JP2008168322A - Fe EROSION-SUPPRESSED LEAD-FREE SOLDER ALLOY - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide resin flux cored solder effective for cost reduction, without losing the characteristics as those of solder, suppressing the iron leaching of a tip end and a dip tank, reducing the consumption of the tip end caused by freedom from lead in solder. <P>SOLUTION: Disclosed is a lead-free solder alloy in which the leaching of a tip end and a dip tank is suppressed by adding 0.01 to 0.1 mass% Fe and 0.01 to 0.1 mass% Ge to a lead-free solder alloy essentially consisting of Sn. Also disclosed is resin flux cored solder using the same. Further, by incorporating P or Ge therein, the leaching of a tip can be further reduced, and its wettability can be improved as well. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to a lead-free solder alloy containing Sn as a main component and containing no lead, and more particularly to a lead-free solder alloy for cored solder in which the erosion of Fe is suppressed.

  Conventionally, Sn—Pb solder represented by Sn—Pb eutectic solder has been used as a solder alloy used for connection and joining in the electronics industry. However, in recent years, the toxicity of lead has been regarded as a problem, and a solder alloy that does not contain lead (hereinafter referred to as “lead-free solder” or “lead-free solder alloy”) has been demanded, and many types of lead-free solder alloys are now proposed. Has been. Among them, for example, lead-free solder alloys such as Sn-Cu, Sn-Ag, Sn-Ag-Cu, and Sn-Ag-Bi-In are already in practical use.

  However, lead-free alloys erode (also referred to as “corroded”) the iron part of the soldering iron tip used in manual soldering, and the tip wears out. There was a problem of shortening.

  The cause is that Sn, which is the main component of lead-free solder, easily reacts with iron on the tip. This phenomenon occurred even with conventional Sn-Pb solder, but the wear rate of the tip increased due to the increase in the Sn content accompanying the lead-free solder alloy. It is coming.

Also, lead-free solder has a higher melting point than Sn-Pb solder, and the tip temperature is set higher, leading to a further increase in the tip erosion rate. Patent Document 1 proposes that the tip is subjected to nickel plating with a thickness of several μm, because the tip is worn due to the solder metal element eluting into the solder.
JP 2005-125349 A (Fuji Electric)

  Conventionally, with regard to reducing the wear of the tip, there has been no proposal to solve the problem with the composition of the solder alloy, which mainly reinforces the tip. In addition, not only the soldering iron tip but also Fe in the solder bath (also called dip bath) is eroded. In this case, problems such as holes in the solder bath may occur. That is, the present invention aims to provide a lead-free solder alloy that suppresses Fe erosion of lead-free solder and is effective in extending the life of the soldering iron tip and solder bath in manual soldering. . Note that, in terms of Fe erosion, the soldering iron tip and the solder bath have the same meaning, and are not limited to the tip and the solder bath. Therefore, these are hereinafter referred to as “tips”.

  The present invention comprises Sn as a main component, including both 0.01 to 0.1% by mass of Fe and 0.01 to 0.1% by mass of Ge, optionally 0.1 to 0.5% by mass of Co, 0.1 to 0.5% by mass of Ni, and In. It is a lead-free solder alloy for flux cored solder characterized by containing at least one of 0.1 to 10.0 mass%, P from 0.01 to 0.05 mass%, and Ga from 0.01 to 0.05 mass%.

  By using both Fe and Ge as simultaneous additive elements in lead-free solder containing Sn as a main component, Fe erosion can be suppressed more than when Fe and Ge are used alone. Fe and Ge can easily form an intermetallic compound with each other, serve as a barrier for the Fe plating layer at the tip, and are effective in suppressing wear of the tip and the like.

  In addition, Fe alone is prone to dross when manufacturing a solder alloy, and it is difficult to stably manufacture it. By using together with Ge, it can be stably added to the solder alloy, and can be easily put into practical use.

  In addition, the addition of Ni, Co, P, or Ga is effective in improving wettability. Furthermore, the addition of In, P, and Ga is further effective in suppressing the corrosion of Fe plating. Fe and Ge are segregated on the surface of the tip and the like, and at the same time, are easily combined with oxygen, and therefore move from the surface of the tip and the like to the solder surface where oxygen is present. Like Fe and Ge, In, P, and Ga are easily combined with oxygen, and the connection between Fe and Ge with oxygen can be relaxed, and Fe and Ge can be stably present on the Fe plating surface such as the tip.

