Vertical interconnection structure and method between LTCC and PCB based on high-frequency transmission
Technical field
The present invention relates to the transmission of broadband high-frequency signals (DC-35GHz), belong to electrical interconnection field, especially a kind of base
Vertical interconnection structure and method between the LTCC and PCB of high-frequency transmission.
Background technique
With low-temperature co-fired ceramics (Low Temperature Cofired Ceramics, hereinafter referred to as LTCC) and printing
The continuous maturation of circuit board (Printed Circuit Board, hereinafter referred to as PCB) technology, in the miniaturization of current product, more function
Under the demand driving of energyization, two kinds of components realize that high frequency, the demand of high density interconnection are higher and higher in Complex Structural System.In the past
Box body isolation, spun gold (or gold ribbon) cascade mode is mostly used to realize interconnection, but this interconnecting method the space occupied is big, signal
Transmission range is long, and loss is big, and is unfavorable for the application of high-frequency signal.
Summary of the invention
The technical problems to be solved by the present invention are: in view of the problems of the existing technology, providing one kind and being kept pouring in based on height
Vertical interconnection structure and method between defeated LTCC and PCB.It can realize DC-35GHz broadband high-frequency signals between LTCC and PCB
Transmission, and its structure be vertical interconnection structure, designed interconnection architecture be based on ball grid array (Ball Grid Array, below
Abbreviation BGA) welding structure, it is conducive to miniaturization, the highdensity system integration.With reference to package assembly side of the BGA device on PCB
Formula is obtained a kind of LTCC and is vertically assembled on PCB component, transmits high-frequency signal by a large amount of simulation analysis and verification experimental verification
Design.
The technical solution adopted by the invention is as follows:
Vertical interconnection structure includes: between a kind of LTCC and PCB based on high-frequency transmission
LTCC component, for the LTCC ceramic wafer over-assemble component of corresponding electronic device;LTCC ceramic wafer upper surface is set
Set the LTCC component upper epidermis microstrip line for transmitting signal, the similar axle construction of the first LTCC component, use for transmitting signal
In the similar axle construction of the 2nd LTCC component and shielding via hole of transmitting signal;It is arranged inside LTCC ceramic wafer for transmitting signal
LTCC component internal layer strip line;LTCC component upper epidermis microstrip line one end passes through the first similar axle construction of LTCC component, with
The connection of LTCC component internal layer strip line one end;The LTCC component internal layer strip line other end and the similar axle construction of the 2nd LTCC component connect
It connects, shielding via hole is evenly distributed on LTCC component upper epidermis microstrip line, the similar axle construction of the first LTCC component, LTCC component internal layer
Strip line and the 2nd LTCC component quasi-coaxial structure periphery;
The component of corresponding electronic device is arranged in PCB component on pcb board;PCB welded plate upper surface is arranged for transmitting
The PCB component upper epidermis microstrip line of signal, the similar axle construction of the first PCB component for transmitting signal, for transmitting signal
The similar axle construction of 2nd PCB component and shielding via hole;PCB component internal layer for transmitting signal is set inside PCB welded plate
Strip line;The first similar axle construction of PCB component is connect with PCB component internal layer strip line one end;PCB component internal layer strip line is another
End is connect by the 2nd similar shaft assembly of PCB with PCB component upper epidermis microstrip line one end;Shielding via hole is evenly distributed on PCB group
Part upper epidermis microstrip line, the similar axle construction of the first PCB component, PCB component internal layer strip line and the 2nd PCB component quasi-coaxial knot
Around structure;Welder carries out plant ball bonding on the pad of the 2nd similar axle construction of LTCC component for soldered ball, then will plant
The LTCC component of good soldered ball is assembled on PCB component using standard SMT process, as a device so that the 2nd LTCC
The similar axle construction of component is hung down by coaxial configuration interconnection in soldered ball, with the first PCB component, realization LTCC component with PCB component
Straight interconnection;Wherein signal transmission route is the LTCC upper epidermis microstrip line → similar axle construction of the first LTCC component → LTCC core band
Similar axle construction → the soldered ball of shape line → the 2nd LTCC component → PCB upper epidermis BGA pad → the first similar axle construction of PCB component →
The PCB internal layer strip line → similar axle construction of the 2nd PCB component → PCB upper epidermis microstrip line.
