SEMICONDUCTOR MEMORY MODULE WITH REVERSE MOUNTED CHIP RESISTOR
A semiconductor memory module having a reverse mounted chip resistor, and a method of fabricating the same are provided. By reverse mounting the chip resistor on the semiconductor memory module, the resistive material is protected, thereby preventing open circuits caused by damage to the resistive material. Also, a chip-resistor connection pad of a module substrate is formed to extend higher from the module substrate than other connection pads connected to other elements. Thus, the resistive material of the chip resistor does not contact the module substrate, thereby preventing poor alignment and defective connections.
This application claims the benefit of Korean Patent Application No. 10-2006-0109070, filed on Nov. 6, 2006, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
BACKGROUND1. Field of the Invention
The present invention relates to a semiconductor memory module, and more particularly to a semiconductor memory module with a reverse mounted chip resistor, and a method of fabricating the same.
2. Description of the Related Art
Semiconductor memory modules include not only semiconductor memory chips, but also passive devices such as capacitors and resistors, which are all generally mounted on a module substrate. Generally, the resistor of a memory module is mounted in the form of a chip resistor beside an external connection port of a module substrate. The chip resistor helps control the current within the circuit and typically drops the voltage.
Because of substantially similar ends of the chip resistor, which are used when mounting the chip resistor to the module substrate, the chip resistor may be mounted with either the surface with the resistive material facing upward, or the surface with the protective layer 5.
However, when the resistive material faces upward the resistive material is exposed and both the resistive material and the electrode are susceptible to physical damage during assembly or handling by a user. Accordingly, the electrode can peel off or the resistive material can break, causing an open circuit. Moreover, when a mounting facility grips the chip resistor with a vacuum nozzle to place the chip resistor onto the module substrate, the vacuum nozzle must grip the uneven surface of the resistive material and the protection layer, which can cause pickup errors and misalignment.
These problems may be partially solved when the resistive material faces downward during mounting. However, even in this case, the chip resistor may be slanted because the resistive material and protection layer are higher than the plated electrodes.
SUMMARYEmbodiments of the present invention provide a reliable semiconductor memory module that prevents open circuits due to damage to a resistive material within a chip resistor and a defective connection caused by slanting of the chip resistor.
Embodiments of the present invention also provide a method of fabricating a reliable semiconductor memory module that prevents open circuits due to damage to a resistive material within a chip resistor and a defective connection caused by slanting of the chip resistor. According to an embodiment of the present invention, a semiconductor memory module includes a module substrate having a chip-resistor pad and a chip resistor reverse mounted onto the chip-resistor connection pad of the module substrate. The chip resistor includes an insulating substrate, a resistive material portion on the insulating substrate, and a metal electrode electrically connected to the resistor material portion and located on the insulating substrate. The chip-resistor connection pad is higher than other connection pads of the module substrate, to prevent the resistive material portion of the chip resistor from contacting the module substrate.
The above and other features and advantages of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings in which:
The present invention will now be described more fully with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. The invention may, however, be embodied in many different forms, and should not be construed as being limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of the invention to those skilled in the art. In the drawings, the thicknesses of layers and regions are exaggerated for clarity.
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In experiments, the chip resistors mounted according to embodiments of the present invention displayed positive results with very few or substantially no defects of external appearance, passed an electrical test, and did not fail heat cycling (about -25 to about 125 ° C.).
According to some embodiments of the present invention, a chip resistor is reverse mounted onto a module substrate to protect and prevent damage to the resistive material and avoid open circuits. Furthermore, connection pads connected to the chip resistor are formed to extend higher from the module substrate than other connection pads to prevent a defective connection of the chip resistor that could occur if the resistive material of the chip resistor were to contact the module substrate or the insulating dam.
While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the present invention as defined by the following claims.
Claims
1-7. (canceled)
8. A method of fabricating a semiconductor memory module, comprising:
- patterning a copper layer on a surface of a module substrate to form connection pads;
- coating a photoresist on the module substrate including the connection pads;
- patterning the photoresist to expose a part of the connection pads on which a chip resistor having a resistive material will be mounted;
- forming a copper layer on the part of the connection pads exposed by the photoresist pattern, to form chip-resistor connection pads;
- removing the photoresist from the module substrate; and
- mounting the chip resistor onto the chip-resistor connection pads.
9. The method of claim 8, wherein the module substrate is formed by stacking a plurality of copper clad laminates formed of thin copper layers on both sides of an epoxy plate.
10. The method of claim 8, wherein the forming of the copper layer is performed such that the resistive material of the chip resistor does not contact the module substrate.
11. The method of claim 8, further comprising forming an insulating dam to prevent a short between the chip-resistor connection pads after removing the photoresist and before mounting the chip resistor.
12. The method of claim 8, wherein forming the copper layer on the connection pad includes forming the copper layer of the connection pad by electroplating.
13. The method of claim 8, wherein the mounting of the chip resistor on the chip-resistor connection pad comprises:
- printing solder paste on the chip-resistor connection pad;
- aligning and placing the chip resistor onto the solder paste; and
- thermally treating the module substrate, chip resistor, and solder paste to solder the chip-resistor onto the connection pad.
14. A method of fabricating a semiconductor memory module, comprising:
- patterning a copper layer on a surface of a module substrate to form connection pads including chip-resistor connection pads;
- coating a photoresist on the module substrate including the connection pads;
- patterning the photoresist to expose a part of the connection pads excluding the chip-resistor connection pads on which a chip resistor will be mounted;
- decreasing the height of the exposed connection pads;
- thereafter, removing the photoresist from the module substrate; and
- mounting a chip resistor onto the chip-resistor connection pads.
15. The method of claim 14, wherein the module substrate is formed by stacking a plural of copper clad laminates formed of thin copper layers on both sides of an epoxy plate.
16. The method of claim 14, wherein the copper layer formed on the module substrate is high enough to prevent the resistor material portion of the chip resistor from contacting the module substrate.
17. The method of claim 14, further comprising forming an insulating dam on the module substrate to prevent a short between the chip-resistor connection pads after removing the photoresist and before mounting the chip resistor.
18. The method of claim 14, wherein the mounting of the chip resistor on the chip-resistor connection pad comprises:
- printing solder paste on the chip-resistor connection pads;
- aligning and placing the chip resistor onto the solder paste; and
- thermally treating the module substrate, the chip resistor, and the solder paste to solder the chip resistor onto the chip-resistor connection pads.
19-31. (canceled)
Type: Application
Filed: Jun 27, 2011
Publication Date: Oct 20, 2011
Inventors: Hyun-Seok CHOI (Chungcheongnam-do), Hyung-Mo Hwang (Chungcheongnam-do), Yong-Hyun Kim (Gyeonggi-do), Hyo-Jae Bang (Chungcheongnam-do), Su-Yong An (Chungcheongnam-do)
Application Number: 13/169,663
International Classification: H01L 21/58 (20060101);