JP2002289652A - Semiconductor device tape carrier and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent excess melting of copper of a lead wire in a lower part of a solder resist and suppress the whisker of tin plating in a semiconductor device tape carrier. SOLUTION: The solder resist 6 is applied in a position except its terminal portion on a copper foil wiring pattern 3 which is formed on a dielectric film 1 via an adhesive layer 2, thereafter, a thin tin-plated layer of 0.01 to 0.2 μm in thickness is formed on the terminal portion as first tin plating treatment, and a pure tin layer 4a and a tin-copper alloy layer 5a of 0.20 μm or less are formed by heat treatment. Then, a pure tin plating layer of 0.15 to 0.80 μm in thickness is formed on the terminal portion as a second tin plating treatment, and a pure tin layer 4b of 0.15 to 0.80 μm in thickness and a tin-copper alloy layer 5b of 0.20 μm or more in thickness are formed by heat treatment.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tape carrier for semiconductor devices such as a TAB tape carrier, which is a precision electronic component, and more particularly, to tin plating on a wiring pattern of a copper foil when copper is solder resisted. And a tin plating method.

[0002]

2. Description of the Related Art The structure of a conventional TAB tape carrier is as follows.
As shown in FIG. 2, a predetermined wiring pattern 3 is formed on a copper foil bonded to an insulating film 1 made of a polyimide resin via an adhesive layer 2 (FIG. 2A). Then, a solder resist 6 is printed and applied as an insulating layer at a predetermined position except for the terminal portions such as the copper leads 3a (FIG. 2B). The pure tin plating layer 4 is formed by electroless tin plating in order to provide the improved bonding property.
FIG. 2C shows a structure in which a tin-copper alloy layer 5 is formed by a heat treatment (FIG. 2D).

[0003] The work of mounting the TAB tape carrier on a semiconductor device is performed, for example, as shown in FIG.
The C chip 7 is arranged so as to be located in the device hole, and the inner lead projecting into the device hole and the electrode of the semiconductor element 7 are aligned, and then pressure-bonded by a bonding tool. Gold bumps 8 are formed on the electrodes of the semiconductor element 7, and when pressed against the copper leads 3a in a heated state, the tin plating melts to form a gold-tin alloy,
The electrode and the inner lead are joined.

[0004]

In general, tin plating is
It is widely used in electronic components because of its excellent corrosion resistance and solderability.

However, in the above-described conventional TAB tape carrier, when electroless tin plating is performed, as shown in FIG. 4, copper excessively dissolves at the edge (end) below the solder resist 6, There is a problem that a groove-eroded portion (excess melting portion 9) is formed in the copper lead 3a, and the lead strength is reduced.

In general, electroless tin plating is precipitated by substitution with copper. In this case, the pretreatment liquid for electroless tin plating hardly penetrates below the solder resist, and organic substances and contaminants remain on the copper surface. At the time of electroless tin plating, the reaction speed is remarkably increased, and copper is excessively dissolved.

[0007] More recently, the demand for fine wiring patterning has become stronger, and the plating area has become smaller.
A difference occurs in the reaction rate during electroless tin plating. In particular, the reaction rate of the electroless tin plating is increased in the fine part, and the copper is excessively dissolved to lower the lead strength.

As another problem, it is well known that whiskers (whisker-like crystals) are generated when the tin plating film is left immediately after tin plating, and the generation of whiskers is a cause of short-circuit especially in a fine pitch pattern. Because
Various studies have been made. As means for suppressing tin whiskers, (1) nickel, copper,
Form a lead, solder, tin-nickel alloy, tin-copper alloy layer. (2) Perform reflow treatment after plating. (3) Anneal by heating after plating. (4) Change the tin plating to another tin-alloy plating or another metal plating. (5) Change to tin plating that contains several percent or more lead. Etc. are known.

However, the method of (1) for applying the undercoating increases the cost because the undercoating step is provided. In the method (2) of performing reflow treatment after plating, even if thick and uniform plating is performed first, the plating thickness varies after reflow, and furthermore, there arises a problem that the tin plating surface is oxidized. The method of performing the annealing treatment after the plating of the above (3) has an effect of suppressing whiskers in a short period of time, but cannot completely prevent whisker growth in a long period of about 6 months. There is a problem that should not be. the above
In the methods (4) and (5), gold plating and solder plating are sometimes performed. However, gold plating has a high cost, and solder plating has problems such as difficulty in controlling the plating film composition and film thickness.

Accordingly, an object of the present invention is to solve the above-mentioned problems, to prevent excessive dissolution of copper in a lead wiring below a solder resist, that is, to prevent copper from being eroded at the time of a solder resist, and to perform base plating or alloy plating. Without any cost,
It is another object of the present invention to provide a highly reliable tin-plated semiconductor device tape carrier having a tin-plated structure and capable of suppressing tin-plated whiskers without impairing the tin-plated characteristics, and a method of manufacturing the same.

[0011]

Means for Solving the Problems In order to achieve the above object, the present invention is configured as follows.

(1) The tape carrier for a semiconductor device according to the first aspect of the present invention is provided on a copper foil wiring pattern formed on an insulating film via an adhesive layer, at a predetermined position excluding a terminal portion thereof. A solder resist is applied, and a thin tin plating layer having a thickness of 0.01 to 0.2 μm is formed on the terminal portion, and a heat treatment is performed.
A tin-copper alloy layer having a thickness of 0.1 μm or less is formed, and a pure tin plating layer having a thickness of 0.15 to 0.80 μm is further formed thereon.

(2) The tape carrier for a semiconductor device according to the first aspect of the present invention, wherein the pure tin plating layer is heat-treated to have a thickness of 0.15 to 0.8.
It is characterized in that a pure tin layer having a thickness of 0 μm and a tin-copper alloy layer having a thickness of 0.20 μm or more are formed.

(3) The method for manufacturing a tape carrier for a semiconductor device according to the third aspect of the present invention is a method for manufacturing a tape carrier for a semiconductor device, the method comprising the steps of: After applying a solder resist to the position of the above, as a first tin plating process on the terminal portion,
Apply a thin tin plating layer with a thickness of 0.01 to 0.2 μm,
By heating, pure tin layer and thickness 0.20μm
The following tin-copper alloy layer is formed, and then, as a second tin plating process, a pure tin plating layer having a thickness of 0.15 to 0.80 μm is formed on the terminal portion, followed by heat treatment. A pure tin layer having a thickness of 0.15 to 0.80 μm and a tin-copper alloy layer having a thickness of 0.20 μm or more.

(4) The invention according to claim 4 is the manufacturing method according to claim 3, wherein a pure tin plating layer having a thickness of 0.3 to 0.6 μm is formed as the second tin plating treatment. By heat treatment, a thickness of 0.25 to 0.30
μm pure tin layer and 0.20 to 0.25 μm thick tin
It is characterized by forming a copper alloy layer.

(5) The invention of claim 5 is the invention of claim 3 or 4
In the manufacturing method described above, the first tin plating process and the second tin plating process are performed by electroless plating.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on the illustrated embodiment.

FIG. 1 shows a method of manufacturing a TAB tape carrier as an example of a tape carrier for a semiconductor device according to the present invention. First, a predetermined photoresist is applied to a tape carrier on which a copper foil is formed on a polyimide resin insulating film 1 via an adhesive layer 2 and dried, and then exposed through a photomask having a predetermined wiring lead pattern. ,
After the development, etching is performed to obtain FIG.
A predetermined fine wiring pattern 3 is formed as shown in FIG.

Next, as shown in FIG. 1 (b), a part of the copper pattern of the tape carrier in which the copper fine wiring pattern 3 is formed on the polyimide-polyimide insulating film 1, that is, on the copper pattern, Solder resist 6 is placed at a predetermined position excluding terminal portions such as copper leads 3a.
Is applied by a printing method.

Next, as shown in FIG. 1C, a thin tin plating layer having a thickness of 0.01 to 0.2 μm is formed on the terminal portion such as the copper lead 3a as a first tin plating process. Then, by performing a heat treatment at 130 ° C. for 10 minutes, copper is diffused into the tin plating layer, and a tin plating layer containing substantially no copper, that is, a pure tin layer 4a and a thickness of 0.20 μm or less are formed. Copper diffusion tin plating layer, ie tin-
The copper alloy layer 5a is formed.

Thereafter, as shown in FIG. 1 (d), a pure tin is formed on the terminal portion (copper lead 3a, etc.) of the tape carrier, that is, on the first tin plating layer as a second tin plating process. A tin plating layer is formed with a thickness of 0.15 to 0.80 μm, and heat treatment is performed at 100 to 150 ° C. for 5 to 90 minutes to diffuse copper into the tin plating layer, and a thickness of 0. A substantially copper-free tin plating layer having a thickness of 15 to 0.80 μm, that is, a pure tin layer 4b;
A copper diffusion tin plating layer of 0 μm or more, that is, a tin-copper alloy layer 5b is formed.

FIG. 1E shows a state in which the surface of the copper lead 3a finally has a layer structure of the pure tin plating layer 4 and the tin-copper alloy layer 5.

The TAB tape carrier formed in this manner is thinly tin-plated during the first tin plating process. Therefore, even if the solder resist 6 is present, the excessively dissolved copper locally exists. The degree to which 9 is formed is practically negligible. Then, at the time of the second tin plating, even if the plating solution enters the lower surface of the solder resist 6, the tin-copper alloy layer 5a is formed on the copper surface, and the copper foil may not come into contact with the plating solution. Since there is no,
Local electrolytic corrosion does not occur, and therefore, the excessive copper dissolution portion 9 shown in FIG. 4 is not formed on the copper lead 3a. Therefore, it is possible to eliminate the inconvenience that the copper lead 3a has the excessively melted copper 9 and the strength of the copper lead 3a is weakened.

In the above-described TAB tape carrier manufacturing method, the heat treatment after the first tin plating may not be performed, and only the pure tin layer 4a may be formed.

The thickness of the first thin tin plating layer is 0.0
1 to 0.2 μm is preferred. When the thickness of the first thin tin plating layer exceeds 0.2 μm, the effect of suppressing whiskers is reduced, and the possibility of excessive dissolution of copper (excess dissolution portion 9) described with reference to FIG. 4 is increased. Because.

On the other hand, the reason for setting the thickness of the pure tin layer 4 in the second tin plating process to 0.15 to 0.80 μm is as follows.
If the thickness is less than 0.15 μm, the bonding property of the inner lead becomes difficult, and if the thickness exceeds 0.8 μm, the plating will be dripped and cause a short circuit. Further, the thickness of the tin-copper alloy layer 5 by the second tin plating treatment is set to 0.20 μm.
The reason for setting m or more is that if it is less than 0.20 μm, the whisker suppression effect becomes insufficient.

The mounting operation of the TAB tape carrier on a semiconductor device is performed, for example, as shown in FIG.
The C chip 7 is arranged so as to be located in the device hole, and the inner lead projecting into the device hole and the electrode of the semiconductor element 7 are aligned, and then pressure-bonded by a bonding tool. Gold bumps 8 are formed on the electrodes of the semiconductor element 7, and when pressed against the copper leads 3a in a heated state, the tin plating melts to form a gold-tin alloy,
The electrode and the inner lead are firmly joined.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A predetermined resist is applied to a tape carrier of 25 μm copper foil formed on a polyimide resin insulating film 1 via an adhesive layer 2 and dried, and then a photo having a predetermined wiring lead pattern is formed. After exposure and development through a mask, etching was performed to produce a lead pattern.

First, a solder resist 6 is printed on a part of a copper wiring pattern of a tape carrier for a semiconductor device in which a fine copper pattern 3 is formed on a polyimide resin insulating film 1, and then a first tin plating process is performed. To form a tin plating layer of 0.01 to 0.2 μm,
The heat treatment was performed at 00 ° C to 150 ° C for 5 minutes to 90 minutes to form a pure tin layer 4a and a tin-copper alloy layer 5a.

Next, as a second tin plating treatment, a pure tin plating layer is formed in a thickness of 0.3 to 0.6 μm,
Pure tin layer 4b by heat treatment at 50 ° C. for 5 to 90 minutes
Is 0.2 to 0.3 μm, and the tin-copper alloy layer 5b is 0.15
One having a thickness of 0.25 μm was prepared.

Here, the tin plating may be formed by either electrolytic or electroless plating, but the electroless plating is used because the plating thickness has less variation.

The electroless tin plating solution is 580M manufactured by Ishihara Chemical Co., Ltd.
And treated at 70 ° C. for 5 to 500 s. After the first tin plating, heat treatment is performed at 100 to 150 ° C. for 5 to 90 minutes, and the heat treatment after the second tin plating is performed at 100 to 150 ° C.
Heated for 5 to 90 minutes. With respect to the sample thus manufactured, the excess solubility of copper was evaluated by cross-sectional observation. The results are shown in Table 1 as tin plating conditions and copper excess solubility evaluation results.

[0033]

[Table 1]

As can be seen from Table 1, when the first tin plating thickness was in the range of 0.01 to 0.2 μm, no excessive dissolution of copper was observed. On the other hand, the case where only the electroless tin plating corresponding to the second tin plating treatment was performed after the solder resist printing like the sample 1 (the case without the first tin plating treatment), and the case where the first When the tin plating thickness was 0.2 μm or more, excessive dissolution of copper was observed.

Next, the thickness of pure tin plating is
Measure the total tin thickness with a fluorescent X-ray film thickness meter, (total tin thickness)
(Pure tin thickness) is subtracted from the above to determine the thickness of the tin-copper alloy layer, and from January to June (30 days, 60 days, 90 days, 180 days)
Day) The whiskers were observed for each of the 150 inner leads after standing by using an optical microscope of 200 times, and the number of whiskers generated was counted. Table 2 shows the tin plating conditions, tin plating thickness and whisker evaluation results.
As can be seen from Table 2, when the tin-copper alloy layer was less than 0.20 μm (samples 2, 5, 8, 11, and 14), it was observed that the number of whiskers generated increased as the number of elapsed days increased. This shows that the thicker the tin-copper diffusion layer is, the more effective it is to suppress tin whiskers.

[0036]

[Table 2]

In the above embodiment, a tape carrier having a copper foil of 25 μm was used. However, a tape carrier having a copper foil of 10 μm was used for the same evaluation as above. In the following, the phenomenon of excessive dissolution of copper did not occur, but it was observed that excessive dissolution was promoted in cases exceeding 0.2 μm.

[0038]

As described above, according to the present invention, the following excellent effects can be obtained.

According to the tape carrier for a semiconductor device of the present invention and the method of manufacturing the same, a solder resist is printed on a part of a conductor fine pattern of a copper foil applied on an insulating film such as a polyimide resin via an adhesive layer. After applying, 1
As the second tin plating treatment, a thickness of 0.01 to 0.20
A thin tin plating layer having a thickness of μm is formed, and a pure tin layer and a tin-copper alloy layer are formed by heat treatment. At the time of this first tin plating treatment, a thin tin plating having a thickness of 0.01 to 0.20 μm is applied. Is practically negligible.

Then, as a second tin plating treatment,
Forming a pure tin plating layer of 0.15 to 0.80 μm or more,
The heat treatment makes the tin-copper alloy layer 0.20 μm or more and the pure tin layer 0.15 to 0.80 μm. At the time of the second tin plating treatment, since the tin-copper alloy layer has already been formed on the surface of copper, even if the plating solution enters the lower surface of the solder resist, the copper foil contacts the plating solution. This does not mean that there is no local electrolytic corrosion. This makes it possible to suppress excessive dissolution of copper in the lead portion below the solder resist. Further, even if metal plating other than tin plating is not performed, tin whiskers can be suppressed at relatively low cost, and a highly reliable tin plating film can be obtained.

Further, in the second tin plating treatment, the pure tin layer has a thickness of 0.15 to 0.80 μm, so that the bonding property of the inner lead is good and no plating dripping occurs. Further, since the second tin-copper alloy layer has a thickness of 0.20 μm or more, a sufficient whisker suppression effect can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view showing the structure of a tape carrier of the present invention for each process.

FIG. 2 is a sectional view showing the structure of a conventional tape carrier for each process.

FIG. 3 is an assembly diagram in which a semiconductor device is configured by mounting an IC chip on the tape carrier of the present invention.

FIG. 4 is a cross-sectional view showing the phenomenon of excessive dissolution of copper.

[Explanation of symbols]

 Reference Signs List 1 insulating film made of polyimide resin 2 adhesive layer 3 wiring pattern 3a copper lead 4 pure tin plating layer 4a, 4b pure tin layer 5 tin-copper alloy layer 5a, 5b tin-copper alloy layer 6 solder resist 9 excessive melting part of copper

Continued on the front page (72) Inventor Yu Sugano 3-1-1, Sukekawa-cho, Hitachi-shi, Ibaraki F-term in the cable plant of Hitachi Cable, Ltd. (Reference) 4K022 AA02 AA42 BA21 BA35 CA08 CA09 DA01 EA01 4K028 CA01 CB02 CB03 CC04 CD01 5E343 AA02 AA18 AA33 BB09 BB12 BB14 BB17 BB24 BB34 BB52 DD32 ER11 ER12 GG01 GG03 GG06 GG18 5F044 MM03 MM23 MM25 MM26

Claims (5)

[Claims] 1. A solder resist is applied to a predetermined position excluding a terminal portion on a copper foil wiring pattern provided on an insulating film via an adhesive layer, and a thickness of 0.1 mm is applied to the terminal portion. By forming a thin tin plating layer having a thickness of 0.1 to 0.2 μm and performing a heat treatment, a pure tin layer and a tin-copper alloy layer having a thickness of 0.20 μm or less are formed. A tape carrier for a semiconductor device, comprising a pure tin plating layer having a thickness of 80 μm. 2. The tape carrier for a semiconductor device according to claim 1, wherein the pure tin plating layer is heat-treated to form a pure tin layer having a thickness of 0.15 to 0.80 μm and a thickness of 0.20 μm or more. The tape carrier for a semiconductor device according to claim 1, wherein a tin-copper alloy layer is formed. 3. A solder resist is applied to a predetermined position excluding a terminal portion on a copper foil wiring pattern provided on an insulating film via an adhesive layer, and then a first time is applied to the terminal portion. As a tin plating process, a thin tin plating layer having a thickness of 0.01 to 0.2 μm is applied, and a heat treatment is performed to form a pure tin layer and a tin-copper alloy layer having a thickness of 0.20 μm or less, As a second tin plating process, a pure tin plating layer having a thickness of 0.15 to 0.80 μm is formed on the terminal portion, and a heat treatment is performed to form a pure tin plating layer having a thickness of 0.15 to 0.5 μm.
A method for producing a tape carrier for a semiconductor device, comprising forming a pure tin layer having a thickness of 80 μm and a tin-copper alloy layer having a thickness of 0.20 μm or more. 4. The method according to claim 3, wherein
As the second tin plating treatment, the pure tin plating layer
A pure tin layer having a thickness of 0.25 to 0.30 μm and a thickness of 0.1 to 0.6 μm are formed and heat-treated.
A method for manufacturing a tape carrier for a semiconductor device, comprising forming a tin-copper alloy layer having a thickness of 20 to 0.25 μm. 5. The method according to claim 3, wherein
A method for manufacturing a tape carrier for a semiconductor device, wherein the first tin plating and the second tin plating are performed by electroless plating.