  The lead-free solder of the present invention contains Sn as a main component and contains both 0.01 to 0.1% by mass of Fe and 0.01 to 0.1% by mass of Ge. By using both Fe and Ge, erosion of Fe can be suppressed more than when Fe and Ge are used alone.

  Even if the addition of Fe to the solder is a simple substance with a known technique, there is an effect of suppressing the corrosion of Fe plating such as the tip. However, the effect is further increased by adding Fe and Ge simultaneously. Fe and Ge can easily form intermetallic compounds with each other, and Fe—Ge intermetallic compounds are segregated on the surface of the tip or the like. Furthermore, since this Fe-Ge intermetallic compound has a high melting point, once Fe-Ge is segregated on the surface of the Fe plating such as the tip, it becomes a barrier for the Fe plating layer such as the tip, and it suppresses the corrosion of the Fe plating. It is effective.

  In addition, Fe alone is prone to dross when manufacturing solder alloys, and it is difficult to manufacture stably. By using together with Ge, it can be stably added to the solder alloy, and can be easily put into practical use.

  If the Fe and Ge content is less than 0.01% by mass, the effect of suppressing the erosion of Fe plating is small, and if it exceeds 0.1% by mass, the solder alloy turns black and the tip etc. carbonizes, affecting the wettability. As a result, the solder characteristics may be lost. In order not to lose the characteristics of the solder alloy used conventionally while maintaining the erosion control effect, both elements are preferably 0.01 to 0.05% by mass.

  In addition, adding Ni or Co is effective in improving wettability. Furthermore, the addition of In, P, and Ga is further effective in suppressing the corrosion of Fe plating. Fe and Ge are segregated on the surface of the tip and the like, and at the same time, are easily combined with oxygen, and therefore move from the surface of the tip and the like to the solder surface where oxygen is present. Like Fe and Ge, In, P, and Ga are easy to be combined with oxygen, relax the bond between Fe and Ge with oxygen, and make Fe and Ge stably exist on the surface of the iron plating such as the tip.

  If the Ni and Co content is less than 0.1% by mass, the effect on wettability is small.If the Ni and Co content is 0.5% by mass or more, the melting point rises and the soldering temperature rises. The effect of biting is also reduced, and the characteristics as solder are lost. In order not to lose the characteristics of the conventionally used solder alloy while maintaining the effect of erosion control and wettability of Fe plating, both elements are preferably 0.1 to 0.3% by mass.

  If the content of In is less than 0.1% by mass, there is no effect in improving the suppression of the erosion of the tip or the like, and if it exceeds 10.0% by mass, the strength decreases. In consideration of the improvement of Fe erosion suppression effect and the balance of strength, 0.1 to 10.0% by mass is preferable, and 0.1 to 8.0% by mass is more preferable.

  If the P and Ga content is 0.01% by mass or less, there is no effect in improving the control of the tip and the like, and if it is 0.05% by mass or more, the solder alloy turns black, and the tip is carbonized, resulting in wettability. There will be an impact. In order to improve the erosion-inhibiting effect and not lose the characteristics even when compared with the solder alloys used conventionally, both elements are preferably 0.01 to 0.05% by mass.

  In the present invention, Ag may be contained in an amount of 2.5 to 4.0% by mass and Cu may be contained in an amount of 0.3 to 1.0% by mass. This is used in a general lead-free solder alloy, and even if these elements are contained, the present invention is effective in suppressing biting of a tip or the like. Needless to say, the solder alloy of the present invention can be used as a cored solder.

  In this specification, Sn is tin, Ag is silver, Cu is copper, Fe is iron, Ge is germanium, Co is cobalt, Ni is nickel, In is indium, P is phosphorus, Ga is gallium, and Bi is bismuth. , N represents nitrogen.

  Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. In addition, an Example demonstrates by comparing and examining the erosion of the tip of a soldering iron. However, in the case of a stainless steel or iron solder bath, the same result as the tip is produced from the viewpoint of Fe erosion.

