Patent Application
20120292088
1. Technical Field
The disclosure relates to electronic devices, and more particularly to electronic devices with circuit boards on which electrical components are attached.
2. Related Art
A capacitor is usually connected with a printed circuit board by fixing contacts of the capacitor to solder pads of the circuit board by solder reflowing. However, for printed circuit boards with vias passing through the solder pads, during the reflow soldering, part of the liquefied solder wicks down into the vias, frequently causing insufficient solder to remain on the solder pads. An insufficient solder condition causes loose connections between the contacts and the solder pads.
To prevent such problems, vias of some printed circuits board are filled with metal by plating in order to prevent liquefied solder from flowing into the vias during reflow soldering. Therefore, solder preserved on the solder pads is sufficient to make good electrical connections between the solder pads and the contacts.
Although capable of preventing such problems, filling the vias with metal is expensive. Also, filling vias with metal can cause unwanted changes in the dimensions of the solder pads. When the sizes of the solder pads, connected to the contacts of the capacitor, are not identical, the capacitor on the solder pads may slide relative to the circuit board during reflow soldering, and, therefore, after the liquefied solder is hardened, the capacitor deviates from the position where the capacitor is supposed to be.
According to one embodiment, an electronic device comprising a circuit board and an electrical component is disclosed. The circuit board has a first surface and includes a solder pad array including solder pads. The solder pad array is disposed on a first surface of the circuit board, and the circuit board further has vias passing through the solder pads. The electrical component is disposed on the first surface and between two of the solder pads next to each other. The electrical component comprises two contacts electrically connected to the two solder pads next to each other. A line passing through the centers of the two contacts forms an acute angle with a line passing through the centers of the two solder pads next to each other.
According to another embodiment, a method is provided of electrically connecting an electrical component having two contacts to two corresponding solder pads of a circuit board, wherein vias pass through the solder pads. The method uses reflow soldering to permanently connect the electrical component to the solder pads. Solder paste is applied to each solder pad (which is preferably circular) along only a narrow (i.e., less than 180° and preferably less than 90°) outer arc segment of the solder pad. Solder paste is not applied to the via passing through the center of the solder pad. The center of each contact of the electrical component is positioned at least one solder pad radius away from the center of its corresponding solder pad. With the electrical component so oriented, a first line passing through centers of the two contacts forms an oblique angle of between 45 and 90 degrees, and more preferably, between 65 and 70 degrees, with a second line passing through centers of the two solder pads. Moreover, a first of the two contacts intersects an outer edge of the corresponding solder pad on substantially only one side of the second line, and a second of said two contacts intersects an outer edge of its corresponding solder pad on substantially only an opposite side of the second line. Reflow soldering is then applied to the contacts of the electrical component to the solder pads. This method of connecting electrical components is systematically, consistently, and automatically applied to each of a plurality of electrical components to a circuit board.
Unless otherwise specified, the same reference numbers are used throughout the drawings to refer to the same or like elements of embodiments, and wherein:
In the following description, for the purpose of explanation, numerous specific details are set forth in order to provide a thorough understanding of the detailed embodiments. It will be apparent, however, that one or more embodiments may be practiced without these specific details. In other instances, well-known structures and elements are schematically shown in order to simplify the drawings.
Refer to
In this embodiment, the circuit board 100 is a double-side-printed circuit board which has a first surface 101 and a second surface 102 opposite to the first surface 101. The circuit board further comprises two solder pad arrays 119 respectively disposed on the first surface 101 and the second surface 102. Each solder pad array 119 comprises solder pads 110. The solder pads 110, which are circular, are formed on the first surface 101 and the second surface 102 through, for example, screen printing or plating.
Each solder pad 110 on the first surface 101 is coaxially aligned with a solder pad 110 on the second surface 102. The circuit board 100 has vias 112 passing through the circuit board 100 so that an entry 117 of each via 112 is on the first surface 101 and the other entry 118 of each vias 112 is on the second surface 102.
As shown in
By, for example, plating, a conductive layer 114, as shown in
The dimensions of the circuit board 100 are illustrated as the following. In
In
The electrical component 200, such as a capacitor, comprises two contacts 210. The electrical component 200 is located between two adjacent solder pads 110; the two adjacent solder pads 110 are electrically connected to the pair of the contacts 210 with solder. A line D1 passing through the centers of the pair of the contacts 210 forms an oblique angle θ with a line D2 passing through the centers of the pair of the solder pads 110.
If the distance from the contact 210 to the center of the solder pad 110 closest to such contact 210 is not long enough, during reflow soldering, the liquefied solder is likely to wick into the vias. Therefore, the amount of solder remaining on the solder pad 110 may be insufficient to securely electrically connect such contact 210 to the solder pad 110.
To solve this problem, and as illustrated in
With the electrical component 200 so oriented, and its contacts so displaced from the centers of their corresponding solder pads, the angle θ between lines D1 and D2 is acute, and typically between 45 and 90 degrees. In some embodiments, the angle θ is in a range from 65 degrees to 70 degrees. In some embodiments, the acute angle θ equals 67.5 degrees, so that the distance from the contact 210 to the solder pad 110 closest to the contact 210 is longest.
In
Since the line passing through the pair of the adjacent contacts forms the acute angle θ, which may be close to 67.5 degrees, relative to the line passing through the centers of the pair of adjacent solder pads, the distance from the contact to solder pad closest to such contact is appropriate. This distance would be long enough to prevent the liquefied solder originally disposed on the solder pad from flowing into the via during reflow soldering, and, therefore, the problem of bad or no electrical connection between the contact and the solder pad due to insufficient solder is avoided.
| Number | Date | Country | Kind |
|---|---|---|---|
| 100117850 | May 2011 | TW | national |
This non-provisional application claims priority under 35 U.S.C. §119(a) on Patent Application No(s). 100117850 filed in Taiwan, R.O.C. on May 20, 2011, the entire contents of which are hereby incorporated by reference.
