CN1285443C - Rare earth contained SnAgCuEr tin based leadless solder and its preparation method - Google Patents

Abstract

The present invention relates to SnAgCuEr tin-base lead-free solder containing rare earth and a preparation method thereof, which belongs to the technical field of manufacturing lead-free solder for electronic packaging in microelectron industry. The SnAgCuy tin-base lead-free solder containing rare earth comprises 2 to 5 wt% of Ag, 0.2 to 1 wt% of Cu, 0.025 to 1.0 wt % of commercial rare earth Er and Sn as the rest. The present invention has the preparation method that mixed salt composed of (1 to 1.6 wt %) of potassium chloride and (0.8 to 1.2 wt%) of lithium chloride is melted and poured on Sn; after the Sn is melted, weighed Ag and Cu are added into Sn liquid to melt the Ag and Cu; then, the commercial rare earth Er is pressed into the mixed salt and Sn-Ag-Cu alloy by a bell jar of which the wall is provided with holes; the bell jar is rotated, temperature is preserved for 1 to 2 hours, and the mixed salt on the surface is removed after agitation, stationary placement and solidification. The SnAgCuy tin-base lead-free solder containing rare earth of the present invention has the advantages of few alloy components, strong practicability, low cost, no pollution and convenient smelting, and wetting technological properties, microstructures and metallurgy quality are improved.

Description

Contain SnAgCuEr tin base leadless soldering-flux of rare earth and preparation method thereof

Technical field

A kind of SnAgCuEr tin base leadless soldering-flux that contains rare earth and preparation method thereof belongs to the assembling of microelectronic industry electronics and uses lead-free brazing manufacturing technology field.

Background technology

Over past ten years, researched and developed out multiple lead-free solder alloy both at home and abroad, patent just relates to hundreds of.The lead-free solder alloy of research mainly concentrates on three temperature sections and several alloy series at present.Wherein, most representative is the middle-temperature section lead-free solder alloy, as Sn-Cu, Sn-Ag, Sn-Zn binary system alloy, and ternary alloy such as Sn-Ag-Cu, Sn-Ag-Bi, Sn-Zn-Bi or multicomponent alloy more.

Basic demand to lead-free brazing should comprise: fusion temperature should be near the SnPb eutectic temperature, and fusion temperature is suitable little at interval; Wetability or soldering processes performance are preferably arranged, and good wetability can reduce weld defect, improve soldering productivity ratio; Good physical and mechanical property as the stability of intensity, creep-resistant property, heating power fatigue resistance, metallography tissue, satisfies the reliability requirement of electronic product; Performances such as good electricity is led, thermal conductance should be arranged in addition; Chemical property is also very important, makes soldered fitting that good corrosion resistance be arranged; Lead-free brazing should not comprise new toxic component; The solder cost is low, in order to applying etc.

From the domestic and international research present situation, most widely used middle-temperature section can realize aborning in a short time unleaded alternative will be Sn-Cu, Sn-Ag binary alloy system and Sn-Ag-Cu ternary alloy system or more multicomponent alloy solder based on this.The Sn-Cu solder will be mainly used in wave-soldering, and the Sn-Ag-Cu brazing filler metal will be mainly used in reflow welding.The Sn-Ag-Cu brazing filler metal alloy species that occurs in the world is a lot of at present, representational SnAgCu is that the patent brazing filler metal alloy has: Sn-(3.5-7.7) Ag-(1-4) Cu-(0-10) Bi[U.S. Pat P5527628], Sn-(2-5) Ag-(0-2.9) Cu-(0.1-3) Ni[U.S. Pat P 5863493], Sn-3.0Ag-0.5Cu[Japan Patent JPP 3027441] and Sn-(2-5) Ag-(0.2-1) Cu-(0.025-1) RE[Chinese patent ZL 02123528.7] etc.

