CN108422117A - The method for preparing the unleaded interconnection solder joint of polycrystalline structure by applying electric current - Google Patents
The method for preparing the unleaded interconnection solder joint of polycrystalline structure by applying electric current Download PDFInfo
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- CN108422117A CN108422117A CN201810102951.8A CN201810102951A CN108422117A CN 108422117 A CN108422117 A CN 108422117A CN 201810102951 A CN201810102951 A CN 201810102951A CN 108422117 A CN108422117 A CN 108422117A
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- solder joint
- remelting
- solder
- pad
- polycrystalline structure
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K28/00—Welding or cutting not covered by any of the preceding groups, e.g. electrolytic welding
Abstract
The method for preparing the unleaded interconnection solder joint of polycrystalline structure by applying electric current, belong to material preparation and connection area, suitable for preparing the unleaded interconnection solder joint being orientated with polycrystalline, the solder joint polycrystalline ratio of making reaches 100%, can significantly improve the service reliability of unleaded interconnection solder joint.The advantage of the invention is that the unleaded interconnection solder joint of various structures can be prepared, such as docking, overlap joint and ball grid array (Ball Grid Array, BGA) solder joint encapsulating structure etc., the unleaded interconnection solder joint ensured has polycrystalline structure；Simple process and low cost is honest and clean, is no different with traditional solder joint preparation process other than being powered in remelting preparation process；The unleaded interconnection solder joint obtained simultaneously disclosure satisfy that the demand of practical application.
Description
Technical field
The present invention is the method for preparing the unleaded interconnection solder joint of polycrystalline structure by applying electric current, belongs to material preparation and connect
Field is suitable for preparing the unleaded interconnection solder joint being orientated with polycrystalline, and the solder joint polycrystalline ratio made through the invention reaches
100%, the service reliability of unleaded interconnection solder joint can be significantly improved.
Background technology
Solder joint plays the effects that mechanical connection and electric signal transmission in microelectronic component, be microelectronics Packaging can not or
Scarce component part.Nowadays, on the one hand, microelectronic component constantly develops to micro-, light, thin and multifunction direction；On the other hand,
Encapsulated space reduces, and current density increases, and chip heat production increases, and the working environment residing for solder joint becomes unprecedented harshness.
Moreover, because the variation of environment temperature and frequently switching on for power supply, the greatest differences of coefficient of thermal expansion are led between different encapsulating materials
The ess-strain that solder joint is born is caused to further increase.Therefore, solder joint becomes the weak link in electronic device, electronic device
Reliability and service life depend greatly on the reliability of solder joint.
Isotropism is often presented in traditional SnPb eutectic solder solder joints, and this is mainly due to Sn and Pb two-phases to weld in SnPb
Distribution in point is relatively uniform, but Pb is toxic, and european union directive has been banned from use, therefore lead-free brazing obtains in recent years
Development.However, different from SnPb solder joints, unleaded interconnection solder joint shows strong anisotropy, this is because unleaded interconnection
Solder joint is usually made of monocrystalline or limited a β-Sn crystal grain, and β-Sn have the crystal structure of body-centered tetragonal, lattice constant a
=b=0.5632, c=0.3182, c/a=0.546 has strong anisotropy.Therefore, unleaded interconnection weldering can be seriously affected
The reliability of point, the crystal orientation of each crystal grain and its reliability are closely related in solder joint.For example, in Thermal Cycling
In, if plane where the c-axis of β-Sn crystal grain and pad is close to parallel, the CTE mistakes between solder and bonding pad material in solder joint
With larger, the interconnection solder joint with this crystal orientation will be easier fail；For another example, in electrotransport process, weldering
The diffusion rate of atom is influenced by β-Sn crystal grain in point, and atom will be apparently higher than along the c-axis diffusion rate of β-Sn crystal grain along a
Axis or b axis will be easier to fail with plane where pad with c-axis close to the solder joint that vertical crystal is orientated.Therefore, exist
Polycrystalline structure is formed inside Lead-Free Solder Joint, makes it that isotropism be presented, and has very important meaning to the reliability of the company's of raising solder joint
Justice.
