HK1181349A - Solder paste flux composition and lead-free soldering paste containing same - Google Patents

Description

Flux composition and lead-free solder paste containing the same

The present application relates to a flux composition for a no-clean lead-free solder paste and a lead-free solder paste comprising the flux composition. More specifically, the lead-free solder paste of the present application possesses better coating and printing ability for a long time, and in addition it is capable of remaining fresh and soft (without refrigeration) at room temperature for a longer period of time.

Background

Most conventional flux (flux) compositions for lead-free solder pastes mainly comprise rosin-based resins such as gum rosin or gum rosin, polymerized rosin, hydrogenated rosin, and any active agent including: an organic bromide and an organic acid for increasing the activation capacity, and a thixotropic agent (thixotropicagent), such as hydrogenated castor oil, to form a viscous liquid, which is then dissolved in a flux solvent and lead-free solder powder is introduced into the solvent to form a solder paste. Typically, the solvent of the fluxing agent typically has a boiling point of 200 ℃ to 300 ℃, typically a polyol ether having a boiling point of 200 ℃ to 300 ℃, such as diethylene glycol butyl ether or tripropylene glycol methyl ether.

Existing lead-free solder pastes usually need to be stored at-20 ℃ to 5 ℃ in order to obtain a shelf life of up to 6 months. In the storage period, these solder pastes are generally likely to change during the storage period, and cause a "skinning phenomenon". When the "skinning phenomenon" occurs, the viscosity of the solder paste changes, the surface hardens, and it appears as if it has a skin. Thus, the storage and use of the lead-free solder paste are seriously affected.

Therefore, there is a need to develop a more reliable flux composition for a no-clean lead-free solder paste and a lead-free solder paste containing the flux composition, whereby the lead-free solder paste can not only prevent the skinning phenomenon and the viscosity change caused by the aging of the solder paste, but also have a longer shelf life even at room temperature (ambient temperature), particularly at a temperature of 5 to 30 ℃, and at the same time, can maintain the ability to maintain the multi- (re-) printability at room temperature for a prolonged period of time, and can function well even after the shelf life is exceeded.

Summary of The Invention

Based on the extensive research, the present inventors have developed a more reliable flux composition for lead-free solder paste, which possesses good coating and printing capabilities, and can be used for multiple printing; in addition, the lead-free solder paste thus obtained does not need to be refrigerated, and can keep the interior and surface of the solder paste fresh and soft even when stored at room temperature, and can be stored for a long time.

The invention provides a soldering flux composition for a no-clean lead-free soldering paste, which comprises mineral oil or pine oil as a solvent.

According to one embodiment of the present invention, a solder flux composition for a no-clean type lead-free solder paste includes mineral oil and/or pine oil as a solvent for the solder flux composition.

According to still another embodiment of the present invention, a flux composition for a no-clean type lead-free solder paste includes rosin (rosin) or resin (resin) or rosin-based resin (rosin-based resin); C12-C14 alkanedioic acids; mineral oil; and/or pine oil.

According to still another embodiment of the present invention, a flux composition for a no-clean type lead-free solder paste includes

(a) 35-48% by weight of a rosin or resin or rosin-based resin,

(b)0 to 8% by weight of succinic acid, glutaric acid and/or adipic acid,

(c) 5-15% by weight of dodecanedioic acid and/or tetradecanedioic acid,

(d)0 to 8% by weight of a thixotropic agent,

(e)0 to 5% by weight of an organic bromide, preferably an organic dibromoalkenyldiol compound,

(f) 1-15% by weight of a mineral oil,

(g) 20-40% by weight of pine oil.

According to still another embodiment of the present invention, a flux composition for a no-clean type lead-free solder paste includes

(a) 35-48% by weight of a rosin or resin or rosin-based resin,

(b) 1-8% by weight of succinic acid, glutaric acid and/or adipic acid,

(c) 5-15% by weight of dodecanedioic acid and/or tetradecanedioic acid,

(d) 2-8% by weight of a thixotropic agent,

(e) 2-5% by weight of an organic bromine compound, preferably an organic dibromoalkenyldiol compound,

(f) 2-15% by weight of a mineral oil,

(g) 20-40% by weight of pine oil.