United States Patent (USP) 5,527, the eutectic composition Sn-4.7%Ag-1.7%Cu of the SnAgCu solder of 628 reports, its fusing point is 217 ℃, but this invention solder creep strength is not good.In addition, United States Patent (USP) 4,929,423 lead-free brazing Sn-(0.08-20%) Bi-(0.01-1.5%) Ag-(0.02-1.5%) Cu-0.01%P-(0-0.2%) mishmetals that provide be mainly used in the pipeline soldering, and the alloy constituent element are many, and practicality is relatively poor.United States Patent (USP) 6,361,742 have introduced two kinds of SnAg and SnAgCuBi lead-free brazings that add rare earth, but the wetability of SnAg solder is relatively poor, in brazing process, can cause the dissolving of copper matrix, and SnAgCuBi not only the alloy constituent element is many because solder contains Bi, easily produce low melting point eutectic, and rare earth is single rare earth element.Chinese patent 01128184.7 has been introduced a kind of lead-free brazing that contains rare earth that is applicable to Electronic Packaging and assembling and soldering, its middle rare earth is that the mishmetal of La and Ce or La and Ce mishmetal add one among Pr, the Nd or two kind, Sn-(0.1-5%) Ag-(0.1-1%) Cu-(0.1-8%) Bi-(0.1-7.5%) In-(0-8%) Sb-(0.01-2%) rare earth.This patent is pointed out, in order further to reduce fusing point, has added a certain amount of In, Bi element.Yet, along with the quickening of unleaded process, some big companies released one after another unleaded crest welder and unleaded Re-current welder, the peak temperature of its soldering can reach about 250 ℃, therefore, and under these circumstances, the fusing point problem of lead-free brazing no longer is very distinct issues.In addition, contain Bi solder easy generation when soldering and sting end defective, and easily form low melting point eutectic with lead, therefore responsive to lead contamination, and the fragility of Bi also is an adverse factors.In addition, Bi is plumbous byproduct, uses the solder that contains Bi must strengthen exploitation to lead ore, causes the pollution to environment.The abundance of In in the earth's crust is very low, and costs an arm and a leg, and is not suitable for extensive use.Therefore, add some,, obviously do not improve under the prerequisite of The comprehensive performance having, become no longer necessary as In, Bi etc. in order to reduce the element of solder fusing point.

Summary of the invention

The present invention is directed to problems of the prior art, provide a kind of alloy constituent element less, it is convenient to smelt, and cost is low, is easy to control impurity lead content, and wettability is good, has suitable intensity and fusion temperature, and microscopic structure and metallurgical quality are improved.

The SnAgCuEr tin base leadless soldering-flux that contains rare earth involved in the present invention is characterized in that: contain percentage by weight and be 2～5% Ag, and 0.2～1% Cu, 0.025～1% rare earth Er, all the other are Sn.

The invention provides a kind of preparation method who contains the SnAgCuEr tin base leadless soldering-flux of rare earth, it is characterized in that:

(1) by weight with potassium chloride: lithium chloride=(1～1.6): the salt-mixture of (0.8～1.2) is watering on the tin that is weighing up after the fusing down at 450 ℃～550 ℃;

(2) temperature is risen to 600 ℃～800 ℃, treat tin fusing after, load weighted silver, copper are joined in the middle of the tin liquor of fusion, stir, form alloy;

(3) treat its fusing evenly after, rare earth Er is pressed into rapidly in the alloy of above-mentioned fusion with stainless steel bell jar with holes on the wall, rotate bell jar;

(4) treat that rare earth melts fully after, be incubated 1～2 hour, stir, make the alloy homogenising, leave standstill and come out of the stove, solidify the salt-mixture that the surface is removed in the back.

Performance after improving with the rare earth Er contained lead-free brazing of formal specification the present invention of chart below by the test data of some examples, and compare with the traditional SnAgCu solder that obtains under the same conditions.

Table 1 is 10 kinds of rare earth Er contained tin base leadless soldering-fluxes and traditional SnAgCu solder component list, forms in the table all to be weight percentage, and Er represents rare earth erbium, gives the liquidus temperature and the solidus temperature of each solder simultaneously.The liquidus curve of solder and solidus temperature record by slow cooling curve.As can be seen from Table 1, example 1～10 of the present invention has the fusion temperature scope close or lower with the SnAgCu lead-free brazing, as shown in Figure 3, is fit to present unleaded soldering processes condition.

Table 2 is comparisons of example 1～10 of the present invention and traditional SnAgCu lead-free brazing shear strength and spreading area.As can be seen from the table, the shear strength of example 1～10 of the present invention is suitable with traditional SnAgCu solder, but under the condition of same Ag content, adds the solder of rare earth Er and sprawl better technological properties, as shown in Figure 4, is applicable to the microelectronic industry surface-assembled.

Fig. 1 and Fig. 2 are respectively the rare earth Er contained tin base leadless soldering-flux of the present invention and the comparison of traditional SnAgCu solder microscopic structure.As can be seen, the solder microscopic structure of adding rare earth Er is tiny, and the crystalline structure that does not add rare earth Er is thick, high directivity, fragility are big.This has also disclosed the reason that rare earth Er contained lead-free brazing can improve the solder metallurgical quality from microcosmic angle.

In addition, because the density of Er is slightly larger than Sn, during alloy smelting, rare earth can not swim in the surface of Sn base alloy, makes that smelting process is more convenient to carry out.

Description of drawings:

Fig. 1: rare earth Er contained SnAgCuEr does not have the microscopic structure of lead solders.

Fig. 2: traditional SnAgCu does not have the microscopic structure of lead solders.

Fig. 3 Er content is to the influence of Sn3.8Ag0.7Cu brazing filler metal alloy fusion temperature.

Fig. 4 Er is to the influence of Sn3.8Ag0.7Cu brazing filler metal alloy spreading area.

The specific embodiment

Example 1: the potassium chloride and the 20 grams lithium chloride salt-mixtures of 26 grams are watered on 95.475 gram tin after the fusing down at 460 ℃.Furnace temperature is risen to 620 ℃, 3.8 gram Ag and 0.7 gram Cu are joined in the middle of the tin liquor after making the fusing of tin and salt-mixture, constantly stir simultaneously, form alloy; Be pressed into rapidly in the middle of the above-mentioned molten alloy with stainless steel bell jar with holes on the wall rare earth Er, and constantly stir, till rare earth melts fully 0.025 gram.Be incubated 1 hour, constantly stir, make the alloy homogenising.Leave standstill and come out of the stove, treat to remove surperficial salt-mixture behind the alloy graining.Furnace temperature is reduced to 360 ℃ the solder piece reheated fusing, stand-by into strips at the angle bar top-pour then.

Example 2: the potassium chloride and the 20 grams lithium chloride salt-mixtures of 26 grams are watered on 95.45 gram tin after the fusing down at 460 ℃.Furnace temperature is risen to 780 ℃, 3.8 gram Ag and 0.7 gram Cu are joined in the middle of the tin liquor after making the fusing of tin and salt-mixture, constantly stir simultaneously, form alloy; Be pressed into rapidly in the middle of the above-mentioned molten alloy with stainless steel bell jar with holes on the wall rare earth Er, and constantly stir, till rare earth melts fully 0.05 gram.Be incubated 1.5 hours, constantly stir, make the alloy homogenising.Leave standstill and come out of the stove. treat to remove surperficial salt-mixture behind the alloy graining.Furnace temperature is reduced to 380 ℃ the solder piece reheated fusing, stand-by into strips at the angle bar top-pour then.

Example 3: the potassium chloride and the 18 grams lithium chloride salt-mixtures of 23.4 grams are watered on 95.4 gram tin after the fusing down at 500 ℃.Furnace temperature is risen to 700 ℃, 3.8 gram Ag and 0.7 gram Cu are joined in the middle of the tin liquor after making the fusing of tin and salt-mixture, constantly stir simultaneously, form alloy; Be pressed into rapidly in the middle of the above-mentioned molten alloy with stainless steel bell jar with holes on the wall rare earth Er, and constantly stir, till rare earth melts fully 0.1 gram.Be incubated 1 hour, constantly stir, make the alloy homogenising.Leave standstill and come out of the stove, treat to remove surperficial salt-mixture behind the alloy graining.Furnace temperature is reduced to 360 ℃ the solder piece reheated fusing, stand-by into strips at the angle bar top-pour then.

Example 4: the potassium chloride and the 20 grams lithium chloride salt-mixtures of 26 grams are watered on 95.25 gram tin after the fusing down at 490 ℃.Furnace temperature is risen to 700 ℃, 3.8 gram Ag and 0.7 gram Cu are joined in the middle of the tin liquor after making the fusing of tin and salt-mixture, constantly stir simultaneously, form alloy; Be pressed into rapidly in the middle of the above-mentioned molten alloy with stainless steel bell jar with holes on the wall rare earth Er, and constantly stir, till rare earth melts fully 0.25 gram.Be incubated 2 hours, constantly stir, make the alloy homogenising.Leave standstill and come out of the stove, treat to remove surperficial salt-mixture behind the alloy graining.Furnace temperature is reduced to 400 ℃ the solder piece reheated fusing, stand-by into strips at the angle bar top-pour then.