(Trowel bite test)
A solder alloy having the composition shown in Table 1 below was prepared, filled with flux to form a cored solder, and formed into a thread of φ0.8. The flux used was ATS manufactured by Ishikawa Metal Co., Ltd., and the flux content was 3% by mass. A prototype cored solder and tip were set on the ironing robot, and soldered solder was supplied to the tip 20,000 times at a constant speed and time.

  The tip temperature was 400 ° C. In addition, the solder feed length was 4.7 mm and the feed speed was 9.4 mm / sec. The iron robot used was model number “UNIX401P” manufactured by Japan Unix, and the tip used was P3D-S (single-sided solder plating) manufactured by the same company. The tip after the test was cut, polished to the center cross section, mirror finished, and photographed. And the area of the part where the tip was eaten was calculated by image processing. In this test, the value when the tip erosion rate was set to 100 when Sn-3.0Ag-0.5Cu was used was calculated.

(Wettability)
The test board was soldered with a trowel robot, a picture of the board after soldering was taken, and the wetting rate was calculated by image processing. The wetting rate was obtained from the following calculation formula.
Wetting rate (%) = 100 x (solder area / land area)
The conditions were as follows: land 3 × 3 mm, land material Cu, substrate material glass epoxy, tip 3 mm driver type, iron temperature 290 ° C and 320 ° C. The solder supply conditions were as follows: primary solder supply rate 1.0 mm, supply rate 20 mm / sec, secondary solder supply rate 2.0 mm, 20 mm / sec. The iron robot used was UNIX 401P manufactured by Japan Unix.

(Melting point measurement)
Differential scanning calorimetry (DSC: Differential scanning) manufactured by Rigaku Corporation
Measured by calorimetry). The test conditions were as follows: the weighing amount was 10 mg, the heating rate was 1 ° C./min, and an N ₂ atmosphere. The composition ratios of Examples and Comparative Examples are shown in Table 1, and the evaluation results are shown in Table 2.

  Comparative Example 1 is a Sn—Ag—Cu base composition. Each Example is compared with the iron erosion rate of Comparative Example 1 as 100%. Note that the results of the melting point and wettability are also shown. In terms of the melting point, the solid phase line refers to a boundary between a solid state and a state where a solid and a liquid coexist. The liquidus is a boundary between a state in which a solid and a liquid coexist and a state in which only the liquid is present. Each melting point is as shown in Table 2.

  Comparative Examples 2 and 3 are cases where Fe and Ge were separately contained. The iron erosion rate decreased to 86% and 81%, respectively, and it was confirmed that the inclusion of these elements had an effect on the reduction of the iron erosion rate.

  On the other hand, Examples 1 to 11 are all cases in which Fe and Ge are simultaneously contained. In all the examples, the trowel biting rate is lower than in Comparative Examples 2 and 3. That is, simultaneous addition of Fe and Ge has an effect of further reducing the trowel biting rate as compared with the case where each element is added alone.

  Example 10 and Example 11 are Sn—Cu and Sn—Ag—In—Bi composition systems. When there is no additive element, they show almost the same erosion rate as Sn-Ag-Cu solder.

  Also in these two cases, when Fe and Ge are added simultaneously, the erosion rate is less than half that of the case where Fe and Ge are individually added to the Sn—Ag—Cu system. This result shows that the effect of adding Fe and Ge at the same time is not simply giving a specific effect to the Sn-Ag-Cu solder alloy, but the effect caused by the reaction with Fe at the tip It is shown that. In other words, the simultaneous addition of Fe and Ge indicates that a solder alloy having any composition is effective in reducing galling.

  Next, the effect on the composition containing other additive elements will be described. Example 3, which shows the case of solder added with Co, which is known to improve wettability, is 65.9% compared to the wettability of 60.1% to 64.9% of Comparative Examples 1 to 3, which is certainly wet. It was effective in improving the sex.

  On the other hand, the trowel biting rate is 79%, which is lower than the three comparative examples. That is, the soldering rate of the solder containing Co and improved in wettability can be reduced by the simultaneous addition of Fe and Ge.

