JP2625662B2 - Electroformed metal body - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention
The present invention relates to a thin and thin electroformed metal body such as a lead connected to a semiconductor chip such as I. 2. Description of the Related Art A metal lead frame is used for assembling a semiconductor device in which a semiconductor chip is integrated with a resin mold and a number of pins are protruded. An extremely thin finger (inner lead) is formed on the lead frame, and the tip of the finger and the electrode of the semiconductor chip are generally connected using solder or other means. Such a thin metal body has been formed by pressing, etching or the like. However, in recent years, when a semiconductor device having a large number of pins is required, the width of the metal body is inevitably becoming narrower, and it is difficult to form the metal body by the above-described pressing and etching. [0003] As a method of solving these drawbacks and being easy to manufacture and capable of forming a fine portion, a metal body using an electroforming technique has recently been developed. FIG. 6 is a cross-sectional view for explaining a method for manufacturing a metal body using the electroforming technique proposed by the present applicant as an example of a lead frame, which is described in JP-A-61-234060. It is a thing. First, as shown in FIG. 6A, a resist layer 2 having a desired pattern is formed on the surface of a substrate 1 made of a conductive metal such as stainless steel. The substrate 1 is a tape-shaped member elongated in the vertical direction toward the paper surface of FIG.
Has the same pattern as the shape of the lead frame to be manufactured. Although not shown, a large number of non-resist portions for forming sprocket holes are provided at both ends of the substrate 1 at predetermined intervals in the vertical direction toward the paper surface. It is formed. Next, the substrate 1 is subjected to a peeling treatment to activate a surface corresponding to the non-resist portion 2a of the substrate 1;
As shown in FIG. 6B, a contact material 3 such as gold, tin, or solder is formed on the non-resist portion 2a by coating or plating, and then electroformed, as shown in FIG.
An electroformed metal layer 4 is formed on the contact material 3. [0007] A part of the laminated body of the substrate 1 and the metal layer thus formed into a single plate is subjected to press working, and a portion corresponding to the finger 5 is bent as shown in FIG. This bent shape includes a flat finger base 5a,
It is composed of an upright portion 5b extending obliquely from the finger base 5a and a tip portion 5c extending parallel to the upright portion 5b. A bump 5d is simultaneously formed on the lower surface of the tip portion 5c by pressing. Next, a second electroforming is performed to form a new electroformed metal layer 6 on the electroformed metal layer 4 as shown in FIG. At this time, the growth rate of the electroformed metal layer 6 is slow because the upright portion 5b of the finger 5 is located at an inclined position, and the tip 5c is connected to the upright portion 5b by a thin neck portion. The cast metal layer 6 grows more, so that the finger 5 has a tip 5c, a finger base 5a and an upright 5
The thickness is increased in the order of b. Finally, as shown in FIG. 6F, when the substrate 1 is peeled off from the contact material 3, the resist layer 2 remains on the substrate 1,
The contact material 3 and the electroformed metal layers 4 and 6 are separated from the substrate 1 to obtain a lead frame having fingers with bumps formed as shown in the figure. This is because the surface of the non-resist part 2a has been subjected to the peeling treatment in advance as described above. The lead frame thus obtained is wound, for example, in a roll form, and transported and supplied to a semiconductor device manufacturing line. Then, using the sprocket holes (not shown) formed in the lead frame as positioning references, the respective electrodes of the semiconductor chip and the bumps 5 of the fingers 5 are used.
and d are thermocompression-bonded, and a semiconductor device is obtained through a subsequent molding step and lead cutting step. According to the manufacturing method proposed by the applicant of the present invention, the leads are formed by electroforming the substrate. Therefore, the entire lead frame is punched by pressing. This method can form a lead that is much narrower than the method of forming a lead, which is an effective method for a semiconductor device having many pins. However, as the number of pins of the semiconductor device is further increased, the width of the lead itself and the pitch between adjacent leads are further reduced, and the mechanical strength of the lead itself is reduced. When the lead after electroforming is lifted off the substrate and peeled, deformation of the lead, entanglement with the adjacent lead, and tearing in the middle tend to occur, making it difficult to obtain a normal lead.
