Patent Application
20180340128
The present invention relates to a press-fit lubricant composition used for a type of connection called press-fit connection.
Use of press-fit connection has been spreading in recent years as a technique for connection between an electronic board and a terminal.
The press-fit connection is a method of establishing electrical contact between a conductive through hole provided in a printed circuit board and a press-fit terminal having a bulged portion wider than the diameter of the through hole by mechanically fixing the press-fit terminal to the through hole by press-fitting without soldering.
Since the press-fit connection does not require soldering when connecting the printed circuit board and the press-fit terminal, it is possible to expect advantages of e.g. providing a lead free printed circuit board, conserving energy by omitting a heat source necessary for soldering, and shortening the process.
On the other hand, since the press-fit connection is a type of connection by press-fitting the press-fit terminal to the through hole, there is a case where the plating on the surface of the press-fit terminal may scrape off and generate plating scraps due to the frictional force between the surface of the through hole and the surface of the press-fit terminal. If the produced plating scraps scatter due to cooling air or vibration, the plating scraps may cause a problem of short circuiting when the plating scraps adhere to a wiring pattern and leads disposed in the vicinity.
A measure taken against the above problem is to capture plating scraps produced at insertion, thus preventing the scattering of the plating scraps. Methods reported so far include, for example, a method of trapping the produced plating scraps inside the through hole by plastic films laminated on both surfaces of a printed circuit board (Japanese Patent Application Publication No. Hei 6-13735), and a method of allowing an adhesive agent or a resin coating applied onto the surface of a press-fit terminal to hold the plating scraps (Japanese Patent No. 3969369, Japanese Patent No. 5337520). A method is also reported of allowing a pasty curing resin to hold the plating scraps and to prevent detachment and slight movement of the press-fit terminal after being cured (Japanese Patent Application Publication No. 2009-16064).
The present invention aims to provide a lubricant composition which makes it possible both to reduce friction at insertion of a press-fit terminal and to maintain connection of the inserted press-fit terminal to a printed circuit board, i.e., a holding force after insertion. Prior art has focused mainly on capturing metal scraps produced. Meanwhile, for the press-fit terminal, the reduction of friction at insertion and the maintaining of the holding performance after insertion are also considered important issues from the respective viewpoints of preventing the production of abrasion powder and preventing detachment of the press-fit terminal. For example, Japanese Patent No. 3969369 also points out the reduction of friction at insertion, but does not seem to pay attention to the maintaining of the holding performance after insertion. Japanese Patent Application Publication No. 2009-16064 refers to prevention of detachment of the inserted press-fit terminal by use of a pasty curing resin. However, in the case of using a pasty resin which has a large surface tension and low flowability, the resin may not always flow sufficiently into a through hole. As a result, there will be a case where it is impossible to achieve sufficient lubricity at insertion or a case where it is impossible to obtain a sufficient contact area between the press-fit terminal and the through hole.
The inventors have found a solution to the problems described above by using a drying oil as a base oil of the lubricant composition. As a result of further studies, the inventors have findings that the above-described problem can be solved by using an unsaturated compound with a specific iodine value. To be more specific, the present invention provides the following lubricant composition.
1. A press-fit lubricant composition comprising an unsaturated compound with an iodine value of 100 or more.
2. The lubricant composition according to item 1, wherein the unsaturated compound is one of a drying oil and a semi-drying oil.
3. The lubricant composition according to item 1, wherein the unsaturated compound is selected from the group consisting of squalene, docosahexaenoic acid (DHA), tung oil, linseed oil, perilla oil, castor oil, safflower oil, sunflower oil, benne oil, rapeseed salad oil, soybean oil, cottonseed oil, rice bran oil, and a mixture thereof.
4. The press-fit lubricant composition according to any one of items 1 to 3, further containing a compound selected from the group consisting of peroxides, azides, metallic soaps, inorganic acids, Lewis acids, organometallic compounds, sulfur, sulfur compounds, amines, thiol compounds, organophosphorus compounds, imidazole compounds, olefin, cyclic ethers, methacrylic acid compounds, acrylic acid compounds, isocyanate compounds, silicone compounds, phenol compounds, urethane compounds, azonitriles, azoesters, azoamides, azoamidines, azoimidazoliums, benzoin derivatives, benzyl ketals, α-hydroxyacetophenones, α-aminoacetophenones, acylphosphine oxides, titanocenes, iodonium salts, sulfonium salts, and mixtures thereof.
