JP7097611B2 - Flux and solder materials - Google Patents

Description

The present invention relates to flux and solder materials containing flux.

Solder used for joining electronic parts and the like is made of a solder material containing a solder alloy and a flux. The flux is blended to improve solderability, and contains various components such as a resin component, an activator component, a solvent component, an antioxidant component, and a thixotropic component (hereinafter, also referred to as a thixotropic agent). I'm out.
Electronic devices, etc., in which electronic components are soldered to a substrate or the like, are expected to be used under various conditions such as high temperature, low temperature, and high humidity. Therefore, the soldered portion is required to have heat resistance, moisture resistance, and the like.
Under high humidity conditions, insulation failure may occur due to moisture adhering to the soldered portion. In particular, under conditions where the temperature changes drastically, dew condensation is likely to occur, and a relatively large amount of water is likely to adhere. Therefore, it becomes necessary to increase the insulation resistance to moisture.

For example, Patent Document 1 describes a flux containing a polymerized fatty acid, an aromatic carboxylic acid and an aliphatic dicarboxylic acid as activators, and further containing a solvent having a solubility in water at a temperature of 20 ° C. of 2 g / 100 g or less. There is.
Patent Document 2 describes a flux containing a thixotropic agent having a specific fatty acid polyamide structure.
It is described in each document that the fluxes described in Patent Documents 1 and 2 can maintain insulation resistance even under constant high humidity conditions.

However, although the flux described in each of the patent documents can maintain a certain degree of insulation resistance under constant high humidity conditions, for example, the humidity also changes significantly under conditions where the temperature changes drastically, so that under such conditions. It is difficult to maintain sufficient insulation resistance. Further, under a condition where the temperature change is large, not only the humidity is high but also a relatively large amount of water such as dew condensation may adhere, but in such a case, it is difficult to sufficiently maintain the insulation resistance.

JP-A-2017-64758 JP-A-2017-64783

The present invention has been made in view of the above-mentioned problems of the prior art, and an object of the present invention is to provide a flux and a solder material capable of sufficiently maintaining insulation resistance even under high humidity conditions.

The flux of the present invention contains a rosin-based resin and a polyester polyol obtained by dehydration condensation of an alcohol and a dicarboxylic acid .
When the polyester polyol is contained in an amount of 0.1% by mass or more and 50% by mass or less with respect to the total amount of the rosin-based resin, and the mass change is measured by thermal weight measurement (TG measurement), the weight loss at 240 ° C. is 15. % Or less for soldering flux.

In the present invention, the alcohol may contain two or more hydroxyl groups.

In the present invention, the alcohol may be an aliphatic alcohol.

In the present invention, the rosin-based resin may have an acid value of 100 KOH mg / g or more and 350 KOH mg / g or less.

In the present invention, the polyester polyol may be contained in an amount of 0.1% by mass or more and 30% by mass or less with respect to the total amount of the solid matter component.

The present invention relating to a solder material includes the flux and a solder alloy.

According to the present invention, it is possible to provide a flux and a solder material capable of sufficiently maintaining insulation resistance even under high humidity conditions.

The graph which shows the time-dependent change of temperature and humidity in a cycle test. Graph of insulation resistance value in the cycle test of an example. Graph of insulation resistance value in the cycle test of an example. Graph of insulation resistance value in the cycle test of an example. Graphs of insulation resistance values in cycle tests of Examples and Comparative Examples.

The flux according to the present invention and the solder material containing the flux will be described below.
The flux of the present embodiment is a flux containing a rosin-based resin and a polyester polyol obtained by dehydration condensation of alcohol and a dicarboxylic acid.

Examples of the rosin-based resin include rosin and a resin which is a derivative of rosin, and the rosin-based resin is not particularly limited as long as it is a known rosin-based resin used as a resin component of a flux. Specific examples thereof include rosin derivative resins such as rosin, hydrogenated rosin, polymerized rosin, disproportionated rosin, and acrylic acid-modified rosin.
The rosin-based resin can be used alone or in combination of two or more.

Examples of the rosin-based resin contained in the flux of the present embodiment include those having an acid value of 100 KOH mg / g or more and 350 KOH mg / g or less, preferably an acid value of 200 KOH mg / g or more and 300 KOH mg / g or less.
When the acid value of the resin is in the above range, the solderability is good. For example, a flux having good solderability can be obtained even if a large amount or no component blended as an activator of the flux is contained. Cheap.

