CN102332332A - Flexible flat cable and manufacturing method thereof, flexible printed substrate and manufacturing method thereof - Google Patents
Flexible flat cable and manufacturing method thereof, flexible printed substrate and manufacturing method thereof Download PDFInfo
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- CN102332332A CN102332332A CN2011101683149A CN201110168314A CN102332332A CN 102332332 A CN102332332 A CN 102332332A CN 2011101683149 A CN2011101683149 A CN 2011101683149A CN 201110168314 A CN201110168314 A CN 201110168314A CN 102332332 A CN102332332 A CN 102332332A
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Abstract
本发明提供一种柔性扁平电缆及其制造方法、柔性印刷基板及其制造方法，能够抑制晶须的产生。本发明所涉及的柔性扁平电缆(1)具备：具有由铜或铜合金构成的导电性基材(100)和设置于导电性基材(100)表面的导电层(102)的导体(10)、设置于导体(10)上方的第1绝缘层(20)以及设置于导体(10)下方的第2绝缘层(22)。导电层(102)由在所述导电性基材(100)上形成的铜-锡金属间化合物层(61)以及在该铜-锡金属间化合物层(61)上形成的残余锡层(62)构成，所述残余锡层(62)至少包含由锡和铋构成的锡-铋固溶体、锡和不可避免的杂质。
The invention provides a flexible flat cable and a manufacturing method thereof, a flexible printed substrate and a manufacturing method thereof, capable of suppressing generation of whiskers. A flexible flat cable (1) according to the present invention includes: a conductor (10) having a conductive base material (100) made of copper or a copper alloy and a conductive layer (102) provided on the surface of the conductive base material (100) , a first insulating layer (20) arranged above the conductor (10) and a second insulating layer (22) arranged below the conductor (10). The conductive layer (102) consists of a copper-tin intermetallic compound layer (61) formed on the conductive substrate (100) and a residual tin layer (62) formed on the copper-tin intermetallic compound layer (61). ), the residual tin layer (62) at least includes tin-bismuth solid solution composed of tin and bismuth, tin and unavoidable impurities.
Description
Technical field
The present invention relates to the manufacturing approach of flexible flat cable, flexible printed board, flexible flat cable and the manufacturing approach of flexible printed board.The present invention be more particularly directed to have flexible flat cable, flexible printed board, the manufacturing approach of flexible flat cable and the manufacturing approach of flexible printed board of the conductive layer of Sn-containing alloy.
Background technology
In recent years use a lot of holding wires in the electric equipment.And when the parts that action is arranged in electric equipment sent signal, these parts and the parts that send signal to these parts were through having flexual flexible flat cable (FFC) or flexible printed board (FPC) is connected.And, be provided with the coating such as tin, silver, gold, nickel of the oxidation that is used to prevent wiring material, corrosion etc. on the surface of the wiring material of FFC and FPC.Here, because tin is soft, easy deformation when exerting pressure.Therefore, when on the wiring layer of the female terminal of hero, applying tin coating,, make tin coating be out of shape, thereby increase the contact area of male terminal and female terminal because male terminal and female terminal is chimeric.Owing to can reduce contact resistance like this, therefore apply tin coating and extensively implemented on the surface of wiring material., when the coating of stanniferous being set, can separate out the acicular crystal that is known as " whisker " here, distribution and other distributions with this coating are short-circuited from this coating on the distribution surface.
So; Known in the past have: the electrical wiring at the electric conductor parts partly applies more than the thickness 0.2 μ m, behind the tin coating of less than 1.0 μ m; Making the ratio of alloy-layer of tin and the electric conductor of tin coating through heat treatment is the electric conductor member manufacturing method (for example, with reference to patent documentation 1) more than 50%.
The electric conductor member manufacturing method of record in the patent documentation 1 is because thereby the temperature more than the fusing point of tin is implemented the alloy-layer that heat treatment forms tin; Therefore amount can be reduced, thereby the generation of whisker can be when unleaded, reduced as the tin layer in the generation source of whisker.
Patent documentation 1: TOHKEMY 2006-127939 communique
Summary of the invention
But; The electric conductor member manufacturing method of record in the patent documentation 1 is because the temperature more than the fusing point of tin is implemented heat treatment; Therefore can produce the big tin of crystal grain through recrystallizing of tin; In this case, stress can't be fully relaxed, thereby the generation of whisker might be difficult to control in the inner generation of electric conductor.
Therefore, the objective of the invention is to, a kind of flexible flat cable, flexible printed board, the manufacturing approach of flexible flat cable and manufacturing approach of flexible printed board that can inhibition of whiskers produces is provided.
In order to reach above-mentioned purpose; The present invention provides a kind of flexible flat cable, and it possesses: have the conductive substrate that constitutes by copper or copper alloy and the conductive layer that is arranged at aforementioned conductive substrate surface conductor, be arranged at the 1st insulating barrier of aforementioned conductor top and the 2nd insulating barrier that is arranged at aforementioned conductor below.Aforementioned conductive layer is made up of the remaining tin layer that forms at the copper that forms on the aforementioned conductive substrate-Sn intermetallic compound layer and on this copper-Sn intermetallic compound layer, and said remaining tin layer comprises Sn-Bi solid solution, tin and the unavoidable impurities that is made up of tin and bismuth at least.
