CN108990312A - It is a kind of for welding the steel mesh of QFN - Google Patents
It is a kind of for welding the steel mesh of QFN Download PDFInfo
- Publication number
- CN108990312A CN108990312A CN201810973215.XA CN201810973215A CN108990312A CN 108990312 A CN108990312 A CN 108990312A CN 201810973215 A CN201810973215 A CN 201810973215A CN 108990312 A CN108990312 A CN 108990312A
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- China
- Prior art keywords
- steel mesh
- qfn
- tin cream
- welding
- ontology
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Classifications
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K3/00—Apparatus or processes for manufacturing printed circuits
- H05K3/30—Assembling printed circuits with electric components, e.g. with resistor
- H05K3/32—Assembling printed circuits with electric components, e.g. with resistor electrically connecting electric components or wires to printed circuits
- H05K3/34—Assembling printed circuits with electric components, e.g. with resistor electrically connecting electric components or wires to printed circuits by soldering
- H05K3/341—Surface mounted components
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41F—PRINTING MACHINES OR PRESSES
- B41F15/00—Screen printers
- B41F15/14—Details
- B41F15/34—Screens, Frames; Holders therefor
- B41F15/36—Screens, Frames; Holders therefor flat
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- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Mechanical Engineering (AREA)
- Electric Connection Of Electric Components To Printed Circuits (AREA)
Abstract
The present invention discloses a kind of for welding the steel mesh of QFN, including steel mesh ontology, it further include the pad hole that several one end are connected at the center of steel mesh ontology and are used for connection corresponding with several dissipating vias of pcb board, the width of each pad hole is sequentially increased on the extending direction at the center from steel mesh ontology to the outer of steel mesh ontology.Tin cream is flowed along pad hole from the center of steel mesh ontology to the outer of steel mesh ontology, the flow velocity of tin cream reduces with the increase of the width of pad hole, and the cross section of tin cream is gradually increased, be conducive to the thick tin cream that sufficiently extends in this way, the thickness of tin cream is thinning, gas to be conducive to make to be piled up in tin cream escapes in time, to reduce the gas content in tin cream, so that stomatal size reduces, correspondingly, be conducive to increase bonding area, promote welding reliability, therefore be conducive to extend the service life of QFN.
Description
Technical field
It is the present invention relates to electronic engineering technical field, in particular to a kind of for welding the steel mesh of QFN.
Background technique
QFN (Quad Flat No-leadPackage, quad flat non-pin package) is a kind of leadless packages, usually
In conformality or rectangle, with no pin, the advantages such as size is small, material ontology is light and thin, heat-sinking capability is strong, comprehensive performance is good, make
Its demand in recent years constantly increases, and is used widely in electronics industry, is particularly suitable for that space is limited and electric heating property is wanted
Seek higher occasion.The center of the bottom QFN is typically provided with the exposed pads of a large area, sufficiently to pass heat from QFN
It is directed at pcb board.In addition, QFN further includes being set to exposed pads periphery with the conductive welding disk for realizing electrical connection.
Correspondingly, for install QFN pcb board be equipped with heat dissipation bonding pad corresponding with QFN and dissipating vias.PCB
The heat dissipation bonding pad of plate provides reliable bonding area for the welding of QFN, and further, the dissipating vias of pcb board will be extra
Power consumption is diffused into copper and connects in bottom plate, provides approach for heat dissipation, consequently facilitating absorbing extra heat.
Steel mesh namely SMT (SMT Stencil) template, are a kind of SMT particular manufacturing crafts, major function is to aid in tin cream
Deposition, so that the tin cream of accurate quantity is transferred on the corresponding position of blank pcb board.Steel mesh is usually one block of very thin steel
Plate is equipped with many pad holes above, and the position of these pad holes and the heat dissipation bonding pad position of pcb board are completely the same, and and pcb board
Dissipating vias be connected.When welding, steel mesh is usually placed on pcb board, and thick tin cream is then applied to steel mesh, tin cream warp
Pad hole flow to pcb board, so that QFN is fixed on pcb board using tin cream.