The acid value in this embodiment means a value measured by the measuring method described in JIS Z 3197.

The flux may contain an activator in order to improve the performance of the flux, but if a large amount of the activator is contained, it may cause voids, or a large amount of the activator component remains in the flux residue, resulting in a decrease in connection reliability. And may cause insulation failure.
When a rosin-based resin having an acid value within the above-mentioned acid value range is used, it is easy to obtain a flux having good solderability even if the amount of the activator is reduced or not. preferable.

The rosin-based resin is preferably transparent or light-colored. When the resin is transparent or light-colored, the flux is less likely to be colored, and erroneous inspection or the like is less likely to occur in the appearance inspection or the like at the solder joint. In addition, the appearance is not impaired by the colored flux residue or the like.

The flux of the present embodiment may contain a resin other than the rosin resin such as an acrylic resin and a polybutadiene resin having a low glass transition temperature together with the rosin resin.
By mixing a resin having a low glass transition temperature other than these rosin-based resins, it is possible to suppress the occurrence of cracks even if the temperature change is large while maintaining the solderability.

The content of the rosin-based resin in the flux of the present embodiment is not particularly limited, but is, for example, 50% by mass or more and 95% by mass or less, preferably 60% by mass or more and 90% by mass or less, and more preferably 70% by mass or less. 90% by mass or less and the like.
When a resin other than the rosin-based resin is contained, the content of the rosin-based resin is, for example, 0.1% by mass or more and 30% by mass or less, preferably 5.0% by mass or more and 15% by mass or less in the total resin components. Is preferable from the viewpoint of maintaining solderability and suppressing cracks.

The polyester polyol is a polyester polyol obtained by dehydration condensation of alcohol and dicarboxylic acid.

Examples of the alcohol include alcohols containing two or more hydroxyl groups in one molecule, that is, diols or triols, and mixtures thereof.
The alcohol may be either aromatic alcohol or aliphatic alcohol.
When the alcohol is an aliphatic alcohol, it becomes easier to maintain the insulating property under high humidity conditions.

In the case of an aliphatic alcohol, the hydrocarbon chain constituting the alcohol may be linear or branched.
As the hydrocarbon chain constituting the aliphatic alcohol, an alcohol having a hydroxyl group bonded to both ends or one end thereof is preferable.

Specific examples of the alcohol include 1,2-ethanediol (ethylene glycol) (C2, linear), 1,3-propanediol (C3, linear), and 1,6-hexanediol (C6, linear). ), Neopentyl glycol (C3, branched), trimethylolpropane (C4, branched), 3-methyl-1,5-pentanediol (C5, branched) and the like.

The dicarboxylic acid may be either a chain dicarboxylic acid or an aromatic dicarboxylic acid.
Specific examples of the dicarboxylic acid include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, phthalic acid, isophthalic acid, and terephthalic acid.
In particular, C6 to C10 chain dicarboxylic acids such as adipic acid, pimelic acid, suberic acid, azelaic acid, and sebacic acid are preferable.

The polyester polyol of the present embodiment can be obtained by subjecting an alcohol and a dicarboxylic acid to a dehydration condensation reaction at an appropriate molar ratio in the coexistence of a catalyst, a solvent and other additives as needed.

The combination of the alcohol and the dicarboxylic acid to be reacted is arbitrary, and for example, 3-methyl-1,5-pentanediol and adipic acid, 1,6-hexanediol and sebacic acid, 1,3-propanediol and sebacic acid, etc. Examples thereof include neopentyl glycol and adipic acid, 1,2-ethanediol and adipic acid, trimethylolpropane and adipic acid, 3-methyl-1,5-pentanediol and trimethylolpropane and adipic acid.

The molecular weight of the polyester polyol of the present embodiment is not particularly limited, and examples thereof include a weight average molecular weight (MW) of usually 300 to 10,000, preferably 400 to 7000.

The polyester polyol of the present embodiment is preferably a polyester polyol that does not easily decompose even at high temperatures. For example, when reflowing when mounting electronic components on a substrate, it is usually heated to a high temperature of about 240 ° C., so by using a polyester polyol that does not easily decompose even after reflowing, the solder joint during use can be used. Moisture resistance can be easily maintained.
As a polyester polyol that does not easily decompose even at high temperatures, a polyester polyol having a weight loss of 15% or less, preferably 12% or less at 240 ° C. when the mass change is measured by thermogravimetric measurement (TG measurement) is used. Can be mentioned.

