Source: http://www.google.com/patents/US6087714?dq=oakley+5,387,949&ei=4yI4T8nkLYa80QG0xqnWAg
Timestamp: 2016-12-04 10:37:31
Document Index: 24309352

Matched Legal Cases: ['art 1', 'art 1', 'art 1', 'art 1', 'art 1', 'art 1', 'art 1', 'art 1', 'art 1', 'art 1', 'art 1', 'art 1', 'art 1']

Patent US6087714 - Semiconductor devices having tin-based solder film containing no lead and ... - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inPatentsIn a lead frame formed out of at least one metal selected from the group consisting of nickel and nickel alloys, copper and copper alloys and iron and iron alloys, the inner lead part is provided with a surface treatment layer of Ag or an alloy containing silver and the outer lead part is provided at...http://www.google.com/patents/US6087714?utm_source=gb-gplus-sharePatent US6087714 - Semiconductor devices having tin-based solder film containing no lead and process for producing the devicesAdvanced Patent SearchTry the new Google Patents, with machine-classified Google Scholar results, and Japanese and South Korean patents.Publication numberUS6087714 APublication typeGrantApplication numberUS 09/298,841Publication dateJul 11, 2000Filing dateApr 26, 1999Priority dateApr 27, 1998Fee statusPaidPublication number09298841, 298841, US 6087714 A, US 6087714A, US-A-6087714, US6087714 A, US6087714AInventorsTakashi Kubara, Matsuo Masuda, Tsuyoshi Tokiwa, Hisahiro TanakaOriginal AssigneeMatsushita Electric Industrial Co., Ltd.Export CitationBiBTeX, EndNote, RefManPatent Citations (6), Referenced by (52), Classifications (43), Legal Events (4) External Links: USPTO, USPTO Assignment, EspacenetSemiconductor devices having tin-based solder film containing no lead and process for producing the devices
US 6087714 AAbstract
In a lead frame formed out of at least one metal selected from the group consisting of nickel and nickel alloys, copper and copper alloys and iron and iron alloys, the inner lead part is provided with a surface treatment layer of Ag or an alloy containing silver and the outer lead part is provided at least with a surface treatment layer of an alloy containing silver and tin of the body-centered cubic structure preferentially oriented in the (101) plane and/or the (211) plane. According to the above-mentioned structure, a semiconductor device that uses a lead frame for electronic parts which does not contain lead, one of the environmentally harmful pollutants, has good characteristics including solder wettability and bonding strength and is of low cost and a process for producing the device are provided.
1. A semiconductor device which uses a lead frame formed out of at least one metal selected from the group consisting of nickel and nickel alloys, copper and copper alloys, and iron and iron alloys wherein an inner lead part of the lead frame is provided with a surface treatment layer of silver or an alloy containing silver and an outer lead part of the lead frame is provided at least with a Sn--Ag surface treatment layer of an alloy containing silver and tin of the body-centered cubic structure preferentially oriented in a (101) plane and/or a (211) plane.
2. A semiconductor device according to claim 1 wherein the Sn--Ag surface treatment layer of the outer lead part is formed from a plating liquor which contains as an acid at least one member selected from the group consisting of alkanesulfonic acids, alkanolsulfonic acids and sulfamic acids, as a tin salt at least one member selected from the group consisting of tin alkane-sulfonates and SnO and as a silver salt at least one member selected from the group consisting of silver alkanesulfonates, Ag2 O and AgO.
The objects of the present invention are to provide a lead frame for electronic parts which does not contain lead, one of the environmentally harmful pollutants, has good characteristic properties including solder wettability and bonding strength and is of low cost, to provide a semiconductor device which uses said lead frame for electronic parts, and to provide a process for producing said lead frame for electronic parts and said semiconductor device.
