JP3188783B2 - Film carrier, film carrier device, and method of manufacturing film carrier - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a film carrier having a metal layer on both surfaces of a polyimide film and mounting a semiconductor element, a mounted film carrier device, and a method of manufacturing a film carrier.

[0002]

2. Description of the Related Art Conventionally, a film carrier used for manufacturing a film carrier device having a semiconductor element mounted thereon is made of copper or copper on one surface of an insulating film such as a polyimide resin via an epoxy resin or polyimide resin adhesive. It has a three-layer structure obtained by bonding a metal foil such as an alloy, and is generally called a three-layer film carrier in which a conductor pattern is formed on the metal foil using a photolithography method.

In recent years, with the rapid development of semiconductor device manufacturing technology, high-performance and multifunctional devices have been developed. As the mounting of these semiconductor elements, those capable of increasing the density and speed of recent film carriers are also possible, that is, those in which the distance between adjacent conductor patterns is small and the generation of noise (noise) can be reduced even when a high-frequency current flows. Is required.

Therefore, recently, an insulating film such as a polyimide resin has metal foils on both sides, and an inner lead connected to a semiconductor element, an outer lead connected to a printed circuit board, and an inner lead are provided on the insulating film surface (upper surface). It has a conductor pattern for connecting the outer leads, and the ground conductor pattern (ground electrode) has a ground metal layer (ground conductor) which is a full-surface metal foil connected to the back surface (lower surface) of the insulating film by a via hole (contact hole). The one generally called a two-metal film carrier having a plate) has been studied (Japanese Patent Laid-Open No. 4-196234).

A via hole is formed by a subtractive method in which a metal layer on the back surface is etched into a predetermined shape and a via hole is formed in an insulating film using hydrazine or a hydrazine mixed solution. As other methods, there are an excimer laser method, a carbon dioxide gas laser method, a method of punching using a mold, a method of removing with a drill, and the like.

However, in the laser method, not only the equipment is expensive, but also the productivity is poor and the cost is high.
In addition, the method of punching using a mold or the method of removing with a drill cannot be used for a high-precision and high-quality film carrier because the shape of the via hole cannot be reduced and burrs and gas are generated. Therefore, a wet etching method in which a via hole is formed in an insulating film using an etchant is most excellent in accuracy, quality, and cost.

As described above, a film carrier for connecting high-performance and multifunctional semiconductor elements requires a large number of conductor patterns for ground (ground electrodes) and conductor patterns for power supplies (power supply electrodes), and the number of conductors becomes extremely large. . Therefore, it is necessary to reduce the distance between the conductor patterns. In a general three-layer film carrier, when a high-frequency current flows through a power supply conductor pattern or the like, electromagnetic induction noise generally called ground bounce is generated. This causes the semiconductor element to malfunction. This is remarkable when the conductor pattern becomes long or when the wiring pitch of the conductor pattern becomes small. Further, in other conductor patterns, when the wiring pitch becomes small, the occurrence of crosstalk becomes remarkable. For this reason, a three-layer film carrier cannot be used as a device for a semiconductor element with high density or high speed.

In addition, a two-metal film carrier which has recently been studied has a via hole (contact hole).
4 (a), the noise (noise) can be suppressed even when a high-frequency current flows, but the via hole has a trapezoidal shape as shown in FIGS. Or rectangular shape, the adhesion strength with the metal layer formed thereafter is low, and the film carrier peels off due to distortion or bending when transporting the film carrier, or peels off in the thermal shock test, causing poor connection. .

Further, in forming via holes of Kapton manufactured by Dupont Toray Co., Ltd. as a polyimide resin, it has been studied to use an alkali hydroxide solution or a mixed solution thereof, or a hydrazine solution or a mixed solution thereof. No specific manufacturing method capable of stably forming a via hole has been established for UPILEX manufactured by Ube Industries, Ltd. and NEOFLEX manufactured by Mitsui Toatsu Chemicals, which are polyimide resins having high chemical resistance and alkali resistance.

