Patent Application
20130240254
1. Technical Field
The present disclosure relates to printed circuit board and method for manufacturing printed circuit board.
2. Description of Related Art
Referring to
However, during the typical manufacturing of the PCB 300, when the permanent mold coating 324 is coated on the copper foil 321, the permanent mold coating 324 is substantially convex shaped with the middle portion higher than the surrounding portion (see
Therefore, there is room for improvement in the art.
Many aspects of the embodiments can be better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the embodiments. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the five views.
The disclosure is illustrated by way of example and not by way of limitation in the figures of the accompanying drawings in which like references indicate similar elements. It should be noted that references to “an” or “one” embodiment in this disclosure are not necessarily to the same embodiment, and such references mean at least one.
Each pad 120 includes a copper foil 121 bonded to the substrate 110 and a solder resist 122 surrounding the copper foil 121. The copper foil 121 is substantially rectangular and defines an opening 124. The opening 124 is substantially rectangular and is arranged in the middle of the copper foil 121. The opening 124 is further coated with solder resist 122. The solder resist 122 is used to prevent the permanent mold coatings 130 from coating on the substrate 110. The solder resist 122 is green lacquer in the embodiment.
The permanent mold coatings 130 in the embodiment are solder paste. The permanent mold coatings 130 are coated on the copper foil 121 with surface mount technology (SMT), to protect the copper foil 121 and further to enhance welding performance of the pad 120. Because the opening 124 is defined in the middle of the copper foil 121 and is coated with the solder resist 122, the permanent mold coatings 130 only cover on the copper foil 121 and surround the opening 124 to form a recess 125. As a result, the permanent mold coatings 130 are dimple-shaped with the middle portion being recessed. By aligning the leads in the recess 125, the operator can easily position the leads of the electronic components and further accurately melt the leads with the pads 120. Furthermore, during the hot-melting process, the recess 125 receives the melted solder to avoid burrs being generated, and the soldered pads 120 are not needed to be washed.
In step S310, a substrate 110 is provided. In the embodiment, the substrate 110 used in printed circuit board 100 is a glass fiber reinforced (fiberglass) epoxy resin with copper foil bonded on to one or both sides.
In step S320, a circuit pattern corresponding to the PCB 100 is designed. Each PCB has a unique function for a particular product and must be designed to perform that function in the space allotted. Board designers use computer-aided design systems with special software to layout the circuit pattern. The circuit pattern includes a plurality of pins corresponding to the pads 120 of the PCB 100 respectively. Each pin defines a vacancy corresponding to the opening 124 of the pads 120.
In step S330, the designed circuit pattern is converted to PCB layout, and the PCB layout is printed on a transparency and becomes known as a PCB mask. The PCB mask further covers on the surface of the substrate with copper foil (referred as the foil surface). The foil surface with the PCB mask pass through a vacuum chamber where a layer of positive photoresist material is pressed firmly onto the entire surface of the foil. A positive photoresist material is a polymer that has the property of becoming more soluble when exposed to ultraviolet light. After passing through the vacuum chamber, the foil surface covered with the PCB mask and photoresist material is exposed to an intense ultraviolet light. Because the mask is clear in the areas of the printed circuit pattern, the photoresist in those areas is irradiated and becomes very soluble.
In step S340, after being exposed to an intense ultraviolet light, the substrate 110 with copper foil is etched to leave the desired pattern including copper tracks 140 and pads 120 having copper foil 121 with an opening 124 defined therein.
In step S350, when removed from the etching solution, the substrate 110 is washed and a PCB eraser is used to remove any film from the tracks.
In step S360, the substrate 110 is further coated with the solder resist 122 to prevent the permanent mold coatings 130 from coating on the substrate 110 and the copper foil 121. In the embodiment, the solder resist 122 is coated surrounding each pad 120 and further coat on opening 124.
In step S370, the permanent mold coatings 130 coat on the copper foil 121 to protect the copper foil 121 from being oxidized and further to enhance welding performance of the pad 120. Because the opening 124 is defined in the middle of the copper foil 121 and is coated with solder resist 122, the permanent mold coatings 130 only cover on the copper foil 121 and surround the opening 124 to form a recess 125. As a result, the permanent mold coatings 130 are dimple-shaped with the middle portion being recessed.
In step S380, the leads of the electronic component is aligned with the recess 125, and further accurately being melt with the pads 120 to solder the electronic component to the PCB 100.
It is to be understood, even though information as to, and advantages of, the present embodiments have been set forth in the foregoing description, together with details of the structures and functions of the present embodiments, the disclosure is illustrative only; and that changes may be made in detail, especially in the matters of shape, size, and arrangement of parts within the principles of the present embodiments to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.
| Number | Date | Country | Kind |
|---|---|---|---|
| 201210067784.0 | Mar 2012 | CN | national |