To attain the above-mentioned objects, the semiconductor device having tin-based solder film which does not contain lead according to the present invention uses a lead frame formed essentially of at least one metal selected from the group consisting of nickel and nickel alloys, copper and copper alloys, and iron and iron alloys wherein an inner lead part of the lead frame is provided with a surface treatment layer of silver or an alloy containing silver and an outer lead part of the lead frame is provided at least with a surface treatment layer of an alloy containing silver and tin of the body-centered cubic structure preferentially oriented in a (101) plane and/or a (211) plane (said surface treatment layer being hereinafter sometimes referred to as the Sn--Ag surface treatment layer). The above-mentioned specific crystal structure of tin can be obtained by regulating the current density at the time of plating. The plating liquor for forming the Sn--Ag surface treatment layer contains as an acid at least one member selected from the group consisting of alkanesulfonic acids, alkanolsulfonic acids and sulfamic acids, as a tin salt at least one member selected from the group consisting of tin alkanesulfonates and SnO, and as a silver salt at least one member selected from the group consisting of silver alkanesulfonates, Ag2 O and AgO. The acid is preferably methanesulfonic acid, hydroxypropanesulfonic acid or isopropanolsulfonic acid. The tin alkanesulfonate is preferably tin methanesulfonate. The silver alkanesulfonate is preferably silver methanesulfonate. The plating liquor may additionally contain as a stabilizer for silver at least one member selected from the group consisting of sulfur compounds, thioamide compounds and thiol compounds, as a stabilizer for tin at least one member selected from the group consisting of carboxylic acids, sulfamic acids, pyrophosphoric acid salts, phenol compounds and chelating agents, and as a crystallization regulator at least one member selected from the group consisting of aromatic sulfonic acid salts, aliphatic sulfonic acid salts, hydantoin compounds, cysteine compounds, aromatic organic amines, aliphatic aldehydes, aromatic aldehydes, nonionic surfactants, amphoteric surfactants and anionic surfactants. To improve the adhesion of the Sn--Ag surface treatment layer to the base material at the outer lead part, the outer lead part may be treated with at least one treating agent selected from hydrochloric acid, nitric acid and sulfuric acid in advance to the formation of the Sn--Ag surface treatment layer. Further, to improve the surface condition and solder wettability, the Sn--Ag surface treatment layer may be treated with a treating agent containing sodium triphosphate.
FIG. 1 is a plan view of a lead frame of one embodiment of the present invention.
Some embodiments of the present invention are described below with reference to the drawings. In the drawings, the same member parts as those of the prior examples are respectively indicated by the same reference numerals, and overlapping explanations are omitted.
The present inventors have made extensive study to overcome the above-mentioned difficulties and resultantly found that tin-silver films containing tin of the body-centered cubic structure preferentially oriented in the (101) plane and/or the (211) plane formed by controlling the crystal orientation prevent the development of cracks and undergo no discoloration and show good solder wettability even after subjected to heating. The tin-silver alloy involves no such problems as limited supply and high cost unlike palladium and shows characteristic properties comparable to those of tin-bismuth, tin-zinc or tin-indium. Though the tin-silver alloy has a higher melting eutectic point of 221° C. than previous tin-lead alloys, it does not need to melt completely to wet when used as plating for the outer lead of a lead frame; it suffices if the alloy reacts with the soldering paste or solder for reflow at their interface at the time of surface packaging and produces a sufficient bonding strength. In fact, the alloy gives a bonding strength and solder wettability comparable to those obtainable by previous lead-containing solder.
After the above-mentioned pretreatment, a Sn--Ag surface treatment layer is provided to the outer lead part 1 by partial plating. The plating liquor used for forming the Sn--Ag surface treatment layer contains as an acid at least one member selected from the group consisting of alkanesulfonic acids, alkanosulfonic acids and sulfamic acids, as a tin salt at least one member selected from the group consisting of tin alkane-sulfonates and SnO, and as a silver salt at least one member selected from the group consisting of silver alkanesulfonates, Ag2 O and AgO. The acid is preferably methanesulfonic acid, hydroxypropanesulfonic acid or isopropanolsulfonic acid. The tin alkanesulfonate is preferably tin methanesulfonate. The silver alkane-sulfonate is preferably silver methanesulfonate. The plating liquor preferably contains 50-200 g/l of an acid, 20-60 g/l of tin in terms of metallic tin amount and 0.5-3 g/l of silver in terms of metallic silver amount.
