JPH03283556A - Ic lead frame - Google Patents

Abstract

PURPOSE:To improve solderability and corrosion resistance without spoiling appearance due to Ag replacement precipitation to outer leads by depositing a glossy Ni plating layer on a lead frame and Pd plating layers at least on outer leads located thereon. CONSTITUTION:A lead frame 1 with specified patterns is spread wholly with glossy Ni plating to form a glossy Ni plating layer 14, which is then treated with Pd strike plating as required. Thereafter, the glossy Ni plating layer at least on outer leads 3 is Pd-plated to form a Pd plating layer 15, and an Ag plating layer 9 is formed at tip 6 of an inner lead 5 by Ag plating. Finally, extra Cu strike plating for Ag plating and Ag plating precipitated on the side face of the inner lead 5 are stripped off to attain a lead frame 1. Hereupon, the thickness of a Pd plating layer 15 is preferably 0.1mum or more. Its reason is that sufficient solderability and corrosion resistance can be attained.

Description

[Detailed description of the invention] <Industrial application field> The present invention relates to a lead frame for IC.

<Prior Art> In general, a resin-sealed semiconductor integrated circuit device (hereinafter referred to as an IC) is manufactured by bonding an IC chip 12 onto an IC chip mounting portion 7, as shown in FIGS. 1 and 3. After that, the electrode part of the IC chip 12 and the Ag plating layer 9 of the tip part 6 of the inner lead 5 are wire-bonded with a very fine wire 11 such as Au, and then molded with a molding resin 13, and the IC package is attached to a printed circuit board. In order to improve the adhesion when attaching to the top, after cutting the outer frame part 2 of the lead frame 1, cut the part including the outer lead part 3.
A solder plating layer 10 is provided to complete the product.

4 is a dam bar and 8 is a pilot hole.

However, in such a process, during hot-dip plating to dip the outer lead part after assembly, the temperature is 200°C.
The resin mold may crack due to thermal shock due to heating exceeding Furthermore, this method has poor productivity and high cost. Furthermore, the IC package, outer leads, etc. are contaminated by the flux used during melting, which causes a decrease in the reliability of the IC.

In order to solve such problems, in recent years, IC chips 12 have been mounted on lead frames in which an Ag plating layer 9 has been formed on the inner lead tips 6 and a soldering layer 10 has been provided on the actor leads. Attach the inner lead tips 6 of the lead frame and the electrodes of the IC chip 12 using Au.
After connecting with the thin metal wire 11, mold resin 13
Integrated molded semiconductor devices have been developed.

<Problem to be solved by the invention> After providing both an Ag plating layer on the tip of the inner lead and a solder plating layer on the outer lead, the I
Attach the C-chip and connect the inner lead tip and the above IC.
The manufacturing process of a semiconductor device which is connected to a chip by a thin metal wire and which are integrally molded with a molding resin is generally as shown below. A solder plating layer is provided on the outer lead portion of the lead frame, and then Cu strike plating is provided on at least the portion where Ag plating should be applied to improve the adhesion of Ag plating, and then Ag plating is applied only to the tip of the inner lead. After that, attach the IC chip and assemble the IC.

However, this method has problems such as the solder eluting into the Ag plating solution and contaminating the plating solution, and the substitution of Ag on the solder, which deteriorates the appearance. After providing Ag plating only or both 88 plating and solder plating on the lead frame, attach the IC chip, connect the inner lead tip and the IC chip electrode with a thin metal wire such as Au, and mold resin. The above-mentioned problems exist in the manufacture of integrally molded semiconductor devices.

Furthermore, conventionally, molten soldering or electroplating has been performed after IC package assembly. However, this method has problems in terms of time and cost, as cracks occur in the mold resin due to thermal shock, IC reliability decreases due to flux contamination, and opportunities for subcontracting to subcontractors increase. Furthermore, a semiconductor device has been developed in which an IC is assembled after providing Ag plating on the inner lead portion of a lead frame and solder plating on the outer lead portion. However, this requires a complicated manufacturing process at the lead frame manufacturing stage, and it is difficult to satisfy both appearance and characteristics because bipolar plating layers are provided on the functional parts of the inner lead and outer lead. there were.

The present invention eliminates these drawbacks of the conventional technology, does not contaminate the Ag plating solution with solder, does not damage the appearance due to substitutional precipitation of 88 on the outer lead part, and provides stable solderability. The purpose is to provide an IC lead frame with high reliability such as corrosion resistance.

Means for Solving the Problems> In order to achieve the above object, the present invention provides a lead frame having an Ifit part on which an IC chip is placed and an outer lead part.
An I plating layer is provided, and a Pd plating layer is provided on at least the outer lead portion above the I plating layer.
A lead frame for C is provided.

