JP2005072173A - Electronic component and solder paste - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electronic component wherein a soldering portion does not easily exfoliate even if a shock is applied from the outside, and solder paste suitable for forming the electronic component. <P>SOLUTION: The main component of middle temperature lead-free solder is Sn, so that a liquidus line temperature becomes nearly 220°C. As a result, the electronic component is subjected to soldering wherein at least one part of constituent components is at least a solidus line temperature 260°C, with Bi of at most the liquidus line temperature 360°C or high temperature solder having Bi as a main component, and the soldering portion is reinforced with a flux residue having an adhesive agent, for brittleness reinforcement. The solder paste is composed of high temperature solder powder and flux containing the adhesive agent. The high temperature solder powder is high temperature solder having Bi or Bi as a main component. The solidus line temperature of the high temperature solder having Bi as a main component is at least 260°C and the liquidus line temperature is not higher than 360°C. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an electronic component in which at least a part of a component is soldered with a high-temperature lead-free solder, and a solder paste suitable for producing the electronic component.

  Conventionally, the solder used for soldering electronic components was an alloy of Pb and Sn. Among Pb-Sn alloys, Pb-63Sn alloy (eutectic solder) has a melting point of 183 ° C, which is the same as the solidus temperature and liquidus temperature. Can be soldered at low temperatures. In general, it is said that the soldering temperature in the case of using eutectic solder is appropriate to the liquidus temperature of the solder +20 to 50 ° C. In the soldering of the eutectic solder, the soldering temperature is 200 to 230 ° C. The temperature of 200 to 230 ° C. is a temperature that does not affect the electronic components and the printed circuit board. Further, since the eutectic solder is excellent in solderability, the eutectic solder has an excellent characteristic that there is little generation of unsolder and voids in the soldered portion. Therefore, the eutectic solder of Pb-Sn has been used for soldering many electronic parts since ancient times.

  By the way, not only eutectic solder having a low melting point but also high-temperature solder having a high melting point may be used for soldering electronic devices and electronic parts. When using high-temperature solder in electronic equipment, it is recommended that soldering be performed in a place where the periphery of the soldering part becomes hot when the electronic equipment is used, for example, where heat is generated when electricity is passed, such as a power transistor or transformer. Use high-temperature solder. In other words, if eutectic solder with a low melting point is used at a high temperature when using electronic equipment, the melting point of the eutectic solder will melt even if the soldered part becomes hot or the solder does not melt. When the temperature is raised to near, the bonding strength is extremely reduced, and the soldered part is peeled off by a slight vibration or impact. Therefore, high-temperature solder is used in places where the temperature is high during use of electronic equipment.

  In addition, as a case where high-temperature solder is used, for example, there are electronic components for soldering lead wires and lead terminals. Electronic components are mounted by soldering to a printed circuit board. When the components that make up the electronic component are soldered with eutectic solder, the electronic components are soldered to the printed circuit board with the same eutectic solder. When soldering for the second time, the soldering temperature becomes higher than the melting point of the eutectic solder, so that the soldering part of the component constituting the electronic component is melted. If the soldering part of the component is thus melted, the soldering part may be peeled off and the electronic part may no longer function. Therefore, in an electronic component in which the soldering that constitutes the electronic component and the soldering that mounts the electronic component are performed twice, high-temperature solder having a higher melting point than eutectic solder is used for the soldering portion of the component.

  Conventional high-temperature solder is Pb-5Sn alloy (solidus temperature: 300 ° C, liquidus temperature: 314 ° C), Pb-10Sn alloy (solidus temperature: 268 ° C, liquidus) Temperature: 301 ° C.), Pb-5Ag (solidus temperature: 304 ° C., liquidus temperature: 365 ° C.) and the like.

  In this way, in conventional electronic devices, Pb-Sn eutectic solder is used for soldering electronic components and printed circuit boards, and the Pb main component is used in places where there is a high temperature atmosphere during use and in soldering parts of electronic component components. High-temperature solder was used.

