CN87100618A

CN87100618A - Insulated aluminum wire

Info

Publication number: CN87100618A
Application number: CN 87100618
Authority: CN
Inventors: 亚利山大·约瑟夫·奥托; 哈里·商
Original assignee: Alcan International Ltd Canada
Current assignee: Rio Tinto Alcan International Ltd
Priority date: 1986-02-06
Filing date: 1987-02-05
Publication date: 1987-08-19
Also published as: JPS62217507A; GB8602927D0; EP0237154A1

Abstract

Insulated aluminum wire provided by the invention, its insulation comprise or the anodised aluminium barrier layer (non-porous) of individual layer, or two layers, that is, and the aluminium oxide skin of an internal barrier anode oxide film and a hydration.Insulated wire can for example carry out anodic oxidation with aluminium or aluminum/magnesium alloy in the tartaric barrier-layer electrolyte by mat continuously, then anodised lead is exposed in the hot water with hydration anode oxide film partly and makes.

Description

Insulated aluminum wire

The present invention relates to come the aluminum steel of electric insulation with anode oxide film.This lead has many different purposes in microelectronics technology.For example, very thin aluminium is generally used for the terminal of integrated circuit is connected with lead frame with the auri lead.Connect or connect or fetch and finish with ball-wedge bonding with wedge-wedge bonding.The gold thread or the aluminum steel that use in welding at present do not insulate.Yet, for the sealing wire of insulation special needs are arranged, especially for very lagre scale integrated circuit (VLSIC), need many chips and lead frame be coupled together with the sealing wire of insulation.

The existence of this needs is because naked sealing wire must avoid lead to contact with lead and lead and circuit contacts when chip is connected to lead frame to a certain extent.Because lead must be at interval be linked to be the loop very greatly and carefully so that will they and they around isolation, this has limited the possible number of leads of chip strictly.Suitably in fact Jue Yuan sealing wire can relax strict how much requirements that are linked to be loop and conductor spacing, because lead and lead and lead and circuit contacts will not cause circuit to break down.

Insulated conductor does not use in welding now because of two reasons.The first, known insulating material and the same lead bondability that seriously damages of dust on the conductive line surfaces on the conductive line surfaces.The second, with common wire insulation materials such as plastics, it is very difficult that the very thin lead that insulate has satisfactorily proved.

Germany patent application DE3335848A discloses and a kind of insulated aluminum wire has been connected to the method for the contact of electronic circuit, and this method relates to the use ultrasonic vibration.Insulated aluminum wire is called for short makes the anodization aluminum steel, and it comprises the pellumina of 0.1 to 1 micron of an aluminium core that 30 to 60 micron diameters are arranged and a bed thickness." pellumina " layer is interpreted as sealing porous anode oxide film.In our processing, the insulating barrier that is provided by this layer is applied to microelectric technique and has proved not enough at large.

To constitute improvement design of the present invention in order illustrating, at first to need to discuss tout court anodised character.Be placed in the electrolyte when an aluminium matter substrate and during as anode, form an oxide-film from the teeth outwards, mat metal on the metal/oxide interface converts oxide to and increases its thickness.According to varying environment, can form two kinds of different anode oxide films:

ⅰ) when electrolyte has significant dissolution to aluminium oxide, form porous anodic oxide film.This comprise a barrier layer that one deck of adjacent metal/oxide interface is thin and a bed thickness many porous layers, in porous layer, have pore to be diffused into the barrier layer from oxide/electrolyte interface.The continuous growth of oxide-film relates to transportation of substances pore up and down, and the final thickness of film mainly is to depend on the anodised time.

ⅱ) when the electrolyte that uses does not have significant dissolution to oxide, form the non-porous or positive retaining layer of one deck anode oxide film.The thickness of this tunic mainly is to depend on anodic oxidation voltage, and generally is 1.0 to 1.4 millimicrons of every volts.

The anodic oxidation of nearly all industry is to draw under the condition of porous anodic oxide film, uses chromic acid, sulfuric acid or oxalic acid to carry out.For most of purposes, the pore in these films needs sealing, and this finishes with the method that film is exposed in the boiling water usually, and boiling water hydration surface alumina oxide makes its protuberance, so that stop up pore in their outer end.Pellumina is a technical term that is applied to this sealing porous anode oxide film.

Barrier film is widely used in electrolytic capacitor as insulator.The present invention is based upon and finds in fact followingly, and promptly non-porous or barrier layer anode oxide film can be formed on the aluminum steel, and this not only provides good insulation performance that other useful characteristics also are provided.An aspect the invention provides the insulated aluminum wire that comprises barrier layer anode oxide film insulation.Under suitable environment, this insulated aluminum wire can satisfy the needs of microelectric technique industry.Yet,, insulation property are further improved by the part barrier layer is converted to alumina hydrate.Therefore in yet another aspect, the invention provides the insulated aluminum wire that comprises one deck internal barriers anode oxide film and the outer field two layers of insulation of one deck hydrated alumina.This product demonstrates the improvement of insulation property in the environment of drying, and performance in a humid environment has less adverse influence.

