Patent Application
20110155450
This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2009-294250 filed on Dec. 25, 2009, the entire contents of which is incorporated herein by reference.
Embodiments described herein relate generally to a printed circuit board and an electronic apparatus.
A related art printed circuit board is used in an electronic apparatus such as a portable computer and has insertion mount devices mounted on a single wiring board. An insertion mount device is, for example, a connector and has lead terminals.
The wiring board of the related art printed circuit board has a first surface, a second surface on a side opposite the first surface, and through holes opened at the first and second surfaces. An inner face of each of the through holes is coated with a conductive plating layer. For each of the through holes, lands are formed on the first and second surfaces of the wiring board to surround respective open ends of the through hole such that the lands are electrically connected to the plating layer.
The insertion mount device is mounted on the first or second surface of the wiring board such that the lead terminals are inserted into corresponding ones of the through holes and soldered to the through holes. The printed circuit board may also have a surface mount device that is soldered onto the land on a side opposite the insertion mount device.
The lead terminals inserted into the through holes may protrude out from the wiring board. When arranging such a printed circuit board in an electronic apparatus, an insulator is provided between distal ends of the lead terminals of the printed circuit board and other parts of the electronic apparatus for electrical insulation.
A general architecture that implements the various features of the invention will now be described with reference to the drawings. The drawings and the associated descriptions are provided to illustrate embodiments of the invention and not to limit the scope of the invention.
Various embodiments according to the invention will be described hereinafter with reference to the accompanying drawings.
In general, according to one embodiment of the invention, a printed circuit board is provided. The printed circuit board includes a wiring board, an insertion mount device having lead terminals, and a flexible insulator. The wiring board has a first surface, a second surface on a side opposite the first surface, and through holes. The insertion mount device is mounted on the first surface of the wiring board such that the lead terminals are inserted into the through holes and are soldered to the through holes. At least one of the lead terminals has a distal end protruding out from a corresponding one of the through holes. The insulator provided on the second surface to cover the distal end of the at least one of the lead terminals.
The display unit 3 has a liquid crystal display panel 6. The display unit 3 is supported on a rear end portion of the housing 4 through a pair of hinge portions 7a, 7b. The display unit 3 is rotatable between a close position in which the display unit 3 is laid on the housing 4 such that the keyboard 5 is covered by the display unit 3 from above and an open position in which the display unit 3 stands up such that the keyboard 5 is exposed.
As shown in
As shown in
The insulating substrate 14 in this embodiment has flexible solder resist layers 151 on a side of the first surface 15. For example, the solder resist layers 151 are made of an insulating and flexible material. The insulating substrate 14 in this embodiment further has a thermosetting resist layer 161 provided on the second surface 16.
Through holes 18 are formed in the printed wiring board 11. The through holes 18 are formed through the insulating substrate 14 in a direction of a thickness of the insulating substrate 14 so as to be opened at the first and second surfaces 15, 16. An inner face of each of the through holes 18 is covered with a conductive plating layer 19.
Lands 20 are formed on the first surface 15 of the insulating substrate 14. Similarly. lands 21 are formed on the second surface 16 of the insulating substrate 14. Each of the lands 20, 21 forms a part of the conductor patterns, and is shaped like a ring that surrounds an open end of corresponding one of the through holes 18. The lands 20, 21 are electrically connected to the plating layer 19 of the corresponding through holes 18 respectively.
Pads 22 are provided on the first surface 15 of the insulating substrate 14. Each of the pads 22 is electrically connected to corresponding one of the conductor patterns and is disposed near one of the lands 20.
An insertion mount device 12 is, for example, a connector to which a large force is applied at a portion that is joined to the printed wiring board 11. The insertion mount device 12 has a body 23, and a pair of lead terminals 24a, 24b which protrude from the body 23. The lead terminals 24a, 24b are arranged parallel to each other at a distance. Each of the lead terminals 24a, 24b has a base end 25 adjacent to the body 23, and a distal end 26. When the insertion mount device 12 is mounted on the printed wiring board 11, the distal end 26 is located on a side of the printed wiring board 11 opposite the body 23.
The lead terminals 24a, 24b of the insertion mount device 12 are inserted into adjacent ones of the through holes 18 in the printed wiring board 11 in a direction from the second surface 16 toward the first surface 15. The insertion mount device 12 is mounted on the second surface 16 of the printed wiring board 11 by reflow-soldering the lead terminals 24a, 24b to the through holes 18.