  Although Example 4 contains Ni, the trowel biting rate is 74%, which is an improvement over Comparative Example 3 containing Ge alone. On the other hand, the wettability of Example 4 is slightly improved from the wettability of Comparative Example 3.

  When Comparative Example 1 was a basic composition of Sn—Ag—Cu, the wettability of Example 4 was almost the same, but the trowel bit rate was improved. From the above, it can be seen that Co and Ni are effective in improving the wettability, and the simultaneous addition of Fe and Ge is effective in reducing the erosion of such a composition system.

  Examples 5 to 8 are examples in which P and Ga are added, and Examples 5 and 6 and Examples 7 and 8 show cases where the contents of P and Ga are different from each other. The iron erosion rate of Examples 5 to 8 is in the range of 12% to 24%, and when P and Ga are further added to the simultaneous addition of Fe and Ge, there is an effect of further reducing the erosion rate.

  In more detail, Example 1, Example 5 and Example 7 contain 0.02% by mass of Fe and Ge, respectively. Example 5 further contains 0.10% by mass of P, and Example 7 contains 0.30% by mass of Ga. These iron erosion rates were 65% for Example 1 and 12% for Example 5 and 22% for Example 7. This is effective in reducing the crack rate.

  Note that Example 5 and Example 7 contain 0.05 mass% or more of P and Ga, and the wettability is lower than that of Comparative Example 1. That is, it is understood that P and Ga affect the wettability when it exceeds 0.05 mass%.

  Example 2, Example 6 and Example 8 are systems in which 0.02% by mass of Fe and 0.05% by mass of Ge are added simultaneously. Example 6 further contains 0.03% by mass of P, and Example 8 contains 0.04% by mass of Ga. These trowel bit rates are 26%, 17%, and 24%, respectively, and the addition of P and Ga also shows the effect of reducing the trowel bit rate.

  On the other hand, the wettability is also 58.0%, 64.8%, and 65.1%, respectively, and when P or Ge is added at a ratio of 0.05% by mass or less, the wettability is improved and the troweling rate is also reduced. It was confirmed that there was an effect. That is, considering the results of Examples 5 and 7, P and Ge are preferably 0.05% by mass or less. Of course, if not contained, there is no effect in improving wettability, and the lower limit is 0.01% by mass or more.

  Example 9 is obtained by adding 0.30% by mass of In to Example 1. The trowel rate has decreased from 65% to 28%. In Example 11, 3.0% by mass of In is contained. This Example 11 also has a very low troweling rate of 26%. In other words, it has been shown that In is effective in reducing the erosion rate in addition to the simultaneous addition of Fe and Ge.

  As described above, the solder alloy to which Fe and Ge of the present invention are added at the same time can reduce the soldering iron erosion. Further, the inclusion of P, Ga, and In can further reduce the rate of erosion. P and Ga are also effective in improving wettability.

Further, even if additive elements such as Co and Ni are included, the soldering iron can be reduced. Furthermore, even with a solder composition system different from the Sn-Ag-Cu system such as the Sn-Cu system and the Sn-Ag-In-Bi system, the erosion of the soldering iron can be reduced.

Claims (11)

A lead-free solder alloy containing Sn as a main component and containing 0.01 to 0.1% by mass of Fe and 0.01 to 0.1% by mass of Ge. The lead-free solder alloy according to claim 1, containing 0.01 to 0.1% by mass of P or 0.01 to 0.3% by mass of Ga. The lead-free solder alloy according to claim 1 containing In. The lead-free solder alloy according to claim 1, containing 0.1 to 0.5 mass% Co or 0.1 to 0.5 mass% Ni. The lead-free solder alloy according to claim 1 containing Ag and Cu. The lead-free solder alloy according to claim 5, containing 0.01 to 0.1% by mass of P or 0.01 to 0.3% by mass of Ga. The lead-free solder alloy according to claim 5 containing In. The lead-free solder alloy according to claim 5, containing 0.1 to 0.5 mass% Co or 0.1 to 0.5 mass% Ni. The lead-free solder alloy according to claim 1 containing Cu. The lead-free solder alloy according to claim 1 containing Ag and Bi. Filled solder using the lead-free solder alloy according to claim 1.