The thickness of the Pd plating layer is preferably 0.1 μm or more.

Further, the lead frame material may be Cu.

Cu alloy or Fe alloy is preferred.

Further, the thickness of the glossy Ni plating layer provided on the surface of the lead frame is preferably 0.1 to 5.0 μm.

Further, it is preferable to provide Cu strike plating on this portion before providing the Pd metal layer of the outer lead portion.

In the following, the invention will be explained in more detail with reference to preferred embodiments shown in the accompanying drawings. The present invention is not limited to these drawings unless the purpose thereof is impaired.

FIG. 1 is a plan view showing the present invention and a general IC lead frame, and FIG. 2 is a sectional view showing an embodiment of an IC package using the IC lead frame according to the present invention.

The lead frame 1 includes an outer frame portion 2, a lead portion 16, and a mounting portion 7.

One or more pilot holes 8 are usually bored in the outer frame 2 for positioning during wire bonding, molding, etc.

The lead portion 16 has an inner lead portion 5 and an outer lead portion 3, which are connection portions of the bonding wires 11.

Outer lead portion 3 of lead portion 16 of lead frame 1
A bright Ni plating layer 14 is provided thereon, and a Pd plating layer 15 is provided thereon. On the other hand, a glossy Ni plating layer 14 is formed on the surface of the tip portion 6 of the inner lead portion 5.
An Ag plating layer 9 is provided thereon via Cu strike plating (not shown).

The material of the lead frame 1 used in the present invention is C.
Any material used as a normal lead frame material such as U, Cu alloy, and Fe alloy may be used. Furthermore, the lead frame 1 of the present invention has an inner lead portion 5 to prevent diffusion and improve corrosion resistance of the lead frame 1. Before forming the Ag plating layer 9 and the Pd plating layer 15 of the outer lead portion 3, it is necessary to apply bright Ni plating to the entire surface of the lead frame 1 in advance.

Here, the lead frame 1 has a glossy N1 layer 14, P
As a method for forming the d plating layer 15 and the Ag plating layer 9, first, the entire surface of the lead frame 1 on which a predetermined pattern has been formed is plated with bright Ni to form the bright Ni plating layer 14, and then Pd is applied as necessary. After applying strike plating, - at least the bright Ni of the outer lead portion 3
Pd plating is performed on the plating layer to form a Pd plating layer 15, and Ag plating layer 9 is formed on the tip end portion 6 of the inner lead portion 5 by Ag plating. Finally, excess Cu strike plating (full surface plating) during Ag plating and Ag plating deposited on the side surface of the inner lead part 5 are removed by stripping and filling. 1 can be obtained.

Here, the thickness of the Pd plating layer 15 is preferably 0.1 μm or more. The reason for this is that Pd plating is 0.1μ
This is because if it is at least m, sufficient solderability and corrosion resistance can be obtained.

There is no need to limit the upper limit, but if the Pd plating is thicker than necessary, not only will the cost increase, but the color tone of lead frame 1 will become the color tone of the Pd plating, changing the appearance. In this case, the upper limit is preferably 0.3 μm.

Moreover, the thickness of the bright Ni plating layer 14 is 0. 1-5.0
Preferably, the thickness is 5.0 μm, as if it is less than 0.1 μm, the solderability is not sufficient.Although it may be more than 5.0 μm, it is set to 5.0 μm in consideration of economical efficiency. Note that if the thickness exceeds 10 μm, cracks may occur in the plating during bending.

Further, the thickness of the Ag plating layer 9 is not limited at all,
The thickness may be sufficient as long as it is necessary for mounting on an IC board and wire bonding, and the plating thickness applied to a normal lead frame is sufficient.

Further, the thickness of the Pd strike plating applied as needed is not particularly limited, but it is sufficient as long as the desired effect can be obtained, and it is preferably as thin as possible.

Furthermore, gloss Ni plating, Pd plating, Ag plating, P
As the plating method such as d-strike plating, a commonly known plating method can be used.

The Pd plating layer 15 provided after the bright Ni plating layer 4 on the outer lead portion 3 may be provided at least on the bright Ni plating layer 4 of the actor lead portion 3.
In the present invention, by providing the Pd plating layer 15 with good solderability on the outer lead part 3, which may be provided on the entire surface of the lead frame 1, contamination of the Ag plating solution by conventional solder and the contamination of the Ag plating solution on the solder plating layer are avoided. It is possible to prevent poor appearance due to the substitution of Ag with , and to provide an excellent lead frame.