  By the way, when an electronic device breaks down or its function deteriorates, the electronic device is disposed of without being repaired or upgraded. Electronic equipment to be disposed of can be recovered and reused for case resin, frame metal, display glass, etc., but soldered printed circuit boards and electronic components are difficult to collect because they are difficult to collect. Had been landfilled.

  When acid rain with high acidity comes into contact with printed circuit boards and electronic components disposed of underground, that is, printed circuit boards and electronic components soldered with Pb-Sn eutectic solder or Pb-based high-temperature solder, There was a problem that the Pb component might be eluted and mixed into groundwater. Therefore, recently, the use of Pb has been regulated, and lead-free solder containing no Pb has been used.

  In general, lead-free solder contains Sn as the main component, and Ag, Cu, Sb, Zn, Bi, In, etc. are added as appropriate. Lead-free solder, which is widely used at present, is Sn-3Ag -0.5Cu (solidus temperature: 217 ° C, liquidus temperature: 220 ° C), Sn-3.5Ag (solidus temperature, liquidus temperature: 220 ° C), Sn-0.75Cu (solidus temperature, Liquid temperature: 227 ° C). When soldering these medium-temperature lead-free solders at a liquidus temperature of + 20-50 ° C like Pb-Sn eutectic solder, the liquidus temperature was originally higher than that of Pb-Sn eutectic solder. A high intermediate temperature lead-free solder further increases the soldering temperature and affects the electronic components and the printed circuit board. Therefore, the liquidus temperature +20 to 40 ° C. is appropriate as the soldering temperature when using the medium temperature lead-free solder. Therefore, the high-temperature lead-free solder used in combination with these medium-temperature lead-free solders must have a solidus temperature of 260 ° C. or higher, which is higher than the soldering temperature of the medium-temperature solder.

  As mentioned above, the high-temperature solder used for soldering components of electronic equipment and electronic components requires a solidus temperature of 260 ° C or higher, but even the most heat-resistant electronic components and printed circuit boards have a temperature of 400 ° C or higher. Heating may cause thermal damage, so the soldering temperature is limited to 400 ° C. As described above, since the soldering temperature is up to 400 ° C., the liquidus temperature of the high-temperature solder is desirably 360 ° C. or lower.

  When making high-temperature solder with Sn as the main component, the liquidus temperature can be increased as much as possible by adding a little higher amount of high melting point Ag, Cu, etc. to the Sn main component, but the solidus temperature must be 220 ° C. Appears in the vicinity. Therefore, a lead-free solder containing Sn could not produce a high-temperature solder having a solidus temperature of 260 ° C. or higher.

  By the way, one of the applicants of the present application has proposed a Bi-based solder as a lead-free solder that does not damage the substrate even when soldered to a conductor of a fragile glass substrate and has excellent heat resistance (Patent Literature). 1). The solder of this Patent Document 1 is alloyed with any one of Ag, Cu, and Zn that can be eutectic with Bi, and the conditions are that it solidifies and expands so as not to damage the glass, and is solid for heat resistance. The phase line temperature is 200 ° C or higher.

One of the applicants of the present application has also proposed using Bi-based solder for soldering through terminals of a cylindrical through-type ceramic capacitor (Patent Document 2). The reason for using the Bi-based solder here is that when the inner electrode of the capacitor and the through terminal are soldered, the inner electrode peels off from the inner wall of the capacitor structure or the structure is cracked. Is to prevent. That is, when the penetration terminal of the capacitor and the inner surface electrode are soldered and the solder is solidified, the general solder is solidified and contracted, so that it peels off from the inner wall of the structure or cracks in the structure. Therefore, in Patent Document 2, a material in which Ag, Au, In, Sn, Sb, Zn or the like is added to a Bi main component is used as a material that does not shrink during solidification.
Japanese Patent Laid-Open No. 13-353590 Japanese Patent Laid-Open No. 13-205477

