CN201550366U

CN201550366U - Steel mesh

Info

Publication number: CN201550366U
Application number: CN2009201699111U
Authority: CN
Inventors: 王宁; 陈晓晨
Original assignee: Huawei Device Co Ltd
Current assignee: Huawei Device Co Ltd; Huawei Device Shenzhen Co Ltd
Priority date: 2009-08-31
Filing date: 2009-08-31
Publication date: 2010-08-11
Anticipated expiration: 2019-08-31

Abstract

The utility model discloses a steel mesh opening, which relates to the technology of surface-mounting, and solves the problem that continuous tin electrodeposit or soldered ball is produced between the neighboring pads pressed by solder paste after the surface-mounting is completed. The steel mesh opening provided by the utility model is arranged corresponding to the pad of PCB, and bulges facing toward the internal part of the opening are arranged one the two sides of the opening. The utility model is mainly used in the steel mesh adopting SMT technology, particularly in the steel mesh by welding castle type module.

Description

Steel mesh

Technical field

The utility model relates to surface mounting technology (SMT, Surface Mount Technology), relates in particular to used steel mesh in the surface mounting technology.

Background technology

In making the electronic product process, need to adopt surface mounting technology (SMT, Surface MountTechnology) that various components and parts are welded on the printed circuit board (PCB) (PCB, Print Circuit Board).Comparatively Chang Yong surface mount process flow process is: at first need be coated with tin cream (Pastedeposition) on the one side of PCB, and then the components and parts that will need to weld mount on the correspondence position of PCB (ComponentPlacement), carry out reflow soldering (Dry and Reflow) after finishing the mounting of components and parts, so just finished PCB and wherein simultaneously gone up mounting of components and parts, through finishing surface mount after the assay was approved.Coating tin cream 2 processes on substrate 3 as shown in Figure 1, the tin amount of coating is the key factor that influences welding quality.The tin amount is to be determined by the shape of the open design of steel mesh 1 and size.Good steel mesh opening design guarantees good stripping result, can not cause solder shorts, open circuit or produce the tin ball, and guarantee that good hardware connects and soldering reliability.

Along with development of Communication Technique, the radio circuit utilization is more and more, all needs to use radio circuit as equipment such as wireless terminal product, wireless base stations.The performance index of radio circuit wherein directly influence the quality of entire product.For the more performance index is arranged, radio circuit is often made the radio-frequency module of a castle, is welded on the big plate PCB by the secondary assembling then.Because the radio-frequency module of castle does not have pin, need castle weldering end is directly welded.Fig. 2 is the outline drawing of certain radio-frequency module, belongs to the castle weldering end of no pin.

There are the following problems for steel mesh opening in the prior art: adopt when realizing that automatic SMT welds, if the steel mesh design is unreasonable, this can make that the tin cream of coating is too much, can push the tin cream on the pad after radio-frequency module mounted, thereby make the company's of generation tin between the adjacent pad of extruding back, even produce soldered ball.

Summary of the invention

Embodiment of the present utility model provides a kind of steel mesh, makes castle-type module tin can not occur connecting after mounting.

For achieving the above object, embodiment of the present utility model adopts following technical scheme:

A kind of steel mesh, this steel mesh comprises at least one opening, described opening is corresponding to the pad setting on the PCB, and is provided with projection more than towards open interior at described opening with corresponding position, module to be welded institute overlay area.

The steel mesh opening that the utility model embodiment provides is provided with the projection towards open interior, when utilizing this steel mesh opening coating tin cream, tin cream can coatedly not gone up in the pairing place of projection, thereby forms the breach corresponding with projection on the tin cream that in the end forms.So, distance on the adjacent pad between the tin cream will increase because of the existence of breach, even module to be welded is mounted the back tin cream is produced extruding, and tin cream can not connect yet between the adjacent pad of extruding back, more can not produce soldered ball, improve the quality that mounts.

The utility model embodiment is applied in the attachment process of castle-type module, can effectively promote the castle-type module welding quality, avoid the generation of Lian Xi or tin ball problem, promote crudy and efficient, avoided quality risk.

Description of drawings

In order to be illustrated more clearly in the utility model embodiment or technical scheme of the prior art, to do to introduce simply to the accompanying drawing of required use in embodiment or the description of the Prior Art below, apparently, accompanying drawing in describing below only is embodiment more of the present utility model, for those of ordinary skills, under the prerequisite of not paying creative work, can also obtain other accompanying drawing according to these accompanying drawings.