The polyester polyol contained in the flux of the present embodiment may be obtained from a commercially available product. For example, Kuraray polyols P-510, P-1010, P-2010, P-3010, P-4010, P-5010, P-6010, F-510, F-1010, F-2010, F-3010, P- 2011, P-520, P-1020, P-2020, P-1012, P-2012, P-530, P-2030, P-2050 (manufactured by Kuraray), Nippon Run 136, 141, 164, 4002, 4040, 4009 , 4010, 3027, 4073, 1004, 4042, 5018, 5035, 800, 1100 (manufactured by Tosoh), URIC SE-2003, 2606 (manufactured by Itoh Oil Chemicals), Tessrack 2455, 2459, 2460, 2461, 2462, 2464, 2469, 2471 (manufactured by Hitachi Chemical), Polylite RX-4800, OD-X-2251, OD-X-2523, OD-X-2420, OD-X-102, OD-X-2108 (manufactured by DIC), Examples include the ETERNCOLL 3000 series (manufactured by Ube Kosan Co., Ltd.).

The content of the polyester polyol in the flux of the present embodiment is not particularly limited, but is, for example, 0.1% by mass or more and 30% by mass or less, preferably 0, with respect to the total amount of solid components in the flux. .1 mass% or more and 27% by mass or less, more preferably 0.1% by mass or more and 20% by mass or less.
In the present embodiment, the total amount of the solid matter component means the total mass of the solid matter component other than the solvent component (volatile component) in the flux.

In the flux of the present embodiment, the ratio of the content of the polyester polyol to the rosin-based resin is not limited, but for example, the polyester polyol is 0.1% by mass or more and 50% by mass or less with respect to the total amount of the rosin-based resin. It is preferably contained in an amount of 0.1% by mass or more and 45% by mass or less, and more preferably 0.1% by mass or more and 25% by mass or less.
When the ratio of the polyester polyol content to the rosin is in the above range, it is preferable from the viewpoint of maintaining the insulating property under high humidity conditions.

In addition to rosin and polyester polyol, the flux of the present embodiment may contain known flux components such as an activator component, a solvent component, an antioxidant component, and a thixotropic component (thixotropic agent).
Each of these components can be added to the flux as needed, and any component may or may not be contained.

The flux of the present embodiment may further contain an organic acid, a halogen-based activator, and other activator components.
The organic acid is not particularly limited as long as it is a known component used as an activator component of a flux. Examples thereof include glutaric acid, succinic acid, methylsuccinic acid, azelaic acid, adipic acid, sebacic acid, stearic acid, benzoic acid, dodecanedioic acid, maleic acid, cyanuric acid and the like.
The organic acid can be used alone or in combination of two or more.

The content of the active agent such as the organic acid in the flux is not particularly limited, but is, for example, 0.5% by mass or more and 20% by mass or less, preferably 3.0% by mass or more and 10% by mass or less. Can be mentioned.

Activator components other than organic acids, for example, amine halogen salts, halogen-based activators such as halogen compounds, imidazole-based activators, and the like can be used.
The content of the halogen-based activator in the flux is not particularly limited, but it is blended so that the concentration of the entire halogen in the flux is 1.0% by mass or less, preferably 0.5% by mass or less. Is preferable.
The content of the imidazole-based activator in the flux is not particularly limited, but for example, it may be blended so as to be 0.1% by mass or more and 1.0% by mass or less.

The activator may be used alone or in combination of two or more of each type. The total amount of the activator in the flux is not particularly limited, and examples thereof include 0.1% by mass or more and 20% by mass or less.

The activator component may generate a gas that causes voids when heated, or a large amount of the activator component may remain in the flux residue, which may cause deterioration of connection reliability and insulation failure, so prevent these. In order to do so, it is conceivable to reduce the activator component, but there is also a problem that the solderability is lowered when the activator component is reduced.
Since the flux of the present embodiment contains the rosin-based resin as described above, the solderability can be maintained even if the activator component is reduced.

The solvent component is not particularly limited as long as it is a known component used as the solvent component of the flux. For example, glycol ethers such as diethylene glycol monohexyl ether (hexyl diglycol), diethylene glycol dibutyl ether (dibutyl diglycol), diethylene glycol mono 2-ethylhexyl ether (2 ethyl hexyl diglycol), diethylene glycol monobutyl ether (butyl diglycol); n -Alipid compounds such as hexane, isohexane and n-heptane; esters such as isopropyl acetate, methyl propionate and ethyl propionate; ketones such as methyl ethyl ketone, methyl-n-propyl ketone and diethyl ketone; ethanol and n- Examples thereof include alcohols such as propanol, isopropanol, isobutanol, octanediol, 3-methyl-1,5-pentanediol.
The solvent can be used alone or in combination of two or more.