There has been a problem that manufacturing costs have risen. An object of the present invention is to solve the above-mentioned problems of the prior art and to provide an electroformed metal body which can be easily peeled off from a substrate without causing a large number of electroformed metal bodies to be damaged and can be manufactured at low cost. . [0014] In order to achieve the above object, the present invention provides a method of forming a resist layer on a conductive sheet by leaving a non-resist portion so that a portion corresponding to an electroformed metal body is exposed. formed, electroformed metal body to the non-resist portion is formed thicker so as to exceed the surface of the resist layer and then pressed against the carrier film <br/> having an adhesive layer on the conductive sheet and the surface, The carrier film is picked up on the adhesive layer side. According to the above structure, the electroformed metal body is thicker than the thickness of the resist layer and further exceeds the upper surface thereof.
When the carrier-side adhesive layer is pressed from above, the adhesive layer will be strongly pressed against the electroformed metal body, so that it will not excessively adhere to the resist layer, and should be peeled off by picking up the electroformed metal body. Can be. Embodiments of the present invention will be described below in detail with reference to the drawings. FIGS. 1 to 3 are perspective views showing the steps of manufacturing a film carrier with bumps according to an embodiment of the present invention.
Is a sectional view of a main part corresponding to each step of FIGS. 1 to 3, and FIG. 5 is a perspective view of a finger. First, as shown in FIGS. 1A and 4A, an adhesive layer 11 is applied with a predetermined width on a base film 10 having high heat resistance such as polyimide.
A conductive sheet 12 made of a stainless steel thin plate is adhered on top,
Thus, a substrate 13 having a surface provided with conductivity is formed. The base film 10 has the same width as a carrier tape described later, and has sprocket holes 10a formed at regular intervals along both side edges. The conductive sheet 12
It is also possible to use a metal other than stainless steel, for example, nickel, but in this case, anodize the surface,
It is necessary to perform a release treatment using selenous acid or chromic acid. Next, as shown in FIGS. 1 (b) and 4 (b), a first resist layer 14 of a photosensitive material is applied on the conductive sheet 12 of the substrate 13, and a sprocket hole 10a is formed thereon. Then, a pattern film (not shown) is overlaid, and then, ultraviolet rays,
The first resist layer 14 is irradiated with an electron beam to form a pattern 14
b (except the non-resist part 14a) is exposed and cured. This phenomenon is further caused, and a concave portion 12a is formed in the conductive sheet 12 corresponding to the non-resist portion 14a by performing chemical etching or electrolytic etching such as electrolytic grinding. The concave portion 12a is for forming a bump, and by controlling the etching conditions, a sufficient depth can be realized even though it is a fine pattern. Next, as shown in FIGS. 1C and 4C, after the first resist layer 14 is removed by a solvent such as acetone or methylene chloride, the first resist layer 14 is placed on the conductive sheet 12 of the substrate 13. A second resist layer 15 made of a photosensitive material is applied. Then, another pattern film (not shown) is again formed on the second resist layer 1 by using the sprocket holes 10a.
After superimposed on 5 , ultraviolet light,
By irradiating an electron beam, a predetermined non-resist portion 15a is formed on the second resist layer 15 as shown in FIGS.
To form This non-resist portion 15a has the same pattern as the lead frame to be manufactured, and FIG. 1 shows only the fingers for simplification of the description. A pattern is also formed at the same time (however, a sprocket is not formed on the lead frame, and a pattern therefor is not formed). Next, as shown in FIG. 2, the substrate 13 on which the second resist layer 15 has been formed is sent to an electrolytic tank 16 and
As shown in (e), the non-resist part 15a is electroformed using a material such as copper or nickel, and the electroformed metal layer 17 is formed slightly thicker than the second resist layer 15 on the non-resist part 15a. . Thus, in the non-resist portion shown in FIG. 4E, a finger 17b having a bump 17a at the tip is formed, and a lead frame having a predetermined shape as a whole is formed. Finally, as shown in FIG. 3, a carrier tape 18 made of polyimide or the like having the same width as the base film 10 and having sprocket holes 18a formed at regular intervals along both ends, and a process shown in FIG. 4 is superimposed between the pair of pressing rollers 19 and 20 and fed.