Example 5: the potassium chloride and the 25 grams lithium chloride salt-mixtures of 32.5 grams are watered on 95 gram tin after the fusing down at 500 ℃.Furnace temperature is risen to 720 ℃, 3.8 gram Ag and 0.7 gram Cu are joined in the middle of the tin liquor after making the fusing of tin and salt-mixture, constantly stir simultaneously, form alloy; Be pressed into rapidly in the middle of the above-mentioned molten alloy with stainless steel bell jar with holes on the wall rare earth Er, and constantly stir, till rare earth melts fully 0.5 gram.Be incubated 1.5 hours, constantly stir, make the alloy homogenising.Leave standstill and come out of the stove, treat to remove surperficial salt-mixture behind the alloy graining.Furnace temperature is reduced to 380 ℃ the solder piece reheated fusing, stand-by into strips at the angle bar top-pour then.

Example 6: the potassium chloride and the 20 grams lithium chloride salt-mixtures of 26 grams are watered on 94.5 gram tin after the fusing down at 490 ℃.Furnace temperature is risen to 650 ℃, 3.8 gram Ag and 0.7 gram Cu are joined in the middle of the tin liquor after making the fusing of tin and salt-mixture, constantly stir simultaneously, form alloy; Be pressed into rapidly in the middle of the above-mentioned molten alloy with stainless steel bell jar with holes on the wall rare earth Er, and constantly stir, till rare earth melts fully 1 gram.Be incubated 1.2 hours, constantly stir, make the alloy homogenising.Leave standstill and come out of the stove, treat to remove surperficial salt-mixture behind the alloy graining.Furnace temperature is reduced to 360 ℃ the solder piece reheated fusing, stand-by into strips at the angle bar top-pour then.

Example 7: the potassium chloride and the 20 grams lithium chloride salt-mixtures of 26 grams are watered on 97.775 gram tin after the fusing down at 460 ℃.Furnace temperature is risen to 680 ℃, 2 gram Ag and 0.2 gram Cu are joined in the middle of the tin liquor after making the fusing of tin and salt-mixture, constantly stir simultaneously, form alloy; Be pressed into rapidly in the middle of the above-mentioned molten alloy with stainless steel bell jar with holes on the wall rare earth Er, and constantly stir, till rare earth melts fully 0.025 gram.Be incubated 2 hours, constantly stir, make the alloy homogenising.Leave standstill and come out of the stove, treat to remove surperficial salt-mixture behind the alloy graining.Furnace temperature is reduced to 400 ℃ the solder piece reheated fusing, stand-by into strips at the angle bar top-pour then.

Example 8: the potassium chloride and the 20 grams lithium chloride salt-mixtures of 26 grams are watered on 96 gram tin after the fusing down at 510 ℃.Furnace temperature is risen to 800 ℃, 2 gram Ag and 1 gram Cu are joined in the middle of the tin liquor after making the fusing of tin and salt-mixture, constantly stir simultaneously, form alloy; Be pressed into rapidly in the middle of the above-mentioned molten alloy with stainless steel bell jar with holes on the wall rare earth Er, and constantly stir, till rare earth melts fully 1 gram.Be incubated 2 hours, constantly stir, make the alloy homogenising.Leave standstill and come out of the stove, treat to remove surperficial salt-mixture behind the alloy graining.Furnace temperature is reduced to 400 ℃ the solder piece reheated fusing, stand-by into strips at the angle bar top-pour then.