The content of the solvent component in the flux is not particularly limited, and examples thereof include 20% by mass or more and 70% by mass or less, preferably 30% by mass or more and 60% by mass or less.

The thixotropic component is not particularly limited as long as it is a known component used as a thixotropic component of flux. Examples thereof include hydrogenated castor oil, fatty acid amides, oxyfatty acids, waxes and the like.
The content of the thixotropic component in the flux is not particularly limited, and examples thereof include 3.0% by mass or more and 20% by mass or less, preferably 5.0% by mass or more and 10% by mass or less.

The flux of the present embodiment may further contain other additives.

The flux of the present embodiment can be used as a liquid flux such as post flux, but is also used as a flux for solder materials such as solder paste and solder.

The solder material of the present embodiment includes each of the above fluxes and a solder alloy.
The solder alloy may be a lead-free alloy.
The solder alloy is not particularly limited, and may be either a lead-free (lead-free) solder alloy or a leaded solder alloy, but a lead-free solder alloy is preferable from the viewpoint of environmental impact.
Specific examples of the lead-free solder alloy include alloys containing tin, silver, copper, zinc, bismuth, antimony and the like, and more specifically, Sn / Ag, Sn / Ag / Cu, Sn. / Cu, Sn / Ag / Bi, Sn / Bi, Sn / Ag / Cu / Bi, Sn / Sb, Sn / Zn / Bi, Sn / Zn, Sn / Zn / Al, Sn / Ag / Bi / In, Sn Examples thereof include alloys such as / Ag / Cu / Bi / In / Sb and In / Ag. In particular, Sn / Ag / Cu is preferable.

The content of the solder alloy in the solder material is not particularly limited, and examples thereof include 80% by mass or more and 95% by mass or less, preferably 85% by mass or more and 90% by mass or less.

When the solder material of the present embodiment is a solder paste obtained by mixing the solder alloy and the flux of the present embodiment, for example, the solder alloy is 80% by mass or more and 95% by mass or less, and the flux is 5% by mass. It is preferable that the mixture is in an amount of% or more and 20% by mass or less.

The conditions for using the solder material of the present embodiment can be appropriately set according to the object to be soldered and the like, and are not particularly limited. For example, the temperature rise rate during preheating: 1.0. ~ 3.0 ° C / sec, preheat temperature: 150 to 190 ° C / 60 to 100 seconds, heating rate during solder melting: 1.0 to 2.0 ° C / sec, melting temperature: 219 ° C or higher and 30 seconds or longer, Reflow peak temperature: 230 to 250 ° C. and other conditions can be mentioned.

When the flux of the present embodiment is blended with a solder material, it can maintain insulation resistance under high humidity conditions, particularly under conditions where a large amount of water such as dew condensation is generated.

The solder material of the present embodiment is suitable for electrical connection of electronic components, particularly electronic components used under conditions of drastic temperature changes such as in-vehicle, outdoor displays, and mobile phones.

The flux and solder materials according to the present embodiment are as described above, but it should be considered that the embodiments disclosed this time are exemplary in all respects and are not restrictive. The scope of the present invention is shown by the scope of claims, not the above description, and is intended to include all modifications within the meaning and scope equivalent to the scope of claims.

Next, examples of the present invention will be described together with comparative examples. The present invention is not construed as being limited to the following examples.

(Making flux)
Using the materials shown in Table 1 and Table 2, the fluxes used in each Example and Comparative Example were prepared with the formulations shown in Table 2.
In the production method, each material was put into an appropriate container, heated to around 170 ° C., and mixed until all the materials were uniformly dissolved to obtain each flux.

The content ratio X1 (mass%) of the polyester polyol in the solid material in Table 3 indicates the ratio of the mass of the polyester polyol in the solid material obtained by removing the solvent from the flux, and is calculated by the following formula.

X1 = X2 / (100-X3) x 100
X2 = Content ratio of polyester polyol in flux (% by mass)
X3 = Solvent content in flux (% by mass)
In this embodiment, X3 is 41.8 (mass%).

Further, the content ratio (mass%, total amount of rosin-based resin) X4 (mass%) of the polyester polyol in Table 3 is calculated by the following formula.