It is well known that the stomata of certain area can be generated in the exposure pad for welding QFN, increased if stomata is reduced with passing through
The defects of adding the pad hole area of steel mesh and increasing tin cream area, then can generate sputtering, soldered ball, therefore due to the size of pad hole
It is limited so that these stomatas cannot be completely eliminated.Generally, it is desirable that stomatal size is less than the 50% of bonding area, just can guarantee
Electronic component reliable operation where QFN.
By taking the active view of attached drawing 1 as an example, there are five dissipating vias for the heat dissipation bonding pad setting of pcb board, one of them is located at
The center of pcb board, four additional is located on the diagonal line of pcb board and distribution annular in shape.For the dissipating vias of the pcb board
Distribution mode is in the steel mesh of " rice " type distribution using pad hole, and this " rice " font aperture mode is that current steel mesh is the most popular
Aperture mode.However, the pad hole width due to this steel mesh is constant always, the tin cream with higher temperature is easily caused to exist
It is expanded when flowing through the interlude of these pad holes, to generate large volume of bubble.As shown in Fig. 2, this to work as tin
When cream flows through the steel mesh of this " rice " font aperture, under the observation of X-ray (X-ray detection), bonding area is up to 60%, gas
Hole area accounting is relatively large, so that QFN soldering reliability is still limited, causes the service life of QFN relatively short.
Summary of the invention
In view of this, the purpose of the present invention is to provide a kind of for welding the steel mesh of QFN, it is conducive to extend making for QFN
Use the service life.
Its concrete scheme is as follows:
The present invention provides a kind of for welding the steel mesh of QFN, including steel mesh ontology, further includes:
Several one end are connected at the center of the steel mesh ontology and connect for corresponding with several dissipating vias of pcb board
Logical pad hole, the width of each pad hole prolonging to the outer of the steel mesh ontology at the center from the steel mesh ontology
It stretches and is sequentially increased on direction.
Preferably, the two sides of the pad hole are specially the linear type side of two extended line inclination intersections.
Preferably, the two sides of the pad hole are specially two arc-shaped sides of protrusion or opposing recesses relatively.
Preferably, the steel mesh ontology is specially rectangular steel mesh ontology, and the pad hole specifically includes four, described in four
Pad hole is in crossing distribution.
Preferably, four pad holes are distributed in opposite side midpoint line respectively and are formed by symmetrical center line.
Preferably, four pad holes are distributed in respectively in the symmetrical center line where diagonal line.
Preferably, the junction of two pad holes of arbitrary neighborhood, which is equipped with, is used for knuckle connecting the two.
With respect to the background art, the present invention provides a kind of for welding the steel mesh of QFN, including steel mesh ontology, if further including
Dry one end is connected at the center of the steel mesh ontology and is used for the pad of connection corresponding with several dissipating vias of pcb board
Hole, the width of each pad hole is on the extending direction at the center from the steel mesh ontology to the outer of the steel mesh ontology
It is sequentially increased.
Since the width of the pad hole is at the center from the steel mesh ontology to the extension of the outer of the steel mesh ontology
It is sequentially increased on direction, so that tin cream is flowed along the pad hole from the center of steel mesh ontology to the outer of the steel mesh ontology,
The flow velocity of tin cream reduces with the increase of the width of the pad hole, and the cross section of tin cream is gradually increased, and is conducive to fill in this way
Divide the thick tin cream that extends, the thickness of tin cream is thinning, so that the gas for being conducive to make to be piled up in tin cream escapes in time, to subtract
Gas content in small tin cream correspondingly, is conducive to increase bonding area, promotes welding reliability so that stomatal size reduces,
Therefore it is conducive to extend the service life of QFN.
Detailed description of the invention
In order to more clearly explain the embodiment of the invention or the technical proposal in the existing technology, to embodiment or will show below
There is attached drawing needed in technical description to be briefly described, it should be apparent that, the accompanying drawings in the following description is only this
The embodiment of invention for those of ordinary skill in the art without creative efforts, can also basis
The attached drawing of offer obtains other attached drawings.