The common diameter range of aluminum steel is from 10 to 1000 microns.The lead that uses in microelectric technique industry at present, general diameter is 25 to 30 or 100 to 400 microns.Diameter is not easy to make at the line below 10 microns.At the line of diameter more than 1000 microns, can prove with the additive method insulation more attractive.

Lead can be with fine aluminium or aluminium alloy manufacturing.The intensity that fine aluminium can be used in lead is not most important place, and has the advantage that can form smooth flawless anode oxide film in the above.Aluminium-1%-silicon line typically uses in microelectric technique industry, and can be used for making insulated wire of the present invention.But it comprises silicon phase particle, and this particle can form defective on the surface of lead in anodised process.At most cases, this defective is inessential.Relevant when critical when defective, preferably adopt single-phase aluminium alloy, aluminium-1%-magnesium for example, it is than fine aluminium intensity height, and is to be used for best alloy of the present invention.The attendant advantages of almag is that the anode oxide film that forms is more crisp, the help welding that can followingly chat face to face and state.

Reach significant electric insulation, the barrier layer anode oxide film should be 0.01 micron thickness at least.It is inconvenient making the barrier film that surpasses about 0.3 micron thickness, because under the high anode oxidation voltage that requires, dielectric can puncture.The scope of the optimum thickness of barrier film generally is 0.1 to 0.25 micron.

As noted above, when the barrier layer anode oxide film is exposed in heat or the boiling water, that outer surface becomes hydration and be subjected to suitable expansion.Chemical change is complicated, but being summarised as of can being similar to:

Gamma-Al ₂O ₃+ H ₂O → Al ₂O ₃H ₂O.

Resulting film has a two-layer structure, comprises an internal barrier anode oxide film, and this film preferably should be from 0.01 to 0.15 micron thickness, though there is not strict lower limit on the thickness; And the skin of monohydrate alumina, this layer generally can from 0.01 to 0.8 micron, is more typically from 0.1 to 0.5 micron thickness.Extremely thin aqua oxidation aluminium lamination can not improve the insulation property of barrier film significantly.Because the spallation danger of association is arranged, make the aqua oxidation aluminium lamination that surpasses 0.8 micron thickness and not exclusively the hydration internal barrier be inconvenient.

Insulated wire mat anodised aluminium line under suitable condition forms.Electrolyte is a kind of electrolyte that aluminium oxide is not had remarkable dissolution under selected anodic oxidation condition.We find, can use a kind of weak (by weight up to 5%) tartaric acid solution easily, be buffered to one from 5 to 7 pH value with ammonium hydroxide, but it is well-known, also can use other acid such as oxalic acid, citric acid and boric acid, and, buffer, other concentration and other the pH value scope of suitable other arranged also for these acid.The anodised technology in barrier layer has introduction flat the receiving of for example S. Wei Nike (S.Wernick) and R. in " surface treatment of aluminium " literary composition that (R.Pinner) shown.

Electrolyte is suitable for being placed under the atmospheric temperature.The voltage that applies should be high enough to guarantee the film ramp, rather than the high dielectric breakdown that must make film.Electrolysis time should be enough to make anode film thickness energy near theoretical maximum, and generally can be in 15 to 60 seconds scope.Anodic oxidation is easily to carry out on the quantity-produced basis under these conditions, when making lead pass through a groove electrolyte on guide groove process, one of guide groove also serves as electrical current carriers.

After the anodic oxidation, lead is rinsed, and can be placed in the hot water then, so that make the outer surface hydration of alumina barrier layer.Water temperature generally is at least 80 ℃, but for fear of damaging anodic oxide coating owing to bubble, water had better not seethe with excitement.In the technology of sealing porous anode oxide film, well-known, can doping in the water to promote aquation.The degree of alumina hydration effect depends on that especially it is exposed to the duration in the hot water.Open-assembly time may obtain satisfied aqua oxidation aluminium lamination, and not destroy the internal barrier anode oxide film fully from 5 or preferably from 10 to 120 seconds.

For example, have the lead of the nascent oxide-film of 0.17 micron thickness, be dipped in the boiling water about 40 seconds, formation is about the second layer hydrated oxide layer of 0.5 micron thickness on 0.08 micron nascent oxide of remainder.

With accompanying drawing the present invention is described, wherein:

Fig. 1 is the ideal profile figure that passes through SI semi-insulation aluminum steel of the present invention of magnification ratio; And

Fig. 2 is its terminal is linked to the microcircuit of lead frame with fine rule a top view.

Consult Fig. 1, lametta 10 is to be made by aluminium-1%-magnesium alloy, has on its surface to comprise two layers insulation. Internal barrier anode oxide film 12 is to cover by being approximately four times of thick hydrated aluminas of internal layer outer 14. In anode oxidation process, it is to carry out at 16 places, metal/oxide interface that metal transition becomes oxide. The aquation of aluminium oxide is to be begun to carry out by oxide/air or oxide/liquid surface 18.

Fig. 2 represent one comprise by a series of little contacts 24 round the chip 20 of microcircuit 22, each little contact is to be connected to pad 28 on the lead frame 30 with fine aluminum wire 26. All lead major parts are parallel to each other, but have two pairs to intersect 32 among the figure, and contact with each other, and they need to insulate for this reason, break down avoiding.

Line 26 is to use routinely sphenocephaly to carry out to

corresponding contact

24,28 welding, and line passes sphenocephaly and is depressed at contact, vibrates then to spread out metal wire it is adhered on the contact. There is on line insulation just can not realize reliably adhering to. So it is enough crisp requiring the form of insulation, just can come off when needed, in order to stay naked metal end, this naked metal end energy mat wedge bonder spreads out and makes it adhere to contact. It is enough crisp being found this purposes at the dielectric film of this narration. Really, the anode oxide film that forms at almag is known to be more crisp.

The resistance of microelectronics industry requires can depict as shown in Figure 2 to sentence the overlapping two wires of X pattern 32, so that top line is to contact and press down bottom line with bottom line with enough power, makes the bottom line bending. The two-lines of contact conducts electricity in the time of 20 volts and should not surpass 10 like this^-12Peace, and breakdown voltage should be at minimum numerical value for example more than 20 volts, but it depends on the purposes of appointment.

Now the present invention is described with following Example.

As 35 micron diameters aluminium-1%-magnesium line of figure is to clean with electrochemical method in high solutions of chlorine and attenuate (electrobrightening) till its diameter is 30 microns.The anodic oxidation of this line be at room temperature with 105 volts down have pH value be 6 3%(by weight) carry out in tartaric acid/Ammonia, to form the sun retaining layer anode oxide film of about 0.13 micron thickness.During this continuous anodic oxidation operation, before entering solution, lead is pulled through a charged pulley.Lead is to be pulled through solution with time of staying of 40 seconds.

When leaving solution, lead is to wash in water.Then, lead also is pulled through in 98 ℃ water continuously with time of staying of 35 seconds.Wash and hydration barrier layer anode oxide film like this.One group of sample is not by hydration.

The sample of these lines, with some bonding machines on thick film gold by wedge bonding.Wedge-wedge bonding intensity approximately is 15 to restrain-be better than more than the 12 gram lower limits, and this lower limit is that microelectric technique industry is high-quality device requirement.The lower wedge bonding intensity that depends on purposes can be low to moderate 8 grams, even the .25 gram also can be qualified.To leakage current between the contact wire of barrier layer hydration and unhydrated anode oxide film all is to test under 40 volts condition.

For the sample of hydration, after 60 seconds, the leakage current of Line To Line is 7 * 10 in the nitrogen of drying ^-13Peace.For unhydrated sample, after 60 seconds, the leakage current of Line To Line is 2 * 10 in the nitrogen of drying ^-12Peace.

Claims

1, insulated aluminum wire is characterized in that, insulating barrier comprises a barrier layer anode oxide film.

2, the described insulated aluminum wire of claim 1 is characterized in that, the average thickness of barrier film is from 0.1 to 0.25 micron.

3, insulated aluminum wire is characterized in that, insulating barrier comprises two layers, the aluminium oxide skin of an internal barrier anode oxide film and a hydration.

4, the described insulated aluminum wire of claim 3 is characterized in that, internal barrier is 0.01 micron at least, and the aluminium oxide skin of hydration is from 0.001 to 0.8 micron.

5, the described insulated aluminum wire of arbitrary claim of claim 1 to 4 is characterized in that, lead is to be made by fine aluminium or a kind of single-phase rich aluminium alloy.

6, the described insulated aluminum wire of claim 5 is characterized in that, lead is to be made by a kind of single-phase aluminum/magnesium alloy.

7, a kind of microelectronic component that comprises at least one integrated circuit and at least one lead frame is characterized in that, carries out integrated circuit and lead frame being connected to each other with the described insulated aluminum wire of arbitrary claim of claim 1 to 6.

8, a kind of method of making insulated aluminum wire, it is characterized in that this method comprises: aluminum steel stands anodic oxidation in electrolyte, this electrolyte does not have significant solvability to aluminium oxide, the result forms a barrier layer anode oxide film thereon, then anodised line is exposed in the hot water, with this film of hydration partly and form the aluminium oxide skin of a hydration thereon.

9, the described method of claim 8 is characterized in that, lead is continuously successively by the groove of anodic oxidation electrolyte is housed, and passes through hot water storgae then.