5. The press-fit lubricant composition according to any one of items 1 to 4, further containing a thickener.
6. An electrical contact point wherein the lubricant composition according to any one of items 1 to 5 is applied to any one or both of a press-fit terminal and a through hole of a printed circuit board.
7. A press-fit connection method comprising applying the lubricant composition according to any one of items 1 to 5 to any one or both of a press-fit terminal and a through hole of a printed circuit board.
The present invention makes it possible both to reduce friction at insertion of the press-fit terminal and to connect the press-fit terminal to the printed circuit board after the insertion. According to the composition of the present invention, it is possible to insert the press-fit terminal to the printed circuit board without using a mechanical force of e.g. a hydraulic cylinder or a crank mechanism, or even in the case of using a mechanical force, with a low load of about 65% or less of that without lubricant.
A base oil constituting a lubricant composition of the present invention contains an unsaturated compound with an iodine value (I2g/100 g) of 100 or more, and preferably 130 or more. The iodine value is preferably 1000 or less, more preferably 500 or less, and still more preferably 380 or less. Note that the iodine value is a value measured in accordance with JIS K0070.6. Moreover, in the present specification, a “liquid component” means a component which is derived from an additive and is in the liquid state at normal temperature (25° C.), in addition to the unsaturated compound.
The unsaturated compound includes a drying oil and a semi-drying oil. The drying oil refers to a fatty oil which, if left in air, reacts with oxygen to solidify and dry. The semi-drying oil is an oil intermediate between the drying oil and the non-drying oil, and its iodine value is typically 100 to 130. Specific examples of the drying oil and the semi-drying oil include squalene, docosahexaenoic acid (DHA), tung oil, linseed oil, perilla oil, castor oil, safflower oil, sunflower oil, benne oil, rapeseed salad oil, soybean oil, cottonseed oil, and rice bran oil.
The viscosity at 25° C. of the base oil of the present invention is 2 mPa·s or more, preferably 5 mPa·s or more, and more preferably 10 mPa·s or more, and 100,000 mPa·s or less, preferably 10,000 mPa·s or less, and more preferably 250 mPa·s or less. The lubricant composition of the present invention containing such a base oil is preferable because it is easily introduced between a press-fit terminal and a through hole formed in a printed circuit board and can be expected to contribute to good connectivity thanks to a large connectable area. In particular, the viscosity at 25° C. of the base oil is 2 mPa·s or more, preferably 5 mPa·s or more, and more preferably 10 mPa·s, and the apparent variation of viscosity at 25° C. is preferably 5% or less within the shear rate range of 10 to 1000 s−1. In this case, the viscosity at 25° C. of the base oil is preferably 100,000 mPa·s or less, more preferably 10,000 mPa·s or less, and still more preferably 250 mPa·s or less. Such a base oil is preferable because the lubricant composition pushed out to the edge of the through hole at insertion of the press-fit terminal flows as a Newtonian fluid and is easily introduced into the through hole with passage of time, and thus the base oil can be expected to contribute to good connectivity thanks to a large connectable area.
The content of the unsaturated compound in the lubricant composition of the present invention is preferably 7% by mass or more, more preferably 10% by mass or more, and still more preferably 15% by mass or more with respect to the total mass of the lubricant composition. The content of the unsaturated compound within such a range is preferable because it is possible to prevent the press-fit terminal from being pulled off thanks to the curing of the lubricant composition.
The lubricant composition of the present invention can consist only of the base oil, but can contain various additives as necessary which can usually be used for the lubricant composition. Such additives include a rust inhibitor, an oxidation inhibitor, an oiliness agent, a metal deactivator, an anti-wear agent, an extreme pressure agent, and a solid lubricant. The content of these additives in the lubricant composition is typically 0.1 to 20% by mass.
The lubricant composition of the present invention can also contain various curing accelerators in order to promote curing in the atmosphere at room temperature.
The curing accelerator includes at least one of peroxides, azides, metallic soaps, inorganic acids, Lewis acids, organometallic compounds, sulfur, sulfur compounds, amines, thiol compounds, organophosphorus compounds, imidazole compounds, olefin, cyclic ethers, methacrylic acid compounds, acrylic acid compounds, isocyanate compounds, silicone compounds, phenol compounds, and urethane compounds.