The present invention applies the preparation method of electric current during welding spot remelting using butt welding point, has successfully been prepared unleaded
Polycrystalline solder joint, this is because under the action of electric current, during welding spot remelting, internal forming core core increases, after solidification
A variety of crystal orientations are formd inside solder joint.Inventor has found that polycrystalline solder joint has more excellent by subsequent failtests
Good service reliability, including electromigration reliability and heat fatigue reliability etc. achieve the excellent of the SnPb solders of beyond tradition
Good reliability, this is because the mechanical performance of lead-free brazing such as SnAgCu is excellent compared with SnPb solders, meanwhile, both there is performance
Excellent polycrystalline welding spot structure, therefore, polycrystalline leadless solder welding spot such as SnAgCu is reliable compared with the military service of SnPb solder polycrystalline solder joints
Property significantly improves.
Invention content
The purpose of the present invention is be significantly lower than polycrystalline structure solder joint for Lead-Free Solder Joint monocrystalline or twin structure reliability
Feature prepares the unleaded interconnection solder joint with polycrystalline structure.The synthesis service reliability of polycrystalline structure solder joint is more excellent, than
Such as, the solder joint with a certain kind orientation is with excellent electromigration reliability, and the solder joint with another kind orientation is with excellent
Heat fatigue reliability, and the heat fatigue of polycrystalline solder joint or electromigration reliability fall between, and with uniformity.For
One encapsulating structure, the number of solder joint is up to hundreds and thousands of, and the failure of any one solder joint can all cause the entirety of encapsulating structure
Failure, at this point, the polycrystalline solder joint identical service condition lower service life it is consistent advantage it is more prominent, while there is polycrystalline structure solder joint
Assembly life-span prediction is more consistent and accurate, it is seen then that the unleaded interconnection solder joint of polycrystalline structure prepared by the present invention can significantly improve
The comprehensive performance and service reliability of solder joint.
In order to achieve the above object, present invention employs following technical solutions.
A method of the unleaded interconnection solder joint of polycrystalline structure being prepared by applying electric current, welding spot structure can be docking, take
Connect with bga component etc., specifically include following steps：
(1), the making of pad or chip is carried out according to actual needs, and is purged oxide and the pollution of bond pad surface
Object；It such as uses aqueous solution of nitric acid to remove the oxide on the surfaces such as pad, the surfaces such as pad is removed using acetone or alcohol etc.
Pollutant；
(2), when making docking or ovelapping spot weld, prepare solder, prepare for the remelting preparation of follow-up polycrystalline structure solder joint；
When making ball grid array (Ball Grid Array, BGA) solder joint encapsulating structure, then prepared firstly the need of by solder
At solder ball, then uses remelting processing rework profile to carry out solder ball and connect with the remelting of pad or chip, be cooled to room
Temperature, the obtained pad or chip with salient point are prepared for the follow-up remelting preparation with polycrystalline structure solder joint package assembling；
(3), it makes docking or when ovelapping spot weld, soldering paste is applied between two pads, using remelting processing rework profile,
And during welding spot remelting butt welding point be powered, carry out solder joint remelting prepare, be cooled to room temperature, docked accordingly or
Ovelapping spot weld；
When preparing bga structure, pad with salient point or chip that step (2) has prepared are passed through into weight
Process of smelting rework profile is welded on hollow piece or missing solder disk, and is powered to encapsulating structure during welding spot remelting, is carried out
Prepared by the remelting of solder joint, be cooled to room temperature, obtain corresponding BGA solder joints；
(4), the unleaded interconnection solder joint prepared is inlayed, ground and is polished, to obtain electron backscatter diffraction
(Electron Backscattered Diffraction, EBSD) data, and analyze data.