Example 9: the potassium chloride and the 20 grams lithium chloride salt-mixtures of 26 grams are watered on 94.775 gram tin after the fusing down at 450 ℃.Furnace temperature is risen to 600 ℃, 5 gram Ag and 0.2 gram Cu are joined in the middle of the tin liquor after making the fusing of tin and salt-mixture, constantly stir simultaneously, form alloy; Be pressed into rapidly in the middle of the above-mentioned molten alloy with stainless steel bell jar with holes on the wall rare earth Er, and constantly stir, till rare earth melts fully 0.025 gram.Be incubated 2 hours, constantly stir, make the alloy homogenising.Leave standstill and come out of the stove, treat to remove surperficial salt-mixture behind the alloy graining.Furnace temperature is reduced to 400 ℃ the solder piece reheated fusing, stand-by into strips at the angle bar top-pour then.

Example 10: the potassium chloride and the 20 grams lithium chloride salt-mixtures of 26 grams are watered on 93 gram tin after the fusing down at 460 ℃.Furnace temperature is risen to 720 ℃, 5 gram Ag and 1 gram Cu are joined in the middle of the tin liquor after making the fusing of tin and salt-mixture, constantly stir simultaneously, form alloy; Be pressed into rapidly in the middle of the above-mentioned molten alloy with stainless steel bell jar with holes on the wall rare earth Er, and constantly stir, till rare earth melts fully 1 gram.Be incubated 2 hours, constantly stir, make the alloy homogenising.Leave standstill and come out of the stove, treat to remove surperficial salt-mixture behind the alloy graining.Furnace temperature is reduced to 400 ℃ the solder piece reheated fusing, stand-by into strips at the angle bar top-pour then.

Table 1 brazing filler metal alloy composition and fusion temperature

Example	Sn(wt％)	Ag(wt％)	Cu(wt％)	Er(wt％)	Liquidus temperature (℃)	Solidus temperature (℃)
							Comparative Examples	95.5	3.8	0.7	0	217.1	215.6
Embodiment 1	95.475	3.8	0.7	0.025	219.5	213.4
							Embodiment 2	95.45	3.8	0.7	0.05	217.8	213.0
Embodiment 3	95.4	3.8	0.7	0.1	216.9	212.6
							Embodiment 4	95.25	3.8	0.7	0.25	215.6	208.3
Embodiment 5	95	3.8	0.7	0.5	216.9	211.3
							Embodiment 6	94.5	3.8	0.7	1.0	217.1	212.6
Embodiment 7	97.775	2	0.2	0.025	223.8	212.6
							Embodiment 8	96	2	1.0	1.0	222.9	216.5
Embodiment 9	94.775	5	0.2	0.025	219.7	214.7
							Embodiment 10	93	5	1.0	1.0	218.2	213.9

Table 2 shear strength and spreading area

Example	Shear strength (MPa)	Spreading area (mm2)
			Comparative Examples	67.2	57.7
Embodiment 1	71.4	59.0
			Embodiment 2	65.5	57.6
Embodiment 3	64.6	62.8
			Embodiment 4	43.4	67.5
Embodiment 5	52.7	60.6
			Embodiment 6	55.0	59.2
Embodiment 7	66.3	52.0
			Embodiment 8	52.7	52.5
Embodiment 9	59.5	57.6
			Embodiment 10	62.1	58.2

Claims (3)

1, a kind of SnAgCuEr tin base leadless soldering-flux that contains rare earth is characterized in that: contain percentage by weight and be 2～5% Ag, and 0.2～1% Cu, 0.025～1% rare earth Er, all the other are Sn.

2, a kind of preparation method who contains the SnAgCuEr tin base leadless soldering-flux of rare earth is characterized in that it may further comprise the steps:

(1) by weight with potassium chloride: lithium chloride=(1～1.6): the salt-mixture of (0.8～1.2) is watering on the tin that is weighing up after the fusing down at 450 ℃～550 ℃;

(2) temperature is risen to 600 ℃～800 ℃, treat tin fusing after, load weighted silver, copper are joined in the middle of the tin liquor of fusion, stir, form alloy;

(3) treat its fusing evenly after, above-mentioned rare earth Er is pressed into rapidly in the alloy of above-mentioned fusion with stainless steel bell jar with holes on the wall, rotate bell jar;

(4) treat that rare earth melts fully after, be incubated 1～2 hour, stir, make the alloy homogenising, leave standstill and come out of the stove, solidify the salt-mixture that the surface is removed in the back.

3, preparation method according to claim 2, wherein the temperature range in the step (1) is 490 ℃～510 ℃, the temperature range in the step (2) is 680 ℃～720 ℃.

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