An electrical component with a chip that is mounted on a carrier substrate in a flip chip arrangement is disclosed.
The chip plane equipped with component structures can have coefficients of thermal expansion α1, α2 differing from one another in different directions, depending on the crystal axes. This is particularly the case for surface acoustic wave chips with a piezoelectric substrate whose physical properties exhibit anisotropy. The coefficients of thermal expansion α1, α2, are generally larger than the coefficient of thermal expansion αp of the underlying carrier substrate. In case of a change in temperature, the change in length of the chip is greater than that of the carrier substrate.
The chip is mechanically fixed to the carrier substrate by means of solder joints (bumps). These solder joints are therefore subject to mechanical stresses that arise due to the difference Δα1=|αp−α1| and Δα2=|αp−α2| in the coefficients of thermal expansion of the chip and the carrier substrate. In case of differing coefficients of thermal expansion of the chip and the carrier substrate, the outermost bumps and the carrier substrate, in particular, are subject to the strongest stresses form the shearing force F(F1, F2) acting on them. F1 is the force component in the first preferred direction x1. F2 is the force component in the second preferred direction x2.
In some embodiments, an electrical component is formed with a flip chip arrangement in which the smallest shearing forces possible act on the outermost bumps.
The distance between the centers of the terminal bumps in the, direction x1 is L1 at a first temperature T1 and L2 at a second temperature T2. The linear thermal expansion ΔL=|L1−L2| of the chip area in direction x1 defined by the terminal bumps is ΔL=α1L1ΔT, where ΔT=|T1−T2|. A shearing force component F1 that is proportional to ΔL arises in this direction. In some embodiments, it is sought to keep the shearing force component F1 as low as possible. Taking into account the given coefficients of thermal expansion, a bump arrangement is sought in which the distance between the terminal bumps in the direction of the maximum expansion difference is smaller than the distance between the terminal bumps in the direction of minimum expansion difference.
An electrical component with a carrier substrate and a chip that is mounted on the carrier substrate with a flip-chip arrangement is disclosed. The carrier substrate has a coefficient of thermal expansion αp. The chip has a coefficient of thermal expansion α1 in a first preferred direction x1, where Δα1=|αp−α1| is the first expansion difference. In a second preferred direction x2, the chip has a second coefficient of thermal expansion α2, where α2=|αp−α2| is the second expansion difference.
The distance between the orthogonal projections of the bump centers of the terminal bumps in direction x1 onto the x1 axis is Δx1. The distance between the orthogonal projections of the bump centers of the terminal bumps in direction x2 onto the x2 axis is Δx2. Here we have Δx1<Δx2 for Δα1>Δα2 and Δx1>Δx2 for Δα1<Δα2. With such a bump arrangement, the shearing force arising from temperature changes and acting on the terminal bumps can be successfully minimized.
First preferred direction x1 is preferably defined to be the direction in which the component has the largest expansion difference, Δα1. Second preferred direction x2 is preferably defined to be the direction in which the component has the lowest expansion difference, Δα2.
Distances Δx1, Δx2 are preferably selected relative to one another such that the components F1, F2 of shearing force F are substantially equal to one another.
Axes x1, x2 define a coordinate system {x1,x2}, which corresponds to a two-dimensional space, on the surface of which the chips are arranged.
Axes x and y are oriented along the along the intersecting chip edges. The chip edges are preferably rectangular in form, i.e., the first and second chip edges are perpendicular to one another. In case of chip edges running parallel to one another, axes x, y define a rectangular coordinate system {x, y}. The first chip edge is oriented, for instance, along the x axis and the second chip edge along the y axis.
In general, axes x, y, x1 and x2 can be oriented at an arbitrary angle relative to one another. In one variant, at least one of axes x1, x2 can run parallel to axis x or y, but that is not a necessary condition. The coordinate system {x1, x2} can coincide with coordinate system {x, y}. The (possibly rectangular) coordinate system. {x1, x2} can be rotated by an angle β2>0 relative to coordinate system {x, y}; see
It is advantageous to arrange bump rows on the bottom side of the chip parallel to the respective chip edge. In one variant, several bumps can be arranged on a line parallel to a first chip edge (in direction x) and/or parallel to the second chip edge (in direction y). The bumps can also be arranged in a row that is preferably situated centrally on the lower surface of the chip. The bumps can also be arranged along the four chip edges in a peripheral area of the chip around the chip edges.
The bump rows are preferably arranged along direction x1 of the maximal expansion difference. The distance between the bumps situated terminally in direction x1 or optionally in the same row, is preferably smaller than the distance between the bump rows in which the terminally situated bumps in direction x2 are situated.
In one variant, several bumps can be arranged on a line along first preferred direction x1 and/or along second preferred direction x2.
In one variant, all bumps are arranged in two rows parallel to direction x2 of minimal expansion difference. The distance between these rows is Δx1. Distance Δx1 is smaller in this case than the length of the row (measured between the centers of the terminal bumps of the row). The length of the chip edges can be adapted to the bump arrangement in such a manner that the mutually parallel-oriented rows are arranged in the edge areas of the chip. The terminal bumps of the chip are preferably turned toward the corners of the chip surface here. In this case, the first chip edge (in direction x1) is shorter than the second chip edge (in direction x2).