Fig. 1 is the schematic diagram of the steel mesh demoulding in the prior art;

Fig. 2 is the outline drawing of certain radio-frequency module;

Fig. 3 is the schematic diagram of steel mesh commonly used in the prior art;

Fig. 4 a is the opening schematic diagram of first kind of steel mesh among the utility model embodiment;

Fig. 4 b is the schematic diagram after the opening of steel mesh among Fig. 4 a moves laterally;

Fig. 5 a is the opening schematic diagram of second kind of steel mesh among the utility model embodiment;

Fig. 5 b is the schematic diagram after the opening of steel mesh among Fig. 5 a moves laterally

Fig. 6 a is the opening schematic diagram of the third steel mesh among the utility model embodiment;

Fig. 6 b is the schematic diagram after the opening of steel mesh among Fig. 6 a moves laterally.

Embodiment

At present the open design of steel mesh commonly used as shown in Figure 3, the pad size among the figure on the dotted line 4 expression PCB of outer ledge, the size of the inner corresponding steel mesh opening of solid line 5 expressions, the part of double dot dash line 6 expressions module region correspondence to be welded; As can be seen from Figure, steel mesh opening generally is that upward the pad size is identical with PCB, perhaps dwindles a bit according to a certain percentage.Among the utility model embodiment steel mesh opening is carried out irregularly shaped design, below in conjunction with the accompanying drawing among the utility model embodiment, technical scheme among the utility model embodiment is clearly and completely described, obviously, described embodiment only is the utility model part embodiment, rather than whole embodiment.Based on the embodiment in the utility model, those of ordinary skills are not making the every other embodiment that is obtained under the creative work prerequisite, all belong to the scope of the utility model protection.

It among Fig. 4 a the partial top view of steel mesh 7, demonstrated the part steel mesh opening 8 (polygon among the figure shown in the fine line) on the steel mesh 7 among the figure, below steel mesh opening 8 and pad 9 (rectangle among the figure shown in the fine dotted line) contrast on the PCB are explained, steel mesh opening 8 among the utility model embodiment is provided with corresponding to the pad on the PCB 9, and in the projection 10 towards opening 8 inside of being provided with of this opening 8.

Serious part is module to be welded institute overlay area owing to be squeezed on the tin cream, in Fig. 4 a, exemplary with than heavy line 11 right side parts as module to be welded institute overlay area, so, in order to make the serious problems such as tin or tin ball that partly can not occur connecting that are squeezed, shown in Fig. 4 a, the utility model embodiment is arranged on projection 10 and corresponding position, module to be welded institute overlay area, that is: among the figure than the position of heavy line 11 right side part correspondences.

When utilizing this steel mesh opening coating tin cream, tin cream can coatedly not gone up in protruding pairing place, thereby forms the breach corresponding with projection on the tin cream that in the end forms.So, distance on the adjacent pad between the tin cream will increase because of the existence of breach, even module to be welded is mounted the back tin cream is produced extruding, and tin cream can not connect yet between the adjacent pad of extruding back, more can not produce soldered ball, improve the quality that mounts.The utility model embodiment is applied in the attachment process of castle-type module, can effectively promote the castle-type module welding quality, avoid the generation of Lian Xi or tin ball problem, promote crudy and efficient, avoided quality risk.

Because the opening on the steel mesh generally is adjacent, in order to guarantee that adjacent both sides tin cream can not occur and link to each other or the soldered ball phenomenon, the utility model embodiment is arranged on the dual-side place of opening with described projection, specifically shown in Fig. 4 a.

When practice, can be any geometry with the shape set of projection 10, for example: rectangle, semicircle, half elliptic or triangle etc.Certainly, in order to satisfy the design of various user's requests, steel mesh opening 8 is shaped as arbitrary geometry towards an end of inside modules to be welded (being heavy line 11 right side parts) in the utility model, that is: Fig. 4 a medial end portions 12 can adopt arbitrary geometry, for example: rectangle, semicircle, triangle or half elliptic etc.

Can combination in any between top convex shape and the end shape.For example: Fig. 4 a is that projection adopts rectangle, end to adopt the embodiment of rectangle, and Fig. 5 a is that projection adopts rectangle, end to adopt semicircular embodiment, and Fig. 6 a is that projection adopts semicircle, end to adopt the embodiment of rectangle.Also have a lot of other combinations between present embodiment protrusions shape and the end shape, just do not give unnecessary details one by one here.

No matter which kind of combination above-mentioned convex shape and end shape adopt, and the utility model embodiment also can further comprise following scheme: with on the opening 8 with the dual-side of the module to be welded institute corresponding part in overlay area between ultimate range be set as the corresponding width of going up pad less than PCB.By decreased distance, can avoid tin cream after fusing after the reflow soldering, to cause the inner tin that connects of pin so that the coated tin cream of module to be welded institute overlay area counterpart reduces relatively, further improved welding quality.

