JPH02250363A - Leadframe and its manufacture - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a lead frame and a method for manufacturing the same.

[Prior Art and its Problems] When mounting an IC chip on a lead frame, it is necessary to ensure a predetermined area for the inner leads due to wire bonding accuracy and bondability of the inner leads. On the other hand, there is an increasing demand for semiconductor elements with a large number of pins for high-density packaging and high-density wiring, and along with this, there is a demand for shortening the pitch of some lead frames.

When manufacturing a multi-pin lead frame by conventional photolithography, a mask pattern is formed using a photosensitive resist resin with high resolution.

However, even if a highly accurate mask pattern is used for a multi-pin lead frame, current etching techniques cannot perform etching according to the pattern.

This is because existing etching techniques dissolve and remove metal through an isotropic chemical reaction, which inevitably causes lateral expansion, so-called side etch or undercut.

Therefore, even if the precision of the mask pattern is improved, there is a limit to the etching process, so there is a drawback that the lead frame cannot be miniaturized. Additionally, side-etched lead frames have a disadvantage of poor strength.

As a way to suppress side etching during etching,
JP-A-57-16169 discloses applying vertical centrifugal force to the substrate to be etched and forming a corrosion-resistant layer on the end surface during etching. Further, Japanese Patent Application Laid-Open No. 56-29672 discloses the use of an etching solution mixed with a suspension of oxidation-activated carbon particles. However, at present, no satisfactory results have been obtained.

Furthermore, with the increase in the number of lead frames, it has become difficult to secure a wire bonding area for the lead frame. This is because it is generally desirable that the lead width and lead spacing of a lead frame be 1:1, and as the number of pins increases, the lead width becomes smaller as the lead spacing increases.

In order to accommodate the increase in the number of bins and to ensure the lead width necessary for wire bonding, the lead spacing must be narrower than usual. On the other hand, it is said that the optimum distance for etching is 80% or more of the thickness of the lead frame material. Therefore, if the lead width becomes narrow, there is a drawback that it adversely affects the etching process.

The present invention has been made in view of these points, and an object of the present invention is to provide a lid frame that has sufficient strength even after microfabrication and has a sufficient wire bonding area, and a method for manufacturing the same. do.

[Means for Solving the Problems] The present invention provides a mount portion for mounting a semiconductor, and an inner lead located near the mount portion to which a semiconductor element on the mount portion is electrically connected by bonding. and an outer lead part that is integrated with the inner lead part and supports the inner lead part, in which a metal adhesion layer is provided on the etched end surface of the inner lead part so that the upper surface of the inner lead part is Provided is a lead frame characterized by an expanded version of the lead frame.

The present invention also provides a step of forming a mask pattern on a lead frame material, a step of etching the lead frame material on which the mask pattern is formed to form a lead frame body, and an inner lead portion of the lead frame body. Provided is a method for manufacturing a lead frame, comprising the step of expanding the upper surface of the inner lead portion by applying a metal adhesion layer to the etched end surface of the lead frame.

Here, the metal coated on the inner lead is one that improves the bondability of the inner lead, and
The metal adhesion layer obtained has a certain level of mechanical strength and is corrosion resistant.

As such, A u s A g SS n
Examples include solder. Further, as a method for depositing these metals, ordinary metal deposition methods such as electroplating, electroless plating, vapor deposition, and sputtering can be used.

Further, the thickness of the metal adhesion layer is set to be approximately 100 to 120 μm over the entire lead width.

This is because the width of the bonding area required during the wire bonding process is about 100 to 120 μm. The actual thickness of the metal adhesion layer is approximately 60μ
The etching processing limit is approximately 20 m.
The thickness is between 30 μm and 30 μm.

[Function] According to the lead frame and its manufacturing method of the present invention, since the metal adhesion layer is provided on the etched end surface of the inner lead portion of the lead frame, the upper surface of the inner lead portion is expanded, thereby ensuring sufficient bonding. It is possible to secure the area and improve the reliability of wire bonding.

[Example] Hereinafter, one embodiment of the present invention will be briefly described with reference to the drawings.

FIG. 1(a) is a plan view of the lead frame material. Further, FIG. 1(b) is a sectional view taken along line 1-1' in FIG. 1(a).

10 in the figure is a lead frame material made of 42 alloy and having a plate thickness of 150 μm. A predetermined pattern of photosensitive resist resin 12 was printed on this lead frame material 10 by screen printing to form a mask pattern. Figure 2 (
a) is a plan view of the lead frame material after printing the photosensitive resist resin pattern 12; Further, FIG. 2(b) is a sectional view taken along line 2-2' in FIG. 2(a).

Thereafter, the lead frame material after the photosensitive resist resin pattern was printed was etched to create a lead frame body 14. A plan view and a sectional view of the lead frame main body at this time are shown in FIGS. 3(a) and 3(b), respectively.

Next, the top surface of the lead frame body 14 obtained was plated with silver to a thickness of about 20 μm to provide a metal adhesion layer 16 in order to secure a wire bonding area, and the top surface of the lead frame body 14 was enlarged. In this silver plating step, pretreatment, base plating, substitution prevention treatment, silver plating, base peeling, and washing and drying were performed in this order. Here, base plating is a process performed to improve the wettability between the lead frame material and the plating metal, and specifically,
(Metals or alloys such as uSNi, 5n-Ni, Pb-8n, etc. are used. The thickness of the deposit is usually 0.1
From about μm to several μm.

Further, in the silver plating process, the current density is increased and the processing time is increased in order to achieve thick deposition. A plan view and a sectional view of the lead frame main body at this time are shown in FIGS. 4(a) and 4(b), respectively.

The lead frame thus obtained had a sufficient wire bonding area and sufficient strength.

[Effects of the Invention] According to the present invention, a lead frame having a sufficient bonding area and sufficient strength can be obtained.

[Brief explanation of drawings]

FIG. 1(a) is a plan view of a lead frame material used in an embodiment of the present invention, and FIG. 1(b) is a cross section taken along line 1-1' in FIG. 1(a). Figure 2 (Ca) is a plan view of the lead frame material after the photosensitive resin pattern has been printed on the lead frame material, and Figure 2 (b) is
3(a) is a plan view of the lead frame body after etching, and FIG. 3(b) is a sectional view taken along 2-2' in FIG. 2(a). 3 in (a)
4 is a plan view of the lead frame body after metal adhesion treatment, and FIG. 4(b) is a sectional view taken at 4-4' in FIG. 4(a). FIG. 10... Lead frame material, 12... Photosensitive resist resin pattern, 14... Lead frame body, 16
...Metal adhesion layer. Applicant's representative Patent attorney Takehiko Suzue Figure 1 (a) Figure 1 (b) Figure 2 (a) Figure 2 (b) Figure 3 (a) Figure 3 (b) Figure 4 (a) Figure 4(b)

Claims (2)

[Claims] (1) A mount part for mounting a semiconductor, an inner lead part located near the mount part and to which the semiconductor element on the mount part is electrically connected by bonding, and integrated with the inner lead part. and an outer lead portion supporting the inner lead portion, wherein a metal adhesion layer is provided on the etched end surface of the inner lead portion to expand the upper surface of the inner lead portion. . (2) A step of forming a mask pattern on a lead frame material, a step of etching the lead frame material on which the mask pattern is formed to form a lead frame body, and an etching end face of an inner lead portion of the lead frame body. A method for manufacturing a lead frame, comprising the step of expanding the upper surface of the inner lead part by applying a metal adhesion layer to the lead frame.