CN109451650A - A kind of low stress printed circuit that can improve surface mount device welding spot reliability - Google Patents
A kind of low stress printed circuit that can improve surface mount device welding spot reliability Download PDFInfo
- Publication number
- CN109451650A CN109451650A CN201811170332.9A CN201811170332A CN109451650A CN 109451650 A CN109451650 A CN 109451650A CN 201811170332 A CN201811170332 A CN 201811170332A CN 109451650 A CN109451650 A CN 109451650A
- Authority
- CN
- China
- Prior art keywords
- pcb
- pcb board
- stress
- solder joint
- groove
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Classifications
-
- 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
- H05K1/00—Printed circuits
- H05K1/02—Details
- H05K1/0271—Arrangements for reducing stress or warp in rigid printed circuit boards, e.g. caused by loads, vibrations or differences in thermal expansion
-
- 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
- H05K1/00—Printed circuits
- H05K1/18—Printed circuits structurally associated with non-printed electric components
- H05K1/181—Printed circuits structurally associated with non-printed electric components associated with surface mounted components
Abstract
The invention discloses a kind of low stress printed circuit boards (PCB) for improving surface mount device welding spot reliability.By the part flexible structure of PCB below device, solder joint thermal stress is reduced, improves reliability.PCB flexible structure position includes pad array corner, region between center or both.When pcb board expands with heat and contract with cold, the deformation of softer part PCB, can directly reduce corner solder joint stress under the solder joint of corner.The softer PCB deformation in pad array center reduces the stress transmitted to corner solder joint.PCB locally softens between center and corner, and the stress transfer of central PCB deformation diagonal section solder joint has been isolated.Specifically, the hardness of pcb board regional area is reduced using groove or embedment flexible material structure.Groove or flexible material can also be embedded in inside PCB mono- side opening of PCB, and production uses pcb board hot pressing, and the methods of machine cuts and flexible material filling are realized.
Description
Technical field
The present invention relates to the printed circuit board applied in surface mount device, especially a kind of to improve solder joint reliable
The structure and manufacturing process of the low stress printed circuit board of property.
Background technique
The thermal stress reliability of surface mount device solder joint is a common problem.Surface mount device passes through multiple welderings
Lattice array is placed on printed circuit board (Printed Circuit Board, PCB), realizes the electricity and machine of device and pcb board
Tool connection.The problem of solder joint thermal stress reliability derive from surface mount device and pcb board different heat expansion coefficient, device it is swollen
For swollen coefficient about at 3-10ppm/ DEG C, the coefficient of expansion of pcb board is usually 14-17ppm/ DEG C.When temperature increases, pcb board is flat
The expansion rate in face direction is bigger than device, and solder joint between the two receives pcb board on device angle and the thrust of edge direction.Temperature
Just the opposite when reduction, the shrinkage ratio device of pcb board is big, and pcb board draws solder joint to device center direction.In addition, temperature change
Also device and pcb board can be caused in the warpage of plank vertical direction, solder joint there may be the stress of stretching or compression in vertical direction.
Solder joint stress is obtained at device different location also significant difference, and the solder joint on device edge especially angle is because from device center
Position is remote, and all PCB regions in solder joint area can all increase stress.Leave that devices center is remoter, and solder joint stress is bigger.
But solder joint stress is not directly proportional at a distance from solder joint to center, numerous computer finite element simulations and the fracture of actual experiment solder joint
Degree show 2-3 on pad array edge, especially angle arrange solder joint inside the stress ratio that solder joint is subject to it is several times greater more than.In device
On part edge, especially angle, solder joint stress suddenly rises.The solder joint of variation in use process repeatedly, soft solder material is easy
By ess-strain repeatedly, there is fatigue fracture.The stress that solder joint on four angles of device is subject to is maximum, generally also can be first
Fracture failure.
The previous method for reducing surface mount device solder joint stress was mainly both direction: first is that making device and pcb board
Thermal expansion coefficient is as close possible to reducing the source of stress.Such as increase the glass fibre solder reduction plank of pcb board laminate
The coefficient of expansion, but it can only be a small amount of raising in how many situation that the material within the scope of controllable costs, which improves,；Second is that reducing device
The hardness of part and pcb board absorbs the stress that PCB expands with heat and contract with cold by deformation, to reduce the stress being applied on solder joint.It reduces
Pcb board hardness generallys use the soft PCB layer pressurizing resin of glue and using glass fibre ratio less in resin, and changes in material is also
It is more troublesome.In addition reduction hardness method is the optimization of pcb board thickness, all using relatively thin plank below device.Device
Thin PCB of large area can be reduced the stress of solder joint below, but mechanical strength reduces, as mobile phone falls in use process
Pcb board may be damaged.
Summary of the invention
Main innovation point of the invention is the uneven hardness within the scope of the sub- in-plane manufacture surface mount device of pcb board
Plank.Flexible structure and the region of small area are set up at PCB key position under pad array, these positions include solder joint battle array
Arrange corner, the partial region between center or both.Remaining majority device area PCB does not change, and keeps original hardness.
Local stress-buffer layer and separation layer of the soft region as plank in-plane of small area on PCB, can effectively reduce pcb board
Son, which expands with heat and contract with cold, brings the stress of device solder joint, while without pcb board below all thinned devices, being able to maintain certain plate
Sub- mechanical strength.
Flexible structure within the scope of surface mount device is the slot empty in the local small area region manufacture in PCB plane direction
Ditch or flexible material structure.In the thickness direction of pcb board, it is thus necessary to determine that the thickness of groove or flexible material structure and with
Relative position between each laminate layers of PCB.
Detailed description of the invention
The sectional view of Mount Device on Fig. 1 traditional PCB plate
Fig. 2 low stress pcb board examples of implementation 1: the soft PCB region in solder joint corner
Fig. 3 low stress pcb board examples of implementation 2: the soft PCB region in solder joint center
Fig. 4 low stress pcb board examples of implementation 3: the soft PCB region between solder joint corner and center
Fig. 5 low stress pcb board thickness direction groove or flexible material sectional view
A kind of manufacturing process of Fig. 6 low stress pcb board groove
The component label of attached drawing is as follows: 1 Mount Device；2 pad arrays；3 printed circuit boards (PCB)；4 solder masks；5 bronze medals
Layer；6 laminated resins；7PCB plate groove structure；8PCB flexible material structure；9 use interim glue；10 machine cuts mouths
Specific embodiment
The preferred embodiments of the present invention will be described in detail with reference to the accompanying drawing, so that advantages and features of the invention energy
It is easier to be readily appreciated by one skilled in the art, so as to make a clearer definition of the protection scope of the present invention.
Fig. 1 is the sectional view of Mount Device on traditional PCB plate.Mount Device 1 passes through on 2 connecting PCB board 3 of pad array.
Pcb board 3 is made of multilayer material, the solder mask 4 including multilayer, layers of copper 5 and laminated resin 6.In order to illustrate PCB slot below
The relative thickness of ditch and flexible material structure and PCB, the present invention uses sample of the four layers of copper PCB as examples of implementation, practical special
Benefit application is suitble to single layer and the pcb board of multiple layer of copper.
PCB expands with heat and contract with cold when pcb board the property such as coefficient of expansion and hardness below device solder joint directly affect temperature change
It is applied to the stress of solder joint.Other than PCB material, the thickness of PCB has an impact to plank hardness, the easier shape of thinner plank
Become, the stress for being applied to high reliability risk solder joint on solder joint especially edge and angle is lower.Traditional PCB plate needs certain thickness
Degree maintains mechanical strength, also has the limitation of pcb board technique, pcb board cannot be made very thin, and the usual sub- thickness of pcb board is in 0.8-
1.0mm.Therefore the thermal stress of device solder joint is big, and welding spot reliability reduces.