The plating may be conducted, for example, by the jet plating method using a sparger. The temperature of the liquor is preferably 15˜35° C., more preferably 25° C. Plating film of good quality can be obtained at current densities in the range of 15-25 A/dm2. Current densities over the above-mentioned range causes the increase of (220) plane orientation and resultant deterioration of film quality.
A 42 material alloy sheet was worked into the form of a lead frame and then subjected to a washing treatment and then, if necessary, to a heat treatment step to remove the stress which had remained in the substrate after the punching operation with a press.
Then, the lead frame was treated with a treating agent containing hydrochloric acid at 30° C. for 15 seconds to remove the impurities on the surface and to etch the surface at the same time.
Then, partial plating of a Sn--Ag surface treatment layer was applied to the outer lead part 1 at a current density of 20 ASD (A/dm2). A plating liquor containing SnO, Ag2 O and 150 g/l of methanesulfonic acid was used. The concentration of SnO was 40 g/l in terms of metallic tin and that of Ag2 O was 2 g/l in terms of metallic silver. The above-mentioned plating liquor additionally contained 5 g/l of 2-aminobenzene thiol, 5 g/l of naphthalenesulfonic acid monopolyethylene glycol ether and 80 g/l of bisphenol A dipolyethylene glycol ether.
The plating method used was the jet plating method using a sparger, the flow rate of the plating liquor was 400 l/min and the temperature of the liquor was 25° C. The anode electrode used was an insoluble electrode comprising a titanium base material and a mixture of iridium oxide and tantalum oxide coated thereon. The plating thickness was 8 μm and the silver content of the plating was 2% by weight.
Then, the exposed part of the initially formed copper underlayer plating onto which the silver plating and Sn--Ag plating had not been applied was removed and further, to remove the silver which had leaked to the side of the lead, the silver which had leaked onto the frame surface was removed electrically. Thereafter the Sn--Ag treatment layer of the outer lead part was subjected to an etching treatment by dipping it in a treating agent containing 120 g/l of sodium triphosphate at a liquid temperature of 60° C. for 30 seconds to improve solder wettability. Finally the lead frame was immersed in a discoloration preventing agent, and then washed with water and dried to obtain a finished product.
Upon examining the crystal orientation with an X-ray diffraction apparatus, it was confirmed that the plating obtained was a tin-silver plating layer containing tin of the body-centered cubic structure preferentially oriented in the (101) plane and the (211) plane. The solder wettability was evaluated by using a solder wettability tester (Solder Checker, SWET 100, mfd. by TARUTIN Co., Ltd.) with a tin-lead (H63S) solder at a bath temperature of 230° C. The flux used was R-100-40 (non-halogen type). At the same time, the outer lead part 1 was bent at an angle of 90° to observe the state of peeling of the plating film. Resultantly, the initial zero-cross time, the zero-cross time after heating at 175° C. for 24 hours and the appearance were all good as shown in Table 1.
An alloy 194 sheet was worked into the form of a lead frame and then subjected to a washing treatment and then if necessary, to a heat treatment step to remove the stress which had remained in the substrate after the punching operation with a press.
After the partial plating of silver had been conducted, a pretreatment was carried out with a treating agent containing 50 g/l of sulfuric acid at 30° C. for 15 seconds. After the pretreatment, partial plating of Sn--Ag was applied to the outer lead part 1 at a current density of 24 ASD (A/dm2). The plating liquor used in the present Example contained 40 g/l, in terms of metallic tin of SnO, 2 g/l, in terms of metallic silver, of AgO, and 150 g/l of methanesulfonic acid and additionally contained as additives 5 g/l of 4,4-aminodiphenyl sulfide, 5 g/l of naphthalenesulfonic acid mono-polyethylene glycol ether and 80 g/l of bisphenol A dipolyethylene glycol ether. The plating was conducted by jet plating using a sparger at a flow rate of plating liquor of 400 l/min and at a plating liquor temperature of 25° C. The anode electrode used was an insoluble electrode comprising a titanium base material and a mixture of iridium oxide and tantalum oxide coated thereon. The Sn--Ag plating had a thickness of 8 μm and a silver content of 2.5%. Then, the exposed part of the initially formed copper underlayer plating onto which the silver plating and Sn--Ag plating had not been applied was removed and further, to remove the silver which had leaked to the side of the lead, the silver which had leaked onto the frame surface was removed electrically. Thereafter the Sn--Ag treatment layer of the outer lead part was subjected to an etching treatment by dipping it in a treating agent containing 120 g/l of sodium triphosphate at a liquid temperature of 60° C. for 30 seconds to improve solder wettability. Finally the lead frame was immersed in a discoloration preventing agent, and then washed with water and dried to obtain a finished product.
