JP3205089B2 - Method for producing multilayer conductor 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 method for manufacturing a multilayer conductor film carrier.

[0002]

2. Description of the Related Art As the performance of ICs increases with each generation, higher densities and higher speeds of ICs are expected to realize higher performance. At the same time, the number of pins in the package has been increased and the number of pins has been reduced.
It is well known that crosstalk occurs between signal conductors during electrical operation as a problem associated therewith, causing electrical malfunction.

[0003] Looking at this with respect to a multilayer conductor film carrier, the conventional multilayer conductor film carrier has a problem in increasing the number of pins and reducing the number of pins. The problems are roughly classified into those based on the structure of the base material and those based on the relationship between the thickness of the base material and the diameter of the through hole as described below.

<Problems Based on the Structure of the Base Material> The structure of the base material of the conventional multilayer conductor film carrier is 50 μm.
Since a thin film layer of about 0.5 μm is formed on both sides of the polyimide (Kapton) base by sputtering directly without using an adhesive, through holes are formed between the different layers of the conductor to allow electrical conduction. Thereafter, in order to obtain a generally required thickness of 25 to 35 .mu., A copper deposition layer is formed by an additive plating method. At this time, since the copper plating is applied in layers on the entire surface of the copper foil including the signal circuit and the ground surface, the following problem occurs.

For example, in order to obtain a lead width of 50 μm for the inner lead and a lead width of 150 μm for the outer lead, unnecessary portions are first masked with a photoresist, and copper is deposited at a predetermined place by electroplating. Since the exposed areas of the portions are different, variations in the concentration density of the plating current occur. As a result, irregularities in the lead thickness occur, and mechanical strength and bonding failure frequently occur. It can be easily predicted that such a problem will be amplified in future packages in which the number of pins is increasingly increased and the number of pins is reduced.

[0006] Delamination between plating and a copper foil at a portion where a high-load mechanical stress is applied, such as a bonding process for an inner lead and an outer lead, and metal deterioration due to a difference in physical properties between the plated copper and the copper foil occur.

<Problems based on the relationship between the thickness of the base material and the diameter of the through hole> For example, in a product in which the number of leads is 500 pins or more, the pitch of the inner leads is 100 μ or less, and the pitch of the outer leads is 250 μ, Considering positional accuracy and the like, it is necessary for the fine pattern to realize a hole diameter of 70 μm or less.

On the other hand, in order to increase the number of pins and reduce the number of pins,
In manufacturing, the thicker the base material is, the easier it is to secure the pattern accuracy, but it is inconsistent with the processing technique for drilling holes. As a conventional technique for making holes, there are roughly the following methods.

[0009] Mechanical processing method [0009] Since a hole is mechanically drilled with a drill or a punch, an extremely small hole of 100 µ or less cannot be processed. Therefore, it cannot respond to fine pitch. For example, if the base material thickness is 50μ or more,
Alternatively, when an adhesive is further present, the processing accuracy is further reduced.

Laser processing method There are methods using a carbon dioxide gas laser, a yag laser, and an excimer laser. For example, a minimum processing of 30 μm is possible, but when a large amount of processing energy is consumed in proportion to the base thickness and the adhesive thickness. At the same time, it takes a long time to drill holes. That is, as the material thickness, the hole diameter, and the adhesive increase, the energy and the processing time increase, and the cost increases.

Chemical treatment For example, when holes are made in a base material such as polyimide, a mask is applied except where holes are made, and then etching is performed using a strong alkali chemical. In drilling holes, etching time and processing accuracy depend on the material thickness.
In addition, there is a disadvantage in that the hole has a tapered shape peculiar to etching. It becomes more apparent as the pore size decreases. For example, if a hole of 50 μm is to be made, the diameter actually becomes about 100 μ at the bottom of the taper. For this reason, it is not possible to make a very small hole. There is also a problem of waste liquid pollution.

[0012]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned various problems, and to cope with the increase in the number of pins and the reduction in the number of pins. In addition to making it possible to open, a ground layer separated by an insulating layer is formed on the other side of the lead pattern on one side, and the conductor circuit formed on one side is electrically connected to the ground layer on the other side The purpose of the present invention is to prevent the occurrence of crosstalk and to avoid an electrical malfunction.

[0013]

According to the present invention, a base film having a metal foil serving as a ground layer adhered to the back surface is used as a base material. Then, after a device hole and a slit located around the device hole are formed in the base film and the metal foil, a conductive foil is bonded to the surface of the base film. Next, a resin is poured into the slit, a portion corresponding to the slit of the conductive foil is also penetrated to form a through hole in the resin, and a through hole plating is performed in the through hole so as to contact the metal foil. A lead pattern is formed from the foil.