In addition, the glossy Ni plating layer 14 provided under the Pd plating layer 15 has finer crystals and is easier to control than matte Ni plating, and also serves as a diffusion prevention layer for the lead frame material metal, and has excellent corrosion resistance. Therefore, the IC chip 12 is attached to the lead frame 1, the tip part 6 of the inner lead part of the lead frame 1 and the electrode part of the IC chip 12 are connected with a thin metal wire, and the semiconductor device is integrated with the mold resin 13. Useful for improving IC reliability such as solderability.

Further, if necessary, a Pd strike-muffing layer formed as a base for the Pd plating layer 15 may be provided on the entire surface of the lead frame 1 or at least on the base portion of the Pd plating layer 15.

The lead frame 1 of the present invention has an IC as shown in FIG.
The IC chip 12 is placed on the chip placement part 7, wire bonded to the tip part 6 of the inner lead part and the IC chip 12 using the bonding wire 11, and finally molding resin 13 is molded to assemble the IC package.
The dam bar 4 of the outer frame part 2 and the outer lead part 3 can be cut, and the outer lead part 3 can be bent and used.

In addition, unlike the finished product plating, the lead frame of the present invention does not require solder plating on the outer lead portion 3 after IC assembly. The problem of contamination of the package and outer lead portion 3 is also eliminated.

As a result of the above results, it is possible to save time and cost in manufacturing.
The appearance and reliability of the IC can be improved, and it has become possible to consistently produce semiconductor devices of stable quality.

In addition, in FIG. 2, as an example, the Ag plating layer 9 is provided at the tip 6 of the inner lead part, but the present invention may be provided with the Ag plating layer instead of the Ag plating layer as long as the purpose is not impaired.
A plating layer of Au, AJ2°Cu, Pd, etc. may be provided.

<Example> The present invention will be specifically explained below based on Examples.

(Example 1) As shown in FIG. 2, a glossy Ni plating layer 14 was applied to the Cu alloy lead frame 1 to prevent diffusion and improve corrosion resistance.
．． It was provided with a thickness of 0.01 to 10 μm. The glossy Ni plating thickness is fluorescent X#ji! It was measured with a film thickness meter. The conditions for this bright Ni plating are as follows.

Glossy Ni plating bath (Watt bath) NiS04/6H20: 250 g/11NfCJ
! 2.6H2〇 2 5 0
g / Juri 183B0,50 g / u #61 (Secondary brightener): 5cc/f (Ebara Nice Light Co., Ltd.) #63 (Primary brightener): 10CC/A (Ebara Nice Light Co., Ltd.) Temperature
60℃ Current density 4 A/d m' anode
After that, the entire surface of the lead frame 1 was plated with a Pd strike to improve the adhesion of the Pd plating. This Pd
The strike plating conditions are as follows.

Pd Strike plating solution: Paradex Strike II (EEJA) Metal Pd
Concentration: 0.5g/j! Temperature: 40°C Current density: 4 A/dm' Anode: A 0.1 μm Pd rough layer 15 was provided on the outer lead portion 3 in the form of a platinum-plated titanium plate. Pd
The plating thickness was measured using a fluorescent X-ray film thickness meter. The conditions for this Pd plating are as follows.

Pd plating solution: Varadex s 1o (EEJA) Metallic Pd concentration
: 25g/42 Temperature = 60℃ Current density: 4 A/dm2 Anode: Platinum plated titanium plate and Cu strike plating on the tip 6 of the inner lead! An Ag plating layer 9 was provided across the entire surface. This Ag plating condition is A
G plating solution Silvershed 220 (Meltex)
The metal Ag concentration was 65 g/A, the temperature was 65° C., and the current density was 60 A/dm'. The anode was a platinum-plated titanium plate.

Finally, excess Cu strike plating was applied to the entire surface of the lead frame and Ag deposited on the side of the inner lead.
was removed by peeling and S treatment. The peeling conditions were as follows: 30g/f1 of Entrip S (Meltex)
%NaCN was 50g/j2, the temperature was 40°C, and the peeling S treatment time was 20 seconds.

IC chip 12 is attached to lead frame 1 obtained by manufacturing lead frames by changing the thickness of the glossy Ni plating under the above conditions.
was attached, the inner lead tip 6 and the electrode part of the IC chip 12 were connected with a thin metal wire 11, and they were integrated with a molding resin, and then the outer frame part 2 and the dam bar 4 were cut out to complete the IC package.

Table 1 shows the results of evaluation on the following items.