Fig. 1 is the rice font aperture schematic diagram of the pad hole of existing steel mesh；
The distribution schematic diagram of bubble under the aperture mode that Fig. 2 is Fig. 1；
Fig. 3 is provided by the first specific embodiment of the invention for welding the aperture mode figure of the steel mesh of QFN；
The distribution schematic diagram of bubble under the aperture mode that Fig. 4 is Fig. 3；
Fig. 5 is the aperture mode figure based on another steel mesh developed on the basis of Fig. 3；
Fig. 6 is steel mesh aperture mode figure of the Fig. 3 after adding knuckle；
Fig. 7 is steel mesh aperture mode figure of the Fig. 5 after adding knuckle；
Fig. 8 is provided by second of specific embodiment of the present invention for welding the aperture mode figure of the steel mesh of QFN；
Fig. 9 is the aperture mode figure based on another steel mesh developed on the basis of Fig. 8.
Appended drawing reference is as follows:
Steel mesh ontology 1, pad hole 2 and dissipating vias 3.
Specific embodiment
Following will be combined with the drawings in the embodiments of the present invention, and technical solution in the embodiment of the present invention carries out clear, complete
Site preparation description, it is clear that described embodiments are only a part of the embodiments of the present invention, instead of all the embodiments.It is based on
Embodiment in the present invention, it is obtained by those of ordinary skill in the art without making creative efforts every other
Embodiment shall fall within the protection scope of the present invention.
In order to enable those skilled in the art to better understand the solution of the present invention, with reference to the accompanying drawings and detailed description
The present invention is described in further detail.
Fig. 3 to Fig. 7 is please referred to, Fig. 3 is provided by the first specific embodiment of the invention for welding the steel mesh of QFN
Aperture mode figure；The distribution schematic diagram of bubble under the aperture mode that Fig. 4 is Fig. 3；Fig. 5 is another based on what is developed on the basis of Fig. 3
The aperture mode figure of kind steel mesh；Fig. 6 is steel mesh aperture mode figure of the Fig. 3 after adding knuckle；Fig. 7 is that Fig. 5 was being added
Steel mesh aperture mode figure after crossing fillet.
The embodiment of the invention discloses a kind of for welding the steel mesh of QFN, including steel mesh ontology 1 and several pad holes 2.
Wherein, steel mesh ontology 1 is placed on pcb board, pad hole 2 be located at on the heat dissipation bonding pad of pcb board, and with pcb board
Dissipating vias 3 is connected.Specifically, pcb board is substantially square, and is arranged on pcb board there are five dissipating vias 3, one of them
Dissipating vias 3 is set to the center of pcb board, and four additional dissipating vias 3 is located on the diagonal line of pcb board, and this four dissipate
The hot annularly distribution of via hole 3.Certainly, the structure of dissipating vias 3 can make corresponding adjustment according to actual conditions on pcb board, no
It is limited to this.
One end of several pad holes 2 is connected at the center of steel mesh ontology 1, and the width of each pad hole 2 is in steel mesh sheet
It is sequentially increased on the center of body 1 to the extending direction of the outer of steel mesh ontology 1, correspondingly, flows through the tin cream of each pad hole 2
Flow velocity becomes smaller, so that tin cream changes from small to big in the cross section of flow direction, thickness is thinning, convenient for making the gas being piled up in tin cream
It being escaped during tin cream flowing, the stomatal size when welding QFN plate reduces, correspondingly, is conducive to increase bonding area,
Welding reliability increases therewith, therefore is conducive to extend the service life of QFN.
In the first specific embodiment, it is preferable that as shown in Fig. 3, the two sides of pad hole 2 are specially two extensions
The linear type side of line inclination intersection, forms a miner diameter end towards the V-type pad hole 2 at 1 center of steel mesh ontology, makes the stream of tin cream
Fast constant variation, so that the gas in tin cream be made to stablize evolution.
In this specific embodiment, steel mesh ontology 1 is substantially square, and pad hole 2 specifically includes four in crossing distribution
Pad hole 2, one end of each pad hole 2 be located at 1 center of steel mesh ontology dissipating vias 3 be connected, and four additional dissipate
Hot via hole 3 is respectively correspondingly arranged in the centre of four pad holes 2, so that the tin cream of each pad hole 2 is further by dissipating vias 3
It radiates, the quantity and set-up mode of certain dissipating vias 3 are not limited to this.
