portion of the electronic components. Mounted circuit board or package. 9. The mounting circuit board or mounting according to claim 8, wherein the high-purity Sn region is present in a part of the joint in any of a dot shape, a lump shape, and a layer shape. package. 10. The mounting according to claim 8, wherein a coating barrier layer made of a metal or an alloy that wets the solder is present adjacent to the high-purity Sn region in a part of the joint. Circuit board or mounting package. 11. The mounted circuit board or mounted package according to claim 10, wherein the coating barrier layer made of a metal or an alloy wettable with the solder adjacent to the high-purity Sn region is Ni or a Ni alloy. 12. The thickness of the coating barrier layer made of a metal or an alloy that wets the solder adjacent to the high-purity Sn region has a thickness of 1 to 1.
The mounting circuit board or mounting package according to claim 10, wherein the mounting circuit board or mounting package has a thickness of 5 μm. 13. The Sn purity of the high-purity Sn region is 4N.
9. It is (99.99%) or more, It is characterized by the above-mentioned.
13. The mounted circuit board or mounted package according to any one of 1 to 12. 14. The method according to claim 8, further comprising a step of leaving at a low temperature for a predetermined period or more and a step of disassembling by applying an external force.
A disassembling method for disassembling the mounted circuit board or the mounted package described in any of the above.