Patent Application
20160204077
In the electronics manufacturing industry, an electronic device such as a semiconductor chipset module is generally fabricated by employing a surface-mount technology (SMT) for incorporating a plurality of electronic components onto a surface of a substrate. Those surface-mounted components may include not only active elements such as a resistor, an inductor and a capacitor, but also passive elements such as a transistor and a die.
Among the above-described surface-mounted components, a the may be mounted onto a substrate by using a bonding technique such as wire bonding and/or hip-chip bonding. When the wire bonding technique is used, the die may be attached to a die pad defined on a surface of the substrate. Then, electrical interconnections may be made between electrodes of the die and corresponding bonding wire pads defined on the surface of the substrate by connecting them with bonding wires.
In contrast, when the flip-chip bonding technique is used, electrical interconnections between the die and the substrate may be made without using bonding wires, First, the die may be flipped over and disposed close to the substrate such that a surface of the die having thereon the electrodes faces the surface of the substrate, and solder bumps deposited on the electrodes are aligned with corresponding flip-chip die pads defined on the surface of the substrate. Then, the solder bumps are reflowed to complete the interconnections therebetween.
In the above-described flip-chip bonding, organic solderability preservative (OSP) films made of an organic compound are deposited on metal films of the flip-chip die pads in order to suppress oxidation of the metal films and enhance adhesiveness of the solder bumps. Especially, the OSP films are known to promote dispersion of the solder bumps being reflowed within an area where the OSP films have been formed and thereby serve to define the boundaries of the interconnections.
Unfortunately, however, in manufacturing electronic devices by using flip-chip bonding, instances of defective products caused by, e.g., contact errors between the die and the substrate have been reported, and damaged OSP films have been blamed as one of the factors creating the contact errors. By way of illustration, as shown in
Accordingly, a series of efforts have been made to figure out what causes the damage to the OSP films and leads to the above-described errors. The investigators have speculated the oxidation process performed on the substrate to be one of the major factors. That is as one of the finishing processes for pads and at pins of the substrate, the oxidation process is performed to provide an oxide film for insulation on a predetermined portion therebetween, as shown in
This oxide film acts as a solder mask and plays a key role in establishing to reliable connection between the substrate and an external device when the electronic device is mounted thereon. For example, the electronic device is mounted onto a test board connected to a measurement means in order to conduct a performance test to detect whether or not the electronic device is defective. The accuracy of the test results may be guaranteed only when the pads and pins of the substrate are properly connected to corresponding conductor areas of the test board.
However, when the oxidation process is being performed, the predetermined position of the substrate on which the oxide film is to be formed as well as the OSP films may be exposed and vulnerable to a process environment, e.g., an etchant that is used to perform the oxidation process. Then, the OSP films, which are made of an organic matter, may be partially or entirely damaged by being subjected to a chemical reaction with the etchant. As a result, contact errors may occur between the die and the substrate, as can he seen from regions B and C of
In order to avoid the above problem, a finishing process for forming a solder resist on the bottom surface of the substrate by using photoimageable solder resist (PSR) ink may he considered as an alternative to the oxidation process. However, the PSR process has been found less desirable because of its complexity and high cost and extra time required.
The example embodiments are best understood from the following detailed description when read with the accompanying drawing figures. It is emphasized that the various features are not necessarily drawn to scale. In fact, the dimensions may be arbitrarily increased or decreased or clarity of discussion. Wherever applicable and practical, like reference numerals refer to like elements.
In the following detailed description, for purposes of explanation and not limitation, representative embodiments disclosing specific details are set forth in order to provide a thorough understanding of the present teachings. However, it will be apparent to one having ordinary skill in the an having had the benefit of the present disclosure that other embodiments according to the present teachings that depart from the specific details disclosed herein remain within the scope of the appended claims. Moreover, descriptions of well-known apparatuses and methods may be omitted so as to not obscure the description of the representative embodiments. Such methods and apparatuses are clearly within the scope of the present teachings.
It is to be understood that the terminology used herein is for purposes of describing particular embodiments only, and is not intended to be limiting. Any defined terms are in addition to the technical and scientific meanings of the defined terms as commonly understood and accepted in the technical field of the present teachings.
As used in the specification and appended claims, the terms ‘a’, ‘an’ and ‘the’ include both singular and plural referents, unless the context clearly dictates otherwise. Thus, for example, ‘a device’ includes one device and plural devices.
As used in the specification and appended claims, and in addition to their ordinary meanings, the terms ‘substantial’ or ‘substantially’ mean to with acceptable limits or degree. For example, ‘substantially cancelled’ means that one skilled in the an would consider the cancellation to be acceptable.
As used in the specification and the appended claims and in addition to its ordinary meaning, the term ‘appmximately’ means to within an acceptable limit or amount to one having ordinary skill in the art. For example, ‘approximately the same’ means that one of ordinary skill in the an would consider the items being compared to be the same.
Relative terms, such as “above,” “below,” “top,” “bottom,” “upper” and “lower” may be used to describe the various elements' relationships to one another, as illustrated in the accompanying drawings. These relative terms are intended to encompass different orientations of the device and/or elements in addition to the orientation depicted in the drawings. For example, if the device were inverted with respect to the view in the drawings, an element described as “above” another element, for example, would now be “below” that element. Similarly, if the device were rotated by 90° with respect to the view in the drawings, an element described “above” or “below” another element would now he “adjacent” to the other element; where “adjacent” means either abutting the other element, or having one or more layers, materials, structures, etc., between the elements.
First, at step S1, a substrate configured such that electronic components are mounted onto one surface thereof is provided, as a component of an electronic device. This substrate provided at this step corresponds to a substrate in accordance with an embodiment of the present invention. The type of the substrate is not limited to a specific one, but includes at least substrates called a package substrate and a primed circuit board (PCB). Furthermore, the substrate includes not only a substrate for which the manufacture of an electronic, device using only flip-chip bonding is a prerequisite, but also a substrate having a structure with which an electronic device is manufactured using both flip-chip bonding and wire bonding. However, since the structure of the former substrate corresponds to part of the structure of the latter substrate, the following description is given with focus on the structure of the latter substrate in order to avoid the redundancy of description.
As illustrated, in
As illustrated in
Furthermore, the pads of the substrate 1 further include bonding wire pads (also called bonding pads) 112 that are used for connection to bonding wires. Each of the bonding wire pads 112 includes a first metal film 112a made of conductive metal, such as copper. Furthermore, the bonding wire pad 112 may further include a second metal film 112b formed on the first metal film 112a and made of metal, such as gold or nickel. The second metal film 112b becomes a bonding area to which a bonding wire is connected. The second metal film 112b is stacked on the first metal film 112a, and the stacking may be performed by a method known in the relevant technical field, such as electroless gold plating. electrolytic soft gold plating, or the like. Furthermore, the second metal film 112b is not necessarily formed, and may be formed separately from step S1.
Moreover, the pads of the substrate 1 further include a bonding wire die pad 113 that is used to fasten the die to which wire bonding is applied, to the substrate 1. The bonding wire die pad 113 may include a first metal film 113a made of conductive metal, such as copper, and a second metal film 113b formed on the first metal film 113a and made of metal, such as gold or nickel, like the bonding wire pad 112. However, the structure of the bonding wire die pad 113 in accordance with an embodiment of the present invention is not limited to the above-described structure, but may have a structure different from that of the
Meanwhile, as illustrated in
Subsequent to step S1, a die also called a semiconductor die, a chip, or a monolithic microwave integrated chipset (MMIC)), that is one of the components of the electronic device, is mounted onto the substrate by flip-chip bonding at step S2. More specifically, as illustrated in
Thereafter, a molding process is performed on the die 2 mounted onto one surface of the substrate 1 at step S3. The molding process in accordance with the present embodiment is performed by supplying molding material 3 around the die 2 brought into contact with the flip-chip die pads 111 via the deformed solder bumps 22,′ applying a predetermined temperature and/or a predetermined pressure to the molding material 3 within a mold and then hardening the molding material 3, thereby allowing the molding material 3 to cover all or parts of one surface 10a of the substrate 1 (for example, the first conductor area 11 or the die 2), at least the OSP films 111b, and thus preventing it or them from being exposed to the outside, as illustrated in
Thereafter, as illustrated in
The method in accordance with the present embodiment is performed through the above-described steps S1 to S4.
In accordance with the above-described method, in the manufacture of the electronic device including both the OSP films for flip-chip bonding and the oxide film for insulation from unintended electrical connection, although the overall substrate is exposed to the oxidation process that is performed to form the oxide film, the OSP films are covered with molding material that acts as a protection medium, and are thus protected from a chemical reaction with material for the oxidation process. Accordingly, contact errors between the solder dumps provided on the electrodes of the die and the die pads of the substrate, for example, solderability-related errors, attributable to damage to the OSP films can be reduced. Furthermore, this case can reduced time and costs, compared to the case of replacing an oxide film with PSR ink.
Meanwhile, a method in accordance with an embodiment of the present invention may include another step in addition to steps S1 to S4. More specifically, the method in accordance with the present embodiment may include the step of assembling components including the substrate 1 for example, step Sa of mounting another electronic component on the substrate 1, as illustrated in
Meanwhile, a method in accordance with an embodiment of the present invention may include an additional step, for example, step Sb of mounting a complete electronic device D1 on a test board D2 and then conducting a test, as illustrated in
Furthermore, one or more processes, such as the inspection of the substrate onto which the electronic component has been mounted, laser marking, and/or singulation, may be performed after step S2.
In addition, the method in accordance with the present embodiment may be performed by a plurality of agents. By way of example, step S1 may he performed by a substrate manufacturer, steps S2 to S4 and Sa may be performed by a package assembly manufacturer, and step Sb may he performed by another electronic device manufacturer. In this case, the step of transferring the intermediate product or finished product of the electronic device from one agent to another agent may be added to each of the steps.
Although the specific embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible without departing from the scope and spirit of the invention as disclosed in the accompanying claims.
While the invention has been shown and described with respect to the preferred embodiments, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the following claims.
