KR20060041654A - Solder alloy and method for fe-leaching prevention - Google Patents

Abstract

(Task) When soldering a Sn-Ag-Cu lead-free solder alloy containing Sn as a main component using a soldering device coated with Fe or an Fe-based alloy, Fe solution of the soldering device member coated with Fe or Fe-based alloy Provided are a method of preventing and a solder alloy for preventing Fe dissolution.

Solution: Ag: 0.3% by mass or more and 4.0% by mass or less, Cu: 0.1% by mass or more and 1.0% by mass or less, Co: 0.001% by mass or more and 0.5% by mass or less, Ni: 0.01% by mass or more and 0.1% by mass or less, as necessary. The solder alloy of the alloy composition which remainder becomes substantially Sn is used.

Description

Fed-resistant solder alloy and Fed-resistant method {SOLDER ALLOY AND METHOD FOR Fe-LEACHING PREVENTION}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solder alloy for preventing Fe dissolution of a member coated with Fe or an Fe-based alloy (a phenomenon in which a part of the base material melts into the molten solder during soldering) and a method for preventing Fe dissolution. In particular, the present invention relates to a solder solution for preventing Fe dissolution and a method for preventing Fe dissolution of a soldering device member used when soldering a printed board by manual soldering.

Conventionally, Pb-Sn alloy was used for soldering a printed board. This Pb-Sn alloy has a melting point of 183 ° C in the eutectic composition (Pb-63Sn) and enables soldering at a relatively low temperature. Therefore, the electronic component which is weak in heat has a small heat effect and also has excellent solderability. Therefore, it is characterized by low soldering or less soldering defects such as solder dewetting. However, since the Pb-Sn alloy contains a Pb component which is harmful to the human body, so-called "lead-free solder" containing no Pb has recently been used for soldering electronic devices.

Lead-free solder is mainly composed of Sn. Lead-free solder alloys currently used include Sn-3.5Ag (melting point: 221 ° C), Sn-0.7Cu (melting point: 227 ° C), and Sn-9Zn (melting point: 199 ° C). And third alloys such as Ag, Cu, Zn, Bi, In, Sb, Ni, Cr, Co, Fe, Mn, P, Ge, Ga, in addition to binary alloys such as Sn-58Bi (melting point: 139 ° C) It adds an element suitably.

"...- based alloy" as used in the present invention means an alloy containing at least the component thereof. In the case of the binary alloy as described above, the secondary alloy itself and the binary alloy are further added. It is an alloy which added 1 or more types of 3 elements. For example, the Sn-Zn system refers to an alloy obtained by adding one or more of the above-described third elements to the Sn-Zn alloy itself and Sn-Zn, and the Sn-Ag system refers to the Sn-Ag alloy itself and Sn-Ag. The alloy which added 1 or more types of said 3rd elements is said.

Currently, the mainstream of Sn-Ag-Cu-based lead-free solder alloys is Sn-Ag-Cu-based lead-free solder alloys such as Sn-3Ag-0.5Cu and Sn-3.5Ag-0.75Cu. Sn-Ag-Cu-based lead-free solder alloy can cope with all processes such as manual soldering, flow soldering, reflow soldering, etc., and has excellent solder strength and solderability. Do.

Other lead-free solder alloys actually used include low-cost flow soldering solder alloys such as Sn-Cu-based alloys such as Sn-0.7Cu lead-free solder alloys, and low melting temperature reflow soldering alloys as Sn-Zn-based alloys. Although there are solder alloys and Sn-In-based solder alloys, there are very few ratios.

Manual soldering refers to manual soldering and is performed using soldering iron (soldering iron). Manual soldering is performed for correcting flow soldering or reflow soldering, or for soldering components attached to the back. The soldering iron has a structure in which a soldering iron tip is attached to the tip of the soldering iron body incorporating a heater.

Cu and Cu alloys are used as the base materials of the iron tip, and in order to prevent the soldering of Cu by Sn on the tips of soldering, Fe plating or Fe plating is performed in addition to Ni plating. Covering is performed.

However, the solder alloy used for manual soldering is replaced by the Sn-Ag-Cu-based lead-free solder alloy currently used in conventional Sn-Pb-based solder alloys, which consumes so much iron tip that the soldering iron tip life of the soldering iron is about 1 It is known to be / 3.

Conventionally, it is proposed to use a solder alloy in which Fe is added in an amount of 0.01% by mass to 0.2% by mass as a means of suppressing erosion of the Fe coating layer of the iron tip when lead-free solder is used (Patent Document 1). However, although the compounding of Fe to the lead-free solder alloy has an effect of suppressing the erosion of the Fe coating layer per the same soldering time, the Fe coating layer is eventually eroded because the wettability of the solder is significantly inhibited to prolong the soldering time.

[Patent Document 1] Japanese Unexamined Patent Publication No. 2003-62688

An object of the present invention is a soldering device member coated with Fe or Fe-based alloys when soldering with a Sn-Ag-Cu lead-free solder alloy containing Sn as a main component using a member coated with Fe or Fe-based alloys. It is to provide a solder alloy and a method for preventing Fe dissolution to prevent Fe dissolution.

The reason why the Fe dissolution phenomenon becomes remarkable is that the content of Sn in the solder that is easy to dissolve Fe increases due to the replacement of lead-free solder, and that the solder itself has poor wettability and takes about twice the soldering time due to the soldering iron. The soldering temperature of the solder tip is increased by about 40 ° C from the melting temperature (about 220 ° C) of the Sn-Ag-Cu-based solder-free solder alloy to the melting temperature (about 220 ° C) of the conventional Sn-Pb-based solder alloy. The use temperature also rose from 350 ° C to 420 ° C, which is the usage temperature of the Sn-Pb system solder alloy, to 380 ° C to 450 ° C, which is the usage temperature of the Sn-Ag-Cu system lead-free solder alloy. Reaction with Fe advanced and the coating layer became easy to erode.

The present inventors use solder to which a small amount of Co is added to the Sn-Ag-Cu-based lead-free solder alloy, so that Co is dispersed in the Sn-Ag-Cu-based lead-free solder alloy to prevent Fe from being dissolved, so that the soldering iron Fe lysis of the pharyngeal tip was found not to occur well to complete the present invention.

The solder alloy for preventing Fe dissolution according to the present invention is composed of Ag: 0.3% by mass or more and 4.0% by mass or less, Cu: 0.1% by mass or more and 1.0% by mass or less, Co: 0.001% by mass or more and 0.5% by mass or less, and the balance substantially consists of Sn. It is a solder alloy of an alloy composition.

In order to improve the fatigue resistance of the solder alloy, the solder alloy composition may contain Ni in an amount of 0.01% by mass or more and 0.1% by mass or less.

The present invention contains 0.001% by mass or more and 0.5% by mass or less of Co when soldering a Sn-Ag-Cu lead-free solder alloy containing Sn as a main component using a solder member coated with Fe or an Fe-based alloy. It is a method of preventing the Fe dissolution of a soldering device member coated with Fe or an Fe-based alloy, wherein soldering is performed using a Sn-Ag-Cu-based lead-free solder alloy.

Soldering equipment members that are prone to Fe dissolution which are prevented by Fe dissolution according to the present invention include soldering iron tips used for manual soldering, soldering iron tips used for soldering robots, and soldering irons used for repair devices. Iron tip, and the like.

This member is coated by Fe plating on Fe plating or Ni plating as described above. Fe plating also includes Fe-based alloy plating such as Fe-C alloys.

Best Mode for Carrying Out the Invention

Here, although the solder dissolution prevention mechanism is not always clearly identified by the solder alloy of the present invention, it is assumed as follows.

That is, "Fe dissolution" is a phenomenon in which Fe powder contained in a member or the like in contact with the solder is consumed during soldering, and in general, Fe powder is dissolved in molten solder.

As described above, the cause of Fe dissolution during the soldering using the lead-free solder alloy is that the alloy is formed by the reaction (interdiffusion) of Sn and Fe, which is easily dissolved in Sn in the molten solder. The higher the Sn content, the higher the Fe solubility.

This phenomenon also occurs in the case of stainless steel, and melting of stainless steel occurs. Since stainless steel is one species of Fe-based alloy, it is referred to herein as Fe dissolution including this case.

As can be seen from this, it can be seen that in order to prevent the Fe dissolution that is found in the lead-free solder alloy, the amount and the speed at which Fe can be dissolved can be limited.

The amount and speed of such dissolution depend on the solder composition and the temperature. Therefore, in order to suppress the rate with which Fe melt | dissolves with Sn in solder, as can be understood also by the prior art, it can suppress by adding Fe to Sn beforehand. However, in the molten state, the dissolved Fe is hardly dissolved in Sn after solidification, and even if a small amount of Fe is dissolved, the FeSn compound is precipitated (crystallized) during solidification. Brings rise.

In the periodic table, Fe is a metal belonging to Group 8, and Co and Ni belonging to the same Group 8, Cr belonging to Group 6, etc. are called transition metals and have similar properties. Most of the transition metals, like Fe, do not have a solid solution in Sn and precipitate as a compound, resulting in an increase in liquidus temperature, but Ni and Co have a property of lowering the melting temperature by forming a process composition. The present inventors paid attention to this point.

When Ni or Co is added to the Sn-Ag-Cu system lead-free solder alloy, they are dissolved in Sn during melting. Particularly, in the case of Co, if a small amount of Co is dissolved in the Sn-Ag-Cu-based lead-free solder alloy, the same kind of transition metals such as Fe, Ni, Cr, and the like cannot be dissolved anymore, so that the Fe-based alloy member or Fe Alternatively, it has been found that dissolution of the member coated with the Fe-based alloy is suppressed. As a result of experiment, although Ni has the same effect, when Ni is added to Sn-Ag-Cu system alloy, since liquidus temperature rises, the allowable amount is limited and a large amount of Ni cannot be added. On the other hand, addition of Co is effective even if it is a trace amount rather than Ni, and even if it is an amount equivalent to Ni, an increase in liquidus temperature is not confirmed.

The optimum amount of Co added to the Sn-Ag-Cu-based lead-free solder alloy is determined according to the Sn content, and when Sn is about 95% or more, preferably 0.001% by mass or more and 0.5% by mass or less, more preferably 0.01% by mass. It is more than% and 0.1 mass% or less.

When the amount of Co is less than 0.01% by mass, in particular 0.001% by mass, the effect of suppressing Fe dissolution of the device member coated with Fe or Fe-based alloy does not appear, while when the amount of Co is greater than 0.1% by mass, especially 0.5% by mass It may cause an increase in liquidus temperature, which may cause deterioration of workability.

According to the present invention, a solder alloy composition particularly suitable for manual soldering is realized, and the solder alloy according to the present invention has particularly good wettability.

The melting temperature of the Sn-Ag-Cu system lead-free solder alloy and the zero cross time by the mesicograph method are shown in Table 1 described later. The composition of lead-free solder suitable for manual soldering is solder with a zero cross time of less than 3 seconds.

Here, the addition of Ag to Sn significantly improves the wettability of the solder alloy. The addition of Ag to the Sn-based lead-free solder is effective by adding 0.3% by mass or more, and especially by adding 3.0% by mass or more, improves the wettability of the solder alloy. When Ag is added in an amount of 4.0% by mass or more, the melting temperature of the solder alloy is increased. Therefore, the Fe melting rate increases because the set temperature of the soldering iron must be increased.

In addition, the addition of trace amounts of Cu to the Sn-based lead-free solder not only improves the strength of the solder alloy, but also lowers the melting temperature of the solder alloy to improve wettability.

The addition of Cu is preferably at least 0.1% by mass, preferably at least 0.5% by mass, to exhibit the desired effect, and when it is added in excess of 1.0% by mass, the melting temperature of the solder alloy is increased. Therefore, the set temperature of the soldering iron must be increased. Therefore, Fe dissolution becomes large.