For these reasons, a film carrier and a film carrier device which do not generate noise even when a high-frequency current flows and have high connection reliability have not been obtained.

[0011]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems of the prior art, and does not generate noise even when a high-frequency current flows, and has a high connection reliability. An object is to provide a method for manufacturing a carrier device and a film carrier.

[0012]

In order to achieve this object, the present invention relates to a method in which a polyimide resin is applied to one side of two metal foils and then cured by heating. Laminate the polyimide film side of the film with a polyimide varnish, then remove the metal foil on the back side, remove the polyimide resin and polyimide varnish, form a via hole, then form a metal layer on the back side, and with the metal foil on the front side with the via hole In the film carrier in which the metal layer on the back side is electrically connected, the via hole has, in its cross-sectional shape, an intersection of a line connecting each contact point of the metal foil on the periphery of the via hole and the contact point of the metal foil on the back side with the length of the polyimide varnish portion of the via hole. 1μ length from varnish to polyimide varnish
m or more.

Hereinafter, the present invention will be described in detail with reference to the drawings. 1 to 3 show schematic sectional views of a via hole portion of the film carrier of the present invention. In each figure, 1 is a front surface metal foil, 2 is a back surface metal foil, 3 is a front surface side polyimide resin, 4 is a back surface side polyimide resin, 5 is a polyimide varnish, 6 is a via hole, 7 is formed after forming a via hole. Each shows a metal layer. 4 and 5, the same reference numerals indicate the same components.

As shown in FIGS. 1 to 3, the via hole 6 of the present invention has a sectional shape in which a line connecting each contact point of the metal foil 1 on the peripheral edge of the via hole and the metal foil 2 on the back surface (indicated by a dotted line in each drawing). The length from the intersection of the length (L) of the polyimide varnish portion of the via hole and the length (L) of the via hole to the polyimide varnish 5 (indicated by 1 in each figure) must be 1 μm or more, preferably 3 μm or more. In other words, in removing the polyimide resin and the polyimide varnish, the polyimide varnish portion is removed in a larger amount than the surrounding polyimide resin portion. In this way, by removing the polyimide varnish part more than the surroundings,
Adhesion with the metal layer 7 formed thereafter is increased, and connection reliability can be improved.

In this case, the thickness of the metal foils 1 and 2 on both surfaces is not particularly limited, but is preferably 9 to 35 μm in consideration of the workability and etching property of the formation of the conductor pattern on the front surface and the formation of the via hole on the back surface. Also, the thickness of the polyimide resin 3, 4 layers is not particularly limited,
Considering the etching properties and high frequency characteristics,
0 μm is preferred. Furthermore, the polyimide varnish 5 used for bonding is not particularly limited, but is preferably 1 to 50 μm in consideration of the etching cost.

The shape of the via hole 6 as viewed from the rear surface side may be circular, elliptical, rectangular, rhombic, or the like without any problem.

FIGS. 4 and 5 are schematic sectional views of a via hole portion of a conventional film carrier. In the via hole, a polyimide varnish portion is not removed in a larger amount than a peripheral polyimide resin portion. The removal amount increases obliquely toward the portion in contact with 2, and in FIG. 5, the removal amount is the same as a whole. When the via hole 6 is formed in such a cross-sectional shape, the adhesion to the subsequently formed metal layer is significantly reduced.

Next, a method for forming a via hole according to the present invention will be described. In the formation of the via hole, after etching the metal foil on the back surface into a predetermined shape, the polyimide resin and the polyimide varnish are further etched. The aqueous solution used for this etching has a hydrazine concentration of 2
00-1000 ml / l, preferably 500-900 ml / l in consideration of processing time and liquid life, alkali hydroxide concentration 50-700 g / l, preferably 200-450 g / l in consideration of cross-sectional shape and processing time. At a liquid temperature of 20 to 90 ° C., preferably 40 to 70 ° C.
Etching is performed at a temperature of ° C. to have a predetermined cross-sectional shape. By performing such a process, a via hole can be formed stably even with a polyimide resin having high chemical resistance and alkali resistance, and the etching rate of the polyimide varnish portion is further increased, thereby stably forming a via hole having a desired cross-sectional shape. It can be formed without reducing productivity.