The pad or chip are selected from Cu, Cu/Ni/Au, Cu/Cu6Sn5；
The solder or soldering paste are selected from bianry alloy SnCu series, SnAg series, SnZn series, SnBi series or SnIn systems
Row, or selected from ternary alloy three-partalloy SnAgCu series, SnAgBi series or SnAgIn series, or it is selected from quaternary SnAgBiIn series leadless
Solder；
The galvanization current density is 1 × 102To 1 × 106A/cm2；
Remelting in the step (2) and step (3), temperature range select 200 DEG C to 700 DEG C.
The step (2) and (3 cooling is selected from the cooling of furnace cooling, air-cooled, air-cooled, water cooling or oil cooling with step
Mode.
The advantage of the invention is that the unleaded interconnection solder joint of various structures can be prepared, such as docking, overlap joint and BGA solder joints envelope
Assembling structure etc., the unleaded interconnection solder joint ensured have polycrystalline structure, and solder joint polycrystalline ratio reaches 100%；It is simple for process, at
This is cheap, is no different with traditional solder joint preparation process other than being powered in remelting preparation process；What is obtained simultaneously is unleaded mutual
Even solder joint disclosure satisfy that the demand of practical application.
Description of the drawings
Fig. 1：The X-ray images of bga structure；
Fig. 2：It is not added with the EBSD data that the Sn3.0Ag0.5Cu solder BGA solder joints of mono-crystalline structures are presented in electric current；
(a) EBSD distribution of orientations figure (superposition crystal boundary distribution map)；(b) (001) and (100) pole figure；(c) misorientation is distributed
Figure；
Fig. 3：It is not added with the EBSD data that the Sn3.0Ag0.5Cu solder BGA solder joints of twin structure are presented in electric current；
(a) EBSD distribution of orientations figure (superposition crystal boundary distribution map)；(b) (001) and (100) pole figure；(c)50°、60°、70°
Misorientation distribution function and misorientation distribution map；
Fig. 4：Apply electric current in remelting preparation process, the Sn3.0Ag0.5Cu solders BGA of polycrystalline structure is presented after cooling
The EBSD data of solder joint；
(a) EBSD distribution of orientations figure (superposition crystal boundary distribution map)；(b) (001) and (100) pole figure；(c) misorientation is distributed
Figure；
Fig. 5：The picture of Cu/Sn3.5Ag/Cu solder banjo fixing butt jointings；
Fig. 6：Apply electric current in remelting preparation process, the Sn3.5Ag solder banjo fixing butt jointings of polycrystalline structure are presented after cooling
EBSD data；
(a) EBSD distribution of orientations figure；(b) crystal boundary distribution map；(c) (001) and (100) pole figure；(d) misorientation distribution map；
Fig. 7：The EBSD data of the linear solder joint of Sn3.0Ag3.0Bi3.0In solders with polycrystalline structure；
(a) EBSD distribution of orientations figure；(b) crystal boundary distribution map；(c) (001) and (100) pole figure；(d) misorientation distribution map；
Fig. 8：The electromigration SEM figures of the linear solder joint of Sn3.0Ag3.0Bi3.0In solders with polycrystalline structure shown in Fig. 7
Piece；
(a)0h；(b)168h；(c)336h；(d)504h；
Fig. 9：The linear solder joint electromigration condition lower bound of Sn3.0Ag3.0Bi3.0In solders with polycrystalline structure shown in Fig. 7
Face intermetallic compound thickness situation of change；
Figure 10：The EBSD data of the linear solder joint of Sn3.0Ag3.0Bi3.0In solders with mono-crystalline structures；
(a) EBSD distribution of orientations figure；(b) (001) and (100) pole figure；(c) misorientation distribution map；
Figure 11：The electromigration SEM figures of the linear solder joint of Sn3.0Ag3.0Bi3.0In solders with mono-crystalline structures shown in Figure 10
Piece；
(a)0h；(b)168h；(c)336h；(d)504h；
Figure 12：Under the conditions of the linear solder joint electromigration of Sn3.0Ag3.0Bi3.0In solders with mono-crystalline structures shown in Figure 10
Compound thickness situation of change between interface metal.