When the insertion mount device 12 is mounted on the second surface 16, gaps between the lead terminals 24a, 24b and the plating layers 19 of the through holes 18 are filled with solder 27, and the base ends 25 of the lead terminals 24a, 24b protrude from the second surface 16 of the printed wiring board 11. Solder fillets 28 are formed between the base ends 25 and the lands 21 on the second surface 16.
Further, the distal ends 26 of the lead terminals 24a, 24b are disposed outside the through holes 18 and protrude from the first surface 15 of the printed wiring board 11. That is, the lead terminals 24a, 24b are soldered to the through holes 18 such that they extend through the through holes 18 respectively.
The distal ends 26 of the lead terminals 24a, 24b protruding from the first surface 15 are covered with solder resist layers 151 respectively. While the distal ends 26 of the lead terminals 24a, 24b abut the solder resist layers 151 respectively in this example, the distal ends 26 of the lead terminals 24a, 24b may be separated from the solder resister layers 151 respectively by, for example, the solder 27.
According to the printed wiring board 11 having the configuration described above, it is possible to prevent the distal ends 26 of the lead terminals 24a, 24b protruding from the first surface 15 of the printed wiring board 11 from contacting the inner wall portion 4rb of the top wall 4b, which may otherwise cause a short-circuit. Further, because the distal ends 26 of the lead terminals 24a, 24b are covered with the solder resist layers 151, it is not necessary to provide a separate insulating member between the printed wiring board 11 and the inner wall portion 4rb of the top wall 4b of the housing 4. Accordingly, the number of components can be reduced.
A surface mount device 13 is, for example, a chip capacitor which is lighter in weight and smaller in shape than the insertion mount device 12. The surface mount device 13 has a body 30, and first and second electrodes 31a, 31b. The first electrode 31a is disposed on one end of the body 30 and the second electrode 31b is disposed on the other end of the body 30.
The first electrode 31a of the surface mount device 13 is reflow-soldered to a land 20 corresponding to the through hole 18 into which one of the lead terminals 24a is inserted. The first electrode 31a is provided near an open end of the through hole 18 on the first surface 15. A solder fillet 32 is formed between the first electrode 31a and the land 20.
The second electrode 31b of the surface mount device 13 is reflow-soldered to a pad 22. A solder fillet 33 is formed between the second electrode 31b and the pad 22.
As shown in
Next, a method of manufacturing the printed circuit board 10 will be described further with reference to
First, a printed wiring board 11 having pads 22 and through holes 18 coated with plating layers 19 is provided. The printed wiring board 11 is held such that the first surface 15 of the printed wiring board 11 faces upward. A flexible resist film is printed on the first surface 15 of the printed wiring board 11 in advance. A thermosetting resist film 161 is printed on the second surface 16 of the printed wiring board 11 in advance. In this condition, a solder paste is printed on the lands 20 and the pads 22 on the first surface 15 of the printed wiring board 11.
A screen mask is used when printing the solder paste and the resist film. The screen mask has openings in positions corresponding to the lands 20 and the pads 22. The screen mask is laid onto the first surface 15 of the printed wiring board 11 at the time of printing the solder paste. The solder paste is pressed into the opening portions of the screen mask using a squeegee, and is printed onto the lands 20 and the pads 22.
In this manner, as shown in
Then, the surface mount device 13 is provided onto the first surface 15 of the printed wiring board 11 using, for example, a surface mounter, so that first and second electrodes 31a, 31b of the surface component 13 are placed on the corresponding land 20 and pad 22. The first electrode 31a is located near the through holes 18.
Subsequently, the printed wiring board 11 is placed inside a reflow furnace and is heated in the reflow furnace. The solder layers 35 are melted by this heating, so that a gap between the first electrode 31a and the land 20 and a gap between each second electrode 31b and the pad 22 are filled with molten solder. A part of the molten solder is further spread into the open end of the through hole 18 from the first electrode 31a.
Thereafter, the printed wiring board 11 is taken out from the reflow furnace and cooled to harden the molten solder. Consequently, as shown in
Next, as shown in
After providing the solder paste, as shown in
Then, the printed wiring board 11 is placed inside the reflow furnace and heated in the reflow furnace again. The solder layers 36 are melted by this heating, so that a gap between each the of the lead terminals 24a, 24b and the corresponding plating layer 19 and a gap between the distal end 26 of the lead terminal 24a and the first electrode 31a of the surface mount device 13 are filled with molten solder.
Subsequently, the printed wiring board 11 is taken out from the reflow furnace and cooled to harden the molten solder. Consequently, as shown in
According to the first embodiment, when the insertion mount device 12 is mounted on the second surface 16 of the printed wiring board 11, the distal ends 26 of the lead terminals 24a, 24b of the insertion mount device 12 protrude from the first surface 15 of the printed wiring board 11 and stay outside corresponding ones of the through holes 18. Each of the distal ends 26 of the lead terminals 24a, 24b abuts on the solder resist layer 151 and deforms the solder resist layer 151 toward the outside of the corresponding through hole 18.
Therefore, contact between the distal ends 26 of the lead terminals 24a, 24b and the inner wall portion of the housing 4 can be avoided. Accordingly, it is not necessary to provide a separate insulator between the first surface 15 of the printed wiring board 11 and the inner wall portion of the housing 4, whereby the number of components can be reduced and the manufacturing process can be simplified. Moreover, in this embodiment, because the solder resist layer 151 is provided by printing, displacement of the solder resist layer 151 is prevented.
Further, because the insertion mount device 12 and the surface mount device 13 can be mounted opposite to each other on respective sides of the through holes 18, it is advantageous in that high-density mounting is achieved.
In addition, because a gap between the distal end 26 of the lead terminal 24a and the corresponding solder resist layer 151 is filled with solder 27, a cavity is hardly created inside the through hole 18 when the insertion mount devices 12 and the surface mount devices 13 are soldered to the printed wiring board 11. Consequently, for example, even when temperature of the printed circuit board 10 rises, the solder 27 is prevented from being peeled off due to expansion of air inside the through holes 18. As a result, reliability on electrical connection between the printed wiring board 11 and the insertion mount device 12 is improved.
As shown in
After providing the solder paste, the protectors 152 are applied on portions of the solder resist layer 151 on the second surface 16 of the printed wiring board 11 where the distal ends 26 of the lead terminals 24a, 24b of the insertion mount device 12 face, i.e. portions with which open ends of the through holes 18 are covered. The protectors 152 include, for example, a thermosetting adhesive.
Then, as shown in
Each of the distal ends 26 of the lead terminals 24a, 24b abuts on the solder resist layer 151 and deforms the solder resist layer 151 and the protector 152 toward the outside of the corresponding through hole 18.
Subsequently, the printed wiring board 11 is placed inside a reflow furnace and heated in the reflow furnace. The solder layers 36 are melted, so that a gap between the lead terminals 24a, 24b and the plating layers 19 and a gap between the base ends 25 of the lead terminals 24a, 24b and the lands 21 are filled with molten solder. In addition, the protectors 152 are hardened to protect the respective solder resist layers 151.
Then, the printed wiring board 11 is taken out from the reflow furnace and cooled to harden the molten solder. Consequently, as shown in
Also in the second embodiment, the lead terminals 24a, 24b of the insertion mount device 12 protrude from the through holes 18. However, each of the distal ends 26 of the lead terminals 24a, 24b abuts on the solder resist layer 151 and deforms the solder resist layer 151 toward the outside of the corresponding through hole 18.
Therefore, contact between each of the distal ends 26 of the lead terminals 24a, 24b and the inner wall portion of the housing 4 can be avoided. Accordingly, it is not necessary to provide a separate insulator between the first surface 15 of the printed wiring board 11 and the inner wall portion of the housing 4, so that the number of components can be reduced.
Further, in the second embodiment, because the protectors 152 protect the solder resist layers 151 respectively, the solder resist layers 151 are prevented from being worn or crushed between the distal ends 26 of the lead terminals 24a, 24b and the inner wall of the housing 4.
This configuration can obtain the same effect as in the second embodiment of the invention. Moreover, because the protector 152 can be applied at once, the manufacturing process is simplified.
In implementing the invention, the surface mount device is not limited to a chip capacitor. For example, the surface mount device may be other kinds of chip component or a small outline package (SOP). Likewise, the insertion mount device is not limited to a socket. For example, the insertion mount device may be a PGA semiconductor package.
In addition, the electronic apparatus according to the invention is not limited to a portable computer, and may be, for example, a personal digital assistant (PDA).
While certain embodiments have been described, these embodiments have presented by way of example only, and are not intended to limit the scope of the invention. Indeed, the novel structures and apparatuses described herein may be embodied in variety of other forms; furthermore, various omissions, substitutions and changes in the form of the structures and apparatuses described herein may be made without departing of the spirit of the invention. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| JP 2009-294250 | Dec 2009 | JP | national |