Sn-Ag-Cu-based lead-free solder alloy suitable for manual soldering is preferably composed of Ag: 0.3% by mass or more and 4.0% by mass or less, Cu: 0.1% by mass or more and 1.0% by mass or less, and the remainder is Sn. The composition of the Sn-Ag-Cu system lead-free solder alloy is Ag: 3.0% by mass or more and less than 4.0% by mass, Cu: 0.1% by mass or more and less than 1.0% by mass, and the rest is Sn.

By adding Co at 0.001% by mass or more and 0.5% by mass or less, preferably 0.01% by mass or more and 0.1% by mass or less in accordance with the present invention, these lead-free solder alloys can be used for the plating of Fe or Fe-based alloys of the soldering iron tip. The Fe can be reduced.

In this way, the solder alloy composition which concerns on this invention used for the Fe dissolution prevention method of the soldering member which coat | coated Fe or Fe type alloy is Ag: 0.3 mass% or more and 4.0 mass% or less, Cu: 0.1 mass% or more and 1.0 mass% Hereinafter, Co: 0.001 mass% or more and 0.5 mass% or less, and remainder is the solder alloy of the alloy composition which consists essentially of Sn. Preferably, such a solder alloy is an alloy comprising Ag: 3.0% by mass or more and 4.0% by mass or less, Cu: 0.1% by mass or more and 1.0% by mass or less, Co: 0.01% by mass or more and 0.1% by mass or less, with the balance being substantially Sn. It is a solder alloy of composition.

According to this invention, fatigue resistance of a solder alloy can be improved by adding a trace amount of Ni to the solder alloy composition of the solder used for the Fe dissolution prevention method of the soldering member which coat | coated Fe or Fe system alloy. Ni added can not be expected to improve the fatigue resistance when Ni is less than 0.01% by mass, Ni when more than 0.1% by mass Ni precipitates and the melting point of the solder alloy rises to around 300 ℃, so the set temperature of the soldering iron Since it must be raised, the Fe dissolution increases.

Although the form of the solder alloy which concerns on this invention may be in any form, since it is used for correction | amendment of flow soldering or reflow soldering, and the soldering of the parts attached behind from a viewpoint of Fe dissolution prevention, so-called resin is included. It is often used as a solder flux cored solder.

Here, the resin-based solder is formed by pre-existing almost 3% of the flux in the center of the linearly formed solder, and is one of the well-known types of solder alloys that can simultaneously supply and supply the solder alloy. One thing. Of course, the flux at that time is also known, and there are, for example, rosin-based or halogen-based, but rosin-based is preferable today. In addition, the flux composition used for resin insertion solder is already prescribed | regulated to JIS, and also in this case, what is necessary is just to employ | adopt it, and there is no special limitation.

Next, the effect of this invention is demonstrated further more concretely by an Example.

Example

Resin solder of each solder alloy composition shown in Table 1 was produced, the land of the printed circuit board was soldered, and the usage number of the iron tip was investigated. The results of the solder alloy composition, its melting temperature, the zero cross time of the wet balance method, and the number of times the iron tip can be used are summarized in Table 1 in the same manner.

Solder composition Sn Ag Cu Co Ni Etc Melting temperature (℃) Zero cross time Usage count Solidus Liquidus (sec) (point) Example 1 Balance One 0.5 0.01 - 217 227 2.3 2180 Example 2 Balance 0.3 0.5 0.01 0.01 218 228 2.5 2230 Example 3 Balance 3 0.5 0.01 - 217 220 1.5 2877 Example 4 Balance 3 0.5 0.1 0.01 218 221 1.6 2746 Example 5 Balance 3.5 One 0.01 - 217 233 1.5 2843 Example 6 Balance 3.9 0.5 0.01 - 217 229 1.3 3201 Example 7 Balance 3.9 One 0.1 - 218 231 1.4 2981 Example 8 Balance 3.9 One 0.1 0.1 218 233 1.4 2874 Comparative Example 1 Balance - 0.5 - - 227 231 4.0 780 Comparative Example 2 Balance - 0.7 - - Fe 0.05 227 230 3.6 1463 Comparative Example 3 Balance 0.3 0.5 - - 217 228 2.6 985 Comparative Example 4 Balance 0.1 0.7 - - 217 228 3.1 820 Comparative Example 5 Balance 3.5 One One 217 270 3.2 1830 Comparative Example 6 Balance - - - - Pb 37 183 183 0.8 3506 Comparative Example 7 Balance 3.0 0.5 - 0.25 218 320 1.9 1980

The test conditions for obtaining these results were as follows.

(1) the number of uses of the iron tip

Land Shape: Round

Land size: 0.8mm in diameter

Soldering iron temperature: Melting temperature ± 160 ℃ of solder alloy

Iron Tip Material Structure: Base Material Cu

Base Ni plating (thickness 50㎛)

Surface Fe Plating (Thickness 30㎛)

Resin Solder

Resin Solder Diameter: 0.5mm

Grade of flux: AA (JIS Z 3283)

Flux content: 3 mass%

(2) Melting temperature (JIS Z 3198-1)

Measurement Method: Differential Scanning Calorimetry (DSC)

Temperature rise rate: 5 ° C / min Carrier gas: Air

(3) Measurement of wettability by the wet balance method (JIS Z 3198-4)

Immersion Depth: 2mm

Immersion Speed: 5mm / sec

Immersion time: 10 seconds

Solder temperature: 250 ℃

Use flux: 25% IPA solution of ww rosin

In the solder alloy of the present invention containing 0.001% by mass or more and 0.5% by mass or less of Co, the number of times of use of the iron tip can be used close to 3000 times, whereas the number of times of use of resin-containing solder containing no Co of the comparative example is 1000 times or less. Only about 1500 times could be used for the resin-entry solder using the solder alloy disclosed in Patent Document 1.

Conventional Sn is achieved by using a solder alloy in which Co: 0.001% by mass or more and 0.5% by mass or less, preferably Co: 0.01% by mass or more and 0.1% by mass or less is added to the Sn-Ag-Cu based lead-free solder alloy of the present invention. Even though Sn-Ag-Cu-based lead-free solder alloys, which have a higher solder dissolution rate than the Pb-based solder alloys, are used, the soldering iron used for manual soldering has less soldering iron, and the iron coating layer, which is a solder tip, has a shorter solder tip life. 3 times longer

Claims (7)

Ag: 0.3 mass% or more and 4.0 mass% or less, Cu: 0.1 mass% or more and 1.0 mass% or less, Co: 0.001 mass% or more and 0.5 mass% or less, and the Fe fusion prevention solder alloy which remainder consists essentially of Sn. The solder alloy for preventing Fe dissolution according to claim 1, wherein Co is 0.01 mass% or more and 0.1 mass% or less. The solder alloy for preventing Fe dissolution according to claim 1 or 2, wherein Ag is 3% by mass to 4.0% by mass. The solder alloy for preventing Fe dissolution according to any one of claims 1 to 3, wherein Cu is 0.5% by mass or more and 1.0% by mass or less. The solder alloy for preventing Fe dissolution according to any one of claims 1 to 4, wherein the solder alloy further contains Ni: 0.01% by mass or more and 0.1% by mass or less. Ag: 0.3 mass% or more and 4.0 mass% or less, Cu: 0.1 mass% or more and 1.0 mass% or less, Co: 0.001 mass% or more and 0.5 mass% or less, Ni: 0.01 mass% or more and 0.1 mass% or less, as needed. A method for preventing Fe dissolution of a soldering device member coated with Fe or an Fe-based alloy, wherein an additional solder alloy having an alloy composition substantially consisting of Sn is used. A method of soldering with a Sn-Ag-Cu lead-free solder alloy containing Sn as a main component using a soldering member coated with Fe or an Fe-based alloy, the method comprising Co at 0.001% by mass or more and 0.5% by mass or less of Co A method of preventing Fe dissolution of a member coated with Fe or an Fe-based alloy, wherein the solder is soldered using a Sn-Ag-Cu-based lead-free solder alloy.