JP2012238771A - Underfill having dilatancy characteristics - Google Patents

Abstract

In a semiconductor package in which a solder bump such as BGA having a lead-free solder composition is formed and a semiconductor device is connected to a mounting substrate, electronic component mounting such as a semiconductor package having excellent impact resistance and high connection reliability is provided. To do.
A semiconductor device having a solder terminal such as a GA, a mounting substrate connected to the semiconductor device, and a connection structure such as a semiconductor package comprising an underfill interposed between the semiconductor device and the mounting substrate. By using a composition having a dilatancy characteristic for the underfill, it is possible to dramatically reduce the impact applied to the solder joint with respect to impact such as dropping, and to improve impact characteristics such as drop resistance. Further, by selecting a composition having an anti-oxidation effect on the solder joint in the underfill, connection reliability over time is improved.
[Selection] Figure 1

Description

The present invention relates to an electronic device mounted with an electronic component, and more particularly to an underfill of a semiconductor package mounted with a semiconductor such as a CSP package.

2. Description of the Related Art In recent years, in portable information devices typified by mobile phones, the progress of miniaturization and weight reduction and multi-functionalization of devices has been rapid, and semiconductor packages mounted on these portable information devices have also been miniaturized. For mounting these semiconductor packages, BGA (Ball
A fine solder ball represented by (Grid Array) is often used.
On the other hand, the lead-free solder alloy such as Sn—Cu, Sn—Ag—Cu, Sn—Cu—Ni is used for the solder balls used in the semiconductor package in consideration of the influence on the environment. Solder bonding is performed by a so-called reflow method.

In addition, mobile information devices are constantly exposed to the risk of impact loads such as dropping due to their usage environment, and of course, even for mounted semiconductor packages, drop impact loads and mechanical loads. Therefore, it is necessary to guarantee the reliability of these loads.
Therefore, various proposals have been made to improve the impact resistance characteristics of the solder connection portion using BGA or the like.

For example, as disclosed in Patent Document 1 and Patent Document 2, focusing on the alloy composition, a proposal for improving the strength of a solder joint against a drop impact, or as disclosed in Patent Document 3, on the surface of an Ag or Cu foil material. Proposal for improving drop strength by using a brazing material sheet having an Sn layer, as disclosed in Patent Document 4, a solder ball is used to relieve stress generated in a solder ball joint due to dropping by using an underfill resin. Proposals have been made in which the joint is less likely to break. Further, Patent Document 5 proposes that dilatancy is imparted to the composition of the underfill to improve the underfill impregnation property, thereby suppressing the generation of voids and improving the reliability.
However, in the above proposals and the like as well, defects such as breakage of solder joints due to impacts such as dropping are currently occurring, and a technique that further improves connection reliability is demanded.

JP 2005-254298 A JP 2004-154845 A JP 2006-272449 A JP 2009-152501 A JP 2009-57575 A

In view of the above situation, the object of the present invention is to provide a semiconductor package in which a solder bump such as a BGA having a lead-free solder composition is formed to connect a semiconductor device and a mounting substrate, and has excellent impact resistance and high connection reliability. It is to provide electronic component mounting such as a semiconductor package.

In order to achieve the above-described object, the present invention has been made through extensive studies, and as a result, a semiconductor device having a solder terminal such as a BGA, a mounting substrate connected to the semiconductor device, and an underlayer interposed between the semiconductor device and the mounting substrate. By using a composition with dilatancy characteristics in the underfill for the connection structure such as semiconductor package made of fill, the impact on the solder joints is dramatically reduced with respect to the impact such as dropping. The impact characteristics can be improved.
In other words, against the impact on the solder joints in the semiconductor package caused by impact such as dropping, the underfill with intervening dilatancy characteristics can alleviate the drop impact and dramatically reduce the load on the solder joints. It becomes.
Further, by selecting a composition having an antioxidant effect on the solder joint as the underfill composition, the connection reliability over time is improved, and as a result, the reliability is synergistically improved.

Since the semiconductor package using the underfill of the present invention can improve the drop impact resistance, even in an electronic device such as a portable information device exposed to danger of dropping, a connection failure caused by dropping occurs. It can be expected to reduce.

The model figure showing the connection of a semiconductor package. The model figure showing the change of the distortion of a solder joint part and a semiconductor device at the time of giving a drop impact to the semiconductor package using the conventional underfill. The model figure showing the change of the distortion of the solder joint part and semiconductor device at the time of giving a drop impact to the semiconductor package using the underfill of the present invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

As shown in FIG. 1, the semiconductor package is often composed of a BGA type semiconductor device (1), a solder bump (2), a mounting substrate (3), and an underfill (4) as an example of the semiconductor device. .
And in the conventional semiconductor package, many thermosetting resins, such as an epoxy resin, are used as an underfill.
These thermosetting resins use capillary action to permeate the space between the BGA type semiconductor device (1) and the mounting substrate (3) and then heat cure. There are still problems such as remaining.
There is also a proposal for improving the impregnation property by imparting dilatancy characteristics to the underfill as in Patent Document 5, but the void has not been completely eliminated.
In addition, when a thermosetting resin is used, there is a problem that it is difficult to perform rework work such as defective products generated in the work process.

Next, a phenomenon in which a semiconductor package is damaged due to a drop impact will be described.
When the underfill (4) of the semiconductor package shown in FIG. 1 is a thermosetting resin such as an epoxy resin, as shown in FIG. The state was shown as (A), the moment when the drop impact was applied was shown as (B), and the state after the drop impact was added was shown as (C). At the moment when the drop impact is applied, the portion that is most likely to be deformed by the drop impact force (in the model diagram, a semiconductor device is assumed) is deformed, and similarly, the solder bump (2) joined is also deformed. Thereafter, the state before the drop impact is applied by the restoring force is approached, but at that time, it is considered that a crack may occur at the joint between the solder bump and the semiconductor device.

Furthermore, the case where the underfill composition having the dilatancy characteristic of the present invention is used will be described with reference to FIG. By using a composition having dilatancy characteristics for the underfill (4) of the semiconductor package shown in FIG. 1, the bonding state of the semiconductor device, the solder bump, and the mounting substrate before the drop impact is applied as shown in FIG. D), the moment when the drop impact was applied, (E), and the state where the drop impact was applied for a while was represented by (F). At the moment when the drop impact is applied, as in the conventional semiconductor package, the portion that is most likely to be deformed by the drop impact force (in the model diagram, a semiconductor device is assumed) is slightly deformed, but the dilatancy characteristic immediately acts, In order to mitigate the impact, the degree of deformation of the semiconductor device is small, and accordingly, the deformation of the solder bump is also small, and it is considered that the joint between the solder bump and the semiconductor device is not damaged.

The underfill having the dilatancy characteristics of the present invention is not particularly limited with respect to its composition and properties, the amount used for the semiconductor package, and the like as long as it has the dilatancy characteristics that are the effects of the present invention.
Regarding the composition, thermosetting resins such as epoxy resins, urethane resins, engineering plastics, glycerin, polyhydric alcohols, etc. can be used as the liquid composition, and fillers such as silica and silicone resin powder can be used as the solid composition. Can be used. And it is also possible to use combining the 1 type or multiple types of each said composition according to a use.
In addition, there is no limitation as long as it can be injected into a semiconductor package, and any properties are acceptable in a state where the underfill having the dilatancy characteristics of the present invention is injected into a junction portion of the semiconductor package, liquid, gel, A jelly-like shape can be exemplified, and those having light weight and flexibility are preferable in consideration of the influence on solder bumps and semiconductor packages.

As an effect of the underfill having the dilatancy characteristic of the present invention, when a repair work is required when manufacturing a semiconductor package or joining to the semiconductor package electronic device, a thermoplastic resin can be used for the liquid composition, This can be achieved by selecting a composition that can be removed using a solvent or the like.
Furthermore, as an effect of the underfill having the dilatancy characteristic of the present invention, it is possible to select a composition that does not require removal of the flux used for bonding, and to make it a property. Improvement of manufacturing workability and application applications are widened.

By using glycerin or polyglycol for the underfill composition having the dilatancy characteristics of the present invention, oxidation of solder bumps is suppressed, deterioration with time is suppressed, and the reliability of solder joints is improved.

DESCRIPTION OF SYMBOLS 1 BGA type semiconductor device 2 Solder bump 3 Mounting board 4 Underfill 5 Crack which arose in solder bump junction part

Claims (4)

A semiconductor package comprising a semiconductor device having a solder bump, a mounting substrate, and an underfill, wherein the underfill uses a composition having a dilatancy characteristic. 2. The semiconductor package according to claim 1, wherein the underfill contains a composition having an antioxidant effect. 3. The semiconductor package according to claim 1, wherein the composition having dilatancy characteristics is silica and / or silicone resin. 5. The semiconductor package according to claim 2, wherein the composition having an antioxidant effect is glycerin and / or polyglycerin glycol.

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