According to an embodiment of the present invention, there is also provided a lead-free solder paste including any one of the flux compositions described above.

The invention adopts a novel soldering flux solvent system in the formula of the lead-free soldering paste: mineral oil and/or pine oil, which solves the problem of hardening of the soldering paste after long-term storage. Without being bound by theory, the flux composition of the present invention provides an insulating layer of a lead-free solder paste, isolates oxygen and/or moisture from the air, and prevents direct contact of oxygen and/or moisture with the solder paste particles.

It has also been unexpectedly found in the flux solvent of the present invention that the combined use of C4-C6 alkanedioic acids and/or C12-C14 alkanedioic acids in the flux composition advantageously helps to prevent the solder paste from hardening and skinning during storage. Therefore, the lead-free solder paste of the present invention, including the solder powder contained therein, is inert and stable in long-term storage.

In the present invention, when the lead-free solder powder is added, the obtained lead-free solder paste has a longer life, does not require any refrigeration equipment, and can be stored. Therefore, the Surface Mount technology method, namely the step Printing Process and the Refiow solving Process, is more economical, and the solder paste can be stored for a longer time for later use.

With the specific flux composition of the present invention, the lead-free solder paste can be fresh, soft, and ready-to-use (ready-to-use) even at medium room temperature, i.e., without low temperature, and can remain stable for a long time, e.g., up to 300 hours, during storage.

Detailed Description

The flux composition for a no-clean type lead-free solder paste of the present invention generally comprises rosin or a resin or a rosin-based (base) resin as a main component. These rosin or resin or rosin-based resin may be rosin or resin or rosin-based resin which can be used in the art in the lead-free solder paste.

Examples of the rosin-based resin include gum rosin (gum rosin), polymer rosin (polymer), and hydrogenated rosin (hydrogenated rosin). While the rosin or resin that can be used in the present invention includes, for example, rosin, modified rosin (modified rosin), rosin-modified resin (rosin-modified resin), and/or synthetic resin (synthetic resin). The above rosins or resins or rosin-based resins can be used independently or in combination.

The rosin or resin or rosin-based resin of the present invention preferably comprises (comprises) from about 35 wt% to about 48 wt%, more preferably from about 38 wt% to about 45 wt%, and still more preferably greater than 40 wt% of the rosin or resin or rosin-based resin, based on the total weight of the flux composition. The content of the rosin or resin or rosin-based resin can be selected as required by one of ordinary skill in the art. In order to improve the bondability (coalescence) capability of the lead-free solder paste of the present invention, it is preferred that the flux composition comprises greater than about 35% by weight of rosin or resin or rosin-based resin. When the rosin or resin or rosin-based resin is too high, an excessive amount of residue remains on the surface of the substrate after the reflow soldering operation, and cracks may occur after heating and cooling. Furthermore, by absorbing moisture and obtaining temperature, the core residues tend to corrode the base metal, with the result that the electronic properties of the printed circuit board are also affected.

Instead of the entire prior art glycol ether solvent, the solvent preferably used in the lead-free solder paste flux composition of the present invention is mineral oil (solvent #1) and/or pine oil (solvent # 2).

Preferably, the mineral oil is a light paraffin oil, such as the product available from Rajol, india. The paraffin oil used in the present invention may be pharmaceutical grade light paraffin oil having a specific gravity of 0.815-0.835 g/cc. The Pine Oil may be commercially available Pine Oil, for example, three different grades of Pine Oil, i.e., 50% Pine Oil (Pine Oil), 65% Pine Oil and 85% Pine Oil, and the boiling point ranges corresponding to the three grades of Pine Oil are 168-230 ℃, 170-225 ℃ and 190-225 ℃, respectively. The most preferred pine oil in the present invention is 65% pine oil having a boiling point of 170 ℃ to 225 ℃.

The flux composition preferably comprises 1-15% by weight of mineral oil, more preferably 5-13% by weight, and even more preferably in the present invention more than 7% by weight of mineral oil, such as light paraffin oil, based on the total amount of the flux composition. If the present invention includes less than 1% by weight of mineral oil, the rheology of the lead-free solder paste of the present invention will be affected. More specifically, the ability to apply solder paste by pushing and pulling the squeegee (squeegee) becomes slow. This affects the printing quality of the solder paste on the circuit board.