X4 = X1 / X5 × 100
X5 = Content ratio of rosin resin to solid component (% by mass)

X5 (% by mass) indicates the ratio of the rosin-based resin to the solid component obtained by removing the solvent from the flux, and is calculated by the following formula.

X5 = X6 / (100-X3) x 100
X6 = Content ratio of rosin resin in flux (% by mass)
X3 = Solvent content in flux (% by mass)
In this embodiment, X3 is 41.8 (mass%).

<Solder paste>
Solder alloy powder (Sn-3.0% Ag-0.5% Cu, particle size 20-38 μm) and each of the fluxes are mixed at a ratio of 88 ± 1% by mass and 12 ± 1% by mass to form a paste. Each solder material (solder paste) of the above was prepared.

(Test board)
The test substrate uses the solder materials of each of the above-mentioned Examples and Comparative Examples, and has a printed thickness of 100 μm on the substrate (IPC-B-25: conductor width of comb-shaped electrode 0.318 mm, conductor spacing 0.318 mm). Was printed using a metal mask and heat-treated once under the following temperature conditions.
<Temperature condition>
・ Preheat temperature rise rate: 1.0 to 3.0 ° C / sec Preheat temperature: 150 to 190 ° C / 60 to 100 seconds ・ Solder melting rate: 1.0 to 2.0 ° C / sec Melting temperature: 219 ° C or higher 45 seconds or longer Peak temperature: 240 ° C
Atmosphere

(Measurement test of insulation resistance value)
Temperature: 10 ° C to 80 ° C, relative humidity: 30% RH to 95% RH, applied voltage: DC50V, number of cycles: 30 cycles in each of the four test substrates prepared using the above-mentioned Examples and Comparative Examples. A cycle test was performed under the conditions.
As a test device, an ion migration evaluation device (AMI-150-U-25) manufactured by ESPEC was used.
FIG. 1 shows a graph showing the time course of temperature and humidity in the chamber of the test device under these test conditions.
During the test, it was visually confirmed that dew condensation water had adhered to the windows except for the device when the temperature was 70 ° C. and the relative humidity was 95% RH.
Under these conditions, each test board was energized and the insulation resistance value (Ω) was measured.
The test board whose insulation resistance value (Ω) was not less than 1 × 10 8 (Ω) was regarded as OK, and the test board whose insulation resistance value (Ω) was not less than 1 × 10 8 (Ω) was regarded as NG.
The results are shown in Table 3.
Further, graphs showing changes in the insulation resistance value of each test substrate are shown in FIGS. 2 to 5.

As shown in Table 3 and FIGS. 2 to 5, none of the test substrates of the examples had a minimum insulation resistance value of 1 × 10 to the 8th power (Ω) or less.
On the other hand, in all the comparative examples, the insulation resistance value was 1 × 10 to the 6th power (Ω) or less.

Claims (8)

It contains a rosin-based resin and a polyester polyol obtained by dehydration condensation of alcohol and dicarboxylic acid.
When the polyester polyol is contained in an amount of 0.1% by mass or more and 50% by mass or less with respect to the total amount of the rosin-based resin , and the mass change is measured by thermal weight measurement (TG measurement), the weight loss at 240 ° C. is 15. % Or less for soldering flux. The flux according to claim 1, wherein the alcohol contains two or more hydroxyl groups. The flux according to claim 1 or 2, wherein the alcohol is an aliphatic alcohol. The flux according to any one of claims 1 to 3, wherein the rosin-based resin has an acid value of 100 KOH mg / g or more and 350 KOH mg / g or less. The flux according to any one of claims 1 to 4, wherein the polyester polyol is contained in an amount of 0.1% by mass or more and 30% by mass or less based on the total amount of solid components. The flux according to any one of claims 1 to 5, wherein the polyester polyol is a dehydration-condensation of an aliphatic alcohol and a chain dicarboxylic acid. The alcohol and the dicarboxylic acid are 3-methyl-1,5-pentanediol and adipic acid, 1,6-hexanediol and sebacic acid, 1,3-propanediol and sebacic acid, neopentyl glycol and adipic acid, 1. , 2-Etandiol and adipic acid, trimethylolpropane and adipic acid, 3-methyl-1,5-pentanediol and any combination of trimethylolpropane and adipic acid, any one of claims 1 to 6. The flux described in. A solder material containing the flux according to any one of claims 1 to 7 and a solder alloy.

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