1. Field of the Invention
The invention relates to a module circuit board including a plurality of I/O terminals disposed at an edge of the board, a plurality of soldering pads on its surface for mounting parts such as semiconductor devices, and a barrier formed on its surface to isolate the I/O terminals from solder.
2. Description of the Related Art
A module circuit board for mounting flat type package ICs using a Surface-Mounted Device includes a plurality of I/O terminals plated of gold or flash gold which is formed on its one edge, a plurality of soldering pads on its surface on which the ICs are mounted using a solder reflow process, and a solder resist film formed on the circuit board. In the solder reflow process, some problems occur. That is, during the performance of the solder reflow process, solder balls are formed from melted solder. The solder ball is moved on the resist film, which is disposed between the pads and the terminals. If the solder ball reached the terminal is adhered to the terminal, the circuit board will be defective. To avoid this problem, the following countermeasure has been taken.
In the measure (1), the frequency that the solder ball is formed can be decreased. However, it is difficult to eliminate the formation of the solder ball completely. In the measure (2), the cost performance is not effective because of sealing and removing the tape. Further, if the tape adhesive remains on the terminal, it becomes a problem when the board is connected to the other parts.
An objective of the invention to provide a module circuit board for a semiconductor device having barriers to isolate I/O terminals from solder.
To achieve this objective, a module circuit board for a semiconductor device includes a plurality of pads, on which the semiconductor device is mounted, formed on of the board, a plurality of terminals formed on a side edge of the board, a resist film covering an area between the pads and the terminal on the board and a barrier formed between the pads and the terminals.
The invention will be more particularly described with reference to the accompanying drawings in which:
a) is a plan view of a module circuit board of the first embodiment of the invention,
b) is an enlarged sectional view taken along line I-I′ shown in
a) is a plan view of a module circuit board of the second embodiment of the invention,
b) is an enlarged sectional view taken along line II-II′ shown in
a) is a plan view of a module circuit board of the third embodiment of the invention,
b) is an enlarged sectional view taken along line III-III′ shown in
a) is a plan view of a module circuit board of the fourth embodiment of the invention,
b) is an enlarged sectional view taken along line IV-IV′ shown in
a) is a plan view of a module circuit board of the fifth embodiment of the invention,
b) is an enlarged sectional view taken along line V-V′ shown in
a) is a plan view of a module circuit board of the sixth embodiment of the invention, and
b) is an enlarged sectional view taken along line VI-VI′ shown in
Referring to
According to this first embodiment, if the solder ball is formed when the ICs are mounted on the board 1 during the solder reflow process, the solder ball can not get to the terminals 2 because the wall 5 acts as the barrier. Therefore, as it is not necessary to seal the terminals 2 with tape, process time can be reduced, and the tape adhesive does not remain on the terminals 2. As a result, the number of defective boards is dramatically decreased, and the uniform quality of the board can be achieved.
Referring to
According to the second embodiment of the invention, if the solder ball is formed when the ICs are mounted on the board 1 using the solder reflow process, the solder ball can not get to the terminals 2 because the first wall 15a and the second wall 15b act together as the barrier. Further, if the solder ball runs over the first wall 15a, the solder ball will be stacked between the first wall 15a and the second wall 15b because of a surface tension effect of the solder ball. Therefore, the barrier effect of the second embodiment is more than twice a high as the first embodiment.
Referring to
According to this third embodiment of the invention, if the solder ball is formed when the ICs are mounted on the board 1 using the solder reflow process, the solder ball can not get to the terminals 2 because the solder ball will be stacked in the trench 25 which acts as the barrier. Further, since the trench is formed together with the resist film 4, no additional process to fabricate the board is necessary, as compared to the first and second embodiments. Furthermore, as the circuit patterns formed on the board 1 are plated electrolessly with flash Au, the reflowed solder does not have any influence on the circuit patterns even if the solder runs into the trench 25.
Referring to
According to this fourth embodiment of the invention, if the solder ball is formed when the ICs are mounted on the board 1 using the solder reflow process, the solder ball can not get to the terminals 2 because the solder ball will be stacked in the first trench 35a. If the solder ball runs over the first trench 35a, the solder ball will be stacked in the second trench 35b. Even if the distance between the trenches 35a, 35b is smaller than the diameter of the solder ball, the solder ball will be stacked in the both trenches 35a, 35b because of a surface tension effect of the solder ball. Therefore, the barrier effect of the fourth embodiment is more than twice as high as the third embodiment. Furthermore, similar to the third embodiment, no additional processes to fabricate the board are necessary, as compared to the first and second embodiments because the trench is formed together with the resist film 4.
Referring to
According to the fifth embodiment of the invention, if the solder ball is formed when the ICs are mounted on the board 1 by the solder reflow process, the solder ball can not get to the terminals 2 because the solder ball will adhered to the metal pattern 46, which acts as the barrier. Further, as the metal pattern 46 is formed together with the other circuit pattern such as the power supply line 47, no additional processes to fabricate the board are necessary.
Referring to
According to the sixth embodiment of the invention, if the solder ball is formed when the ICs are mounted on the board 1 using the solder reflow process, the solder ball can not get to the terminals 2 because the solder ball will be stacked in the trench 55. If the solder ball runs over the trench 55, the wall 56 as the second barrier dams the solder ball. If the distance between the trench 55 and the wall 56 is smaller than the diameter of the solder ball, the solder ball will be stacked between the trench 55 and the wall 56 strongly because of a surface tension effect of the solder ball.
While the present invention has been described with reference to illustrative embodiments, this description is not intended to be construed in a limiting sense. Various modifications of the illustrated embodiments, as well as other embodiments of the invention, will be apparent to those skilled in the art on reference to this description. For example, although the walls 5, 15a, 15b, 56 are formed of resin in the first, second and sixth embodiment, these walls 5, 15a, 15b, 56 can be formed of metal, such as gold to which the solder can be adhered easily. If the wall is formed of gold, the solder ball is not only dammed by the wall but also will be adhered onto the wall. Such a gold wall may be pasted on the resist film. Further, although two walls are formed in the second embodiment, it is possible to further increase the number of walls. Furthermore, although two trenches are formed in the fourth embodiment, it is possible to further increase the number of trenches. Therefore, the appended claims are intended cover any such modifications or embodiments as falls within the true scope of the invention.
Number | Date | Country | Kind |
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10-354757 | Dec 1998 | JP | national |
This application claims the priority benefit of Japanese Patent Application No. 10-354757, filed Dec. 14, 1998, the entire subject matter of which is incorporated herein of reference. This application is a divisional application of applicant's application Ser. No. 10/289,358, filed Nov. 7, 2002 now U.S. Pat. No. 6,833,509, which is division of applicant's application Ser. No. 10/022,285, filed Dec. 20, 2001 now U.S. Pat. No. 6,498,306, which is division of applicant's application Ser. No. 09/450,504, filed Nov. 30, 1999, which is now patented, U.S. Pat. No. 6,420,658.
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Number | Date | Country | |
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20050274541 A1 | Dec 2005 | US |
Number | Date | Country | |
---|---|---|---|
Parent | 10289358 | Nov 2002 | US |
Child | 10775232 | US | |
Parent | 10022285 | Dec 2001 | US |
Child | 10289358 | US | |
Parent | 09450504 | Nov 1999 | US |
Child | 10022285 | US |