Pine oil (solvent #2), preferably comprises about 20% to 40% by weight of the total flux composition, more preferably about 25% to 35% by weight, and most preferably more than 26% by weight. If the present invention includes less than 20% by weight of pine oil, the viscosity of the final lead-free solder paste of the present invention is affected, so that the softness of the solder paste exposed to air becomes hard, which affects the reusability of the solder paste. The pine oil preferably used in the present invention is 65% by weight or 85% by weight pine oil.

An active agent, such as an organic dibasic acid, e.g., C12-C14 alkanedioic acid, preferably dodecanedioic acid and/or tetradecanedioic acid, can also be included in the solder flux composition of the present invention. The organic dibasic acid is contained in an amount of 5 to 15% by weight based on the total amount of the flux composition. Preferably, C12-C14 alkanedioic acids are included as the active agent in the flux composition of the present invention in an amount of preferably 8 to 13% by weight, more preferably 9% by weight or more. By including more than about 5% by weight of active agent, particularly dodecanedioic acid and/or tetradecanedioic acid, in the present invention, the effect of the active agent is significantly enhanced.

Preferably, a C4-C6 alkanedioic acid is further included as (co) activator in the solder flux composition of the present invention. The present invention preferably comprises from 1 wt% to 8 wt%, more preferably from 1 wt% to 5 wt%, at least 2 wt% succinic, glutaric and/or adipic acid.

Preferably, the present invention comprises more than 1% by weight of (co) activator, and the solderability (solderability) and wettability of the lead-free solder paste of the present invention will be promoted, while the tin-plating (tinting) of the solder paste will be improved upon heating. The introduction of the active agent and co-active agent will affect the primary soldering function of the solder paste in a reflow soldering process.

In the present invention, it is preferred to use two active agents simultaneously, for example, C4-C6 alkanedioic acids and dodecanedioic acid/tetradecanedioic acid in combination.

According to one aspect of the present invention, a solder flux composition includes, based on the total amount of the solder flux composition,

(a)35 to 48% by weight of a rosin-based resin,

(b) from 0 to 8% by weight, preferably from 1 to 8% by weight, of a C4-C6 alkanedioic acid,

(c) 5-15% by weight of dodecanedioic acid and/or tetradecanedioic acid,

(f) 1-15% by weight of mineral oil, and

(g) 20-40% by weight of pine oil.

Other various types of active agents may also be added to the solder flux composition, including thixotropic agents such as hydrogenated castor oil, organic bromides.

The active ingredients of the present invention, i.e., the oxide inhibitor or remover, are known to those of ordinary skill in the art and can be selected as desired by those of ordinary skill in the art. Preferably, an organic bromine compound can be used in the present invention, and preferably the organic bromide is an organic dibromoalkylene glycol compound, such as 2, 3-dibromo-2-butene-1, 4-diol (e.g., 2, 3-dibromo-2-butene-1, 4-diol having a melting point of 111 ℃ to 116 ℃). Preferably, the organic bromide used in the present invention, such as 2, 3-dibromo-2-butene-1, 4-diol, preferably has a (active) bromine content in the molecule of 0.65 mole or more (e.g., per mole of molecule). When an organic bromide active agent is present in a solder flux composition of the present invention, it preferably comprises from 1 wt% to 5 wt%, more preferably from 2 wt% to 4 wt%, at least 3 wt% of the active ingredient. If the present invention comprises more than 1% by weight of organic bromides, wetting ability of the lead-free solder paste of the present invention can be significantly improved.

The soldering flux of the present invention may include thixotropic agents commonly used in soldering fluxes. The thixotropic agent (thixotropic agent) included in the flux composition is also selectable by one of ordinary skill in the art based on the prior art. Preferably, the thixotropic agent included in the present invention is, for example, hydrogenated castor oil, and typically 1% by weight to 8% by weight, more preferably about 2% by weight to 6% by weight, at least 3% by weight of the thixotropic agent may be used. The lead-free solder paste obtained by the present invention will be assisted by the introduction of a thixotropic agent, especially in an appropriate amount, and will maintain the viscosity of the paste, the paste will have an appropriate stepoil-based printability, and will remain smooth.

