JP2781247B2 - Method for manufacturing connection substrate with micro-projection electrode - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing a connection substrate with minute projection electrodes used as a connector.

In such a connector, all terminals are simultaneously connected to bumps formed on an LSI chip or the like or directly to the terminals by pressure bonding or the like.

[Prior art] In a conventional connection method such as wire bonding or TAB (tape automated bonding), terminals can be taken out only from the periphery of a chip. Since the terminals can be taken out, it is advantageous for increasing the density and has been receiving particular attention in recent years.

FIG. 4 shows an example of a method for manufacturing a conventional connection substrate with minute projection electrodes. In this manufacturing method, as shown in manufacturing steps (1) to (5), after a resist 2 is applied on an insulating substrate 4a to which a copper foil 7 is attached, a wiring conductor pattern 3 is formed by etching, and the resist is formed. Remove. A plating resist 2b for forming the protruding electrode 6 is applied thereon,
In this method, a protruding electrode is formed by plating.

[Problems to be Solved by the Invention] The connection substrate with micro-projection electrodes manufactured by the above-described manufacturing method has low resist position accuracy because the surface on which the resist for plating for forming the projection electrodes is not flat. In addition, there is a problem that air accumulation easily occurs in the resist.

An object of the present invention is to provide a method for manufacturing a connection substrate with minute projection electrodes that solves the above-mentioned problems.

[Means for Solving the Problems] In order to achieve such an object, the present invention provides a process for forming a predetermined wiring conductor pattern on a carrier substrate by plating, and an insulating layer on the wiring conductor pattern. Forming a, a step of removing the carrier substrate, a step of applying a plating resist on the side from which the carrier substrate has been removed, and forming a micro-projection electrode at a predetermined location on the wiring conductor pattern by plating. It is characterized by including.

[Operation] Hereinafter, the present invention will be described in detail with reference to the drawings.

In the step (1), reference numeral 1 denotes a carrier substrate, and a thin metal plate such as aluminum, zinc, tin, iron, and stainless steel can be used. The metal conductive plate is not particularly limited as long as it can be removed by mechanical peeling or etching. Particularly, a metal that can be removed by selective etching with respect to the metal forming the wiring conductor pattern is preferable. Aluminum which is low in cost and excellent in workability is preferred.

A resist pattern 2 is formed on a carrier substrate 1 by a photographic method using liquid resist or DFR (drum film resist) or a screen printing method. In the screen printing method, since a fine pattern cannot be accurately represented due to bleeding of the resist ink, it is preferable to form the resist pattern by a photographic method.

Next, using the carrier substrate 1 as a cathode, a metal such as copper or nickel is deposited on the surface of the carrier substrate 1 other than the portion covered with the resist 2 by electroplating to form a wiring conductor pattern 3. The plating metal is copper,
Nickel, silver, gold and the like can be used, but copper which is low in cost and excellent in conductivity is preferable. After the wiring conductor pattern 3 is formed, the plating resist pattern 2 may or may not be peeled off.

In steps (2) and (3), a polyimide film, a polyetherimide film, a polyetheretherketone film,
Various films such as polyethersulfone film and polyethylene terephthalate film are used as insulating substrates
As 4a, it is adhered with the mounting sheet 5a or bonded with an adhesive. Alternatively, after forming an insulating layer by applying an insulator (solder resist type), the carrier substrate 1 is removed by etching or mechanical peeling. In order to remove the carrier substrate 1, strong stress is applied to the substrate 4a by mechanical peeling, so that it is preferable to remove the carrier 4 by etching.

Next, in the step (4), it is necessary to form a projection electrode on the wiring conductor pattern 3 on the opposite side of the insulating substrate 4a by a screen printing method, a photographic method, or a method of bonding a film for plating resist. Apply a plating resist. Here, the film for plating resist is
This is an insulating film 4a in which a portion corresponding to the protruding electrode 6 is pre-drilled, and the insulating film 4b is bonded to the resist pattern 2 using an adhesive sheet 5b.

In the screen printing method, the positional accuracy with respect to minute projection electrodes is low. In the photographic method, the positional accuracy of the projection electrode portions is also low because the resist surface is not flat. Therefore, it is preferable to form a plating resist by bonding a plating resist film (insulating film 4b).

The above-mentioned insulating substrate is used as a plating resist film
Similar to 4a, various films such as a polyimide film, a polyetherimide film, a polyetheretherketone film, a polyethersulfone film, and a polyethylene terephthalate film can be used. Since it is used as a resist, a polyimide film having excellent dimensional stability is more preferable.

Drilling or punching in the insulating film 4b can be performed by a mechanical method by drilling or punching or by etching of the insulating layer.However, a method of drilling with a numerically controlled drill or mold having excellent productivity is more preferable. preferable. The hole diameter x at the time of drilling is preferably smaller in order to reduce the distance between the protruding electrodes, and it is more advantageous in view of the bleeding of the adhesive. The hole diameter X (μm) is 50 times larger than the diameter A (μm) of the bump electrode 6 (see step (5)).
.Ltoreq.x.ltoreq.A + 100, and preferably 100.ltoreq.x.ltoreq.A + 50. This is also the case in the embodiment shown in FIG.

Examples of a method of aligning the plating resist film include a pin alignment method using a reference hole and a reference pin, or an optical alignment using a positioning mark and a temporary bonding method. In the pin alignment method, an optical alignment method is more preferable because a position shift may occur due to breakage of the reference hole.

The bonding of the insulating film 4b is performed by a normal heat-pressing press.However, when bonding a plating resist film in particular, if the pressing pressure is too high, the hole may be blocked by the spread of the adhesive, so the pressing is performed. The conditions at this time are preferably a temperature of 120 to 250 ° C. and a pressure of 0.5 to 30 kgcm ⁻² .

In step 5, when the protruding electrode 6 is formed by plating, the area of the plating portion with respect to the substrate area is very small, so that charges may concentrate and dendritic plating may grow. Separately, it is preferable to perform plating by providing a dummy substrate having a shape avoiding the protruding electrode dense portion, that is, a shape having a window slightly larger than the electrode dense portion.

The area ratio of this dummy substrate to the bump electrode group is 100
It is preferably at least 500 times, more preferably at least 500 times. Copper, nickel, silver, gold and the like can be used as the plating metal for forming the protruding electrode 6, similarly to the metal for forming the wiring conductor pattern 3, but copper having low conductivity and excellent conductivity is preferable. Among them, particularly preferred is copper sulfate plating or copper pyrophosphate plating in which the growth rate of plating in the vertical direction with respect to the horizontal direction is high and the distance between the protruding electrodes can be reduced.

Since it is difficult to obtain a smooth surface if plating is performed by ordinary continuous energization, plating is performed with intermittent pulses. Taking general acid copper plating as an example, the peak current density i _P = 1 to 6 Ad ^{−2 of} the pulse current, and the pulse period T = 10 to
100 msec, time ratio of pulse current flow (Duty Cycle)
From 20 to 80%, more preferably i _P = ^{2 to 4} Adm ⁻² , T = 20 to 50
It is preferable to perform plating by intermittent pulse plating of msec and Duty Cycle = 50 to 70%.

In order to reduce the connection resistance, it is preferable to apply gold plating to the surface of the bump electrode 6 by electroless plating or the like.

FIG. 2 is a view showing a manufacturing process of another embodiment of the present invention. In FIG. 2, the same parts as those in FIG. 1 are denoted by the same reference numerals. First, in the step (1), two sheets produced in the step (1) in FIG. 1 are bonded together with an adhesive with the wiring conductor pattern 3 side facing each other. In step (2), the protruding electrodes 6 are formed on both sides of the substrate 4 in the same manner as in steps (2) to (5) shown in FIG.

FIG. 3 also shows another embodiment of the present invention. In this connection board, the protruding electrode 6 covers a part of the surface of the insulating film 4b, but is different from the connection board shown in FIG. 1 and FIG. Is different. Two connection substrates shown in FIG. 3 may be bonded in the same manner as in the process shown in FIG.

Example Hereinafter, a connection substrate with fine projections manufactured according to the manufacturing process shown in FIG. 1 will be described, but the present invention is not limited thereto. The connection substrate shown in FIGS. 2 (2) and 3 and the connection substrate shown in FIG. 3 as well as the connection substrate with micro-projections having the structure shown in FIG. 1 (5) manufactured by this manufacturing process. Can be manufactured. Also,
It goes without saying that all of the above are effective for the chemicals such as the resist and the plating conditions.

First, in step (1), a liquid negative resist (KMR747: manufactured by Kodak Co.) is applied onto an aluminum carrier substrate 1 having a thickness of 80 μm, prebaked, and then exposed through a photomask. Rinsing was performed, and finally post-baking was performed to form a resist pattern 2 having a thickness of 4 μm. The thickness of the carrier substrate 1 is 10
It should just be -200 micrometers. The thickness of resist pattern 2 is 1
0 μm or less.

Next, using the aluminum carrier substrate 1 as a cathode,
After forming the wiring conductor pattern 3 by constant current electrolysis at 55 ° C. and 2.7 Adm ^{−2 in} a copper pyrophosphate plating bath, the resist is stripped using a resist stripper (N-530, manufactured by Nagase & Co., Ltd.). Was.

In steps (2) and (3), a polyimide film (Pilalux, manufactured by DuPont) having a thickness of 50 μm and an adhesive layer of 50 μm was placed on the wiring conductor pattern 3 at a temperature of 180 ° C. and a pressure of 3 μm.
After bonding by heating and pressing at kgcm ^-2 for 1 hour, the aluminum carrier substrate 1 was removed by etching in 7% hydrochloric acid.

In step (4), a hole having a diameter of 250 μm is formed by a numerically controlled driller in a portion corresponding to the protruding electrode 6 of a polyimide film (Pilalux manufactured by DuPont) having a thickness of 25 μm and an adhesive layer of 25 μm. Alignment was performed, and a heat and pressure press was performed for 1 hour at a temperature of 180 ° C. and a pressure of 1 kgcm ⁻² to bond a perforated polyimide film onto the wiring conductor pattern.

(5) A portion of the substrate prepared as described above other than the dense portion to be plated is covered with a plating dummy copper plate different from the present substrate, and the plate is formed so as to be electrically connected to the present substrate. went.

The area ratio of the dummy copper plate to the protruding electrode group was 800 times, and a strong oxide film was formed on the surface of the wiring conductor pattern at the time of pressing under heat and pressure. CP-2 (Harshaw Murata) as a brightener for plating to obtain an electrode surface 1.
Add 5cc ^{- 1} and ip = 2.5Adm- ² , T = 30msec, Duty Cycle
= Protruding electrode 6 was formed by intermittent pulse plating of 66%.

Finally, a thin layer of gold having a thickness of about 1 μm was formed on the surface of the bump electrode in an electroless gold plating solution.

The protruding electrode thus obtained was a perfect circle having a height of 30 μm and a diameter of 200 μm, and the surface roughness (distance between the peaks and valleys of the surface irregularities) was 1 μm or less.

[Effects of the Invention] As described above, according to the present invention, the projecting electrodes are formed on the carrier substrate side of the wiring conductor pattern by the plating method, so that the surface on which the projecting electrode forming plating resist is applied is smooth. Therefore, the resist position accuracy is as high as ± 5 μm or less, and since the plating starting surface for forming the bump electrode is smooth, an extremely smooth surface having a bump electrode surface roughness of 1 μm or less can be obtained. There is an effect that the degree can be freely changed as desired.

Therefore, according to the present invention, in order to reduce the connection electrode pitch, a diameter of 200 μm or less, sufficient connection reliability can be obtained, the height can be freely changed, and a fine projection electrode with a surface roughness of 1 μm or less can be used. There is an effect that a connection substrate with minute projection electrodes can be manufactured.

[Brief description of the drawings]

1 is an explanatory view of a manufacturing process of an embodiment of the present invention, FIGS. 2 and 3 are views showing another embodiment of the present invention, and FIG. 4 is a diagram showing a conventional method of manufacturing a connection substrate with minute projection electrodes. FIG. DESCRIPTION OF SYMBOLS 1 ... Carrier board, 2 ... Resist pattern, 3 ... Wiring conductor pattern, 4a ... Insulating substrate, 4b ... Insulating film, 5a, 5b ... Adhesive sheet, 6 ... Protruding electrode.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H01L 21/60 311 H05K 3/24

Claims (1)

(57) [Claims] 1. A step of forming a predetermined wiring conductor pattern on a carrier substrate by plating, a step of forming an insulating layer on the wiring conductor pattern, a step of removing the carrier substrate, and a step of removing the carrier substrate. Applying a plating resist on the side from which the fine protrusion electrodes have been removed, and forming fine protrusion electrodes at predetermined positions on the wiring conductor pattern by a plating method.