Upon examining the crystal orientation with an X-ray diffraction apparatus, it was confirmed that the plating obtained was a tin-silver plating layer containing tin of the body-centered cubic structure preferentially oriented in the (101) plane and the (211) plane. The solder wettability was evaluated under the same conditions as in Example 1. At the same time, the outer lead part 1 was subjected to a bending test to observe the state of peeling. Resultantly, the initial zero-cross time, the zero-cross time after heating at 175° C. for 24 hours and the appearance were all good as shown in Table 1.
The details of the structure of a lead frame for electronic parts formed as a comparative example are described below. A 42-material alloy sheet was worked into the form of a lead frame and then subjected to a washing treatment step and then, if necessary, to a heat treatment step to remove the stress which had remained in the substrate after the punching operation with a press. Then the substrate was subjected to a washing step, copper underlayer plating step and silver partial plating step in the same manner as in Example 1. After the partial plating of silver had been conducted, the outer lead part 1 was subjected, without a pretreatment, to partial plating of Sn--Ag at a current density of 60 ASD (A/dm2). The plating liquor used in the present comparative example contained SnO, AgO and methanesulfonic acid as the base materials. The anode electrode used was an insoluble electrode comprising a titanium base material and a mixture of iridium oxide and tantalum oxide coated thereon. The Sn--Ag plating of the present comparative example had a thickness of 8 μm and a silver content of 2.5%. Then, the exposed part of the initially formed copper underlayer plating onto which the Ag plating and Sn--Ag plating had not been applied was removed and further, to remove the silver which had leaked to the side of the lead, the silver which had leaked onto the frame surface was removed electrically. Thereafter the Sn--Ag treatment layer 6 of the outer lead part 1 was subjected to an etching treatment with a treating agent containing sodium triphosphate to improve solder wettability. Finally the lead frame was immersed in a discoloration preventing agent, and then washed with water and dried to obtain a finished product.
Upon examining the crystal orientation with an X-ray diffraction apparatus, it was confirmed that the plating obtained was a tin-silver layer containing tin of the body-centered cubic structure preferentially oriented in the (220) plane. The solder wettability was evaluated under the same conditions as in Example 1. At the same time, the outer lead part 1 was subjected to a bending test to observe the state of peeling. Resultantly, the initial zero-cross time, the zero-cross time after heating at 175° C. for 24 hours and the appearance were all good as shown in Table 1, but cracks developed in the bending test.
An alloy-194 sheet was worked into the form of a lead frame and then subjected to a washing step and then, if necessary, to a heat treatment step to remove the stress which had remained in the substrate after the punching operation with a press. Then the substrate was subjected to a washing step, copper underlayer plating step and silver partial plating step in the same manner as in Example 1. After the partial plating of silver had been conducted, a pretreatment using a treating agent containing nitric acid was carried out. Thereafter the outer lead part was subjected to partial plating of Sn--Ag. The plating liquor used in the present comparative example contained SnO, AgO and methanesulfonic acid as the base materials. The anode electrode used was an insoluble electrode comprising a titanium base material and a mixture of iridium oxide and tantalum oxide coated thereon. In the present comparative example, a Sn--Ag plating of 8 μm thickness was formed at a current density of 60 ASD (A/dm2). The Sn--Ag plating had a silver content of 2.5%. Then, the exposed part of the initially formed copper underlayer plating onto which the Ag plating and Sn--Ag plating had not been applied was removed and further, to remove the silver which had leaked to the side of the lead, the silver which had leaked onto the frame surface was removed electrically. Thereafter, the Sn--Ag treatment layer 6 of the outer lead part 1 was treated with a treating agent containing sodium triphosphate to improve solder wettability and then, without an etching treatment, the lead frame was immersed in a discoloration preventing agent, and then washed with water and dried to obtain a finished product.
Upon examining the crystal orientation with an X-ray diffraction apparatus, it was confirmed that the plating obtained was a tin-silver layer containing tin of the body-centered cubic structure preferentially oriented in the (220) plane. The solder wettability was evaluated under the same conditions as in Example 1. At the same time, the outer lead part 1 was subjected to a bending test to observe the state of peeling. Resultantly, the initial zero-cross time, the zero-cross time after heating at 175° C. for 24 hours and the appearance were all inferior to those observed in Examples 1 and 2. Cracks developed in the bending test.
This Example is described with reference to FIGS. 5A-5C. Onto a lead frame according to the present invention shown in FIGS. 1 and 2 was coated a die attach resin, an IC chip 7 was fixed to the frame and fixed fast by drying in an oven at 200° C. for 2 hours, and then the lead frame and the IC chip 7 were electrically connected by wire bonding. Then the IC chip 7 was sealed with molding resin 9. While, in the prior art, after the sealing, the oxide layer on the surface of the lead frame was removed and then outer solder plating was applied to the outer lead part 1, the use of the lead frame of the present invention simplified the production steps.
This Example is described with reference to FIGS. 5A-5C. A die attach resin was coated onto a lead frame to which Ag plating alone had been applied, then an IC chip 7 was fixed to the frame and fixed fast by drying in an oven at 200° C. for 2 hours, and then the lead frame and the IC chip 7 were electrically connected by wire bonding. Then the IC chip 7 was sealed with molding resin 9. After the sealing, the oxide layer on the surface of the lead frame was removed, and then an outer solder plating 8 μm in thickness was applied to the outer lead part 1 at a current density of 24 ASD (A/dm2). The plating liquor used contained SnO, AgO and methane-sulfonic acid as the base materials. Thereafter the surface treatment layer 6 containing silver and tin of the outer lead part 1 was treated with a treating agent containing sodium triphosphate to improve solder wettability. The resultant device was washed with water and dried to obtain a finished product. Upon examining the crystal orientation with an X-ray diffraction apparatus, it was confirmed that the tin in the plating layer obtained was of the body-centered cubic structure preferentially oriented in the (101) plane and the (211) plane.
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Instruments IncorporatedSemiconductor device with improved solder jointWO2007092762A3 *Feb 2, 2007Apr 3, 2008Texas Instruments IncSemiconductor device with improved solder joint* Cited by examinerClassifications U.S. Classification257/666, 257/677, 257/787, 257/E23.054, 257/793International ClassificationH01L23/495Cooperative ClassificationH01L2924/181, H01L2224/85439, H01L2924/01322, H01L2924/014, H01L2924/01046, H01L2924/0103, H01L2924/01047, H01L2224/05599, H01L2924/01022, H01L2924/01016, H01L2224/85399, H01L2924/14, H01L23/49582, H01L2924/01077, H01L2924/01045, H01L2924/0105, H01L2924/01082, H01L2924/01044, H01L2924/01023, H01L2924/01015, H01L2924/01011, H01L2924/01029, H01L2224/48091, H01L24/48, H01L2924/01083, H01L2924/00014, H01L2224/48247, H01L2924/01006, H01L2924/01049, H01L2924/01079, H01L2924/01027, H01L2924/01028, H01L2224/484, H01L2924/01073, H01L2924/01078European ClassificationH01L24/48, H01L23/495M1Legal EventsDateCodeEventDescriptionApr 26, 1999ASAssignmentOwner name: MATSUSHITA ELECTRIC INDUSTRIAL CO., LTD., JAPANFree format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:KUBARA, TAKASHI;MASUDA, MATSUO;TOKIWA, TSUYOSHI;AND OTHERS;REEL/FRAME:009924/0021Effective date: 19990412Dec 22, 2003FPAYFee paymentYear of fee payment: 4Dec 17, 2007FPAYFee paymentYear of fee payment: 8Dec 19, 2011FPAYFee paymentYear of fee payment: 12RotateOriginal ImageGoogle Home - Sitemap - USPTO Bulk Downloads - Privacy Policy - Terms of Service - About Google Patents - Send FeedbackData provided by IFI CLAIMS Patent Services