The peroxide is preferably any of hydroperoxide, ketone peroxide, peroxyester, dialkyl peroxide, and peroxydicarbonate. The metallic soap is preferably a metallic soap formed by coordinating a saturated or unsaturated fatty acid or a naphthenic acid to one metal of cobalt, manganese, lead, zinc, nickel, barium, calcium, aluminum, potassium, copper, iron, lithium, and zirconium, more preferably a metallic soap formed by coordinating an unsaturated fatty acid to one of those metals, and particularly preferably cobalt octoate. The inorganic acid is preferably diluted sulfuric acid or diluted hydrochloric acid. The Lewis acid is preferably hydrogen iodide, iodine, zinc triiodide, or boron trichloride. The organometallic compound is preferably a cyclopentadienyl complex. The sulfur compound is preferably one of thiourea based, thiazole based, sulfenamide based, thiuram based, dithiocarbamate salt based, and xanthate based sulfur compounds. The amine is preferably a diamine and particularly preferably trimethylhexamethylenediamine. The thiol compound is preferably a thiol compound having 2 to 4 thiol groups, 12 to 22 carbon atoms at a portion connected to the thiol groups, 4 to 10 oxygen atoms, and 0 to 3 nitrogen atoms. The cyclic ether is preferably a cyclic ether having 2 to 4 glycidyl groups at the end of the molecule, 4 to 20 carbon atoms at a portion connected to the glycidyl groups, 2 to 6 oxygen atoms, and 0 to 4 nitrogen atoms, or a polymer thereof. The isocyanate compound is preferably an isocyanate or a polymer thereof having two or more isocyanate groups and 6 to 14 carbon atoms at a portion connected to the isocyanate groups. Among the above, the metallic soap, the amine, and the cyclic ether are preferable.
The content of such curing accelerating compounds can be 0.01 to 50% by mass, preferably 0.01 to 40% by mass, more preferably 0.01 to 30% by mass with respect to the total mass of the lubricant composition of the present invention.
The lubricant composition of the present invention may also be a grease obtained by adding a thickener thereto. Such a thickener includes a soap thickener such as a lithium soap or a lithium complex soap, a urea based thickener such as diurea, an inorganic thickener such as organoclay or silica, and an organic thickener such as PTFE, but is preferably the inorganic thickener or the organic thickener. The inorganic thickener is more preferable and silica is most preferable.
If the lubricant composition of the present invention contains a thickener, the ratio of the thickener is preferably 0.5 to 85% by mass, more preferably 0.5 to 70% by mass, still more preferably 0.5 to 60% by mass, yet further preferably 1 to 65% by mass, and particularly preferably 5 to 55% by mass with respect to the total mass of the lubricant composition. In the case of 0.5% by mass or more, the thickening effect is exhibited. In the case of 65% by mass or less, a sufficient lubricating effect can easily be obtained because the lubricant composition becomes a grease with appropriate hardness and the lubricant spreads throughout the lubrication portion.
If the lubricant composition of the present invention contains a thickener, the penetration of the lubricant composition is preferably 300 to 475, more preferably 310 to 475, and still more preferably 400 to 430. Note that the penetration is a value which is defined by JIS K2220 and is measured immediately after 60 strokes are performed in a sample by a specified mixer. If the lubricant composition of the present invention is a grease containing a curing accelerator, the curing accelerator may be added at the same time in the preparation of the grease using a base oil, a thickener, and an additive added as necessary, or may be added after the preparation of the grease. Noted that the penetration of a grease refers to a value measured within 30 minutes after the addition of the curing accelerator.
If the lubricant composition of the present invention is used when fastening a first component and a second component together, it is possible to reduce the friction between the first component and the second component because the lubricant composition exists in the liquid state at the fastening, and to connect the first component and the second component together after the fastening.
The connection can be achieved when the lubricant composition of the present invention is cured or thickened by polymerization or crosslinking.
It is possible to cure or thicken the lubricant composition of the present invention by allowing it to stand in the atmosphere at room temperature.
The curing or thickening can proceed by any of radical polymerization, cationic polymerization, coordination polymerization, and vulcanization. A compound which allows the curing or thickening to proceed by radical polymerization is at least one of peroxides, azides, and metallic soaps. A compound which allows the curing or thickening to proceed by cationic polymerization is at least one of an inorganic acid and a Lewis acid. A compound which allows the curing or thickening to proceed by coordination polymerization include an organometallic compound. A compound which allows the curing or thickening to proceed by vulcanization is at least one of sulfur and a sulfur compound.
It is possible to cure or thicken the lubricant composition of the present invention by heating. Compounds for which allow the curing or thickening to proceed by heating include azonitriles, azoesters, azoamides, azoamidines, azoimidazoliums, and so on. Such a curing accelerating compound can be contained at 0.01 to 25% by mass, preferably 0.01 to 10% by mass with respect to the total mass of the lubricant composition of the present invention.
It is also possible to cure or thicken the lubricant composition of the present invention by ultraviolet irradiation. Compounds which allow the curing or thickening to proceed by ultraviolet irradiation include benzoin derivatives, benzyl ketals, α-hydroxyacetophenones, α-aminoacetophenones, acylphosphine oxides, titanocenes, iodonium salts, sulfonium salts, and so on. Such curing accelerating compounds can be contained at 0.01 to 25% by mass, preferably 0.01 to 10% by mass with respect to the total mass of the lubricant composition of the present invention.
Note that the concentration of additive described in the present specification is the concentration of active ingredient. To be more specific, if the additive is a diluted additive, the concentration means the concentration of active ingredient in the diluted additive. Moreover, if the lubricant composition of the present invention is a grease, the concentration of additive is measured with respect to the total mass of the grease lubricant composition.
The lubricant composition of the present invention is applicable to a bulged portion of a press-fit terminal and/or to a through hole. It is possible to apply the lubricant composition of the present invention by immersing the press-fit terminal in the lubricant composition, injecting the lubricant composition with e.g. a spray gun, or using e.g. a brush.
The printed circuit board and the press-fit terminal can be connected together by applying the composition of the present invention thereto, followed by standing in the atmosphere at room temperature (25° C.) or by heating. Those skilled in the art can appropriately select the stand time and the heating time. For example, it is possible to connect the printed circuit board and the press-fit terminal in the atmosphere at room temperature (25° C.) for 1000 hours or more. In the case of connecting this composition by heating, it is preferable to heat the composition at 80 to 150° C. for 24 hours or more. For example, in the case of connecting the composition by ultraviolet irradiation which is formed by adding a curing accelerator to tung oil, it is preferable to perform ultraviolet irradiation for 60 minutes or more.
It is possible to obtain an electronic device using the lubricant composition of the present invention.
It is possible to form an electrical contact point using the lubricant composition of the present invention.
It is possible to carry out a method of establishing electrical connection using the lubricant composition of the present invention.
It is possible to form a contact point for establishing electrical connection by press-fit connection using the lubricant composition of the present invention.
It is possible to carry out a method of establishing electrical connection by press-fit connection using the lubricant composition of the present invention.
Lubricant compositions of Examples and Comparative Examples were prepared.
In Examples 1 to 5 and Comparative Examples 1 and 2, the lubricant composition was the base oil itself.
In Example 6, the lubricant composition was a mixture of 3 parts by mass of diluted solvent of cobalt octoate (commercially available, diluted mineral spirits, containing 12% by mass of cobalt octoate in cobalt atomic ratio concentration) as a curing accelerator, 13 parts by mass of trimethylhexamethylenediamine, and 53 parts by mass of a polymer of 2,2-bis(4-glycidyloxyphenyl)propane with respect to 100 parts by mass of tung oil as the base oil.
In Example 7, the lubricant composition was a grease mixture of 335 parts by mass of silica particles as a thickener, 35 parts by mass of trimethylhexamethylenediamine as a curing accelerator, and 140 parts by mass of a polymer of 2,2-bis(4-glycidyloxyphenyl)propane with respect to 100 parts by mass of tung oil as the base oil. Note that the worked penetration of the grease fabricated in Example 7 was 430 and the worked penetration was measured within 30 minutes after the addition of the curing accelerator.
Each of Comparative Examples 3 and 4 was a commercial one-component epoxy adhesive.
The lubricant composition prepared above was used in the following tests. Tables 1 shows test conditions for the insertion test and the pull test. Tables 2 and 3 show the test results.
The iodine value of the base oil was measured in accordance with JIS K0070.6. To be more specific, the iodine value was calculated using the following equation after dissolving the base oil into cyclohexane, adding a solution of iodine monochloride, allowing it to stand in a dark place, adding potassium iodide and water, performing titration using a solution of sodium thiosulfate, adding a starch solution when the solution turns thin yellow, and continuing titration until blue vanishes.
A=(B−C)×f×1.269/S
A: iodine value
B: amount of 0.1 mol/l sodium thiosulfate solution (ml) used for blank test
C: amount of 0.1 mol/l sodium thiosulfate solution (ml) used for titration
f: factor of sodium thiosulfate solution
S: mass of base oil (g)
1.269: atomic weight of iodine 126.9×1/100
The viscosity of base oil was measured in accordance with JIS Z8803:2011. To be more specific, the viscosity within the shear rate rage of 10 to 1000 s−1 was measured using a cone-plate rotational viscometer with the sample provided between the cone and the plate. For Examples 1 to 7 and Comparative Examples 1 to 2, the tables show viscosities at 25° C. and 100 s−1 as representative values. Note that for Examples 1 to 7 and Comparative Examples 1 to 2, the variation of viscosity within the shear rate range of 10 to 1000 s−1 was within 1%. In addition, for the samples of Comparative Examples 3 and 4 which were semi-solid and exhibited high viscosity at normal temperature, the tables show viscosities measured in accordance with a method and conditions different from the above. To be more specific, for Comparative Example 3, the tables show the viscosity at 23° C. and at 20 rpm using a single cylinder rotational viscometer. For Comparative Example 4, the tables show the viscosity at 25° C. and at 10 rpm using a cone-plate rotational viscometer.
The friction reduction effect (lubricity) of the lubricant composition was evaluated by measuring the “insertion load” at the insertion of the press-fit terminal.
(1) A printed circuit board was fixed to a jig attached to the base of an Autograph.
(2) A distal end of the press-fit terminal was immersed in the lubricant composition and the lubricant composition adhered to the press-fit terminal.
(3) The press-fit terminal was fixed to a jig attached to the drive unit of the Autograph.
(4) The position of the press-fit terminal was adjusted so that the distal end of the press-fit terminal was immediately above a through hole of the printed circuit board.
(5) The press-fit terminal was driven at a constant speed.
(6) An axial force (insertion load) at the insertion of the press-fit terminal into the through hole was measured at 25° C.
Evaluation was carried out based on the relative value, which is 100% without lubricant.
65% or less of the insertion load without lubricant: ◯ (acceptable)
over 65% of the insertion load without lubricant: x (unacceptable)
The “pull load” at the pulling of the press-fit terminal was measured to evaluate to what extent the holding performance of the press-fit terminal was suppressed.
(1) In Examples 1 to 5 and Comparative Examples 1 to 4, the printed circuit board after the insertion of the press-fit terminal was allowed to stand for 72 hours in a thermostatic chamber heated to 100° C. at a normal pressure. In Example 6, the printed circuit board after the insertion of the press-fit terminal was allowed to stand for 72 hours in a room at normal temperature (25° C.) and at normal pressure. In Example 7, the printed circuit board after the insertion of the press-fit terminal was allowed to stand for 24 hours in a room at normal temperature (25° C.) and at normal pressure.
(2) The heated printed circuit board of Examples 1 to 5 and Comparative Examples 1 to 4 was cooled under room temperature (25° C.). Note that the procedures (1) and (2) described above were omitted in the case of measuring the pull load immediately after the insertion of the press-fit terminal.
(3) A printed circuit board was fixed to a jig attached to the base of an Autograph.
(4) A jig attached to the drive unit of the Autograph was driven at a constant speed to pull out the press-fit terminal.
(5) An axial force (pull load) at the pulling of the press-fit terminal from a through hole of the printed circuit board was measured at 25° C.
Evaluation was carried out based on the difference between the value immediately after the insertion of and the value after curing of each lubricant composition, where the pull load immediately after insertion without lubricant is 100%.
The difference between the pull loads before and after curing is +15% or more: ◯ (acceptable)
The difference between the pull loads before and after curing is below +15%: x (unacceptable)
| Number | Date | Country | Kind |
|---|---|---|---|
| 2017-104377 | May 2017 | JP | national |