Preferably, as shown in Fig. 3, four pad holes 2 are distributed in respectively in the symmetrical center line where diagonal line, tin cream
From the center of steel mesh ontology 1 simultaneously from one end for being close to 1 center of steel mesh ontology of four pad holes 2 to the other end of pad hole 2
Flowing, so that fast and easy completes the printing of tin cream under the premise of guaranteeing soldering reliability.It is verified, by the aperture mode shape
At testing result of the welding surface at X-ray as shown in figure 4, bonding area up to 70%, it is clear that relative to existing opening
Mode improves to some extent.
It should be pointed out that four pad holes 2 can also be distributed in opposite side midpoint line respectively is formed by symmetrical centre
On line, as shown in Fig. 5, since the relatively above-mentioned distribution mode of the circulation passage of tin cream is shortened, be conducive to more rapidly complete
The printing of tin cream.
Certainly, the quantity of pad hole 2 and distribution mode are not limited to above-mentioned two situations, symmetrical using other types rule
Distribution mode or irregular symmetrical mode substitute, and have no effect on and achieve the object of the present invention.
In order to make the center of steel mesh ontology 1 that there is certain large volume of tin cream of space, large volume of tin cream
Pressure quickly flows, in the specific embodiment compared with being increased in the past when tin cream being made to enter each pad hole 2 convenient for tin cream
In, the junctions of two pad holes 2 of arbitrary neighborhood, which is equipped with, is used for knuckle connecting the two, shown in specific Fig. 6 and Fig. 7.It needs
It is noted that the radius of knuckle should not be too large, otherwise cause the area of pad hole 2 excessive, easily causes sputtering, soldered ball etc.
Defect.Depending on the radius concrete foundation actual conditions of knuckle, the radius of knuckle is not limited herein.
It can structure to the pad hole 2 in the first above-mentioned specific embodiment be further is improved.
Fig. 8 and Fig. 9 are please referred to, Fig. 8 is provided by second of specific embodiment of the present invention for welding the steel mesh of QFN
Aperture mode figure；Fig. 9 is the aperture mode figure based on another steel mesh developed on the basis of Fig. 8.
In this specific embodiment, the two sides of pad hole 2 are specially two relatively raised or opposing recesses arc-shaped
Side.As shown in Fig. 8, four pad holes 2 are distributed in respectively in the symmetrical center line where diagonal line, wherein each pad hole
2 two sides are made of two relatively raised arc-shaped side plates, so that when tin cream flows to steel mesh sheet from the center of steel mesh ontology 1
When the edge of body 1, tin cream change in flow in flow process is unstable, so that being conducive to tin cream realizes turbulent flow, makes to be piled up in tin
Gas in cream changes with the flowing of tin cream, and the cross section of tin cream also changes in addition, is more advantageous in tin cream
Gas discharge, stomatal size further decrease, and bonding area further increases, and the service life of QFN is further extended.
Similarly, as shown in Fig. 9, the two sides of each pad hole 2 are made of the arc-shaped side plate of two opposing recesses,
Equally make the change in flow of tin cream unstable, be conducive to sufficiently be discharged gas to reduce stomatal size, extend QFN uses the longevity
Life.
In this specific embodiment, four pad holes being made of two relatively raised or opposing recesses arc-shaped side plates
2 can also be distributed in opposite side midpoint line respectively is formed by symmetrical center line, in fact now beneficial effect and above situation phase
Together, details are not described herein.
The steel mesh to provided by the present invention for welding QFN is described in detail above, used herein specifically
Principle and implementation of the present invention are described for a example, the present invention that the above embodiments are only used to help understand
Method and its core concept；At the same time, for those skilled in the art is being embodied according to the thought of the present invention
There will be changes in mode and application range, in conclusion the contents of this specification are not to be construed as limiting the invention.
Claims (7)
1. a kind of for welding the steel mesh of QFN, which is characterized in that including steel mesh ontology (1), further includes:
Several one end are connected at the center of the steel mesh ontology (1) and for corresponding with several dissipating vias (3) of pcb board
The pad hole (2) of connection, the width of each pad hole (2) is from the center of the steel mesh ontology (1) to the steel mesh sheet
It is sequentially increased on the extending direction of the outer of body (1).
2. according to claim 1 for welding the steel mesh of QFN, which is characterized in that the two sides of the pad hole (2) have
Body is the linear type side of two extended line inclination intersections.
3. according to claim 1 for welding the steel mesh of QFN, which is characterized in that the two sides of the pad hole (2) have
Body is two arc-shaped sides of protrusion or opposing recesses relatively.
4. according to claim 2 or 3 for welding the steel mesh of QFN, which is characterized in that the steel mesh ontology (1) is specific
For rectangular steel mesh ontology, the pad hole (2) specifically includes four, and four pad holes (2) are in crossing distribution.
5. according to claim 4 for welding the steel mesh of QFN, which is characterized in that four pad holes (2) are divided respectively
Opposite side midpoint line is distributed in be formed by symmetrical center line.
6. according to claim 4 for welding the steel mesh of QFN, which is characterized in that four pad holes (2) are divided respectively
It is distributed in the symmetrical center line where diagonal line.
7. according to claim 4 for welding the steel mesh of QFN, which is characterized in that two pad holes of arbitrary neighborhood
(2) junction, which is equipped with, is used for knuckle connecting the two.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201810973215.XA CN108990312A (en) | 2018-08-24 | 2018-08-24 | It is a kind of for welding the steel mesh of QFN |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201810973215.XA CN108990312A (en) | 2018-08-24 | 2018-08-24 | It is a kind of for welding the steel mesh of QFN |
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| Publication Number | Publication Date |
|---|---|
| CN108990312A true CN108990312A (en) | 2018-12-11 |
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| CN201810973215.XA Pending CN108990312A (en) | 2018-08-24 | 2018-08-24 | It is a kind of for welding the steel mesh of QFN |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110198594A (en) * | 2019-06-27 | 2019-09-03 | 浪潮商用机器有限公司 | A kind of heat dissipation bonding pad paste solder printing technique and system of the PCBA with the hole via |
| CN111148341A (en) * | 2020-01-11 | 2020-05-12 | 苏州浪潮智能科技有限公司 | PCB with back drilling added in E-PAD area of device and manufacturing method thereof |
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| JP2004158898A (en) * | 2001-06-01 | 2004-06-03 | Nec Corp | Construction method of mounting structure, and mounting structure |
| CN106231813A (en) * | 2016-09-28 | 2016-12-14 | 伟创力电子技术(苏州)有限公司 | A kind of one side the most empty method of backflow of dual platen |
| CN107278049A (en) * | 2017-07-28 | 2017-10-20 | 郑州云海信息技术有限公司 | A kind of design method of PCBA heat dissipation bonding pads steel mesh |
| CN107708319A (en) * | 2017-12-04 | 2018-02-16 | 郑州云海信息技术有限公司 | A kind of boring method of the IC heat dissipation bonding pads with Via steel meshes |
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2018
- 2018-08-24 CN CN201810973215.XA patent/CN108990312A/en active Pending
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2004158898A (en) * | 2001-06-01 | 2004-06-03 | Nec Corp | Construction method of mounting structure, and mounting structure |
| CN106231813A (en) * | 2016-09-28 | 2016-12-14 | 伟创力电子技术(苏州)有限公司 | A kind of one side the most empty method of backflow of dual platen |
| CN107278049A (en) * | 2017-07-28 | 2017-10-20 | 郑州云海信息技术有限公司 | A kind of design method of PCBA heat dissipation bonding pads steel mesh |
| CN107708319A (en) * | 2017-12-04 | 2018-02-16 | 郑州云海信息技术有限公司 | A kind of boring method of the IC heat dissipation bonding pads with Via steel meshes |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110198594A (en) * | 2019-06-27 | 2019-09-03 | 浪潮商用机器有限公司 | A kind of heat dissipation bonding pad paste solder printing technique and system of the PCBA with the hole via |
| CN111148341A (en) * | 2020-01-11 | 2020-05-12 | 苏州浪潮智能科技有限公司 | PCB with back drilling added in E-PAD area of device and manufacturing method thereof |
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Application publication date: 20181211 |
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