Further, matching section is set between the PCB component internal layer strip line and PCB component upper epidermis microstrip line;Institute
Matching section is stated to connect by the 2nd similar axle construction of PCB component with PCB component upper epidermis microstrip line;Matching byte wide is between the
Between the similar axle construction outer conductor internal diameter of two PCB components and PCB component internal layer strip line conduction band slice width degree;2nd PCB component class
Coaxial configuration outer conductor internal diameter is greater than PCB component internal layer strip line conduction band slice width degree.
Further, the LTCC component upper epidermis microstrip line, PCB component upper epidermis microstrip line are all conduction band, and conduction band is situated between
Matter respectively corresponds as LTCC substrate, PCB substrate;LTCC component upper epidermis microstrip line is with stratum inside LTCC ceramic wafer for ground connection
The microstrip line in face, LTCC substrate, PCB substrate thermal expansion coefficient be smaller than 10 × 10-6/ DEG C substrate;LTCC substrate heat is swollen
Swollen coefficient and PCB substrate coefficient of thermal expansion differences are the smaller the better;LTCC component upper epidermis microstrip line, PCB component upper epidermis microstrip line
Characteristic impedance is allWherein εrIt respectively corresponds as LTCC component upper epidermis microstrip line, PCB component
The medium relative dielectric constant of upper epidermis microstrip line conduction band, h respectively correspond as on LTCC component upper epidermis microstrip line, PCB component
The conduction band dielectric thickness of surface layer microstrip line, w respectively correspond as on LTCC component upper epidermis microstrip line conduction band slice width degree, PCB component
Surface layer microstrip line conduction band slice width degree, t respectively correspond as LTCC component upper epidermis microstrip line, PCB component upper epidermis microstrip line conduction band
Thickness degree.
Further, the similar axle construction of the first LTCC component, the similar axle construction of the 2nd LTCC component, the first PCB group
The similar axle construction of part and the 2nd similar axle construction of PCB component are all to transmit the vertical transition hole of signal as inner conductor, with week
The vertical transition hole for enclosing ground connection is outer conductor, using LTCC as the similar axle construction of substrate;The similar axle construction of first LTCC component,
Two LTCC component quasi-coaxial structured medias are LTCC substrate;The similar axle construction of first PCB component and the 2nd PCB component quasi-coaxial
Structured media is PCB substrate;The similar axle construction of first LTCC component, the similar axle construction of the 2nd LTCC component, the first PCB component class
Coaxial configuration and the 2nd PCB component quasi-coaxial architectural characteristic impedance areWherein εrRespectively correspond is first
The similar axle construction of LTCC component, the similar axle construction of the 2nd LTCC component, the similar axle construction of the first PCB component and the 2nd PCB group
Part quasi-coaxial structured media relative dielectric constant, D respectively correspond as the similar axle construction outer conductor internal diameter of the first LTCC component, second
The similar axle construction outer conductor internal diameter of LTCC component, the similar axle construction outer conductor internal diameter of the first PCB component and the 2nd PCB component class
Coaxial configuration outer conductor internal diameter, d are respectively the via diameter of the first similar axle construction of LTCC component, the 2nd LTCC component quasi-coaxial
The via diameter of structure, the similar axle construction via diameter of the first PCB component and the similar axle construction via hole of the 2nd PCB component are straight
Diameter.
Further, the characteristic impedance of the LTCC component internal layer strip line, PCB component internal layer strip line
LTCC component internal layer strip line, PCB component internal layer strip line are respectively corresponded to be printed by conduction band, PCB internal layer of LTCC internal layer track
Line processed is conduction band, using two sides ground plane above and below LTCC internal layer track conduction band, PCB internal layer track conduction band as the band-like of ground plane
Line, εrIt is LTCC component internal layer strip line, PCB component internal layer stripline media relative dielectric constant;H respectively corresponds as LTCC group
Part internal layer strip line dielectric thickness, PCB component internal layer strip line dielectric thickness, w respectively correspond as LTCC internal layer track conduction band
Width, PCB internal layer track conduction band width, t respectively corresponds to be led for LTCC internal layer track conduction band thickness, PCB internal layer track
Tape thickness.
Vertical interconnection method includes: between a kind of LTCC and PCB based on high-frequency transmission
The setting of step 1:LTCC ceramics plate surface is for transmitting the LTCC component upper epidermis microstrip line of signal, believing for transmitting
Number the similar axle construction of the first LTCC component, the similar axle construction of the 2nd LTCC component for transmitting signal and shielding via hole;
LTCC component internal layer strip line for transmitting signal is set inside LTCC ceramic wafer;PCB printing board surface is arranged for transmitting
The PCB component upper epidermis microstrip line of signal, the similar axle construction of the first PCB component for transmitting signal, for transmitting signal
The similar axle construction of 2nd PCB component and shielding via hole;PCB component internal layer for transmitting signal is set inside PCB printed board
Strip line;LTCC component is the structure that respective chip is assembled on LTCC ceramic wafer;PCB component is to be assembled on pcb board accordingly
The structure of electronic device;Step 2:LTCC component upper epidermis microstrip line one end passes through the first similar axle construction of LTCC component, with
The connection of LTCC component internal layer strip line one end;The LTCC component internal layer strip line other end and the similar axle construction of the 2nd LTCC component connect
It connects, shielding via hole is evenly distributed on LTCC component upper epidermis microstrip line, the similar axle construction of the first LTCC component, LTCC component internal layer
Strip line and the 2nd LTCC component quasi-coaxial structure periphery;The first similar axle construction of PCB component and PCB component internal layer strip line
One end connection;The PCB component internal layer strip line other end is by the 2nd similar shaft assembly of PCB, with PCB component upper epidermis microstrip line one
End connection;Shielding via hole is evenly distributed on PCB component upper epidermis microstrip line, the similar axle construction of the first PCB component, in PCB component
Layer strip line and the 2nd PCB component quasi-coaxial structure periphery;
Step 3: soldered ball carries out plant ball bonding on the pad of the 2nd similar axle construction of LTCC component, then will plant soldered ball
LTCC component as a device, assembled on PCB component using standard SMT process, so that the 2nd LTCC component class
Coaxial configuration realizes the vertical interconnection of LTCC component and PCB component by coaxial configuration interconnection in soldered ball, with the first PCB component;
Wherein signal transmission route be the LTCC upper epidermis microstrip line → similar axle construction of the first LTCC component → LTCC internal layer strip line →
In the similar axle construction → soldered ball of 2nd LTCC component → PCB upper epidermis BGA pad → similar axle construction → PCB of the first PCB component
Layer strip line → similar the axle construction of the 2nd PCB component → PCB upper epidermis microstrip line.
Further, matching section is set between the PCB component internal layer strip line and PCB component upper epidermis microstrip line;Institute
Matching section is stated to connect by the 2nd similar axle construction of PCB component with PCB component upper epidermis microstrip line;Matching byte wide is between the
Between the similar axle construction outer conductor internal diameter of two PCB components and PCB component internal layer strip line conduction band layer;2nd PCB component quasi-coaxial
Structure outer conductor internal diameter is greater than PCB component internal layer strip line conduction band slice width degree.
Further, the LTCC component upper epidermis microstrip line, PCB component upper epidermis microstrip line are all conduction band, and conduction band is situated between
Matter respectively corresponds as LTCC substrate, PCB substrate;LTCC component upper epidermis microstrip line is with stratum inside LTCC ceramic wafer for ground connection
The microstrip line in face, LTCC substrate, PCB substrate thermal expansion coefficient be smaller than 10 × 10-6/ DEG C substrate;LTCC substrate heat is swollen
Swollen coefficient and PCB substrate coefficient of thermal expansion differences are the smaller the better;LTCC component upper epidermis microstrip line, PCB component upper epidermis microstrip line
Characteristic impedance is allWherein εrIt respectively corresponds as LTCC component upper epidermis microstrip line, PCB component
Upper epidermis microstrip line conduction band medium relative dielectric constant, h respectively correspond as table on LTCC component upper epidermis microstrip line, PCB component
Layer microstrip line conduction band dielectric thickness, w respectively correspond as LTCC component upper epidermis microstrip line, PCB component upper epidermis microstrip line conduction band
Slice width degree, t respectively correspond as LTCC component upper epidermis microstrip line, PCB component upper epidermis microstrip line conduction band thickness degree.
Further, the similar axle construction of the first LTCC component, the similar axle construction of the 2nd LTCC component, the first PCB group
The similar axle construction of part and the 2nd similar axle construction of PCB component are all to transmit the vertical transition hole of signal as inner conductor, with week
The vertical transition hole for enclosing ground connection is outer conductor, using LTCC as the similar axle construction of substrate;
The similar axle construction of first LTCC component, the 2nd LTCC component quasi-coaxial structured media are LTCC substrate;First PCB group
The similar axle construction of part and the 2nd PCB component quasi-coaxial structured media are PCB substrate;The similar axle construction of first LTCC component,
The similar axle construction of two LTCC components, the similar axle construction of the first PCB component and the 2nd PCB component quasi-coaxial architectural characteristic impedance areWherein εrIt respectively corresponds as the similar axle construction of the first LTCC component, the similar axle construction of the 2nd LTCC component,
The similar axle construction of one PCB component and the 2nd PCB component quasi-coaxial structured media relative dielectric constant, it is first that D, which is respectively corresponded,
The similar axle construction outer conductor internal diameter of LTCC component, the similar axle construction outer conductor internal diameter of the 2nd LTCC component, the first PCB component are similar
Axle construction outer conductor internal diameter and the similar axle construction outer conductor internal diameter of the 2nd PCB component, d are respectively the first LTCC component quasi-coaxial
The via diameter of structure, the via diameter of the 2nd similar axle construction of LTCC component, the similar axle construction via diameter of the first PCB component
And the 2nd similar axle construction via diameter of PCB component.
Further, the characteristic impedance of the LTCC component internal layer strip line, PCB component internal layer strip line
LTCC component internal layer strip line, PCB component internal layer strip line are respectively corresponded with LTCC
Internal layer track is conduction band, PCB internal layer track is conduction band, on LTCC internal layer track conduction band, PCB internal layer track conduction band
Lower two sides ground plane is the strip line of ground plane, εrIt is that LTCC component internal layer strip line, PCB component internal layer stripline media are opposite
Dielectric constant;H respectively corresponds as LTCC component internal layer strip line dielectric thickness, PCB component internal layer strip line dielectric thickness, and w points
LTCC internal layer track conduction band width, PCB internal layer track conduction band width are not corresponded to, and t respectively corresponds as the printing of LTCC internal layer
Line conduction band thickness, PCB internal layer track conduction band thickness.
In conclusion by adopting the above-described technical solution, the beneficial effects of the present invention are:
1, the vertical interconnection method that the present invention uses, realizes broadband high-frequency signals (DC-35GHz) between LTCC and PCB
Low-loss transmission, return loss S11, which can be realized, is better than -10dB.
2. interconnection architecture uses ball bond mode, occupy little space, density is high, convenient for the miniaturization, multi-functional of system
Change.
3. interconnecting soldered ball uses high lead BGA soldered ball flexible, solder joint stress can be alleviated, improve reliability.
4. relying primarily on SMT technology when assembly, technology relative maturity is resourceful, convenient for promoting.
Detailed description of the invention
Examples of the present invention will be described by way of reference to the accompanying drawings, in which:
Fig. 1 is structure of the invention perspective view of the explosion.
1-LTCC component 2-PCB component
3- soldered ball 4-LTCC upper epidermis microstrip line
The similar axle construction 6-LTCC internal layer strip line of the first LTCC component of 5-
The 2nd LTCC component quasi-coaxial structure division that 7- does not connect with soldered ball
The 2nd LTCC component quasi-coaxial structure bottom that 8- connects with soldered ball
The first PCB component quasi-coaxial structure division that 9- connects with soldered ball
The first PCB component quasi-coaxial structure division that 10- does not connect with soldered ball
The 2nd PCB component quasi-coaxial 13-PCB upper epidermis microstrip line of 11-PCB internal layer strip line 12
Specific embodiment
All features disclosed in this specification or disclosed all methods or in the process the step of, in addition to mutually exclusive
Feature and/or step other than, can combine in any way.
Any feature disclosed in this specification unless specifically stated can be equivalent or with similar purpose by other
Alternative features are replaced.That is, unless specifically stated, each feature is an example in a series of equivalent or similar characteristics
?.
Related description of the present invention:
1, LTCC component upper epidermis microstrip line and PCB component upper epidermis microstrip line are all microstrip lines;LTCC component core band
Shape line and PCB component internal layer strip line are all strip lines, and only respective parameter may not be identical.
2, the similar axle construction of the first LTCC component, the similar axle construction of the 2nd LTCC component, the first PCB component quasi-coaxial knot
Structure, the 2nd similar axle construction of PCB component are all similar axle construction, and it is interior lead that specific structure, which is to transmit the vertical transition hole of signal,
Body, using the vertical transition hole that surrounding is grounded in LTCC component or PCB component as the similar axle construction of outer conductor.
3, PCB component internal layer strip line conduction band layer refers to the conduction band layer of PCB component internal layer strip line.Table on LTCC component
Layer microstrip line conduction band slice width degree, PCB component upper epidermis microstrip line conduction band slice width degree refer respectively to the conduction band layer of respective microstrip line.
4, shielding via hole is the via hole for shielding interference signal.
5, matching section material is track.
6. vertical transition hole refers to the transitional pore vertical with LTCC ceramic wafer or PCB printed board upper and lower surface.
Design principle:
1. material selects
From signal transmission of angle, it is desirable that LTCC substrate and PCB substrate loss of signal in high frequency are sufficiently small, and fissipation factor exists
Reach 1 ‰ or less when 10GHz;Consider from structural strength angle, it is desirable that LTCC connects with the elasticity modulus of PCB welded plate material
Closely, general to choose the PCB substrate with larger elasticity modulus;Consider from reliability perspectives, it is desirable that the heat of LTCC and pcb board material
Coefficient of expansion difference is the smaller the better, is typically chosen thermal expansion coefficient less than 10 × 10-6/ DEG C PCB substrate.Take into account above 3 points,
The 9K7 green of DuPont may be selected in LTCC, and the CLTE-XT substrate of Arlon may be selected in PCB.
In addition to improve the matching interconnected between ceramic material and organic material, two kinds of materials are reduced under temperature changing environment
Thermal stress, intermediate interconnection material select lead content weight percent be greater than 90% tin-lead soldered ball, pass through high lead welding ball
Flexibility drop stress concentration, improves the reliability of interconnection.
2. transmission structure designs
Generally in use, possible signal transmission path are as follows: LTCC upper epidermis microstrip line → the first LTCC component quasi-coaxial
On the structure → LTCC internal layer strip line → similar axle construction of the 2nd LTCC component → LTCC layer BGA pad → soldered ball → PCB
The surface layer BGA pad → similar axle construction of the first PCB component → PCB internal layer strip line → similar axle construction → PCB of the 2nd PCB component
Upper epidermis microstrip line.By transmission path, keep characteristic impedance constant, (each layer transmission structure is set for lamination and structure design such as table 1
Meter) shown in
3. impedance matching
To realize that signal stablizes transmission in wide area frequency range, the transmission path on three kinds of materials will meet impedance
Matching requires, especially intersection of the signal in horizontal transport line and vertical transmission lines.To alleviate impedance caused by structural mutation
Mismatch increases the matching section that the transmission line of one to two sections of different characteristics impedances is used as at interconnection.The length of Optimized Matching section and
Width reduces local impedance, reduces the resistance difference between horizontal transport line and vertical transmission lines, can reach the high-frequency signal of transmission
Requirement.
4. interconnection pad designs
LTCC and two component of PCB pass through between BGA soldered ball realize vertical interconnection, BGA soldered ball needs to protect in integral layout
The uniformity of structure stress is demonstrate,proved, multiple ground connection BGA soldered balls can be set in no signal hop and carry out structural support.Take into account signal
Transmission characteristic and component strength, pad size are designed according to 85% Diameter of Solder Ball.