As shown in (f), the electroformed metal layer 17 is transferred onto the adhesive layer 21 of the carrier tape 18. Then, by applying electroless gold plating to the bumps 17a of the electroformed metal layer 17, a film carrier carrying a lead frame is obtained. Specifically, the sprocket holes 10 of the substrate 13 and the carrier tape 18 are provided between the pressing rollers 19 and 20 heated by a heater (not shown).
a and 18a are used to send them together. Both are conveyed at a constant speed, and are pressed between the pressure contact rollers 19 and 20, so that only the electroformed metal layer 17 formed on the conductive sheet 12 having good releasability adheres onto the carrier tape 18 and the second Is left on the substrate 13 side. Through the above steps, the lead frame made of the electroformed metal layer 17 is transferred onto the carrier tape 18 to obtain a bumped film carrier. The film carrier is wound into, for example, a roll and conveyed and supplied to a semiconductor device manufacturing line, and sprocket holes 18 formed at both ends of a carrier tape 18 are formed.
The bumps 17a at the tips of the fingers 17b are thermocompression-bonded to the respective electrodes of the semiconductor chip with reference to a as a positioning reference, and the semiconductor device is completed through a subsequent molding process and lead cutting process. In such a manufacturing method, since the shape of the bump 17a formed by electroforming is hemispherical as shown in FIG. 5, when the bump 17a is pressure-bonded to the electrode in the concave portion of the semiconductor chip. The risk that the bumps 17a come into contact with the peripheral surface of the concave portion is reduced, that is, the tolerance for lateral displacement at the time of pressing is improved, and the pressing force is concentrated on the top of the hemispherical bump 17a. The bonding strength with the electrode can be increased. The electroformed metal layer 17
1 from which the second resist layer 15 has been removed by stripping
Third, since the electroformed metal layer 17 can be reused by forming it again, the steps from (a) to (d) in FIG. 1 can be omitted next time, and the manufacturing cost can be greatly reduced. Further, the shape of the bump is determined by the etching technique, and the lead frame including the bump and the finger is basically formed by the electroforming technique, so that an extremely fine finger can be easily formed. Further, since the lead frame formed by such electroforming is transferred to a carrier tape having sprocket holes to become a film carrier, it is not necessary to form sprocket holes in the lead frame, and the electroformed portion can be formed. The cost can be reduced as much as possible. As described in detail above, according to the present invention,
Pressing the conductive sheet and carrier film to each other in the plane direction
By doing so, the electroformed metal
Make sure your body is picked up,
Transfer electroformed metal body to carrier film side even without
In addition, the electroformed metal body is peeled from the conductive sheet while being backed by the carrier film.
Therefore, deformation and falling off during carrying can be prevented.
I can .

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view showing a manufacturing process of an electroformed metal body according to one embodiment of the present invention. FIG. 2 is a perspective view showing a manufacturing process of an electroformed metal body according to one embodiment of the present invention. FIG. 3 is a perspective view showing a manufacturing process of an electroformed metal body according to one embodiment of the present invention. FIG. 4 is a sectional view of a main part corresponding to each step of FIGS. 1 to 3; FIG. 5 is a perspective view showing a lead manufactured by the method according to the present invention. FIG. 6 is a fragmentary cross-sectional view showing a conventional lead manufacturing process. DESCRIPTION OF SYMBOLS 10 Base film 10a Sprocket hole 11 Adhesive layer 12 Conductive sheet 12a Depression 13 Substrate 14 First resist layer 14a Non-resist part 15 Second resist layer 15a Non-resist part 16 Electrolyzer 17 Electroformed metal layer 17a Bump 17b Finger 18 Carrier tape 18a Sprocket holes 19, 20 Pressure roller 21 Adhesive layer

   ────────────────────────────────────────────────── ─── Continuation of front page    (72) Inventor Kazuhiko Inoue               4680 Ikata, Fukuoka Prefecture               Kyushu Hitachi Maxell, Ltd.                (56) References JP-A-57-152147 (JP, A)                 JP-A-58-48445 (JP, A)                 JP-A-60-91656 (JP, A)

Claims (1)

(57) Claims A resist layer 15 is formed on the conductive sheet 12 except for a non-resist portion 15a so that a portion corresponding to the electroformed metal body 17 is exposed. The metal body 17 is formed to be thicker than the surface of the resist layer 15, and then the adhesive layer 2 is formed on the conductive sheet 12 and the surface.
1 is pressed against the carrier film 18 having this calibration <br/> rear film 18 being picked up to the adhesive layer 21 side becomes electroformed metal body.