  Since the lead-free solder described in Table 1 of Patent Document 1 has a solidus temperature around 260 ° C., there are some that can be used as a high-temperature solder for double-attached electronic components. However, when a component part of an electronic component is soldered using the lead-free solder of Patent Document 1 and the electronic component is used in an electronic device, if the electronic device is dropped or handled roughly, soldering of the component of the electronic component is performed. In some cases, the attachment point peeled off, resulting in failure of the electronic device. That is, the Bi-based solder has a very fragile property, and therefore, the solder itself is cracked or the soldered portion is peeled off due to impact or vibration.

  The Bi-based solder of Patent Document 2 has various solidus temperature and liquidus temperature. Therefore, a penetrating ceramic capacitor in which penetrating terminals are soldered using Bi-0.01Sn solder (solidus temperature: 200 ° C., liquidus temperature: 270 ° C.) described in Patent Document 2 is manufactured. When a capacitor is soldered onto a printed circuit board with a solder paste made of Sn-3Ag-0.5Cu (solid phase temperature: 217 ° C, liquidus temperature: 220 ° C) lead-free solder, the through terminals are soldered during soldering The Bi-0.01Sn solder melts and cannot function as a capacitor. A through-type ceramic capacitor was similarly produced using Bi-5Ag solder (solidus temperature: 262 ° C., liquidus temperature 298 ° C.) described in Patent Document 2, and this capacitor was Sn-3Ag-0.5 Cu (solidus temperature: 217 ° C, liquidus temperature: 220 ° C) When soldering on a printed circuit board with solder paste made of lead-free solder, Bi-5Ag solder with soldered through terminals will melt There is nothing wrong. However, in the feedthrough capacitor made of Bi-5Ag solder, the soldered part may be easily peeled off when an impact is applied from the outside.

  In the present invention, when an electronic component in which at least a part of the component is soldered with a high-temperature lead-free solder is soldered to a printed circuit board with a medium-temperature lead-free solder, the soldered portion of the electronic component does not melt, Moreover, it is suitable for manufacturing electronic parts and electronic parts in which the soldered part does not easily peel off even when impact is applied from the outside even though brittle Bi or Bi-based lead-free solder is used. It is to provide a solder paste.

  The inventors of the present invention have some Bi-based alloys having a solidus temperature of 260 ° C or higher and a liquidus temperature of 360 ° C or lower. These are high-temperature lead-free solders. However, the Bi-based alloy is brittle, so when used as solder, the soldered part peels off with only a small impact or vibration applied to the soldered part. Therefore, the present invention has been completed by paying attention to the fact that, if the strength of the soldering portion is increased, it becomes possible to withstand peeling and vibration.

  When the electronic component of the present invention is mounted on a printed circuit board and soldered with a medium temperature lead-free solder, the soldered portion of the component of the electronic component does not melt, and brittle Bi or Bi-based solder is used. Despite the use, the soldered part is reinforced with adhesive in the flux residue, so even if impact or vibration is applied to the electronic components, the soldered part does not peel easily and has excellent reliability. Yes. Further, the solder paste of the present invention comprises a high-temperature solder containing Bi or Bi as a main component and a flux containing an adhesive, and thus has a solidus temperature and a liquidus temperature suitable as a high-temperature lead-free solder, After soldering with brittle Bi or high-temperature solder of Bi main component, the adhesive that was present in the solder paste is also left in the flux residue, reinforcing the soldering part and improving the adhesive strength Is.

  According to the present invention, at least a part of the component parts is soldered with a Bi-based high temperature solder having a Bi or solidus temperature of 260 ° C. or higher and a liquidus temperature of 360 ° C. or lower. The electronic part is characterized in that the attaching portion is reinforced with a flux residue containing a thermosetting adhesive.

  Another embodiment of the present invention contains Bi powder or a high-temperature solder powder of a main component of Bi having a solidus temperature of 260 ° C or higher and a liquidus temperature of 360 ° C or lower, and a thermosetting adhesive. It is a solder paste characterized by comprising a flux.