[0019]

Next, examples of the present invention will be described together with comparative examples.

Example 1 Two sheets of electrolytic copper foil (trade name: VLP, manufactured by Mitsui Mining & Smelting Co., Ltd.) having a thickness of 35 μm and 18 μm were each coated with a polyimide resin (trade name: NEOFLEX, manufactured by Mitsui Toatsu Chemicals) at a thickness of 25 μm
It applied so that it might become. Next, using these two copper foils,
The polyimide resin side was bonded via a polyimide varnish. Next, after removing a predetermined portion of the copper foil on the back surface, the hydrazine concentration was 700 mml / l, and the potassium hydroxide concentration was 30.
Using a 0 g / l aqueous solution, the polyimide resin and the polyimide varnish were dissolved and removed by etching at a liquid temperature of 70 ° C. to form a via hole.

The shape of the via hole at this time was as shown in FIG. Next, a metal layer was formed on the back surface, and a film carrier was obtained in which the metal foil on the front surface and the metal layer on the back surface were electrically connected with each other via holes.

For 100 film carriers,
As a thermal shock test, 100 cycles were performed at -65 ° C to 125 ° C. As a result, no connection failure occurred at all 100 pieces.

Example 2 Two sheets of 18 μm thick electrolytic copper foil (trade name: SLP, manufactured by Nihon Denki Co., Ltd.) were each coated with a polyimide resin (trade name: NEOFLEX, manufactured by Mitsui Toatsu Chemicals) at a thickness of 12.5 μm. It applied so that it might become. Next, using these two copper foils, the polyimide resin side was bonded via a polyimide varnish. Next, after removing a predetermined portion of the copper foil on the back surface, the hydrazine concentration was 800 ml / l and the potassium hydroxide concentration was 400 g.
/ L aqueous solution at a liquid temperature of 60 ° C to dissolve and remove the polyimide resin and polyimide varnish by etching.
Via holes were formed.

The shape of the via hole at this time was as shown in FIG. Next, a metal layer was formed on the back surface, and a film carrier was obtained in which the metal foil on the front surface and the metal layer on the back surface were electrically connected with each other via holes.

For 100 film carriers,
As a result of the same thermal shock test as in Example 1 as a thermal shock test, no connection failure occurred at all 100 pieces.

Comparative Example 1 As an aqueous solution for dissolving and removing the polyimide resin and the polyimide varnish, an aqueous solution having a hydrazine concentration of 150 ml / l and a potassium hydroxide concentration of 40 g / l was used.
A via hole was formed in the same manner as in Example 1 except for the following.

The shape of the via hole at this time was as shown in FIG. Next, a metal layer was formed on the back surface, and a film carrier was obtained in which the metal foil on the front surface and the metal layer on the back surface were electrically connected with each other via holes.

For 100 film carriers,
As a result of the same thermal shock test as in Example 1, disconnection (poor connection) occurred in 61 out of 100 pieces.

Comparative Example 2 As an aqueous solution for dissolving and removing the polyimide resin and the polyimide varnish, an aqueous solution having a hydrazine concentration of 100 ml / l and a potassium hydroxide concentration of 120 g / l was used.
A via hole was formed in the same manner as in Example 1 except that the temperature was changed to ° C.

At this time, the shape of the via hole was as shown in FIG. Next, a metal layer was formed on the back surface, and a film carrier was obtained in which the metal foil on the front surface and the metal layer on the back surface were electrically connected with each other via holes.

For 100 film carriers,
As a result of performing the same thermal shock test as in Example 1, 83 out of 100 wires were disconnected.