In addition, with regard to above-mentioned flexible flat cable, Sn-Bi solid solution preferably contains the bismuth below the 3 quality %.
In addition, with regard to above-mentioned flexible flat cable, remaining tin layer preferably further contains solid solution fully and the bismuth crystal of separating out.
In addition; With regard to above-mentioned flexible flat cable; The Sn-Bi solid solution that contains in the conductive layer uses the lattice constant of this Sn-Bi solid solution of X-ray diffraction device mensuration to be preferably, in the scope of a axle below the above 0.585nm of 0.584nm, in the scope of c axle below the above 0.32nm of 0.3185nm.
In addition, with regard to above-mentioned flexible flat cable, the unit cell volume of this Sn-Bi solid solution that the aforementioned Sn-Bi solid solution use X-ray diffraction device that contains in the conductive layer is measured is preferably at 0.1085nm
3Above 0.109nm
3In the following scope.
In addition; In order to reach above-mentioned purpose; The present invention provides a kind of flexible printed board; It possesses: the 1st dielectric film and the 2nd dielectric film, and be arranged between aforementioned the 1st dielectric film and aforementioned the 2nd dielectric film, have the conductive substrate that constitutes by copper or copper alloy and be arranged at the wiring circuit of the conductive layer on aforementioned conductive substrate surface.Aforementioned conductive layer is made up of the remaining tin layer that forms at the copper that forms on the aforementioned conductive substrate-Sn intermetallic compound layer and on this copper-Sn intermetallic compound layer, and said remaining tin layer comprises Sn-Bi solid solution, tin and the unavoidable impurities that is made up of tin and bismuth at least.
In addition, with regard to above-mentioned flexible printed board, Sn-Bi solid solution preferably contains the bismuth below the 3 quality %.
In addition, with regard to above-mentioned flexible printed board, remaining tin layer preferably further contains solid solution fully and the bismuth crystal of separating out.
In addition; With regard to above-mentioned flexible printed board; The aforementioned Sn-Bi solid solution that contains in the conductive layer uses the lattice constant of this Sn-Bi solid solution of X-ray diffraction device mensuration to be preferably; In the scope of a axle below the above 0.585nm of 0.584nm, in the scope of c axle below the above 0.32nm of 0.3185nm.
In addition, with regard to above-mentioned flexible printed board, the unit cell volume of this Sn-Bi solid solution that the Sn-Bi solid solution use X-ray diffraction device that contains in the conductive layer is measured is preferably at 0.1085nm
3Above 0.109nm
3In the following scope.
In addition; In order to reach above-mentioned purpose; The present invention provides a kind of manufacturing approach of flexible flat cable; It possesses: thereby thereby the base material preparatory process of the conductive substrate of preparing to constitute, to implement the plating operation of the base material of tin-bismuth alloy electroplating plating formation band tin-bismuth alloy electroplating coating on the surface of aforementioned conductive substrate, the base material of aforementioned band tin-bismuth alloy electroplating coating is implemented behind the heat treated heat treatment step, aforementioned hot treatment process of the temperature more than the fusing point of aforementioned tin-bismuth alloy electroplating coating to form the refrigerating work procedure of the base material of being with conductive layer and above the base material of the aforementioned band conductive layer of the aforementioned refrigerating work procedure of process, the 1st insulating barrier to be set with the base material that 200 ℃/ cooling rate sec more than is cooled off aforementioned band tin-bismuth alloy electroplating coating by copper or copper alloy, the below is provided with the insulating barrier formation operation of the 2nd insulating barrier.Aforementioned conductive layer is made up of the remaining tin layer that forms at the copper that forms on the aforementioned conductive substrate-Sn intermetallic compound layer and on this copper-Sn intermetallic compound layer, and said remaining tin layer comprises Sn-Bi solid solution, tin and the unavoidable impurities that is made up of tin and bismuth at least.
In addition, with regard to the manufacturing approach of above-mentioned flexible flat cable, the tin-bismuth alloy electroplating plating preferably contains the bismuth below the 10 quality % more than the 3 quality % in pure tin.
In addition, with regard to the manufacturing approach of above-mentioned flexible flat cable, conductive layer preferably comprises the aforementioned Sn-Bi solid solution that contains the bismuth below the 3 quality %.
In addition; In order to reach above-mentioned purpose; The present invention provides a kind of manufacturing approach of flexible printed board, and it possesses: thus the base material that forms the conductive substrate constitute by copper or copper alloy on the 1st dielectric film forms operation, the surface of aforementioned conductive substrate implement the plating operation of tin-bismuth alloy electroplating plating, heat treated heat treatment step, the aforementioned hot of implementing the temperature more than the fusing point of aforementioned tin-bismuth alloy electroplating plating handle the back cool off aforementioned tin-bismuth alloy electroplating to plate the refrigerating work procedure that forms conductive layer and aforementioned refrigerating work procedure with 200 ℃/ cooling rate more than the sec after with the be covered lining operation of aforementioned conductive layer of the 2nd dielectric film.Aforementioned conductive layer constitutes said remaining tin layer by the remaining tin layer that forms at the copper that forms on the aforementioned conductive substrate-Sn intermetallic compound layer and on this copper-Sn intermetallic compound layer and comprises Sn-Bi solid solution, tin and the unavoidable impurities that is made up of tin and bismuth at least.