According to one embodiment of the present invention, a flux includes, based on the total amount of flux,

(a) 35-48% by weight of a rosin or resin or rosin-based resin,

(b) from 0 to 8% by weight, preferably from 1 to 8% by weight, of a C4-C6 alkanedioic acid,

(c) 5-15% by weight of dodecanedioic acid and/or tetradecanedioic acid,

(d)0 to 8% by weight of a thixotropic agent,

(e)0 to 5% by weight of an organic bromine compound,

(f) 1-15% by weight of mineral oil, and

(g) 20-40% by weight of pine oil.

Preferably, according to one embodiment of the present invention, the flux comprises, based on the total amount of flux,

(a) 35-48% by weight of a rosin or resin or rosin-based resin,

(b) 1-8% by weight of succinic acid, glutaric acid and/or adipic acid,

(c) 5-15% by weight of dodecanedioic acid or tetradecanedioic acid,

(d) 2-8% by weight of a thixotropic agent,

(e)2 to 5% by weight of an organic dibromoalkylene glycol compound,

(f) 2-15% by weight of a light paraffin oil,

(g) 20-40% by weight of pine oil.

According to a further embodiment of the invention, hydrogenated castor oil is used in particular as thixotropic agent.

According to still another embodiment of the present invention, 2, 3-dibromo-2-butene-1, 4-diol is used as the organic bromide.

According to another aspect of the present invention, a solder flux composition is provided that includes, based on a total amount of solder flux,

(a) 35-48% by weight of a rosin or resin or rosin-based resin,

(b) 1-8% by weight of succinic acid, glutaric acid and/or adipic acid,

(c) 5-15% by weight of dodecanedioic acid or tetradecanedioic acid,

(d) 2-8% by weight of hydrogenated castor oil,

(e)2 to 5% by weight of 2, 3-dibromo-2-butene-1, 4-diol,

(f) 2-15% by weight of a light paraffin oil,

(g) 20-40% by weight of pine oil.

By adding the solder powder to the flux composition of the present invention, a lead-free solder paste including the flux composition is provided. The solder powder used In the lead-free solder paste of the present invention includes metals and alloys thereof, such as Sn, Ag, Cu, In, Zn, Bi, Ni, Al or alloys thereof. Lead-free solder powders may also use two-component alloys, such as Sn/Ag, Sn/In, Sn/Zn, or three-component alloys, or one or more elements selected from the following: cu, Bi, In, Ni, Ge, Sb, Zn or P, In a two-component or three-component alloy.

In the lead-free solder paste of the present invention, the amount of the solder powder added is usually 85 to 90% by weight, and the content of the flux composition is 10 to 15% by weight. In one particular embodiment, it is preferred that the lead-free solder powder comprises about 99% by weight Sn, about 0.3% by weight Ag, about 0.7% by weight Cu.

In accordance with one embodiment of the present invention, it is preferred that the lead-free solder powder has a mesh size of 25 to 45, 20 to 38, or 15 to 25. For example, the lead-free solder powder is a type 3, 4, 5 lead-free solder powder.

In the present invention, all components are expressed based on the total weight of the flux composition, or the total weight of the lead-free solder paste, unless otherwise specified.

Examples

The present invention will be more specifically illustrated by the following examples, which are not intended to limit the scope of the present invention, but are merely intended to illustrate preferred embodiments of the present invention.

The present invention measures changes in quality, such as printability, wettability and viscosity of lead-free solder paste, caused by aging of the solder paste. The measurement method is as follows:

(i) printing ability (printing ability): lead-free solder pastes of the following formulations were subjected to periodic printing (periodicalprinting) and tested for quality. The printing ability was measured by printing using a screen printing method and a Stencil.

(ii) Wettability (wettability): the lead-free solder paste is laid on a copper plate. The copper plate bearing the cap lead-free solder paste was placed on a hot plate (hot plate) and held at 250 ℃. The wetting state (wetting state) of the solder joint (solder joint) formed on the copper plate was evaluated.

(iii) Viscosity (viscocity): the following formulation viscosity was measured using a Spiral Viscometer model NDJ-79 from PRC according to JIS-Z-3284.

TABLE 1

TABLE 2

Lead-free solder pastes of example 1 and comparative example 1 were prepared in accordance with the above-described composition of components, and their (1) printability, (2) wettability, and (3) viscosity were measured after aging, and the results are shown in Table 2.

TABLE 3

The results show that: in the comparative flux composition using the polyol ether, after 5 hours at room temperature, the surface was hardened and a skinning phenomenon occurred. Without being limited by theory, this change is caused by a reaction between the solder paste and oxygen or moisture in the air or a reaction between an alloy contained in the solder paste and an activator, organic acid contained in the flux.

As can be seen from table 3, the lead-free solder paste containing pine oil and/or paraffin oil of example 1 is better in quality than the solder paste of comparative example 2. In practical use, the solder paste of the present invention can be stored at ambient temperatures of 20 ℃ to 30 ℃ for more than 300 hours, and still maintain good coating (wettability and viscosity) and printability.

Claims (14)

1. A soldering flux composition comprises rosin or a resin or a rosin-based resin, C12-C14 alkanedioic acid, mineral oil and/or pine oil.

2. The solder flux composition of claim 1, comprising, based on the total amount of the solder flux composition,

(a) 35-48% by weight of a rosin or resin or rosin-based resin,

(b)0 to 8% by weight of a C4-C6 alkanedioic acid,

(c)5 to 15% by weight of C12-C14 alkanedioic acids, preferably dodecanedioic acid and/or tetradecanedioic acid,

(d)0 to 8% by weight of a thixotropic agent,

(e)0 to 5% by weight of an organic bromine compound,

(f) 1-15% by weight of mineral oil, and

(g) 20-40% by weight of pine oil.

3. The flux composition of claim 2, wherein the component (f), the mineral oil, is a light paraffin oil, preferably 5-13% by weight of the light paraffin oil.

4. The solder flux composition of claim 2, wherein the component (e) is 1-5% by weight, preferably 2-4% by weight, of the organic bromide; preferably, the organic bromide is an organic dibromoalkenyl diol compound, more preferably 2, 3-dibromo-2-butene-1, 4-diol.

5. The solder flux composition of claim 2, wherein the component (d) is hydrogenated castor oil, preferably 2-5% by weight hydrogenated castor oil.

6. The solder flux composition of claim 2, wherein the component (b) is selected from the group consisting of succinic, glutaric and/or adipic acids, preferably 1-8% by weight of succinic, glutaric and/or adipic acids, more preferably 1-4% by weight of succinic, glutaric and/or adipic acids.

7. The flux composition of claim 2, wherein the rosin or resin or rosin-based resin is selected from modified rosins or resins, preferably rosins, modified rosins, rosin-modified resins and/or synthetic resins, in an amount of preferably 38 to 45% by weight, more preferably 40 to 45% by weight, based on the total amount of the flux composition.

8. The solder flux composition of claim 2, wherein the component (g) is 25-30% by weight pine oil, preferably 65% grade or 85% grade pine oil.

9. The solder flux composition of claim 2, wherein the component (c) is 7-12 wt% dodecanedioic acid and/or tetradecanedioic acid.

10. A lead-free solder paste comprising a lead-free solder powder and the solder flux composition of any one of claims 1-9.

11. A lead-free solder paste according to claim 10 wherein the lead-free solder powder comprises 85 to 90% by weight of the lead-free solder paste.

12. A lead-free solder paste according to claim 11, wherein the lead-free solder powder is a metal or an alloy selected from the group comprising: sn, Ag, Cu, In, Zn, Bi, Ni, Al or combinations thereof.

13. The lead-free solder paste of claim 12 wherein the lead-free solder powder comprises about 99% by weight Sn, about 0.3% by weight Ag, about 0.7% by weight Cu.

14. A lead-free solder paste according to claim 10 wherein the lead-free solder powder has a mesh size of 25 to 45, 20 to 38 or 15 to 25.