Comparative Example 3 An aqueous solution having a hydrazine concentration of 400 ml / l and a potassium hydroxide concentration of 20 g / l was used as an aqueous solution for dissolving and removing the polyimide resin and the polyimide varnish.
A via hole was formed in the same manner as in Example 1 except for the following.

The shape of the via hole at this time was as shown in FIG. Next, a metal layer was formed on the back surface, and a film carrier was obtained in which the metal foil on the front surface and the metal layer on the back surface were electrically connected with each other via holes.

For 100 film carriers,
As a result of performing the same thermal shock test as the example, 4 out of 100
Disconnection occurred in 9 pieces

Comparative Example 4 As an aqueous solution for dissolving and removing the polyimide resin and the polyimide varnish, potassium hydroxide was set to 1 N, and an aqueous solution having a 1: 1 volume ratio of ethyl alcohol was used.
A via hole was formed in the same manner as in Example 1 except that the temperature was changed to ° C. However, the chemical resistance of the polyimide layer was high and sufficient etching could not be performed.

Comparative Example 5 An aqueous solution having a hydrazine concentration of 100 ml / l and a potassium hydroxide concentration of 100 g / l was used as an aqueous solution for dissolving and removing the polyimide resin and the polyimide varnish.
A via hole was formed in the same manner as in Example 1 except that the temperature was set to 0 ° C.

At this time, the shape of the via hole was as shown in FIG. Next, a metal layer was formed on the back surface, and a film carrier was obtained in which the metal foil on the front surface and the metal layer on the back surface were electrically connected with each other via holes.

For 100 film carriers,
As a result of the same thermal shock test as in the example, breakage occurred in 67 out of 100 pieces.

[0039]

As described above, according to the film carrier and the film carrier device of the present invention, noise (noise) does not occur even when a high-frequency current flows, and high connection reliability is obtained.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a via hole in a first example of a film carrier of the present invention.

FIG. 2 is a schematic cross-sectional view of a via hole in a second example of the film carrier of the present invention.

FIG. 3 is a schematic sectional view of a via hole portion in a third example of the film carrier of the present invention.

FIG. 4 is a schematic cross-sectional view of a via hole portion in an example of a conventional film carrier.

FIG. 5 is a schematic cross-sectional view of a via hole portion in an example of a conventional film carrier.

[Explanation of symbols]

1: front surface metal foil, 2: back surface metal foil, 3: front surface side polyimide resin, 4: back surface side polyimide resin, 5: polyimide varnish, 6: via hole, 7: metal layer formed after via hole formation.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Yukihiro Ozawa 1-4-27 Nagano, Gyoda-shi, Saitama (56) References JP-A-2-159013 (JP, A) JP-A-3-237736 (JP, A) JP-A-4-196234 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 21/60 311

Claims (3)

(57) [Claims] 1. A polyimide resin is applied to one surface of two metal foils, respectively, and the two metal foils obtained by heating and curing are bonded to a polyimide film side of a polyimide film with a polyimide varnish. Metal foil,
Remove the polyimide resin and polyimide varnish, form a via hole, then form a metal layer on the back surface, in the film carrier electrically connected the metal foil on the front surface and the metal layer on the back surface in the via hole, the via hole, the via hole, In the cross-sectional shape, the length from the intersection of the line connecting the contact points of the metal foil on the periphery of the via hole and the metal foil on the back surface to the length of the polyimide varnish portion of the via hole to the polyimide varnish is 1.
A film carrier having a thickness of at least μm. 2. A film carrier device obtained from the film carrier according to claim 1. 3. The removal of the polyimide resin and the polyimide varnish for forming the via holes is performed by using an aqueous solution having a hydrazine concentration of 200 to 1000 ml / l and an alkali hydroxide concentration of 50 to 700 g / l at a liquid temperature of 20 to 90 ° C.
The method for producing a film carrier according to claim 1, which is performed by: