JP2003224161A - Semiconductor package and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor package in which a solder ball is easily placed, there is no necessity to form a solder resist, to wash and remove remaining flux after solder joint, and to fill with under fill, etc., electrical insulation is kept even under a high temperature and a humid atmosphere, and solder joint of high joint strength and high reliability is enabled, and a method for manufacturing the package. <P>SOLUTION: This method includes a process wherein a negative photosensitive resin, a photo polymerization starting agent, a heat curing resin and a composition of negative photosensitive resin comprising a compound containing organic acid and/or phenolic hydroxyl group as a curing agent for the heat curing resin are applied to a circuit pattern provided with a solder ball mounting land, a process wherein the land is masked for irradiating with an active energy line, a process wherein the solder ball is placed in a part where is not exposed to the active energy line, and a process wherein heating is performed in a reflow furnace. By this method, metal joint between the solder ball and the land is formed. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention provides a highly reliable semiconductor package in which solder balls are efficiently arranged and the solder balls are reinforced with a resin in a semiconductor package joined to a printed wiring board via solder balls. To get it.

[0002]

2. Description of the Related Art With the recent demand for high functionality, lightness, thinness, shortness, and miniaturization of electronic devices, high-density integration and further high-density mounting of electronic parts have been advanced, and they are used in these electronic devices. Semiconductor packages are becoming smaller and more pins than ever before.

As semiconductor packages have become smaller,
In a package using a lead frame as in the past, miniaturization has reached its limit, so recently, a BGA (Ball) has been used as a chip mounted on a circuit board.
Grid Array) and CSP (Chip Sc)
A new package method of area mounting type, such as a package, has been proposed. In these semiconductor packages, various insulating materials such as plastics and ceramics called a semiconductor mounting substrate, which have electrodes of a semiconductor chip and functions of a lead frame of a conventional semiconductor package, and terminals of a substrate composed of conductor wiring, As the electrical connection method of the wire bonding method or TA
B (Tape Automated Bonding)
Although a system, further, an FC (Flip Chip) system and the like are known, recently, BGA and CSP structures using the FC connection system, which are advantageous for miniaturization of a semiconductor package, have been actively proposed.

For mounting BGA or CSP on a printed wiring board, solder bonding using bumps formed of solder balls is adopted. Flux is used for this soldering, and solder paste may be used together. In particular, the reason why the solder balls are used is that the amount of solder supplied can be easily controlled and a large amount of solder can be supplied, so that the bumps can be made higher. Further, solder bonding is often used also in the method of electrically connecting the electrodes of the semiconductor chip and the terminals of the semiconductor mounting substrate in the manufacturing process of BGA and CSP.

Generally, in solder joining, while removing stains such as oxides on the metal surface of the electrode facing the solder surface,
A soldering flux is used to prevent reoxidation of the metal surface during soldering, reduce the surface tension of the solder, and make it easier for the molten solder to wet the metal surface. As this flux, a flux obtained by adding an activator for removing an oxide film to a thermoplastic resin type flux such as rosin is used.

However, if this flux remains, the thermoplastic resin melts at high temperature and high humidity, and active ions in the activator are liberated, which causes problems such as deterioration of electrical insulation and corrosion of printed wiring. Occurs. Therefore, at present, the above-mentioned problems are solved by cleaning and removing the residual flux after soldering, but there are drawbacks such as environmental problems of the cleaning agent and cost increase due to the cleaning process.

As described above, the function of the flux is to remove oxides from the solder and the metal surface, prevent reoxidation, improve solder wettability (reduce the surface tension), and the flux exists and the metal surface is exposed. If so, the solder will get wet without restriction. Therefore, in general, a solder resist is used on the circuit surface of a semiconductor package or a printed wiring board for the purpose of introducing solder only to a solder joint and protecting the conductor wiring pattern. However, if this solder resist remains in the solder joint portion, problems such as deterioration in connection reliability and failure in solder joint may occur. Therefore, the solder resist should be formed with extreme caution.

Further, the miniaturization and increase in the number of pins of the semiconductor package promotes the miniaturization of the solder balls, and there is a concern that the joint strength and the reliability are deteriorated. Therefore, in order to obtain the reliability of the solder ball connection portion, a study of filling the gap between the chip and the substrate with an insulating resin called underfill to seal and reinforce the bump connection portion has been actively made. However, this requires a step of filling and curing underfill having a high degree of technical difficulty, so that there is a problem that the manufacturing process is complicated and the manufacturing cost is high.

Further, a solder mount method using a ball mounter or screen printing is also used for solder ball placement on a semiconductor package, but the difficulty is increasing with the miniaturization of the solder balls.

[0010]

SUMMARY OF THE INVENTION In view of these problems of the current state of solder joining when mounting a semiconductor package, the present invention provides easy solder ball placement, formation of solder resist, and residual flux after solder joining. Provided is a semiconductor package and a method for manufacturing the same, which does not require cleaning and removal of the underfill, filling of underfill, etc., maintains electrical insulation even in a high temperature and high humidity atmosphere, and enables soldering with high bonding strength and reliability. The purpose is to

[0011]

That is, the present invention provides a negative photosensitive resin having at least one acryloyl group and / or methacryloyl group, a photopolymerization initiator, a thermosetting resin, and the thermosetting resin. As a curing agent for organic acids and /
Alternatively, a step of applying a negative photosensitive resin composition containing a compound having a phenolic hydroxyl group onto a circuit pattern having solder ball mounting lands, a step of irradiating active energy rays by masking the lands, active energy A method of manufacturing a semiconductor package for forming a metal joint between a solder ball and the land by a method including a step of arranging a solder ball on a line unexposed portion and a step of heating with a reflow oven, and the solder ball and the land. The method for manufacturing a semiconductor package further includes a heating step after forming a metal bond with. Furthermore, in the step of disposing the solder ball in the unexposed portion of the active energy ray, the unexposed portion has tackiness, and after selectively holding the solder ball only in the unexposed portion by utilizing the tackiness, It is a method of manufacturing a semiconductor package, which is a step of arranging solder balls at predetermined positions on a circuit pattern.

Further, the present invention is a semiconductor package manufactured by the method for manufacturing a semiconductor package described above.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The negative photosensitive resin composition used in the present invention comprises at least one acryloyl group and / or
Alternatively, a negative photosensitive resin having a methacryloyl group, a photopolymerization initiator, a thermosetting resin, an organic acid for exhibiting a metal oxide film removing action when heated as a curing agent for the thermosetting resin, and / or It is a composition having a tacky property, which has a phenolic hydroxyl group and contains a component which reacts with a thermosetting resin and is incorporated into its skeleton. After coating the circuit surface of a semiconductor package with this composition, the organic acid or phenolic hydroxyl group exerts a reducing action by being heated in a reflow furnace, and the oxide film on the solder ball surface and the land copper foil surface is removed. , Expose the new face.

In order to coat the negative photosensitive resin composition on the entire circuit surface, it may be diluted with a solvent if necessary,
A method such as screen printing, spin coating, or a method in which a film substrate is cast-coated to form a dry film and laminated can be used.

Further, it is preferable to use ultraviolet rays as an active energy ray for photo-curing the negative photosensitive resin composition. By exposing and photo-curing other than the land portion for forming the solder ball bump, the exposed portion of the exposed portion is exposed. The fluidity is reduced, and the area in which the solder spreads during solder joining is restricted to the unexposed portion.

FIG. 1 shows an outline of a process of arranging a solder ball on an unexposed portion. In FIG. 1B, the resin has tackiness in the unexposed portion (5), and the exposed portion (4) does not have tackiness. Therefore, when the resin surface is pressure-bonded to the solder ball (6) as shown in FIG. 1C, the solder ball can be selectively held only in the unexposed portion as shown in FIG. 1D. When the solder balls are arranged by this method, it is not necessary to create a new jig or the like even if the solder ball arrangement pattern changes, and it is possible to suppress an increase in manufacturing cost. The solder balls held in this manner are melted and metal-bonded to the copper lands by being placed in a reflow furnace together with the semiconductor package, and become solder ball bumps.

FIG. 2 schematically shows a step of heating the solder balls in a reflow furnace after the solder balls are arranged. When exposed to a reflow oven, the unexposed portion (5) of the negative photosensitive resin composition
Since the viscosity of the land and the solder ball is reduced while removing the oxide film, the solder ball (7) is sinking and coming into contact with the land while removing the negative photosensitive resin composition by its own weight. As a result, a metal bond is formed without the resin being caught between the solder and the land to form a solder ball bump. In addition, the resin removed by the solder balls moves to the solder ball bump base. The removed negative photosensitive resin composition improves the connection reliability of the finished semiconductor package because the thermosetting component cures and reinforces the solder ball bump base by adding a heating step after forming solder bumps. To do. Further, the heating process also cures the negative photosensitive resin composition in the exposed portion by heat, and a resist layer integrated with the solder ball reinforcing structure is formed on the circuit.

If an organic acid having a metal oxide film reducing function or a compound having a phenolic hydroxyl group remains in the resin as it is, it becomes a factor of deteriorating the electrical characteristics of the semiconductor package. In the present invention, since it reacts with the thermosetting resin contained in the resin composition and is incorporated into the skeleton thereof, the cleaning which is required when using the flux normally used for removing the metal oxide film for solder joining, It becomes possible to omit steps, which contributes to simplification of steps.

[0019]

EXAMPLES Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited thereto.

Example 1. 14 parts by weight of phenol novolac resin (PR-HF-3 manufactured by Sumitomo Bakelite), 48 parts by weight of liquid epoxy resin (RE810NM manufactured by Nippon Kayaku), 12 parts by weight of terephthalic acid, photoreactive monomer (Actilane 440 manufactured by Across Chemicals) 16 By weight, 1.2 parts by weight of a photoinitiator (manufactured by Ciba Specialty Chemicals: Irgacure 651) and 8.8 parts by weight of butyl benzoate were kneaded to obtain a negative photosensitive resin composition.

Next, this negative type photosensitive resin composition is sealed on one side with a sealing resin after mounting a semiconductor chip on the other side, and on the other side as shown in FIG. By a screen printing method, a double-sided rigid printed wiring board on which a land (8) for joining with and was arranged was printed so as to have a thickness of 30 μm. Next, the negative photosensitive resin composition was cured by irradiating it with ultraviolet rays of 250 mJ while masking only a circular portion having a diameter of 270 μm and concentric with the land.

The above sample was pressed with a pressure of 10 KPa for 3 seconds so that the printed surface of the negative photosensitive resin composition faced the solder balls on a flat SUS plate spread with solder balls, and then lifted up. The solder balls were selectively retained only in the unexposed areas of the negative photosensitive resin composition.

The sample in which the solder balls are selectively held is placed in a reflow furnace with the solder ball holding surface facing upward, and the solder balls form metal bonds with the lands to form solder bumps. On the other hand, the negative resin composition in the unexposed area was removed by the solder balls and moved to the solder ball bump base.

Further, the sample on which the solder ball bumps are formed is put into a hot air circulation heater and heated at 150 ° C. for 1 hour to heat-cure the negative photosensitive resin composition, and a resist layer for protecting the circuit. In addition to the above, the resin existing on the base of the solder baud bump was also thermoset to form a structure for reinforcing the base of the solder ball bump.

The sample obtained as described above was mounted on a mother board and put into a temperature cycle test.

Comparative Example 1 Instead of the negative photosensitive resin composition of Example 1, a photosensitive solder resist (PSR-4000-manufactured by Taiyo Ink Co., Ltd.) was used.
AUS5) was printed by screen printing, exposed and developed so that the land portion was opened, and then solder ball bumps were formed using flux, and then the flux residue was removed.

The above sample was also subjected to the temperature cycle test as in the example. The results of the temperature cycle test are shown in Table 1. <Test conditions> -65 ° C 30 minutes ⇔ 150 ° C 30 minutes <Judgment criteria> ○ Conduction resistance change rate of solder ball joint is less than 100% × Conduction resistance change rate of solder ball joint is 100% or more

[0028]

[Table 1]

[0029]

According to the present invention, it is possible to arrange the solder balls efficiently with respect to the semiconductor package connected to the mother board via the solder ball bumps, and the solder ball bumps of the obtained semiconductor package can be arranged. Since the base is protected by the resin, a highly reliable semiconductor package can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing an example of a solder ball arranging step in the present invention.

FIG. 2 is a schematic cross-sectional view showing an example of a step of heating with a reflow furnace of the present invention.

FIG. 3 is a schematic plan view of a circuit side of a double-sided rigid printed wiring board used in Example 1.

[Explanation of symbols]

1. Semiconductor chip 2. Printed wiring board 3. Negative photosensitive resin composition 4. Exposure unit 5. Unexposed area 6. Solder ball 7. Solder ball 8. Land for joining

Claims (4)

[Claims] 1. At least one acryloyl group and / or
Alternatively, a negative photosensitive resin containing a methacryloyl group-containing negative photosensitive resin, a photopolymerization initiator, a thermosetting resin, and a compound having an organic acid and / or a phenolic hydroxyl group as a curing agent for the thermosetting resin. A step of applying a resin composition onto a circuit pattern having solder ball mounting lands,
Metal bonding of the solder ball and the land by a method including a step of irradiating the land with an active energy ray while masking the land, a step of arranging a solder ball in an unexposed area of the active energy ray, and a step of heating with a reflow furnace A method of manufacturing a semiconductor package, comprising: 2. The method of manufacturing a semiconductor package according to claim 1, further comprising a heating step after forming a metal joint between the solder ball and the land. 3. In the step of disposing the solder balls in the unexposed areas of active energy rays, the unexposed areas have tackiness, and the tackiness is utilized to selectively hold the solder balls only in the unexposed areas. 3. The method of manufacturing a semiconductor package according to claim 1, which is a step of arranging solder balls at predetermined positions on the circuit pattern. 4. A semiconductor package manufactured by the method for manufacturing a semiconductor package according to claim 1.