In addition, with regard to the manufacturing approach of above-mentioned flexible printed board, the tin-bismuth alloy electroplating plating preferably contains the bismuth below the 10 quality % more than the 3 quality % in pure tin.
In addition, with regard to the manufacturing approach of above-mentioned flexible printed board, conductive layer preferably comprises the aforementioned Sn-Bi solid solution that contains the bismuth below the 3 quality %.
According to the manufacturing approach of flexible flat cable involved in the present invention, flexible printed board, flexible flat cable and the manufacturing approach of flexible printed board, but flexible flat cable, flexible printed board, the manufacturing approach of flexible flat cable and the manufacturing approach of flexible printed board that can provide a kind of inhibition of whiskers to produce.
Description of drawings
Fig. 1 (a) is the top view of the end of the related flexible flat cable of the 1st execution mode of the present invention, (b) is the sectional view on the A-A line of (a).
Fig. 2 is the sketch map of the lattice of pure tin metal.
The skeleton diagram of the state of Fig. 3 after for flexible flat cable that the 1st execution mode of the present invention is related insertion connector.
Fig. 4 is the skeleton diagram of the conductive surface state of contact of the related flexible flat cable of connector plug and the 1st execution mode of the present invention of connector.
Fig. 5 is the skeleton diagram of the partial cross section of the related flexible printed board of the 2nd execution mode of the present invention.
Fig. 6 is the sectional view after implementing heat treatment, chilling processing at the sectional view behind the enforcement plating on the conductive substrate and to the conductive substrate of this band coating.
Symbol description
1 flexible flat cable, 3 tin atoms, 5 connectors, 7 flexible printed boards, 10 conductors; 12 wiring circuits, 20 the 1st insulating barriers, 22 the 2nd insulating barriers, 24 the 1st dielectric films, 26 the 2nd dielectric films; The 30a axle, 32c axle, 50 connector plugs, 50a front end, 60 tin-bismuth alloy electroplating coating; 61 bronze medals-Sn intermetallic compound layer, 62 remaining tin layers, 100 conductive substrates, 102 conductive layers
Embodiment
The 1st execution mode
The summary that Fig. 1 (a) expression is observed above the end of the related flexible flat cable of the 1st execution mode of the present invention, (b) summary in the cross section of the flexible flat cable on the A-A line of presentation graphs 1 (a).In addition, Fig. 2 representes the sketch map of the lattice of pure tin metal.
The general introduction of the structure of flexible flat cable 1
The related flexible flat cable (FFC) 1 of the 1st execution mode has following structure: conductive layer 102 is set on the surface, between as the 1st insulating barrier 20 of insulating film and the 2nd insulating barrier 22 with the arranged spaced of regulation, sandwich a plurality of conductive substrates 100 as straight angle conductor with rectangle or elliptic cross-section.Particularly; Like Fig. 1 (a) with (b), flexible flat cable 1 possesses: have the conductive substrate 100 and the conductor 10 that covers the conductive layer 102 that is arranged at conductive substrate 100 surfaces, the 2nd insulating barrier 22 that is arranged at the 1st insulating barrier 20 of conductor 10 tops and is arranged at conductor 10 belows that are made up of copper or copper alloy etc.Then, only remove the part of the 1st insulating barrier 20, so that in the end of flexible flat cable 1, the parts on conductive layer 102 surfaces of conductor 10 are exposed to the outside in the distance of stipulating apart from the end of flexible flat cable 1.
About conductive layer 102, use Fig. 6 to specify here.Fig. 6 (a) has added the cross section structure behind the unleaded tin-bismuth alloy electroplating coating 60 that quantitative bismuth forms in the pure tin for the mode that contacts with the surface with conductive substrate 100 is formed on; (b) for through this tin-bismuth alloy electroplating coating 60 is further heat-treated, (temperature more than the fusing point of tin alloy coat heats cooling processing; In case the processing method of cooling off after the fusion, solidifying), the cross section structure behind the conductive layer 102 of formation is: form copper-Sn intermetallic compound layer 61 that constitutes by tin and copper and the remaining tin layer 62 that contains bismuth that on this layer, forms in conductive substrate 100 1 sides.
If, then in remaining tin layer 62, form the Sn-Bi solid solution that constitutes by tin and bismuth in containing the pure tin of unavoidable impurities, adding the tin-bismuth alloy electroplating coating 60 enforcement heat treatments that bismuth forms.The bi concns maximum that contains in this Sn-Bi solid solution is about 3 quality %.
If further increase the bismuth addition in the tin-bismuth alloy electroplating coating 60 and implement heat treatment, then in remaining tin layer 62, form in the Sn-Bi solid solution that constitutes by tin and bismuth, also separate out the bismuth crystal.Particularly, the remaining tin layer 62 in the conductive layer 102 comprises the Sn-Bi solid solution that is made up of tin and bismuth, and remainder is by tin and unavoidable impurities and solid solution and the bismuth crystal of separating out constitutes fully.
The amount of the bismuth atom that here, in tin-bismuth alloy electroplating coating 60, adds is substantially equal to the amount sum of the atom of the bismuth crystal that the amount of the bismuth atom in the Sn-Bi solid solution that in remaining tin layer 62, forms separates out with complete solid solution.