  The electronic component that is the subject of the present invention is an electronic component in which at least a part of the component is soldered and further mounted on a printed circuit board or the like with solder, and soldering is performed twice. For example, semiconductor electronic parts such as die bonding IC elements to die pads, ceramic electronic parts soldering lead terminals to external electrodes formed on the element surface, electrodes formed on the inner and outer surfaces, and through terminals soldered to the inner surface electrodes Bonded feed-through capacitors, circuit board components, etc., in which electronic component elements are soldered to a wiring board, etc. Essentially, since soldering must be performed twice, at least one of the components to be soldered first is required. It is an electronic component that uses high-temperature solder for the part.

  The electronic component of the present invention is obtained by soldering at least a part of the components of the electronic component with high-temperature solder, and a flux containing an adhesive is used for the soldering. At the time of soldering, the flux spreads to the soldering portion, and after the soldering, the spread flux adheres to the soldering portion as a flux residue. However, since the flux contains an adhesive, the flux residue adhering to the soldered portion after soldering has an adhesive action, and the adhesive reinforces the soldered portion. Therefore, the electronic component of the present invention maintains sufficient adhesive strength even if the solder to which the component is soldered is fragile or has weak adhesive strength.

  The high-temperature solder used in the present invention must have a solidus temperature of 260 ° C. or higher and a liquidus temperature of 360 ° C. or lower. The reason why the solidus temperature of the high-temperature solder must be 260 ° C. or higher is that, as described above, the medium-temperature lead-free solder generally used has a liquidus temperature of around 220 ° C. That is, when the soldering temperature of the medium temperature lead-free solder is set to the liquidus temperature +20 to 40 ° C., the highest soldering temperature is 220 ° C. + 40 ° C., 260 ° C. Therefore, the high-temperature solder used for soldering the components of the electronic component must have a solidus temperature of at least 260 ° C. in order not to melt at the second soldering temperature of 260 ° C.

  In addition, the liquidus temperature of the high-temperature solder used in the present invention is set to 360 ° C. or lower when the soldering temperature of the high-temperature solder is set to the liquidus temperature +20 to 40 ° C. This is because when the temperature exceeds ℃, even heat-resistant electronic parts and ceramic substrates are damaged by heat. Therefore, if the soldering temperature with high-temperature solder is controlled to 400 ° C, the liquidus temperature of the high-temperature solder will be 360 ° C or lower.

  The Bi-based high-temperature solder used in the present invention includes Bi-Ag, Bi-Cu, Bi-Sb, and Bi-Zn. Among these alloys, the composition in which the solidus temperature is 260 ° C. or more and the liquidus temperature is 360 ° C. or less is 0.01 to 12% by mass in the Bi-Ag system and 0.01 to 0.8 in the Bi-Cu system. In the Bi-Sb system, Sb is 0.01 to 13 mass%, and in the Bi-Zn system, Zn is 0.01 to 0.1 mass%. The “system” here is not limited to the binary alloy, but also includes those obtained by adding other elements to the binary alloy. However, when other additive elements are added to the Bi-based binary alloy, the predetermined melting temperature intended by the present invention must not be exceeded. The additive element is not limited to a metal but may be a non-metal such as P. P has the effect of preventing surface oxidation and improving solderability. In the present invention, not only Bi-based alloys but also Bi alone having a melting point of 271 ° C. can be used.

  Bi alone has poor solderability, but adding Ag to Bi not only improves solderability but also improves Bi-specific brittleness. If the added amount of Ag is less than 0.01% by mass, solderability improvement and brittleness improvement effects do not appear. However, if Ag exceeds 12% by mass in Bi, the liquidus temperature exceeds 360 ° C, the soldering temperature becomes too high, and the electronic parts and the printed circuit board are thermally damaged.

  Cu has the effect of improving the mechanical strength of the Bi alloy. When the amount of Cu added is less than 0.01% by mass, the effect of improving the mechanical strength does not appear. However, when the amount added is more than 0.8% by mass, the liquidus temperature exceeds 360 ° C.

  Sb also improves the mechanical strength. When the amount is less than 0.01% by mass, the effect does not appear. When the amount exceeds 13% by mass, the liquidus temperature also exceeds 360 ° C.

  Zn can lower the melting point of Bi and obtain a melting point as low as possible within the melting temperature range intended by the present invention. If the added amount of Zn is less than 0.01% by mass, the effect of lowering the solidus temperature does not appear. However, if the added amount of Zn exceeds 0.1% by mass, the solidus temperature further decreases below 260 ° C.

  Here, Bi and Bi-based high-temperature solder are shown in Table 1. Nos. 1 to 14 are examples of high-temperature solder that can be used in the present invention, and Nos. 15 to 18 are examples of high-temperature solder that cannot be used in the present invention.

  The solder paste of the present invention is obtained by kneading a flux containing Bi or Bi-based alloy powder and a thermosetting adhesive. And the flux used for the solder paste of this invention is made to contain the thermosetting adhesive (thermosetting resin, hardening | curing agent) in the flux for conventional solder paste.

  In general, the flux for solder paste is a paste obtained by dissolving solid components such as pine resin, thixotropic agent and activator with a liquid solvent. The pine resin includes polymerized rosin, WW rosin, hydrogenated rosin, etc., the thixotropic agent includes hardened castor oil and organic carboxylic acid derivatives, etc. The activator includes organic acid and amine hydrohalide. Examples of the solvent include ethylene glycol monobutyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether and the like which dissolve the above-mentioned solid components well and have low toxicity.

  The flux used in the solder paste of the present invention is a flux that is used in a conventional solder paste and contains a thermosetting adhesive. The thermosetting adhesive is one that is cured by heating and has an adhesive action, and one suitable for use in the present invention is an epoxy resin. An epoxy resin alone has a thermosetting action, but if a curing agent is further contained at the same time, the effect as a thermosetting adhesive is more strongly exhibited. Examples and comparative examples of the solder paste of the present invention are shown below.

Solder paste of Example 1 High-temperature solder powder: 75% by mass
Bi-0.15Cu (solidus temperature: 270 ° C, liquidus temperature: 270 ° C)
○ Flux containing thermosetting adhesive: 25% by mass
Thermosetting resin 40% by mass
Curing agent 30% by mass
Solder paste flux 30% by mass

Solder paste of Comparative Example 1 High-temperature solder powder: 75% by mass
Bi-5Sn (solidus temperature: 139 ° C, liquidus temperature: 255 ° C)
○ Solder paste flux: 25% by mass

Solder paste of Comparative Example 2 High-temperature solder powder: 75% by mass
Bi-0.15Cu (solidus temperature: 270 ° C, liquidus temperature: 270 ° C)
○ Solder paste flux: 25% by mass

  Using the solder pastes of the above examples and comparative examples, a melting test, a drop test, and an adhesion shear test were performed.

Melting test Using the solder paste of Example 1 and the solder paste of Comparative Example 1, the components of the feedthrough ceramic capacitor were soldered to obtain a test sample. The component parts were soldered by soldering the inner surface electrode and the through terminal of the cylindrical structure with a solder paste.

  The soldering structure of the feedthrough capacitor soldered with the solder paste of Example 1 is shown in FIG. The soldering structure 1 includes a cylindrical ceramic 2 having a hole 2a, an inner surface electrode 3 formed on the inner wall of the hole 2a, a through terminal 5 inserted into the hole 2a, an inner surface electrode 3 and the through terminal 5 In order to join them electrically and mechanically, the solder 6 is filled in the hole 2a, and the soldering part is reinforced with a flux residue 6 containing a thermosetting adhesive.