Pad layer on LTCC selects the slurry of high temperature sintering, such as AuPtPd.The BGA pad that signal is transmitted on PCB, is adopted
With through-hole resin (or metal) consent and after flattening, copper electroplating layer method is made, and the BGA pad on large area ground plane uses resistance
Weldering mode carries out isolation restriction;The preferred ENIG of PCB pad coating (nickel gold) coating.
5. assembly method designs
Such interconnection architecture will guarantee assembly precision in assembly, and otherwise signal will increase loss at interconnection.When assembly
Plant ball bonding of the high lead welding ball on LTCC pad is first carried out, then using the LTCC component with soldered ball as a device, in PCB
It is upper to be assembled using standard SMT process.
Specific embodiment:
According to the signal transmission structure of Fig. 1, the detailed design of each parameter is carried out
LTCC upper epidermis microstrip line: conduction band width 0.42mm, conduction band thickness 0.01mm, dielectric thickness 0.336mm, medium phase
To dielectric constant 7.1.
The first similar axle construction of LTCC component;Inner conductor outer diameter 0.18mm, the equivalent internal diameter 1.66mm of outer conductor (outer conductor tool
Body be distributed as ground connection surface layer away from conductor center 0.83mm and using conductor center as axis, along the uniformly distributed ¢ of radius 0.92mm
The vertical solid ground metal aperture of 0.18mm is constituted), medium relative dielectric constant 7.1.
LTCC internal layer strip line: conduction band width 0.18mm, conduction band thickness 0.01mm, dielectric thickness 0.672mm, medium are opposite
Dielectric constant 7.1;
The 2nd LTCC component quasi-coaxial structure division not connected with soldered ball: inner conductor outer diameter 0.18mm, outer conductor are equivalent
Internal diameter 1.44mm (be specifically distributed as ground connection surface layer away from conductor center 0.72mm and using conductor center as axis, along radius
The vertical solid ground metal aperture of 1.01mm uniformly distributed ¢ 0.18mm is constituted), medium relative dielectric constant 7.1mm.
The 2nd LTCC component quasi-coaxial structure bottom (the LTCC layer BGA pad) inner conductor to connect with soldered ball
0.52mm, outer conductor internal diameter 1.64mm;
Soldered ball (BGA soldered ball connects): inner conductor outer diameter is Diameter of Solder Ball, the equivalent internal diameter 1.64mm of outer conductor;Soldered ball selects ¢
The tin-lead soldered ball of 0.6mm size;Corresponding pad design is having a size of 0.5mm
The first PCB component quasi-coaxial structure division (PCB upper epidermis BGA pad) to connect with soldered ball: inner conductor 0.52mm,
Outer conductor internal diameter 1.64mm;
The first PCB component quasi-coaxial structure division not connected with soldered ball: inner conductor outer diameter 0.2mm, outer conductor are equivalent interior
(outer conductor is specifically distributed as ground connection surface layer away from conductor center 0.46mm and using conductor center as axis, edge diameter 0.92mm
The grounding through hole of radius 0.84mm uniformly distributed ¢ 0.3mm is constituted), medium relative dielectric constant is 2.89.
PCB internal layer strip line: conduction band width 0.32mm, conduction band thickness 0.035mm, dielectric thickness 0.713mm, medium are opposite
Dielectric constant 2.89;
The 2nd similar axle construction of PCB component: inner conductor outer diameter 0.2mm, the equivalent internal diameter 0.92mm of outer conductor, medium is opposite to be situated between
Electric constant 2.89.
PCB upper epidermis microstrip line: conduction band width 0.64mm, conduction band thickness 0.035mm, dielectric thickness 0.254mm, medium phase
To dielectric constant 2.89.
Assembling process is: plant ball bonding of the soldered ball on LTCC pad is first carried out, then the LTCC component for having planted soldered ball
As a device, assembled on PCB using standard SMT process, paste application is on pcb board with a thickness of 0.13mm.Assembling
LTCC-PCB component afterwards using the signal high frequency characteristics between high-precision probe test suite input/output terminal, 10MHz~
Under 36GHz, signal echo loss S11 is smaller, meets the requirement of most occasions.
The invention is not limited to specific embodiments above-mentioned.The present invention, which expands to, any in the present specification to be disclosed
New feature or any new combination, and disclose any new method or process the step of or any new combination.