In addition; Whether can not solid solution and separate out as the bismuth crystal, (for example, heat treatment time is long more to depend on bi concns, the heat treatment time at the initial stage of adding in the tin-bismuth alloy electroplating coating 60; The thickness of then remaining tin layer 62 is more little; Bi concns in this remnants tin layer 62 is high more, thereby separates out easily), the result that also might do not separated out according to condition.
And; Surface at conductive substrate 100; So that the amount of the tin atom that contains in the remaining tin layer 62 reduces and when implementing heat treatment, make remaining tin layer 62 not be purpose from conductive substrate 100 disappearances (not only having only copper-Sn intermetallic compound layer 61); Tin-bismuth alloy electroplating coating 60 forms the thickness that has below the 2 μ m, is preferably the thickness below the above 1.5 μ m of 0.3 μ m, is more preferably the thickness below the above 1.5 μ m of 0.5 μ m.
In addition; The Sn-Bi solid solution that contains in the remaining tin layer 62 uses the lattice constant of this Sn-Bi solid solution of X-ray diffraction device mensuration to be defined as; In the scope of a axle below the above 0.585nm of 0.584nm, in the scope of c axle below the above 0.32nm of 0.3185nm.In addition, the Sn-Bi solid solution that contains in the remaining tin layer 62 uses the unit cell volume of this Sn-Bi solid solution of X-ray diffraction device mensuration to be defined in 0.1085nm
3Above 0.109nm
3In the following scope.As stated; But the bi concns of solid solution is about 3 quality % at most in tin; The lattice constant of Sn-Bi solid solution can change (bi concns increase more, lattice constant is big more) in this concentration range, but when further increasing the bismuth addition; Can separate out the bismuth crystal, the lattice constant of Sn-Bi solid solution can not change yet.
In addition, the lattice constant of Sn-Bi solid solution can use the X-ray diffraction pattern of measuring to as the conductive layer of coating 102 irradiation X ray the time through calculating.In addition, the lattice of pure tin metal be shaped as hexahedron, tin atom 3 is arranged as illustrated in fig. 2.And the long limit of lattice is an a axle 30, and minor face is a c axle 32.A axle 30 is 0.5831nm in the pure tin metal, and c axle 32 is 0.3182nm.Can calculate the volume of lattice by these values, the pure tin metal is 0.10819nm
3Equally, the unit cell volume of Sn-Bi solid solution also can be calculated by the lattice constant of utilizing the X-ray diffraction device to measure, calculate.
The 1st insulating barrier 20 and the 2nd insulating barrier 22
The 1st insulating barrier 20 and the 2nd insulating barrier 22 are respectively by the macromolecular material with insulating properties, and for example PETG (PET) forms.And, respectively the 1st insulating barrier 20 and the 2nd insulating barrier 22 are provided with the bond layer of anti-flammability on a surface, be attached at the surface of conductor 10 again through this bond layer.Bond layer is for example formed as principal component by fire-retardant polyester.
Flexible flat cable 1 is chimeric to connector 5
Fig. 3 representes that flexible flat cable that the 1st execution mode of the present invention is related inserts the summary of the state in the connector, and Fig. 4 representes the summary of the conductive surface state of contact of the flexible flat cable that connector plug and the 1st execution mode of the present invention of connector is related.
As shown in Figure 3, the connector 5 that has inserted flexible flat cable 1 possesses respectively a plurality of connector plugs 50 that a plurality of conductors 10 of having with flexible flat cable 1 are electrically connected.In addition, connector plug 50 is the metal terminal that is formed by metal materials such as copper.And when inserting flexible flat cable 1 in the connector 5, each of the surface of a plurality of conductors 10 contacts with each of a plurality of connector plugs 50, thereby flexible flat cable 1 is embedded in the connector 5.
Chimeric through this, as shown in Figure 4, the front end 50a of connector plug 50 contacts with the surface of conductor 10, and front end 50a exerts pressure to conductor 10 simultaneously.Thus, have on the surface on the conductor 10 of conductive layer 102 of stanniferous and apply pressure, thereby in conductor 10, produce stress from connector plug 50., in conductive layer 102, do not contain under the situation of the related Sn-Bi solid solution of this execution mode, because this pressure, tin atom moves in the inside of conductive layer 102, thereby might produce crystallization again or diffusion phenomena here.In this case, can think that whisker produces, grows to the mode that the outside penetrates with the surface from conductor 10 through the crystallization again or the diffusion phenomena of tin atom.Perhaps; Can think and in conductive layer 102, produce stress, because this stress by the intermetallic compound that generates copper and tin through diffusion in the copper conductive layer 102 that contains in the conductive substrate 100; Tin is extruded to the outside of conductor 10, thereby causes whisker to produce, grow.
But; Conductor that the related flexible flat cable 1 of this execution mode possesses 10 is owing to have on the surface and to contain Sn-Bi solid solution at least and remainder is the remaining tin layer 62 of tin and unavoidable impurities, therefore can suppress tin atom and conductive layer 102 in, spread in the mobile or copper conductive layer 102.The whisker that therefore, can suppress tin is in the generation of the surface of conductor 10, growth.
The manufacturing approach of flexible flat cable 1
Flexible flat cable 1 is made through following each operation.At first, prepare the conductive substrate 100 (base material preparatory process) that constitutes by copper or copper alloy.All characteristics such as mechanical properties such as electrical characteristics such as thermal characteristicss such as the size of conductive substrate 100, thermal conductivity, conductance, tensile strength decide according to the flexible flat cable 1 desired characteristic that will make.Then, utilize the plating method to form tin-bismuth alloy electroplating coating 60, thereby form the base material (plating operation) of band tin-bismuth alloy electroplating coating as coating on the surface of conductive substrate 100.Conductive layer 102 as coating is formed by the same material of material with above-mentioned Fig. 1 explanation.
Next, the base material of band tin-bismuth alloy electroplating coating is implemented the heat treatment (heat treatment step) of the temperature more than the fusing point of tin-bismuth alloy electroplating coating 60.In the heat treatment step, enforcement can be confirmed the heat treatment as tin-bismuth alloy electroplating coating 60 fusions of coating.Then, through behind the heat treatment step at once or in heat treatment step, with the above cooling rate of the 200 ℃/sec base material of salband tin-bismuth alloy electroplating coating (refrigerating work procedure) continuously.Thus; On conductive substrate 100, form conductive layer; Copper-Sn intermetallic compound layer 61 that constitutes by tin and copper that this conductive layer is included in that conductive substrate 100 1 sides form and the remaining tin layer 62 that on this layer, forms; Said remaining tin layer 62 must contain the bismuth that in tin, adds and dissolve in the tin and the Sn-Bi solid solution that forms and the tin and the unavoidable impurities of remainder also can contain the bismuth crystal that solid solution is fully separated out according to condition while the lattice shape that keeps tin.Further, above base material, the 1st insulating barrier is set through the band conductive layer of refrigerating work procedure, simultaneously below the 2nd insulating barrier 22 (insulating barrier formation operation) is set.Thus, can obtain the related flexible flat cable of this execution mode as shown in Figure 11.
The effect of the 1st execution mode
The related flexible flat cable of this execution mode 1 is because through be covered the surface of conductive substrate 100 of the remaining tin layer 62 that contains Sn-Bi solid solution; Therefore can in conductive layer 102, not add lead and suppress generation, the growth of tin whisker; Even whisker produces; Also can suppress to the whisker length that does not produce material injury (that is, a conductor 10 and other conductors 10 be short-circuited infringement) degree.The flexible flat cable 1 of reply RoHS instruction, REACH regulation can be provided thus.For example; Flexible flat cable 1 is being embedded under the situation of connector 5; Owing to form the conductive layer 102 that the ashbury metal by stanniferous-bismuth solid solution constitutes at least at pressures partially; Therefore conductor 10 in, under the situation of generation stress, also can suppress generation, the growth of tin whisker stressing on the conductor 10.
In addition; The flexible flat cable 1 that this execution mode is related is owing to pass through to implement heat treatment and chilling processing formation conductive layer 102 after the surface of conductive substrate 100 plates the ashbury metal of bismuth-containing; Therefore compare with the situation that adopts methods such as flash, end plating, can suppress the cost that the increase of manufacturing process causes increases.
In addition; The related flexible flat cable of this execution mode 1 is owing to be provided with coating on the surface of conductive substrate 100 through the heat treatment in the manufacturing process; Promptly considered the tin-bismuth alloy electroplating coating 60 of the thickness that conductive layer 102 flows and disappears; Therefore can suppress the phenomenon (for example, conductive substrate 100 is called as " revealing copper (red flesh) " phenomenon by the occasion that copper or copper alloy constitute) that conductive substrate 100 exposes from conductor 10 surfaces.
The 2nd execution mode
Fig. 5 representes the summary of the flexible printed board partial cross section that the 2nd execution mode of the present invention is related.
In the related flexible printed board 7 of the 2nd execution mode; Parts with parts same-sign of the flexible printed board 1 related with constituting the 1st execution mode; Also have the related parts of the 1st execution mode roughly the same structure, function,, and specify difference in this omission.
The related flexible printed board 7 of the 2nd execution mode possesses wiring circuit 12, be attached at wiring circuit 12 a face the 1st dielectric film 24 and be attached at the 2nd dielectric film 26 of another face of wiring circuit 12.That is, wiring circuit 12 is arranged between the 1st dielectric film 24 and the 2nd dielectric film 26.In addition, the conductor 10 of wiring circuit 12 and the 1st execution mode likewise has conductive substrate 100 and the conductive layer 102 that covers the conductive substrate surface.
In addition, flexible printed board 7 for example can be through making with being described below.At first, on the 1st dielectric film 24, attach the conductive substrate 100 (base material forms operation) that constitutes by copper or copper alloy.In addition, also can form conductive substrate 100 through depositing electrically conductive property material on the 1st dielectric film 24.
Then, on the conductive substrate 100 that is arranged on the 1st dielectric film 24, form the mask pattern (mask process) that the desired circuit pattern is used.Then, through formed mask pattern is implemented etch processes as mask and to conductive substrate 100, form the substrate (etching work procedure) of the circuit pattern of institute's desirable shape.Then, use the plating method in this substrate, to form tin-bismuth alloy electroplating coating 60 (plating operation).