Specific embodiment
With reference to embodiment, the invention will be further described, but the present invention is not limited to following embodiments.
The following contents combination Fig. 1 and 4 is specifically described embodiments of the present invention.
Embodiment 1：Solder ingredient is Sn3.0Ag0.5Cu (wt.%), and solder interconnection solder joint is presented polycrystalline structure, encapsulates
Size is the making of the bga component of 12mm × 12mm × 1.1mm.
1, it is designed and is made pair on printed circuit board (Printed circuit boards, PCB) according to chip structure
The pad answered, wherein PCB is FR-4 sheet materials, thickness 2.0mm.Pad uses Cu/Ni/Au three-deckers, bottom Cu
The thickness of layer, electroplated Ni layer and top Au layer is respectively 35 μm, 5.0 μm and 0.1 μm, and pad welds film using organic guarantor and carries out surface
Processing；
2, the Sn3.0Ag0.5Cu solders that solder is provided using Japanese Senju Metal Industry Co., Ltd, the pricker being prepared
A diameter of 300 μm of pellet, wherein deposit in refrigerator before solder paste, need take out and carry out from refrigerator before use for 2 hours in advance
It is sufficiently stirred, to restore its viscosity and activity；
3, pad is put into the HNO that prepared volume fraction is 30%330s is impregnated in aqueous solution, to remove its surface
Oxide, then by pad be put into acetone soln impregnate 60s be then dried for standby with removing the pollutant on its surface；
4, suitable weld-aiding cream is coated on chip, by using specified remelting processing rework profile (remelting temperature
245oC is simultaneously kept for 1 minute in 217oC or more), the chip with solder bump is obtained, hot wind remelting device is U.S. PACE public
The Rework workbench (ST-325) of department；
5, the chip upside down with solder bump for obtaining step 4 is on the pad of PCB, using identical with step 4
Remelting processing rework profile carries out remelting again, and butt welding point applies 1 × 10 in reflow process4A/cm2Electric current, will carry
For the chipset of solder bump on the Cu/Ni/Au pads of FR-4PCB, air-cooled solidification obtains bga component, X-ray
Image as shown in Figure 1, periphery array soldered ball totally 228, spacing be 500 μm；
6, bga component is inlayed, its specified cross-section is ground and is polished, made by EBSD observation electric currents
The crystal grain that solder joint is prepared with lower remelting is orientated, and EBSD data are as shown in Figure 4, it is seen then that remelting prepares solder joint and is under the function of current
Polycrystalline structure；
Embodiment 2：Sectional dimension is 400 μm of 400 μ m, and thickness is 300 μm, and the Cu/Sn3.5Ag of polycrystalline structure is presented
(wt.%) making of/Cu banjo fixing butt jointings.The following contents combination Figures 5 and 6 are specifically described embodiments of the present invention, and combine
Fig. 7,8,9,10,11 and 12 illustrate that the electromigration reliability of polycrystalline welding spot structure is better than monocrystalline solder joint.
1, copper pad use Manufacture by line cutting, size be 400 μ m 400 μ m 10mm, purity 99.99wt.%,
Pad is put into the HNO that prepared volume fraction is 30%330s is impregnated in aqueous solution, to remove the oxide on its surface, so
Pad acetone soln immersion 60s is put into afterwards to be then dried for standby to remove the pollutant on its surface；
2, by sticking double faced adhesive tape in the edge printed circuit board (Printed circuit boards, PCB), the size of PCB
For 10mm × 10mm × 2mm, material FR-4, will copper pad to be welded adherency on double faced adhesive tape, ensure pad it is parallel to each other and
Away from being 300 μm；
3, the Sn3.5Ag solder pastes that solder is provided using Japanese Senju Metal Industry Co., Ltd, solder paste are stored before
It needs take out and be sufficiently stirred from refrigerator before refrigerator, use within 2 hours in advance, to restore its viscosity and activity, uses
Cotton swab is by a certain amount of solder paste coated between two copper pads；
4, by using specified remelting processing rework profile (remelting temperature 245oC simultaneously keeps 60s in 217oC or more),
And butt welding point applies 1 × 10 in reflow process4A/cm2Electric current, air-cooled solidification obtains linear solder joint, and hot wind remelting device is
The Rework workbench (ST-325) of PACE companies of the U.S.；
5, linear solder joint is put into acetone soln together with pcb board, linear solder joint is removed, the linear solder joint that Fig. 5 is
Then picture specifies cross section to be ground and polish it, the crystal grain that docking solder joint is observed by EBSD is orientated, EBSD numbers
According to as shown in Figure 6, it is seen then that Cu/Sn3.0Ag3.0Bi3.0In/Cu docking solder joints prepared by remelting have polycrystalline structure；
6, Cu/Sn3.0Ag3.0Bi3.0In/Cu banjo fixing butt jointings prepared by remelting shown in Fig. 7 have polycrystalline structure, by it
It is placed in 1 × 104A/cm2Current density under carry out electromigration experiment, Fig. 8 and Fig. 9 are respectively to have polycrystalline structure shown in Fig. 7
Compound is thick between interface metal under the conditions of the electromigration SEM pictures of the linear solder joint of Sn3.0Ag3.0Bi3.0In solders and electromigration
Spend situation of change；Figure 11 and Figure 12 is respectively the Sn3.0Ag3.0Bi3.0In solder string beads with mono-crystalline structures shown in Figure 10
Compound thickness situation of change between interface metal under the conditions of the electromigration SEM pictures of point and electromigration, it is seen then that there are mono-crystalline structures
Solder joint is either inside solder welding spot or the intermetallic compound situation of change of welding point interface is relatively with polycrystalline structure
Solder joint is violent, and therefore, the electromigration reliability of the linear solder joint of Sn3.0Ag3.0Bi3.0In solders with polycrystalline structure is better than tool
There is the linear solder joint of Sn3.0Ag3.0Bi3.0In solders of mono-crystalline structures.
Claims (6)
1. a kind of method preparing the unleaded interconnection solder joint of polycrystalline structure by applying electric current, the solder joint polycrystalline ratio of making reach
100%, welding spot structure is divided into docking, overlap joint and bga component, which is characterized in that specifically includes following steps：
(1), the making of pad or chip is carried out according to actual needs, and is purged the oxide and pollutant of bond pad surface；
It such as uses aqueous solution of nitric acid to remove the oxide on the surfaces such as pad, the pollution on the surfaces such as pad is removed using acetone or alcohol etc.
Object；
(2), when making docking or ovelapping spot weld, prepare solder, prepare for the remelting preparation of follow-up polycrystalline structure solder joint；
When making ball grid array (Ball Grid Array, BGA) solder joint encapsulating structure, then pricker is prepared into firstly the need of by solder
Then pellet uses remelting processing rework profile to carry out solder ball and is connect with the remelting of pad or chip, is cooled to room temperature, obtains
The pad or chip with salient point arrived is prepared for the follow-up remelting preparation with polycrystalline structure solder joint package assembling；
(3), when making docking or ovelapping spot weld, soldering paste is applied between two pads, using remelting processing rework profile, and
Butt welding point is powered during welding spot remelting, and prepared by the remelting for carrying out solder joint, be cooled to room temperature, docked or overlapped accordingly
Solder joint；
When preparing bga structure, pad with salient point or chip that step (2) has prepared are passed through into remelting work
Skill rework profile is welded on hollow piece or missing solder disk, and is powered to encapsulating structure during welding spot remelting, and solder joint is carried out
Remelting prepare, be cooled to room temperature, obtain corresponding BGA solder joints.
2. a kind of method preparing the unleaded interconnection solder joint of polycrystalline structure by applying electric current described in accordance with the claim 1, special
Sign is that the pad or chip are selected from Cu, Cu/Ni/Au, Cu/Cu6Sn5。
3. a kind of method preparing the unleaded interconnection solder joint of polycrystalline structure by applying electric current described in accordance with the claim 1, special
Sign is that the solder or soldering paste are selected from bianry alloy SnCu series, SnAg series, SnZn series, SnBi series or SnIn systems
Row, or selected from ternary alloy three-partalloy SnAgCu series, SnAgBi series or SnAgIn series, or it is selected from quaternary SnAgBiIn series leadless
Solder.
4. a kind of method preparing the unleaded interconnection solder joint of polycrystalline structure by applying electric current described in accordance with the claim 1, special
Sign is that the galvanization current density is 1 × 102To 1 × 106A/cm2, apply dwell time in solder joint cooled and solidified mistake
After journey start time.
5. a kind of method preparing the unleaded interconnection solder joint of polycrystalline structure by applying electric current described in accordance with the claim 1, special
Sign is that the remelting in the step (2) and step (3), temperature range selects 200 DEG C to 700 DEG C.
6. a kind of method preparing the unleaded interconnection solder joint of polycrystalline structure by applying electric current described in accordance with the claim 1, special
Sign is that the step (2) and the cooling with step (3) are selected from the cooling of furnace cooling, air-cooled, air-cooled, water cooling or oil cooling
Mode.
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| Application Number | Priority Date | Filing Date | Title |
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| CN201810102951.8A CN108422117B (en) | 2018-02-01 | 2018-02-01 | Method for preparing lead-free interconnection welding spot with polycrystalline structure by applying current |
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| CN201810102951.8A CN108422117B (en) | 2018-02-01 | 2018-02-01 | Method for preparing lead-free interconnection welding spot with polycrystalline structure by applying current |
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| CN109396769A (en) * | 2018-12-10 | 2019-03-01 | 北京工业大学 | A kind of preparation method for micro linear docking solder joint in electric field |
| CN109396768A (en) * | 2018-12-10 | 2019-03-01 | 北京工业大学 | Apply the method that transient pulse electric field prepares miniature polycrystalline solder joint |
| CN112103262A (en) * | 2020-09-14 | 2020-12-18 | 大连理工大学 | Method for controlling crystal orientation and microstructure of all-intermetallic compound micro-interconnection welding spot |
| CN114211070A (en) * | 2021-12-31 | 2022-03-22 | 北京工业大学 | Method for preparing solder joint remelting crystal orientation of Sn-based brazing filler metal |
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Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109396769A (en) * | 2018-12-10 | 2019-03-01 | 北京工业大学 | A kind of preparation method for micro linear docking solder joint in electric field |
| CN109396768A (en) * | 2018-12-10 | 2019-03-01 | 北京工业大学 | Apply the method that transient pulse electric field prepares miniature polycrystalline solder joint |
| CN112103262A (en) * | 2020-09-14 | 2020-12-18 | 大连理工大学 | Method for controlling crystal orientation and microstructure of all-intermetallic compound micro-interconnection welding spot |
| CN112103262B (en) * | 2020-09-14 | 2022-09-06 | 大连理工大学 | Method for controlling crystal orientation and microstructure of all-intermetallic compound micro-interconnection welding spot |
| CN114211070A (en) * | 2021-12-31 | 2022-03-22 | 北京工业大学 | Method for preparing solder joint remelting crystal orientation of Sn-based brazing filler metal |
| CN114211070B (en) * | 2021-12-31 | 2023-09-19 | 北京工业大学 | Welding method for enabling welding spot crystal grains to be oriented into multiple twin crystals |
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