  Ten through-type ceramic capacitors in which the through terminals and the inner surface electrodes were soldered with the solder paste of Example 1 and the solder paste of Comparative Example 1 were produced as test samples for the melting test. In the thermostat, hold the main body (ceramic) of the penetrating ceramic capacitor with the penetrating terminal vertical, and suspend a 10g weight on the tip of the lower penetrating terminal. And the temperature in a thermostat was raised to 250 degreeC which is the soldering temperature of Sn-3Ag-0.5Cu lead free solder. It was observed whether or not the through terminal could come out of the through type ceramic capacitor in a constant temperature bath at 250 ° C.

  As a result of the melting test, in all the through-type ceramic capacitors in which the through terminals and the inner surface electrodes were soldered with the solder paste of Example 1, the through terminals did not fall out. On the other hand, in all the through-type ceramic capacitors in which the through terminals and the inner surface electrodes were soldered with the solder paste of Comparative Example 1, the solder in the soldered portion was melted and the through terminals dropped out.

・ Drop impact test
Solder 10 6.4mm x 3.2mm chip resistors with external electrodes formed on both ends separately prepared on a 50mm x 50mm x 0.3t copper plate with the solder paste of Example 1 and the solder paste of Comparative Example 2. This was used as a test sample for the drop impact test. A 100 g weight was attached to the test piece, and the sample was naturally dropped several times from a height of 1 m, and the number of peeled chip resistors at each number of drops was measured. Tables 2 and 3 show the results.
As a result of the drop test, the chip resistor soldered with the solder paste of Example 1 showed no peeling even after 10 drops. On the other hand, the chip resistance soldered with the solder paste of Comparative Example 2 was peeled off by dropping once or twice, and all the chip resistances on the copper plate were peeled off by dropping around 5 times.

-Adhesion shear test Using the solder pastes of Example 1 and Comparative Example 2, eight 3.2 mm x 1.6 mm chip capacitors were soldered to a 32 mm x 16 mm x 0.3 t copper plate to form an adhesion shear test sample. The number of samples was set to 2 and the adhesive shear strength of 16 soldered chip capacitors was measured using a push-pull gauge. As a result of the measurement, the average paste shear strength of the solder paste of Example 1 was 80.2N, and the average paste shear strength of the solder paste of Comparative Example 2 was 44.0N.

  From the result of the melting test, it was found that the electronic component of the present invention is stable without melting and separating the soldered portions of the components of the electronic component even at the second soldering temperature. In addition, the results of the drop impact test and the adhesion shear test revealed that the electronic parts soldered with the solder paste of the present invention were superior in impact resistance and soldering strength to those soldered with the solder paste of the comparative example. .

  The solder paste of the present invention can be applied not only to the soldering of the component parts of the electronic parts that are soldered twice, but also to the soldering of the part that becomes high temperature due to heat generation when the electronic device is used.

It is front sectional drawing of the feedthrough capacitor which shows an example of the electronic component of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Through-type capacitor 2 Ceramic 3 Inner surface electrode 4 Front surface electrode 5 Through terminal 6 High-temperature solder 6 Thermosetting adhesive containing flux residue

Claims (4)

At least a part of the component parts is soldered with a high-temperature Bi-based solder whose Bi or solidus temperature is 260 ° C or higher and whose liquidus temperature is 360 ° C or lower. An electronic component reinforced with a flux residue containing a thermosetting adhesive. 2. The electronic component according to claim 1, wherein the Bi-based high-temperature solder is any one of a Bi-Ag system, a Bi-Cu system, a Bi-Sb system, and a Bi-Zn system. Bi powder or a solid phase temperature of 260 ° C or higher, and a liquidus temperature of 360 ° C or lower, a Bi-based high-temperature solder powder, and a flux containing a thermosetting adhesive Solder paste. 4. The solder paste according to claim 3, wherein the Bi-based high-temperature solder powder is any one of Bi-Ag, Bi-Cu, Bi-Sb, and Bi-Zn alloy powders.

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