Generally speaking, above-mentioned ultimate range can go up 0.85 times to 0.95 times of corresponding width of pad for PCB, and this is a comparatively reasonable range, because if greater than 0.95 times, then the tin cream of Jian Shaoing is not obvious, can not bring the obvious raising of welding quality; If less than 0.85 times, then may cause to open circuit and influence welding quality owing to tin cream is very few, so 0.85 times to 0.95 times is a comparatively reasonable range, and be that 0.90 times of the PCB corresponding width of going up pad is the most suitable implementation with above-mentioned ultimate range.

Shown in Fig. 4 b, Fig. 5 b, Fig. 6 b, in order further to reduce the coated tin cream of module institute's overlay area counterpart to be welded, the utility model embodiment can also be offset a preset length with respect to the last pad of PCB to the module to be welded outside with steel mesh opening, thereby avoid tin cream after melting after the reflow soldering, to cause the inner tin that connects of pin, further improved welding quality.Wherein, Fig. 4 b be scheme among Fig. 4 a with steel mesh opening with respect to the last pad of PCB to module to be welded outside skew one preset length; Fig. 5 b is that the scheme among Fig. 5 a is offset a preset length with respect to the last pad of PCB to the module to be welded outside with steel mesh opening; Fig. 6 b is that the scheme among Fig. 6 a is offset a preset length with respect to the last pad of PCB to the module to be welded outside with steel mesh opening.

In the such scheme the whole outwards skew of steel mesh opening one preset length can also be compensated the problem of the outside tin quantity not sufficient of weldering end, shrink to pad after the tin cream high temperature melting, make module to be welded form full weld appearance, avoid the tin quantity not sufficient and the open circuit problem that causes, improved welding quality.

Generally speaking, above-mentioned preset length is 0.05 times to 0.2 times that PCB goes up pad length, if less than 0.05 times, then can not bring the obvious raising of welding quality; If greater than 0.2 times, very few the causing of the tin cream of module to be welded institute overlay area then may occur and open circuit and influence welding quality.So 0.05 times to 0.2 times is a comparatively reasonable range, and preset length is that PCB goes up 0.1 times of pad length and is the most suitable implementation

The utility model embodiment mainly is used on the steel mesh of SMT technology, particularly weld on the used steel mesh of castle-type module, become irregularly shaped by open design with steel mesh, the position design projection that is being squeezed more serious, dwindle the ultimate range of dual-side or steel mesh opening integral body is moved a preset length laterally, make that as far as possible the tin cream amount that is extruded is more reasonable, make and can not occur the situation that tin cream links to each other between the adjacent pad, can the soldered ball phenomenon not appear, and the design of its projection can make the good tin cream of cloth have a breach, tin cream can flow to this indentation, there when making the extruding tin cream, can improve significantly and rise the castle-type module welding quality, avoid the generation of Lian Xi or tin ball problem, promote crudy and efficient, avoided quality risk.

The above; it only is embodiment of the present utility model; but protection range of the present utility model is not limited thereto; anyly be familiar with those skilled in the art in the technical scope that the utility model discloses; the variation that can expect easily or replacement all should be encompassed within the protection range of the present utility model.Therefore, protection range of the present utility model should be as the criterion by described protection range with claim.

Claims

1. a steel mesh is characterized in that, this steel mesh comprises at least one opening, and described opening is corresponding to the pad setting on the PCB, and is provided with at least one projection towards open interior at described opening with corresponding position, module to be welded institute overlay area.

2. steel mesh according to claim 1 is characterized in that, described projection is arranged on the dual-side place of opening.

3. steel mesh according to claim 1 and 2 is characterized in that, described projection is a geometry.

4. steel mesh according to claim 3 is characterized in that, described geometry is: rectangle, semicircle, half elliptic or triangle.

5. steel mesh according to claim 1 and 2 is characterized in that, on the described opening with the dual-side of the module to be welded institute corresponding part in overlay area between ultimate range go up the corresponding width of pad less than PCB.

6. steel mesh according to claim 5 is characterized in that, described ultimate range is 0.85 times to 0.95 times of the PCB corresponding width of going up pad.

7. steel mesh according to claim 1 and 2 is characterized in that, described opening is offset a preset length with respect to the last pad of PCB to the module to be welded outside.

8. steel mesh according to claim 7 is characterized in that, described preset length is 0.05 times to 0.2 times that PCB goes up pad length.

9. steel mesh according to claim 1 and 2 is characterized in that, described opening is a geometry towards an end of inside modules to be welded.

10. steel mesh according to claim 9 is characterized in that, described geometry is: rectangle, semicircle, half elliptic or triangle.