JPH04199649A - Circuit board - Google Patents

Abstract

PURPOSE:To correspond to a fine pitch as well as to make it possible to reduce the cost of a material by a method wherein a bump for bonding directly on a pad on a semiconductor element, a board and the like is formed at the tip part of a finger by bending a finger lead. CONSTITUTION:In a finger of a circuit pattern, the tip of the finger 1 is bent by a die or the like, a bump 2 is formed at the tip and a gold plating, for example, is applied. The thickness of the bump 2 is made two times thicker or thereabouts than that of the finger 1. Thereby, as the thickness of the bump 2 is made equal to the bump thickness of a bump formed by half etching, the thickness of a lead can be made thin to half or thereabouts of the thickness of a conventional leads. As a result, a pitch further finer than a conventional pitch also becomes possible. Moreover, as the thickness of a material can be made thin, the cost of the material can be inhibited.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a circuit board in which a bump is formed at the tip of a finger for direct bonding to a pad portion of a semiconductor element, a substrate, or the like.

[Prior Art] A conventional circuit board having a bump at the tip of a finger was formed by half-etching the leads as shown in FIG.

[Problem to be Solved by the Invention 1] However, in the above-mentioned prior art, when a part of the finger is bonded to a pad of a semiconductor element, a substrate, etc., and then a physical shock and a thermal shock are applied, the finger is half-etched. There has been a problem in that stress is concentrated at the boundary between the part and the part that is not covered, especially at the base of the finger where the finger strength changes drastically, causing the finger to break. The present invention is intended to solve these problems, and its purpose is to prevent fingers from being cut due to physical or thermal shock.

Furthermore, when it comes to a fine pitch, the etching ability is limited to about twice the finger thickness t, that is, the pitch P company 2t, and it is difficult to achieve a fine pitch due to such restrictions. SUMMARY OF THE INVENTION The present invention is intended to solve these problems, and its purpose is to provide a circuit board that can accommodate fine pitches and reduce material costs.

[Means for Solving the Problems] The circuit board of the present invention has a bump for direct connection to a pad of a semiconductor element, a substrate, etc., formed at the tip of a finger by bending a finger lead.

[Example] The circuit board of the present invention has the structure shown in FIGS. 1(a) and 1(b). 1 is a finger and 2 is a bump. The thickness of the fingers is kept constant to reduce stress on the fingers due to physical and thermal shocks and prevent the fingers 1 from breaking.

Fold the tip of the finger (1) of the circuit pattern using a mold, etc., as shown in Figure 1, and make a bump (
2) and plated with gold, for example. The thickness of the bump (2) is approximately twice the thickness of the finger (1).

If the thickness of the bumps is made equal to that of the bumps formed by half-etching as shown in FIG. 2, the lead thickness will be about half that of the conventional one, making it possible to create even finer pitches than before.

Furthermore, since the material can be made thinner, costs can be reduced.

Each figure from FIG. 3 to FIG. 5 shows each shape in other embodiments of the present invention. These shapes keep the thickness of the half-etch and relative buried constant, reduce stress concentration at the half-etch boundary, and prevent fingers from breaking.

[Effect of the Invention 1] The effect of the present invention is that in a circuit board in which a bump is formed at the tip of the finger, after the finger is bonded to the pad of the semiconductor element and the circuit board by bending the lead to form the bump, the physical or This improves long-term reliability by dispersing the stress concentration on a part of the half-etched finger that occurs when a thermal shock is applied, and preventing the finger from breaking when the above-mentioned impact is applied.

Furthermore, if the bump thickness is kept the same as before, the finger thickness before etching can be half of the previous thickness, making etching at a fine pitch possible. Thereby, the material cost of the circuit board can be reduced.

[Brief explanation of the drawing]

FIG. 1(a) is a plan view showing a bumped circuit board of the present invention, and FIG. 1(b) is a sectional view thereof. FIG. 2(a) is a plan view of a conventional bumped circuit board. FIG. 2(b) is a sectional view thereof. FIGS. 3(a) and 5(b) to 5(a) and 5(b) are plan views and cross-sectional views of other embodiments of the present invention. 1. ・Finger 2...Banbu or above Applicant SE, Iko Epson Co., Ltd. Agent Patent attorney Kizobe Suzuki (and 1 other person) (a) (b) Figure 2

Claims (1)

[Claims] (1) A circuit board characterized in that a bump for directly bonding to a pad portion of a semiconductor element is formed at the tip of the finger by bending a finger lead.