■Corrosion resistance (corrosion products) After manufacturing the IC package, salt water was sprayed for 24 hours, and the presence or absence of corrosion products at the interface between the mold resin and the outer lead portion was examined.

Corrosion resistance (corrosion products): ○ None, Δ Slightly present, × ■Crack occurrence during bending The outer lead part of the IC package was bent, and the plating layer on the surface of the bent part was observed to detect cracks. We investigated whether or not this occurred.

Crack occurrence: No O, △ Slightly present, × present ■ Soldering time Taking into account the heating conditions during the assembly process, use a lead frame heated at 175°C x 8 hours, and apply 6:4 eutectic solder to 23
The solder wetting time was measured using rosin flux after melting at 5°C.

(Comparative Example 1) An IC package was completed in the same manner as in Example 1 except that Pd strike plating was directly provided without providing a bright Ni plating layer. The evaluation results are shown in Table 1.

From Table 1, the IC package using the lead frame of the present invention has a bright Ni plating thickness of 0. If it is 1 μm or more,
It can be seen that lead corrosion resistance and solderability are superior to Comparative Example 1.

In addition, a glossy Ni plating layer of 0.0
It was shown that if the thickness was 1 μm or more, the solder wetting time would be even shorter than in Comparative Example 1.

(Example 2) An IC package was completed in the same manner as in Example 1 except that a 42 alloy (Fe-42%Ni) lead frame was used. The evaluation results are shown in Table 2.

(Comparative Example 2) An IC package was completed in the same manner as in Example 2, except that Pd strike plating was directly provided without providing a glossy Ni brushing layer. The measurement results are shown in Table 2.

From Table 2, if the IC package using the lead frame of the present invention has a glossy Ni plating of 0.05 μm or more,
It can be seen that this sample has better corrosion resistance and solderability than Comparative Example 2.

However, considering corrosion resistance, the thickness of bright Ni plating is 0.
A thickness of 1 μm or more is desirable.

(Comparative Example 3) Example 1 except that Ag plating (5 μm thickness) was directly provided on the tip of the inner lead without providing a bright Ni plating layer, and solder plating (10 μm thick) was provided directly on the outer lead.
An IC package was completed in the same manner as above. The evaluation results are shown in Table 3 together with Examples 1 and 2.

From Table 3, the IC package using the lead frame of the present invention has a bright plating thickness of 0.1 μm, a Pd plating thickness of 0.1
It can be seen that in the case of μm, it is superior to Comparative Example 3 in all aspects of solderability, corrosion resistance, and crack occurrence.

Table 3 <Effects of the Invention> Since the present invention is constructed as described above, the present invention provides a lead frame with excellent solderability, corrosion resistance, and bending workability.

Since the present invention satisfies the purpose of conventional solder plating with Pd plating, the board mounting process can be started immediately after IC assembly, and IC manufacturing time and cost can be reduced.

Also, compared to the conventional case where the IC is assembled after providing Ag plating on the tips of the inner leads and solder plating on the outer leads, since Pd is chemically stable, it is less susceptible to the effects of other solutions than solder. Because it is less susceptible to corrosion and has excellent corrosion resistance, it has become easy to satisfy both the appearance and properties of the outer lead portion of the package.
Furthermore, since the manufacturing process is simplified, the economical efficiency is also very high.

Furthermore, by providing a bright Ni plating layer on the base of the Pd plating, diffusion of the base metal is prevented and corrosion resistance is also improved, which is effective in improving the reliability of the IC.

In addition, since it is effective just by partially plating expensive Pd-plated rice, the lead frame of the present invention is cost-effective, considering the above-mentioned improvements in economy and reliability. It's worth it.

[Brief explanation of drawings]

FIG. 1 is a plan view showing an IC lead frame of the present invention. FIG. 2 is a sectional view showing an embodiment of an IC package using the IC lead frame according to the present invention. FIG. 3 is a sectional view of an IC package using a conventional IC lead frame. Description of symbols 1...Lead frame, 2...Outer frame part, 3...Outer lead part, 4...Dam bar 5...Inner lead part, 6...Tip part of inner lead part, 7... IC chip mounting part, 8... Pilot hole, 9... Ag plating layer, 10... Solder plating layer, 1III° bonding wire 12... IC chip, 13... Mold resin , 14... Glossy Ni plating layer, 15... Pd plating layer, 16... Reed part (metal thin wire) FIG, 1 FIG, 3

Claims (1)

[Claims] (1) In a lead frame having a mounting part on which an IC chip is placed and an outer lead part, a bright Ni plating layer is provided on the lead frame, and a Pd plating layer is provided on at least the outer lead part above the lead frame. A lead frame for IC that is characterized by: