CN202231956U

CN202231956U - Structure for improving appearance of soldering pad to limit solder paste diffusion

Info

Publication number: CN202231956U
Application number: CN2011203725156U
Authority: CN
Inventors: 黎振贵
Original assignee: BAICHENG TECHNOLOGY (KUNSHAN) Co Ltd
Current assignee: BAICHENG TECHNOLOGY (KUNSHAN) Co Ltd
Priority date: 2011-09-28
Filing date: 2011-09-28
Publication date: 2012-05-23
Anticipated expiration: 2021-09-28

Abstract

The utility model discloses a structure for improving appearance of a soldering pad to limit solder paste diffusion. Shape of a window corresponding to a soldering pad which is connected with a surface layer circuit on a solder-mask layer is formed by connecting and defining a plurality of wide side edges and a plurality of fitted side edges, wherein the part which is connected with the surface layer circuit on the soldering pad is corresponding to the fitted side edges of the window on positions; the fitted side edges of the window not only can enable the shape of the solder pad to be regular for effectively preventing the solder paste from diffusion along the circuit, but also enables the window of the structure to reduce the window-opening area relative to a traditional window by the deign of the fitted side edges, thus the diffusion area of the solder paste while pasting through a solder furnace is effectively reduced, the solder paste height of all soldering pads is approximately the same, and the solder paste amount while the PCB is assembled can be effectively controlled; moreover, missing solder caused by insufficient solder paste height is effectively reduced, and the assembling yield is improved.

Description

Improve the structure of pad shape limitation tin cream diffusion

Technical field

The utility model belongs to printed circuit board (PCB) and printed circuit board (PCB) assembling field, relates generally to a kind of structure that is used to improve the diffusion of pad shape limitation tin cream.

Background technology

In printed circuit board (PCB) (PCB); The assembling of electronic devices and components generally realizes through the pad on the printed circuit board (PCB) 1; Pad is the line layer on printed circuit board (PCB), and shape such as generally rounded, rectangle or square interconnects through lead or copper face between pad; After making line layer on the printed circuit board (PCB); Need cover welding resisting layer 3 in printed circuit board surface, this welding resisting layer generally passes through solder-mask printing printing ink (green oil) and baking forms, and need window to welding resisting layer through exposure and development then exposes pad through window 4; During exposure the position that need window on the welding resisting layer (corresponding with pad locations) covered and all the other position exposures, the welding resisting layer that will be positioned at the window's position when developing is then washed formation window and exposed pad off.

In actual production process; Be difficult in exposure the time accomplish the to window accurate contraposition of position and pad; In order still to be coated with anti-solder ink on the back pad that prevents to window, therefore generally can the area of windowing of part pad be strengthened, when promptly making public with develop after the printing ink window greater than pad.Because window area is big, when pad is connected with top layer circuit 2, causes bond pad shapes irregular; And not of uniform size, as shown in Figure 1, when electronic devices and components were assembled the tin stove; Tin cream 5 is softening, because the irregular tin cream that causes of pad that window area is added greatly with the junction, top layer begins diffusion easily in the junction with the top layer circuit, makes the reduction of tin cream height; As shown in Figure 2, the reduction of tin cream height causes empty weldering easily, though this problem that causes empty weldering because of tin cream height deficiency easily; Can improve and solves through the method that increases the tin cream amount, but under the situation of increase tin cream amount, can cause the less pad of area of windowing again; Because of the tin cream amount too much causes the situation of inter-pad short circuits, the assembling yield is difficult to get a promotion under the situation of facing a difficult choice.

The utility model content

In order to overcome above-mentioned defective, the utility model provides a kind of structure of improving the diffusion of pad shape limitation tin cream, can make the bond pad shapes rule and after crossing the tin stove, can make tin cream be evenly distributed, reduce diffusion, thereby effectively improve the assembling yield.

The utility model for the technical scheme that solves its technical problem and adopt is:

A kind of structure of improving the diffusion of pad shape limitation tin cream; Be manufactured with some pads on the printed circuit board (PCB); Wherein there is the part pad to be connected with the top layer circuit; Said printed circuit board surface is coated with welding resisting layer, offers some windows that said pad is exposed on the said welding resisting layer, and said pad is positioned at said window; The window at the pad that is connected with top layer circuit place is connected to define with some identical edges by some spacious and comfortable edges and forms; And the position that connects the top layer circuit on the said pad is corresponding with the position, identical edge of said window, has the gap between the spacious and comfortable edge of said window and the edge of said pad, does not have the gap between the identical edge of said window and the edge of said pad.

Owing to do not have the gap between the identical edge of window and the edge of pad, make the bond pad shapes rule, and effectively stop the direction diffusion of tin cream road along the line, help promoting the assembling yield; Because window has spacious and comfortable edge, egative film and printed circuit board (PCB) contraposition when being convenient to make public; The identical edge of the window of the utility model has not only effectively stoped tin cream road along the line diffusion; And because the design at the edge that coincide makes the window of the utility model reduce the area of windowing than legacy windows; Therefore effectively reduced the diffusion area of tin cream when crossing the tin stove, made the tin cream height of all pads roughly the same, so the tin cream amount can obtain effective management and control when PCB assembles; Effectively reduce the sky weldering that causes because of the tin cream height is not enough, promote the assembling yield.

In actual production; Because there is little deviation in exposure during with egative film and printed circuit board (PCB) contraposition, is not the no gap in the ideal between the identical edge of the rear hatch that possibly cause developing and the edge of pad, but has minim gap; But this minim gap is much smaller than the spacious and comfortable edge of window and the gap between the pad edge; The dealer thinks that this kind minim gap is acceptable, because exist under the situation of this minim gap, still has the beneficial effect under the state of no gap in the ideal.

Said welding resisting layer is anti-solder ink layer, for example green oil.

Said bond pad shapes can be circle, rectangle or square etc.

The shape at said spacious and comfortable edge and said identical edge is consistent with the edge shape of pairing pad.

The window at the pad place that is connected with the top layer circuit also has some fillets edge, and said fillet connects said spacious and comfortable edge and said identical edge along one.

The beneficial effect of the utility model is: the structure of improving pad shape limitation tin cream diffusion of the utility model is the shape of the pairing window of pad that is connected with the top layer circuit on the welding resisting layer to be processed to be connected to define with some identical edges by some spacious and comfortable edges form; And the position that connects the top layer circuit on the said pad is corresponding with the position, identical edge of said window; The identical edge of window not only makes the bond pad shapes rule; Can effectively stop tin cream road along the line diffusion; And because the design at the edge that coincide makes the window of the utility model reduce the area of windowing than legacy windows; Therefore effectively reduced the diffusion area of tin cream when crossing the tin stove, made the tin cream height of all pads roughly the same, so the tin cream amount can obtain effective management and control when PCB assembles; Effectively reduce the sky weldering that causes because of the tin cream height is not enough, promote the assembling yield.

Description of drawings

Fig. 1 is the irregular sketch map of traditional bond pad shapes;

Fig. 2 is traditional pad tin cream height decline sketch map after crossing the tin stove;

Fig. 3 is the utility model structural representation.

Embodiment

Embodiment: a kind of structure of improving the diffusion of pad shape limitation tin cream; Be manufactured with some pads on the printed circuit board (PCB); Said bond pad shapes can be circle, rectangle or square etc., wherein has part pad 1 to be connected with top layer circuit 2, and said printed circuit board surface is printed with welding resisting layer 3; Said welding resisting layer is a green oil; Offer some windows that said pad is exposed on the said welding resisting layer, said pad is positioned at said window, and the window 4 at the pad place that is connected with the top layer circuit is connected to define with some fillets edge 43 one by some spacious and comfortable edge 41, some identical edges 42 and forms; Said fillet connects said spacious and comfortable edge and said identical edge along one; The shape at said spacious and comfortable edge and said identical edge is consistent with the edge shape of pairing pad, and said identical edge is a circular arc, and the position of connection top layer circuit is corresponding with the position, identical edge of said window on the said pad; There is the gap between the spacious and comfortable edge of said window and the edge of said pad, do not have the gap between the identical edge of said window and the edge of said pad.

Owing to do not have the gap between the identical edge of window and the edge of pad, make the bond pad shapes rule, can effectively stop the direction diffusion of tin cream road along the line, help promoting the assembling yield; Because window has spacious and comfortable edge, egative film and printed circuit board (PCB) contraposition when being convenient to make public; The identical edge of the window of the utility model has not only effectively stoped tin cream road along the line diffusion; And because the design at the edge that coincide makes the window of the utility model reduce the area of windowing than legacy windows; Therefore effectively reduced the diffusion area of tin cream when crossing the tin stove, made the tin cream height of all pads roughly the same, so the tin cream amount can obtain effective management and control when PCB assembles; Effectively reduce the sky weldering that causes because of the tin cream height is not enough, promote the assembling yield.

Above-mentioned specification and embodiment are merely the principle and the effect thereof of exemplary illustration the utility model, are not to be the restriction to the utility model, and any creation that falls in the utility model claim scope all belongs to the scope that the utility model is protected.

Claims

1. one kind is improved the structure that pad shape limitation tin cream spreads; Be manufactured with some pads on the printed circuit board (PCB); Wherein there is part pad (1) to be connected with top layer circuit (2); Said printed circuit board surface is coated with welding resisting layer (3), offers some windows that said pad is exposed on the said welding resisting layer, and said pad is positioned at said window; It is characterized in that: the window (4) at the pad that is connected with top layer circuit place is connected to define with some identical edges (42) by some spacious and comfortable edges (41) and forms; And the position that connects the top layer circuit on the said pad is corresponding with the position, identical edge of said window, has the gap between the spacious and comfortable edge of said window and the edge of said pad, does not have the gap between the identical edge of said window and the edge of said pad.

2. the structure of improving the diffusion of pad shape limitation tin cream according to claim 1, it is characterized in that: said welding resisting layer is the anti-solder ink layer.

3. the structure of improving the diffusion of pad shape limitation tin cream according to claim 2, it is characterized in that: said welding resisting layer is a green oil.

4. the structure of improving pad shape limitation tin cream diffusion according to claim 1 is characterized in that: at least a in circular, rectangle and the square of said bond pad shapes.

5. the structure of improving the diffusion of pad shape limitation tin cream according to claim 4, it is characterized in that: the shape at said spacious and comfortable edge and said identical edge is consistent with the edge shape of pairing pad.

6. according to the described structure of improving the diffusion of pad shape limitation tin cream of one of claim 1 to 5; It is characterized in that: the window at the pad place that is connected with the top layer circuit also has some fillets along (43), and said fillet connects said spacious and comfortable edge and said identical edge along one.