Fig. 2 is low stress pcb board examples of implementation 1: the soft PCB region in solder joint corner.Groove 7 or flexible material are in PCB
The corner of plate pad array.At least cover three solder joints of each corner most external.Corner solder joint is directly connected to soft PCB
Plate, the stress that solder joint receives are reduced, and reliability improves.
Fig. 3 is low stress pcb board examples of implementation 2: the 2 soft PCB region in center of solder joint.The soft PCB in center softens, and passes to
The stress of solder joint is lower on edge and angle.
Fig. 4 is low stress pcb board examples of implementation 3: the soft PCB region between 2 corner of solder joint and center.Center is ring-like
Center and the stress of edge PCB has been isolated in PCB groove 7, totally reduces the stress of solder joint on angle.
Fig. 5 is low stress pcb board thickness direction groove or flexible material sectional view.Groove 7 or flexible material 8 can be with
It is embedded in inside pcb board, benefit is can be all routed with top and bottom.Especially Fig. 5 a, flexible material layer directly under solder joint brazing piece,
Solder joint stress can be effectively reduced.
Fig. 6 is a kind of manufacturing process of low stress pcb board groove 7.One layer of interim glue 9 is added between laminate, has then cut
Vertical notch 10 is cut out, then the unwanted part PCB is taken out, the structure of groove is formed on pcb board.
The above description is only an embodiment of the present invention, is not intended to limit the scope of the invention, all to utilize this hair
Equivalent structure or equivalent flow shift made by bright specification and accompanying drawing content is applied directly or indirectly in other relevant skills
Art field, is included within the scope of the present invention.
Claims (10)
1. a kind of low stress printed circuit board (Printed Circuit that can improve surface mount device welding spot reliability
Board, PCB) structure and manufacturing process.It is characterized in that, the pcb board partial region below surface mount device pad array
There are the groove or flexible material for absorbing stress, reduces since surface mount device and pcb board thermal expansion coefficient difference are to device
The thermal stress that solder joint generates, especially on device angle and the larger stress of edge solder joint.
2. low stress pcb board in-plane structure according to claim 1, groove or flexible material are at pad array angle
Portion, between center or both region.Change the hardness and stress of PCB in crucial localized positions, reduction part can be played
The effect that base plate stress or isolation stress transmit on pcb board.
3. the first pcb board in-plane structure that right 2 requires, groove or flexible material are at the angle of pcb board pad array
Portion.At least cover three solder joints of each corner most external.It is farthest to leave device center position for three solder joints on each angle, is subject to
Thermal stress is much larger than internal solder joint.The pcb board region that corner solder joint is directly connected to softens, and reduces pcb board and expands with heat and contract with cold to angle
The stress of portion's solder joint bring, improves welding spot reliability.
4. second of pcb board in-plane structure that right 2 requires, groove or flexible material are in pcb board pad array
Centre at least covers central 3 × 3 spot size regions.The pcb board that center locally softens is when plank expands with heat and contract with cold to device angle
The thermal stress of upper solder joint transmitting becomes smaller, and the most dangerous corner solder joint of stress maximum is not easy to break.
5. the third pcb board in-plane structure that right 2 requires, groove or flexible material are at the angle of pcb board pad array
The upper region between center, width are about spot size or bigger.The soft PCB construction in the part of intermediate region by center and
The stress isolation of corner PCB comes, and as buffer layer, reduces the expand with heat and contract with cold stress of generation of middle part PCB and transmits to corner, drop
The low stress of corner solder joint.
6. pcb board thickness direction structure according to claim 1, groove or flexible material can be to corresponding pcb board
A side opening of the position without surface mount device, can also be embedded in inside pcb board.
7. the ratio that the thickness of the pcb board thickness direction structure that right 6 requires, groove or flexible material is pcb board thickness
Example, for example, about 20-90%.There are layer high molecule resin, layers of copper and solder mask in pcb board, groove or flexible material can generations
For the material of part layer among these.
8. low stress pcb board manufacturing process according to claim 1, groove or flexible material production are using pcb board heat
Pressure, machine cuts and flexible material, which the methods of are filled with, to be realized.
9. the PCB groove structure manufacture that right 8 requires: 1) a kind of mode is by cutting the several PCB layer pressing plates of aperture, then layer
Pressure obtains groove；2) another method is that the pcb board manufacture of normal homogeneous thickness uses electric drill machinery plane cutting after the completion
Thickness of the PCB to needs；2) when the third method is PCB layer pressure, temporary bond glue-line is added at particular needs interface to be separated,
The PCB layer for needing to remove is cut perpendicular to the direction PCB to bonding glue-line, then removes the PCB layer of local thickness.
10. the PCB flexible material structure manufacture that right 8 requires: similar with groove manufacturing process, being a difference in that will be in groove
It is filled with and fills flexible high molecular material, pass through the methods of dispensing and printing.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201810890909 | 2018-08-07 | ||
| CN2018108908997 | 2018-08-07 | ||
| CN201810890899 | 2018-08-07 | ||
| CN2018108909097 | 2018-08-07 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN109451650A true CN109451650A (en) | 2019-03-08 |
Family
ID=65545044
Family Applications (2)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201811170332.9A Pending CN109451650A (en) | 2018-08-07 | 2018-10-09 | A kind of low stress printed circuit that can improve surface mount device welding spot reliability |
| CN201821629212.6U Active CN210518977U (en) | 2018-08-07 | 2018-10-09 | Low-stress printed circuit board capable of improving reliability of surface-mounted device welding spot |
Family Applications After (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201821629212.6U Active CN210518977U (en) | 2018-08-07 | 2018-10-09 | Low-stress printed circuit board capable of improving reliability of surface-mounted device welding spot |
Country Status (1)
| Country | Link |
|---|---|
| CN (2) | CN109451650A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116685055A (en) * | 2022-12-09 | 2023-09-01 | 荣耀终端有限公司 | Circuit board assembly and electronic equipment |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109451650A (en) * | 2018-08-07 | 2019-03-08 | 苏州霞光电子科技有限公司 | A kind of low stress printed circuit that can improve surface mount device welding spot reliability |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2005235997A (en) * | 2004-02-19 | 2005-09-02 | Mitsubishi Electric Corp | Printed board, electronic circuit substrate, and its manufacturing method |
| CN102231944A (en) * | 2011-06-14 | 2011-11-02 | 华为技术有限公司 | Solder joint stress reduction structure and printed circuit board comprising same |
| JP2013089853A (en) * | 2011-10-20 | 2013-05-13 | Keihin Corp | Printed wiring board |
| CN210518977U (en) * | 2018-08-07 | 2020-05-12 | 苏州霞光电子科技有限公司 | Low-stress printed circuit board capable of improving reliability of surface-mounted device welding spot |
-
2018
- 2018-10-09 CN CN201811170332.9A patent/CN109451650A/en active Pending
- 2018-10-09 CN CN201821629212.6U patent/CN210518977U/en active Active
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2005235997A (en) * | 2004-02-19 | 2005-09-02 | Mitsubishi Electric Corp | Printed board, electronic circuit substrate, and its manufacturing method |
| CN102231944A (en) * | 2011-06-14 | 2011-11-02 | 华为技术有限公司 | Solder joint stress reduction structure and printed circuit board comprising same |
| JP2013089853A (en) * | 2011-10-20 | 2013-05-13 | Keihin Corp | Printed wiring board |
| CN210518977U (en) * | 2018-08-07 | 2020-05-12 | 苏州霞光电子科技有限公司 | Low-stress printed circuit board capable of improving reliability of surface-mounted device welding spot |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116685055A (en) * | 2022-12-09 | 2023-09-01 | 荣耀终端有限公司 | Circuit board assembly and electronic equipment |
Also Published As
| Publication number | Publication date |
|---|---|
| CN210518977U (en) | 2020-05-12 |
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