Then, likewise implement the heat treatment (heat treatment step) of the temperature more than the plating fusing point with the 1st execution mode.Behind the heat treatment step, likewise cool off coating (refrigerating work procedure) with the above cooling rate of 200 ℃/sec with the 1st execution mode.Thus; On conductive substrate 100, form the conductive layer 102 that comprises copper-Sn intermetallic compound layer 61 that constitutes by tin and copper and the remaining tin layer 62 that on this layer, forms; Thereby constitute wiring circuit 12, the Sn-Bi solid solution that forms and solid solution and the bismuth of separating out fully while said remaining tin layer 62 contains that lattice shape that the bismuth that in tin, adds keeps tin is dissolved in the tin.Further, through with the 2nd dielectric film 26 lining wiring circuits 12, can make the related flexible printed board of the 2nd execution mode 7.
In addition, whether can not solid solution and separate out as the bismuth crystal, likewise depend on the condition such as initial stage bismuth addition and heat treatment of tin-bismuth alloy electroplating coating 60 with aforementioned flexible flat cable.
The discovery that the inventor obtains
In addition, with regard to the related flexible printed board 7 of the related flexible flat cable 1 of the 1st execution mode and the 2nd execution mode, the following discovery that obtains based on the inventor respectively, and with it as supplementary notes.
That is, the inventor is found as follows: through in the material that constitutes conductive layer 102, adding bismuth, can suppress the generation of tin whisker.Thereby can think through in constituting the material of conductive layer 102, adding the reason that bismuth can suppress the generation of tin whisker: while because in conductive layer 102, to have formed state be that bismuth keeps the lattice of tin to dissolve in the tin of this intracell and the solid solution of bismuth, so can suppress the diffusion of the tin in the conductive layer 102.
In addition; Can think in the refrigerating work procedure after forming the operation (being heat treatment step) of conductive layer 102; Through the base material with the above cooling rate salband tin-bismuth alloy electroplating coating of 200 ℃/sec, thereby the copper that can suppress conductive substrate 100 spreads in tin-bismuth alloy electroplating coating 60 and forms Cu
6Sn
5Deng intermetallic compound (can suppress to continue in the refrigerating work procedure to form copper-Sn intermetallic compound layer 61).Further, owing to can suppress thickization of particles such as tin in the conductive layer 102 through this refrigerating work procedure, thus think and can relax generation as stress in the conductive layer 102 of coating.
The inventor finds from these, as stated, has obtained suppressing the generation of whisker in the related conductive layer 102 of the 1st and the 2nd execution mode, the discovery of growth.
Embodiment 1
Make the conductor of the band tin-bismuth alloy electroplating plating that flexible flat cable uses and as the related conductor of embodiment 1.Particularly, at first make the electroplate liquid (it is the plating bath of 3 quality % that the bismuth alloy of Xiang Xizhong adds concentration) of tin-bismuth alloy electroplating.Then, be the tin-bismuth alloy electroplating coating 60 of 3 quality % through electroplating in conductive substrate 100 surface formation bismuths interpolation concentration.The temperature maintenance of this electroplate liquid at 40 ℃, is set in 100mA/cm with current density simultaneously
2, implement the plating of stipulated time and handle, be 1 μ m thereby make the thickness of tin-bismuth alloy electroplating coating 60.After conductive substrate 100 surface forms tin-bismuth alloy electroplating coating 60, be made as in temperature on 280 ℃ the plate and place the conductive substrate 100 that has formed tin-bismuth alloy electroplating coating, heated for 10 seconds.Then, the surface of confirming tin-bismuth alloy electroplating coating 60 is after the fusion, the conductive substrate that has formed tin-bismuth alloy electroplating coating 60 100 dropped in 25 ℃ the water, from water, takes out after 5 seconds.Thus, obtain implementing 1 related conductor, its surface at conductive substrate 100 has formed the conductive layer 102 that comprises copper-Sn intermetallic compound layer 61 that is made up of tin and copper and the remaining tin layer 62 that contains Sn-Bi solid solution that on this layer, forms.
Embodiment 2
Make the conductor of the band tin-bismuth alloy electroplating plating that flexible flat cable uses and as the related conductor of embodiment 2.Particularly, at first prepare the plating bath of tin-bismuth alloy electroplating (it is the plating bath of 3 quality % that the bismuth alloy of Xiang Xizhong adds concentration) remained on 250 ℃ motlten metal coating bath.Then, the conductive substrate 100 that is made up of copper that has cleaned the surface is in advance dropped in the motlten metal coating bath, implement the fusion plating.Through the dip time of adjustment conductive substrate 100 in the motlten metal plating coating groove, thereby the thickness of coating adjustment that will form on conductive substrate 100 surfaces becomes 1 μ m.Behind the fusion plating, to add concentration be that the conductive substrate 100 of the tin-bismuth alloy electroplating coating 60 of 3 quality % is placed on temperature and is made as on 280 ℃ the plate with having formed bismuth, heated for 10 seconds.Then, the surface of confirming coating is after the fusion, the conductive substrate that has formed coating 100 dropped in 25 ℃ the water, from water, takes out after 5 seconds.Thus; Obtain implementing 2 related conductors, its surface at conductive substrate 100 has formed the conductive layer 102 that comprises copper-Sn intermetallic compound layer 61 that is made up of tin and copper and the remaining tin layer 62 that contains Sn-Bi solid solution and unavoidable impurities that on this layer, forms.
Embodiment 3
About heat treatment temperature
As the temperature of heat treatment step, confirm to be suitable for the temperature more than the fusing point of Sn-Bi solid solution like the following stated ground.
At first, preparation has implemented to add the sample of the tin-bismuth alloy electroplating coating 60 of 3 quality % bismuths on test film made of copper surface.Then, with the condition of explanation among embodiment 1 and the embodiment 2 likewise, this sample of placement and heating for 10 seconds on 280 ℃ of plates that heats of the temperature more than the fusing point of Sn-Bi solid solution.Then, confirm coating surface after the fusion, this sample is dropped in 25 ℃ the water, from water, take out this sample after 5 seconds.Thus, obtain the related sample of embodiment 3.
On the other hand, as comparative example, preparation has implemented to add the related sample of comparative example of the tin-bismuth alloy electroplating coating 60 of 3 quality % bismuths on test film made of copper surface.Then, the sample related to comparative example implemented 5 minutes heat treatment at each temperature 150 ℃, 180 ℃, 210 ℃ of the temperature of the fusing point of not enough Sn-Bi solid solution.Then, after the heat treatment, cool off, process the related sample of comparative example respectively through dropping in 25 ℃ the water.Will be at the sample of 150 ℃ of heating as the related sample of comparative example 1, will be at the sample of 180 ℃ of heating as the related sample of comparative example 2, and will be at the sample of 210 ℃ of heating as the related sample of comparative example 3.
The related sample of respectively that embodiment 3 is related sample and comparative example 1～3 is chimeric with the connector of 100 plugs that are used for flexible flat cable, at room temperature places for 2 weeks.Afterwards, take out each sample, through quantity and the extreme length of determination of electron microscopy at the whisker of the periphery generation of chimeric trace from connector.Its result is shown in table 1.In addition, the generation rate of whisker is obtained by the calculating formula of (the plug number that whisker produces)/(sum of plug).
Table 1
| Embodiment 3 | Comparative example 1 | Comparative example 2 | Comparative example 3 | |
| Heat-treat condition | 280 ℃ * 10 seconds | 150 ℃ * 5 minutes | 180 ℃ * 5 minutes | 210 ℃ * 5 minutes |
| Whisker generation rate (%) | 21 | 56 | 37 | 30 |
| The longest whisker length (μ m) | 11 | 28 | 12 | 15 |
With reference to table 1, it is as shown in the table, and the heat treatment of adopting among the embodiment 3 of passing through the temperature more than the fusing point of tin-bismuth alloy electroplating coating can make the generation rate less than 25% of whisker, and can also make the longest whisker length is 11 μ m.On the other hand; With reference to the result of comparative example 1～3, for heat treatment, though implemented the heating of 3 longer times than embodiment in the temperature of the fusing point of not enough tin-bismuth alloy electroplating coating; But the generation rate of whisker is more than 30%, and the longest whisker length also is more than the 12 μ m.This shows the temperature that the fusing point of the preferred tin-bismuth alloy electroplating coating of heat treatment temperature is above.
Embodiment 4
About the interpolation concentration of bismuth, the lattice constant and the unit cell volume of Sn-Bi
Confirm interpolation concentration, the lattice constant of Sn-Bi and the optimum condition of unit cell volume of bismuth like the following stated ground.
At first, preparation has implemented in pure tin, to add the sample of the tin-bismuth alloy electroplating coating 60 of 3 quality % bismuths on test film made of copper surface.Then, likewise this sample is implemented heat treatment and cooling processing, obtain the related sample of embodiment 4 with embodiment 1～3.On the other hand, as the related sample of comparative example, preparing to have implemented bismuth interpolation concentration respectively is the sample of bismuth-tin alloy coat 60 of 1 quality %, 5 quality %, 10 quality %.Then, likewise these samples are implemented heat treatment and cooling processing, thereby obtain the related sample of comparative example 4～6 with embodiment 1～3.It is 1 quality % that the bismuth of the sample that comparative example 4 is related adds concentration, and it is 5 quality % that the bismuth of the sample that comparative example 5 is related adds concentration, and it is 10 quality % that the bismuth of the sample that comparative example 6 is related adds concentration.
The related sample of respectively that embodiment 4 is related sample and comparative example 4～6 is chimeric with the connector of 100 plugs that are used for flexible flat cable, at room temperature places for 2 weeks.Afterwards, take out each sample, through quantity and the extreme length of determination of electron microscopy at the whisker of the periphery generation of chimeric trace from connector.In addition, use the X-ray diffraction device to measure the related sample of embodiment 4 and comparative example 4～6, calculate lattice constant and unit cell volume from diffraction pattern.Its result is shown in table 2.
Table 2
| Embodiment 4 | Comparative example 4 | Comparative example 5 | Comparative example 6 | |
| Bismuth adds concentration (weight %) | 3 | 1 | 5 | 10 |
| A shaft lattice constant (nm) | 0.58458 | 0.58387 | 0.58432 | 0.58438 |
| C shaft lattice constant (nm) | 0.31856 | 0.31842 | 0.3188 | 0.31875 |
| Unit cell volume (nm 3) | 0.10886 | 0.10855 | 0.10885 | 0.10885 |
| Whisker generation rate (%) | 16 | 31 | 16 | 7 |
| The longest whisker length (μ m) | 10 | 16 | 10 | 6 |
With reference to table 2, add the variation of concentration corresponding to the bismuth in the tin-bismuth alloy electroplating coating 60, the value of the lattice constant of remaining tin layer 62, the value of unit cell volume change, and add concentration and are 5 quality % and be roughly certain value when above.In addition, the generation quantity of whisker and the longest whisker length reduce along with the increase of adding concentration.It is 5 quality % when above that bismuth adds concentration, can confirm to have separated out the bismuth crystal from the parsing of the X-ray diffraction pattern of remaining tin layer 62.When separating out the bismuth crystal, though generation that can inhibition of whiskers, coating has the tendency that hardening becomes fragile.For the flexible flat cable that possesses the conductive layer that contains the bismuth crystal, flexible printed board, really up to the mark, crisp excessively if coating becomes, then can become is not easy operation.This shows that the bismuth in the pure tin adds concentration and is preferably below the above 10 quality % of 3 quality %.
Embodiment 5
About cooling rate
Confirm the optimum condition of the cooling rate of refrigerating work procedure with being described below.
At first, preparing to have implemented bismuth interpolation concentration on test film made of copper surface is the sample of the tin-bismuth alloy electroplating coating 60 of 3 quality %.Then, through this sample being implemented heat treatment in 10 seconds, and cool off, obtain the related sample of embodiment 5 with the above cooling rate of 200 ℃/sec at 280 ℃.On the other hand, as the related sample of comparative example, through cooling rate is adjusted into 50 ℃/sec, 2 ℃/sec cools off, obtain comparative example 7 (cooling rate: 50 ℃/sec) with comparative example 8 (cooling rate: 2 ℃/sec) related sample.
The related sample of respectively that embodiment 5 is related sample and comparative example 7～8 is chimeric with the connector of 100 plugs that are used for flexible flat cable, at room temperature places for 2 weeks.Afterwards, take out each sample, through quantity and the extreme length of determination of electron microscopy at the whisker of the periphery generation of chimeric trace from connector.Its result is shown in table 3.
Table 3
| Embodiment 5 | Comparative example 7 | Comparative example 8 | |
| Cooling rate (℃/sec) | 200 | 50 | 2 |
| Whisker generation rate (%) | 19 | 25 | 29 |
| The longest whisker length (μ m) | 12 | 13 | 16 |
With reference to table 3, for the related sample of the comparative example that cools off with the cooling rate slower than the cooling rate of embodiment 5 7～8, the longest whisker length is more than the 13 μ m.In addition, the generation rate of whisker is below 20% in embodiment 5, and is more than 25% in comparative example 7～8.This shows, the chilling temperature of refrigerating work procedure be preferably 200 ℃/more than the sec.
Execution mode of the present invention and embodiment more than have been described, but the execution mode of above-mentioned record and embodiment do not limit the related invention of the scope of claim.In addition, the whole methods that are combined in the problem that is used for solving invention that should be noted that the characteristic explained among execution mode and the embodiment are not necessarily necessary.
Claims (16)
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| CN104918548A (en) * | 2013-01-29 | 2015-09-16 | 麦迪盖德有限公司 | Shielded twisted pair of conductors using conductive ink |
| CN109308953A (en) * | 2017-07-28 | 2019-02-05 | Smk株式会社 | Photoelectric composite cable |
| CN112453352A (en) * | 2020-12-14 | 2021-03-09 | 江苏金合益复合新材料有限公司 | Preparation method of flexible flat belt continuous casting copper-clad steel |
| CN112951509A (en) * | 2021-01-26 | 2021-06-11 | 北京大学东莞光电研究院 | Flexible flexible flat cable electroplating method |
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| US10973128B2 (en) | 2017-08-30 | 2021-04-06 | Panasonic Intellectual Property Management Co., Ltd. | Flexible printed circuit and imaging apparatus including same |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN104918548A (en) * | 2013-01-29 | 2015-09-16 | 麦迪盖德有限公司 | Shielded twisted pair of conductors using conductive ink |
| US10111599B2 (en) | 2013-01-29 | 2018-10-30 | St. Jude Medical International Holding S.À R.L. | Shielded twisted pair of conductors using conductive ink |
| US10433747B2 (en) | 2013-01-29 | 2019-10-08 | St. Jude Medical International Holding S.À R.L. | Shielded twisted pair of conductors using conductive ink |
| CN109308953A (en) * | 2017-07-28 | 2019-02-05 | Smk株式会社 | Photoelectric composite cable |
| CN112453352A (en) * | 2020-12-14 | 2021-03-09 | 江苏金合益复合新材料有限公司 | Preparation method of flexible flat belt continuous casting copper-clad steel |
| CN112453352B (en) * | 2020-12-14 | 2022-04-15 | 江苏金合益复合新材料有限公司 | A kind of preparation method of flexible flat belt continuous casting copper clad steel |
| CN112951509A (en) * | 2021-01-26 | 2021-06-11 | 北京大学东莞光电研究院 | Flexible flexible flat cable electroplating method |
| CN112951509B (en) * | 2021-01-26 | 2022-04-29 | 北京大学东莞光电研究院 | Flexible flexible flat cable electroplating method |
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