[0014]

In the present invention, a slit is formed in a base film, a resin is poured into the slit, and then a through hole is formed only for the resin. The thickness of the through hole is determined by the thickness of the resin. Since the thickness is not related to the thickness, that is, the thickness can be made smaller than the thickness, a very small through hole can be easily formed. Also,
The lead pattern made of the conductive foil on the front side can be electrically connected to the ground layer made of the metal foil on the back side through a very small through hole.

[0015]

Next, an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 shows an example of the manufacturing method according to the present invention in the order of steps (1) to (8), and the operation of each step is as follows.

(1) Adhesive layers 11 and 12 are formed on the front and back surfaces of the base film 10, and a 35 μm or 70 μm thick metal foil 13 serving as a ground layer is formed on the back surface of the base film 10 by the adhesive layer 12. The adhered material is used as a substrate. (2) Polymerized base film 10 and metal foil 1
2, a rectangular device hole 14 as shown in FIG. 2, slits 15 located at four locations around the device hole 14, and outer lead holes 16 located at four locations around the outside are simultaneously punched.

(3) A copper foil (conductive foil) 17 is laminated on the surface of the base film 10 with the adhesive layer 11. (4) As shown in FIG. 3, a plurality of copper foils 1 corresponding to each slit
After the etching holes 18 are formed in the slit 7, the slits 15 are temporarily closed from behind.
The resin 19 is poured into the inside to a thickness of about 20 to 30 μm.

(5) For the resin 19 of each slit 15, a through hole 20 corresponding to each etching hole 18 is formed.
Drill by laser or by chemical or mechanical method. (6) Etching hole 18 and through hole 20
Inside, through-hole plating 21 is applied so that the peripheral edge of the slit 20 contacts the metal foil 12.

(7) Photoresist 22 on copper foil 17
After exposure and development, the photoresist 22 is peeled off to form a lead pattern 23 of the remaining copper foil 17 as shown in FIG. FIG. 5 is an enlarged view of a part of FIG. (8) A surface treatment plating 24 is applied on the lead pattern 23 on the front side and the through-hole plating 21 on the back side.

In the above-described embodiment, the etching hole 18 is formed in a portion corresponding to the slit 15 of the conductive foil 17, but the etching hole 18 does not necessarily need to be formed by etching. 2
When opening 0, laser may be used to open simultaneously. Also, the device hole 14 and the outer lead hole 16
Although an example is shown in which one slit 15 is provided between the slits, the number of slits is not limited to one, and a plurality of slits may be provided.

[0021]

As described above, according to the present invention, a slit is formed in a base film, a resin is poured into the slit, and a through hole is formed only for the resin. Since the thickness is determined by the above and is not related to the thickness of the base film, that is, the thickness can be made smaller than the thickness, a very small through hole can be easily formed. In addition, since the lead pattern made of the conductive foil on the front side can be electrically connected to the ground layer made of the metal foil on the back side through a very small through hole, it is possible to cope with the increase in the number of pins and the reduction in the number of pins, and to prevent the occurrence of crosstalk Electrical malfunction can be avoided.

[Brief description of the drawings]

FIG. 1 shows an example of a production method according to the present invention in the order of steps (1).
It is sectional drawing of the film carrier shown separately from (8).

FIG. 2 is a plan view showing a process state of FIG. 1 (2).

FIG. 3 is a plan view showing a process state of FIG. 1 (4).

FIG. 4 is a plan view showing a state after a step (7) in FIG. 1;

FIG. 5 is an enlarged view of a part of the above.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Base film 11 * 12 Adhesive layer 13 Metal foil 14 Device hole 15 Slit 16 Outer lead hole 17 Copper foil 18 Etching hole 19 Resin 20 Through hole 21 Through hole plating 22 Photoresist 23 Lead pattern 24 Surface treatment plating

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01L 21/60 311 H01L 23/50

Claims (1)

(57) [Claims] A step of forming a device hole and a slit located therearound in a metal foil bonded to a base film and a back surface thereof; a step of bonding a conductive foil to a surface of the base film; A step of pouring a resin, a step of opening a through hole in the resin by also penetrating a portion corresponding to the slit of the conductive foil, a step of performing through hole plating in contact with the metal foil in the through hole, Forming a lead pattern. A method for manufacturing a multilayer conductor film carrier, comprising: