Non-corrosive soft-magnetic powder

Abstract

The invention relates to a soft-magnetic powder comprising a core of a soft-magnetic material and a coating, the coating comprising an insulation treatment compound and an inhibitor, the inhibitor being: (e) a carboxylic acid with the general formula (I) ##STR00001## wherein R.sup.1 is a single bond or C.sub.1-C.sub.6-alkylene, R.sup.2 to R.sup.6 are each independently H, OH, —X—COOH, C.sub.1-C.sub.6-alkyl, C.sub.2-C.sub.6-alkenyl, C.sub.2-C.sub.6-alkynyl, C.sub.3-C.sub.7-cycloalkyl, C.sub.6-C.sub.12-aryl, COOR.sup.7, OR.sup.8, or two adjacent groups R.sup.2 to R.sup.6 together form a ring, X is a single bond or C.sub.1-C.sub.6-alkylene; R.sup.7, R.sup.8 are C.sub.1-C.sub.20-alkyl; or a salt of the carboxylic acid,
and/or (f) a compound of the general formula (II)
(R.sup.9—O—)(R.sup.10—O—)(R.sup.11—O—)PO  (II) wherein R.sup.9 to R.sup.11 independently of each other indicate C.sub.1-C.sub.20-alkyl, C.sub.2-C.sub.20-alkenyl, C.sub.2-C.sub.6-alkynyl, C.sub.3-C.sub.7-cycloalkyl, C.sub.6-C.sub.12-aryl, unsubstituted or substituted with one or more groups selected from OH and NH.sub.2, or R.sup.9 to R.sup.11 are each independently a polydiol moiety having a molecular weight M.sub.W of 500 to 30000 g/mol which is optionally capped at the end by —C.sub.1-C.sub.20-alkyl and/or at the connection to O atom bonding to P by C.sub.1-C.sub.20-alkylene, or R.sup.10, R.sup.11 are each independently H. The invention further relates to a process for producing the soft-magnetic powder and an electronic component comprising the soft-magnetic powder.

Claims

1. A dry soft-magnetic powder comprising coated particles of a soft-magnetic material, the coating comprising (i) an insulation treatment compound which comprises phosphorous acid and (ii) an inhibitor, the inhibitor being (a) or (b) or a combination of (a) and (b): (a) sodium salt of a carboxylic acid with the general formula (I) or mixtures thereof ##STR00003## wherein Z is a single bond, R.sup.2 to R.sup.6 are each independently H, OH, —X—COOH, C.sub.1-C.sub.6-alkyl, C.sub.2-C.sub.6-alkenyl, C.sub.2-C.sub.6-alkynyl, C.sub.3-C.sub.7-cycloalkyl, C.sub.6-C.sub.12-aryl, COOR.sup.7, OR.sup.8, or two adjacent groups R.sup.2 to R.sup.6 together form a ring, X is a single bond or C.sub.1-C.sub.6-alkylene; R.sup.7, R.sup.8 are C.sub.1-C.sub.20-alkyl; wherein at least one of R.sup.2 or R.sup.6 is a hydroxyl group; (b) compound of the general formula (II)
(R.sup.9—O—)(R.sup.10—O—)(R.sup.11—O—)PO  (II) wherein R.sup.9 is a polydiol moiety having a molecular weight M.sub.W of 500 to 30,000 g/mol which is optionally capped at the end by —C.sub.1-C.sub.20-alkyl and/or at the connection to O atom bonding to P by C.sub.1-C.sub.20-alkylene, wherein the polydiol moiety is polyethylene glycol, polypropylene glycol or poly ethylene/propylene glycol, R.sup.10 is independently H or a polydiol moiety having a molecular weight M.sub.W of 500 to 30,000 g/mol which is optionally capped at the end by —C.sub.1-C.sub.20-alkyl and/or at the connection to O atom bonding to P by C.sub.1-C.sub.20-alkylene, wherein the polydiol moiety is polyethylene glycol, polypropylene glycol or polyethylene/propylene glycol, R.sup.11 is independently H or a polydiol moiety having a molecular weight M.sub.W of 500 to 30,000 g/mol which is optionally capped at the end by —C.sub.1-C.sub.20-alkyl and/or at the connection to O atom bonding to P by C.sub.1-C.sub.20-alkylene, wherein the polydiol moiety is polyethylene glycol, polypropylene glycol or poly ethylene/propylene glycol, and wherein a ratio of the inhibitor coating to the soft magnetic material being not higher than 0.1.

2. The dry soft-magnetic powder according to claim 1, wherein the soft-magnetic material is carbonyl iron powder.

3. The dry soft-magnetic powder according to claim 1, wherein the coating further comprises a resin.

4. The dry soft-magnetic powder according to claim 3, wherein the resin is an epoxy resin, urethane resin, polyurethane resin, phenolic resin, amino resin, silicon resin, polyamide resin, polyimide resin, acrylic resin, polyester resin, polycarbonate resin, norbornene resin, styrene resin, polyether sulfone resin, silicon resin, polysiloxane resin, fluororesin, polybutadiene resin, vinyl ether resin, polyvinyl chloride resin or vinyl ester resin.

5. A process for producing the dry soft-magnetic powder according to claim 1, comprising following steps: (a) coating particles of a soft-magnetic material with a solution comprising an insulation treatment compound, (b) coating the insulated particles of the soft-magnetic material with a solution comprising an inhibitor solved in an organic solvent; (c) coating the insulated particles of the soft-magnetic material with a resin, wherein all coatings are applied in individual steps (a) to (c) or wherein steps (a) and (b) or wherein steps (b) and (c) are carried out in one step and wherein any solution used for coating the soft-magnetic core comprises less than 10 vol % of water based on the total volume of the solution and wherein the ratio of the inhibitor coating to the soft magnetic material being not higher than 0.1.

6. The process according to claim 5, wherein the inhibitor is (a) or (b) or a combination of (a) and (b) (a) a salt of a carboxylic acid with the general formula (I) ##STR00004## wherein Z is a single bond, R.sup.2 to R.sup.6 are each independently H, OH, —X—COOH, C.sub.1-C.sub.6-alkyl, C.sub.2-C.sub.6-alkenyl, C.sub.2-C.sub.6-alkynyl, C.sub.3-C.sub.7-cycloalkyl, C.sub.6-C.sub.12-aryl, COOR.sup.7, OR.sup.8, or two adjacent groups R.sup.2 to R.sup.6 together form a ring, X is a single bond or C.sub.1-C.sub.6-alkylene; R.sup.7, R.sup.8 are C.sub.1-C.sub.20-alkyl; wherein at least one of R.sup.2 or R.sup.6 is a hydroxyl group, (b) a compound of the general formula (II)
(R.sup.9—O—)(R.sup.10—O—)(R.sup.11—O—)PO  (II) wherein R.sup.9 to R.sup.11 are each independently a polydiol moiety having a molecular weight M.sub.w of 500 to 30000 g/mol which is optionally capped at the end by —C.sub.1-C.sub.20-alkyl and/or at the connection to O atom bonding to P by C.sub.1-C.sub.20-alkylene, wherein the polydiol moiety is polyethylene glycol, polypropylene glycol or polyethylene/propylene glycol, or R.sup.10, R.sup.11 besides the definition above can also be each independently H.

7. The process according to claim 5, wherein the soft-magnetic material comprises carbonyl iron powder.

8. An electronic component comprising the dry soft-magnetic powder according to claim 1.

9. The dry soft-magnetic powder according to claim 1, wherein R.sup.9 to R.sup.11 are each independently a polydiol moiety having a molecular weight M.sub.w of 1,000 to 10,000 g/mol.

10. The dry soft-magnetic powder according to claim 1, wherein R.sup.9 is a polypropylene glycol having a molecular weight of 1,500 to 2,500 g/mol.

11. The dry soft-magnetic powder according to claim 1, wherein the ratio of the inhibitor coating to the soft magnetic material being not higher than 0.01.

12. The dry soft-magnetic powder according to claim 1, wherein the inhibitor is a).

13. A process for the manufacture of an electronic component which comprises press molding or injecting molding the dry soft-magnetic powder according to claim 1.

14. A dry soft-magnetic powder comprising coated particles of a soft-magnetic material, the coating comprising an insulation treatment compound and an inhibitor, the inhibitor being a compound of the general formula (II)
(R.sup.9—O—)(R.sup.10—O—)(R.sup.11—O—)PO  (II) wherein R.sup.9 is a polydiol moiety having a molecular weight M.sub.W of 500 to 30,000 g/mol which is optionally capped at the end by —C.sub.1-C.sub.20-alkyl and/or at the connection to O atom bonding to P by C.sub.1-C.sub.20-alkylene, wherein the polydiol moiety is polyethylene glycol, polypropylene glycol or poly ethylene/propylene glycol, R.sup.10 is independently H or a polydiol moiety having a molecular weight M.sub.W of 500 to 30,000 g/mol which is optionally capped at the end by —C.sub.1-C.sub.20-alkyl and/or at the connection to O atom bonding to P by C.sub.1-C.sub.20-alkylene, wherein the polydiol moiety is polyethylene glycol, polypropylene glycol or polyethylene/propylene glycol, R.sup.11 is independently H or a polydiol moiety having a molecular weight M.sub.W of 500 to 30,000 g/mol which is optionally capped at the end by —C.sub.1-C.sub.20-alkyl and/or at the connection to O atom bonding to P by C.sub.1-C.sub.20-alkylene, wherein the polydiol moiety is polyethylene glycol, polypropylene glycol or poly ethylene/propylene glycol.

15. A dry soft-magnetic powder comprising coated particles of a soft-magnetic material, the coating comprising an insulation treatment compound, an epoxy resin and an inhibitor, the inhibitor being (a) or (b) or a combination of (a) and (b): (a) a salt of a carboxylic acid with the general formula (I) ##STR00005## wherein Z is a single bond, R.sup.2 to R.sup.6 are each independently H, OH, —X—COOH, C.sub.1-C.sub.6-alkyl, C.sub.2-C.sub.6-alkenyl, C.sub.2-C.sub.6-alkynyl, C.sub.3-C.sub.7-cycloalkyl, C.sub.6-C.sub.12-aryl, COOR.sup.7, OR.sup.8, or two adjacent groups R.sup.2 to R.sup.6 together form a ring, X is a single bond or C.sub.1-C.sub.6-alkylene; R.sup.7, R.sup.8 are C.sub.1-C.sub.20-alkyl; wherein at least one of R.sup.2 or R.sup.6 is a hydroxyl group; (b) a compound of the general formula (II)
(R.sup.9—O—)(R.sup.10—O—)(R.sup.11—O—)PO  (II) wherein R.sup.9 is a polydiol moiety having a molecular weight M.sub.W of 500 to 30,000 g/mol which is optionally capped at the end by —C.sub.1-C.sub.20-alkyl and/or at the connection to O atom bonding to P by C.sub.1-C.sub.20-alkylene, wherein the polydiol moiety is polyethylene glycol, polypropylene glycol or poly ethylene/propylene glycol, R.sup.10 is independently H or a polydiol moiety having a molecular weight M.sub.W of 500 to 30,000 g/mol which is optionally capped at the end by —C.sub.1-C.sub.20-alkyl and/or at the connection to O atom bonding to P by C.sub.1-C.sub.20-alkylene, wherein the polydiol moiety is polyethylene glycol, polypropylene glycol or polyethylene/propylene glycol, R.sup.11 is independently H or a polydiol moiety having a molecular weight M.sub.W of 500 to 30,000 g/mol which is optionally capped at the end by —C.sub.1-C.sub.20-alkyl and/or at the connection to O atom bonding to P by C.sub.1-C.sub.20-alkylene, wherein the polydiol moiety is polyethylene glycol, polypropylene glycol or poly ethylene/propylene glycol.

16. The dry soft-magnetic powder according to claim 15, wherein the insulation treatment compound is a phosphate comprising compound.

17. The dry soft-magnetic powder according to claim 15, wherein a ratio of the inhibitor coating to the soft magnetic material being not higher than 0.01.

18. The dry soft-magnetic powder according to claim 15, wherein the inhibitor is a).

19. The dry soft-magnetic powder according to claim 15, wherein the insulation treatment compound is a phosphoric acid or salts thereof with at least one element selected from the group consisting of Al, Si, Mg, Y, Ca, B, Zr, and Fe.

20. A process for the manufacture of an electronic component which comprises press molding or injecting molding the dry soft magnetic powder according to claim 15.

Description

EXAMPLES

(1) Preparation of Carbonyl Iron Powder

(2) In the examples, 2.2 kg of carbonyl iron powder (CIP) were filled into a 1.2 L coated tinplate beaker, which was placed into a planetary mixer. After inerting by flushing with N.sub.2, a solution containing 380 mL of acetone, 4.2 g 85% H3PO4 and inhibitor are added. The composition of respective solutions and the results are given in Table 1.

(3) After stirring the slurry with planetary mixer by 30-100 r/min for 30 min at room temperature, the temperature was raised above the boiling point of acetone. After 3 to 4 hours of heat treatment the dry powder was ready to use.

(4) In the comparative example V1 the carbonyl iron powder has been treated with the H.sub.3PO.sub.4 comprising solution without additional inhibitor.

(5) Mixing with Epoxy Resin

(6) The coated CIP powder (100 g) was mixed with epoxy resin (Epikote 1004, Momentive) by dissolving the epoxy resin (2.8 g) in a solvent (20 mL; e.g. acetone, methylethylketone) and addition of 0.14 g of (dicyandiamide) Dyhard 100SH (Firma=Alzchem) as hardener. In a glass beaker the coated CIP is stirred together with the epoxy formulation using a dissolver mixer (IKA, RW20 D2M, 1000 R/min). After mixing the slurry is poured in an aluminum plate, which is then put in a fume hood for 8 h. The resulting dry CIP epoxy plate is milled in a knife mill (Kinematica, Microtron MB550) for 10 seconds to yield the ready to press powder.

(7) Molding and Wiring of Ring Core

(8) 6.8 g (±0.1 g) of the ready to press powder is put into a steel mold (ring type: outer diameter 20.1 mm; inner diameter 12.5 mm; resulting height approximately 5-6 mm) and molded at 440 MPa for a couple of seconds. From the exact mass and height of the ring the density of the ring core is calculated. The ring core is wired (20 windings) with an isolated 0.85 mm copper wire (Isodraht, Multogan 2000MH 62) for determination of the permeability and resistivity.

(9) Measurement of Permeability and Resistivity

(10) An LRC meter (E4980A Agilent) was used to measure permeability of a ring core. All measurements were done at 100 kHz with 0V DC bias. The test AC current of 10 mA was applied to the ring core.

(11) To measure the resistivity of the pressed parts, a power supply was connected in series to a voltmeter and a sample. 300 Volts were applied to a multimeter and the sample connected in series. Voltage reading of a multimeter was used to estimate the resistance of the sample using following equation.
R.sub.sample=R.sub.meter×(V.sub.PS−V.sub.meter)/V.sub.meter,
where R.sub.sample is the resistance of the cylinder, R.sub.meter is the internal resistance of the meter, V.sub.PS is the applied voltage from power supply (=300V), and V.sub.meter the reading from the voltmeter.
Corrosion Test

(12) The used corrosion test is an accelerated test compared to standard climate chamber tests at 85° C. and 85% relative humidity. It results in accelerated corrosion as the specimen is placed directly into water.

(13) A molded ring core as described above is placed upright into a plastic petri dish (Ø 33 mm, 12 mm height). The petri dish is filled with distilled water in a way that half of the ring core is immersed in water. The open petri dish is placed into climate chamber set to 85° C. and 85% relative humidity. After 24 h the petri dish was removed from the climate chamber inspected. If no corrosion is observed the petri dish is filled again with distilled water and is placed into climate chamber set to 85° C. and 85% relative humidity. This is done to a maximum of 7 days. The corrosion resistance was evaluated by inspection of the ring core: + corresponds to no traces of corrosion even after 7 days (168 h); 0 corresponds to corrosion in the range between 48 h to 168 h; − corresponds to corrosion before reaching 48 h.

(14) Test Results

(15) After treatment of the carbonyl iron powder and formation of the compacted samples the permeability, resistivity and the corrosion characteristics were determined as described above.

(16) TABLE-US-00001 TABLE 1 Test results amount of inhibitor Example in the solution resistivity corrosion no. Inhibitor [g] permeability [MΩ] characteristics V1 — — 22 370 − 1 2,5-Dihydroxybenzoic acid 6.6 21 220 0 2 2,6-Dihydroxybenzoic acid 6.6 21 37 0 3 Salicylic acid 6.6 21 280 0 4 Sodium benzoate 6.6 23 88 + 5 Sodium 2,5-dihydroxybenzoate 6.6 21 2600 + 6 Sodium salicylate 6.6 21 290 + 7 Inhibitor A 1.1 23 78 0 8 Inhibitor A 2.2 21 1100 + 9 Inhibitor A 6.6 21 4700 +

(17) In the table inhibitor A is a compound of the general formula (II) wherein R.sup.9 is a polypropylene glycol chain having a molar weight M.sub.w of 1500 to 2500 g/mol which can be purchased as Korantin LUB® by BASF SE.