The lower surface of the chip can be subdivided in at least one direction x, y (or x1, x2) into wide peripheral areas and a central area, with the width of the respective peripheral area preferably exceeding or twice the cross-sectional size of bump. The bumps in this variant are arranged only in the central area. The wide peripheral areas have no bumps.
As a rule, the coefficient of thermal expansion αp of the carrier substrate is less than α1 and/or α2. The coefficient of thermal expansion of the basic material of the carrier substrate can also be modified, more particularly, raised, within certain limits by, for instance, the addition of an additive or filler, and thereby be adapted to the coefficient of thermal expansion α1 and/or α2. Thus one obtains expansion differences Δα1 and/or Δα2 that are as small as possible. It is possible, for instance, to select the material of the carrier substrate such that αp=α1 or αp=α2, i.e., Δα1=0 or Δα2=0.
In some embodiments, for example, it can be the case that Δα2=0, Δα1>0. In this case it is advantageous to arrange the bumps in a row along the second preferred direction x2, so that Δx1=0.
A bump row is understood to be an arrangement of the bumps along one direction in which the bump centers of the bumps arranged in a row lie on a line in this direction.
In relation to direction x1, the bump row is preferably arranged centrally on the lower surface of the chip. In case the bumps are arranged in only one row, the chip can then be stabilized relative to the carrier substrate in the x1 direction such that the lower surface of the chip runs substantially parallel to the surface of the carrier substrate. Spacers that are preferably arranged between the chip and the carrier substrate along first preferred direction x1 in the peripheral areas of the chip can be provided.
In another variant, the material of the carrier substrate can be selected such that coefficient αp lies between α1 and α2. Here it can be the case that α1>α2 or that α1<α2. Coefficient αp is preferably matched to a lower coefficient of thermal expansion, where αp=min{α1, α2}. Coefficient αp can also be matched to the larger coefficient of thermal expansion, where αp=max{α1, α2}.
The bumps (not necessarily the terminal bumps) are preferably arranged on the bottom side of the chip such that the larger bump spacings lie in the direction of the lowest expansion difference, αmin=min{α1, α2}. The bump height and diameter is preferably small, for instance, <100 μm or <50 μm.
On the lower chip surface and the upper side of the carrier substrate, contact surfaces firmly joined to the bumps (UBM=under bump metallization) are provided. In some embodiments, larger contact surfaces are provided for terminal bumps that are more severely stressed during temperature changes than for the remaining bumps, which are less stressed. This variant has the advantage that the surface area of the chip's bottom side that is covered by the centrally arranged bumps can be kept small.
The component structures are preferably arranged on the chip's bottom side. It is also possible, however, to arrange the component structures at least in part in the interior of the chip.
The invention will be explained in detail below on the basis of embodiments and the associated figures. The figures show various embodiments of the invention on the basis of schematic representations not drawn to scale. Identical or identically functioning parts are labeled with the same reference numbers. Shown schematically are:
Input transducer 711 is connected to an input port, and output transducer 721 is connected to an output port. The electrical terminals of the input transducer (or the output transducer) are arranged in
The coupling transducers 712 and 722, 713 and 723 of different tracks are electrically connected to one another and to a ground bump (to a terminally-arranged bump 33 or 34 in
In
The ground bumps connected to the coupling transducers are arranged in the outer bump rows in
In the variant presented in
The bump rows are thus oriented along the direction of maximum expansion difference. The distance x1 between the terminally situated bumps in the same row (31 and 32, 33 and 34) is smaller than the distance between the bump rows which contain the bumps situated terminally in the x2 direction.
In the variant presented in
Carrier substrate 1 shown in
The chip preferably has component structures operating with surface acoustic waves that are arranged on the lower surface of the chip, but are not shown in the figure. Chip 2 has contact surfaces 29 that are electrically connected to contact surfaces 19 of the carrier substrate by means of bumps 31, 32. The lower chip surface is subdivided in first preferred direction x1 into a central area 20, in which bumps 31, 32 are arranged, and peripheral areas 21, 22 (without bumps).
Axis x is oriented along a first chip edge. Axis y is oriented along a second chip edge. First preferred direction x1 is oriented parallel to axis x in the variants according to
The terminally situated bumps 31, 32 in first preferred direction x1 are spaced apart from one another by the amount Δx1. The terminally situated bumps in the second direction x2 (31 and 33 in
First connecting line 41, connecting the centers of the terminally situated bumps 31, 32 (or 33, 34) in direction x1, is directed parallel to direction x1 in
In the general case, e.g., in the variant according to
In
The projections of points 31 and 33 (or 32 and 34) onto axis x1 agree with one another in
In the variant shown in
In the variants according to
In
The cross-sectional size of the chip is a in direction x1 and b in direction x2. In
The formation of the chip with a larger cross-sectional size b in direction x2 of the smaller expansion difference has the advantage that the chip surface can be utilized especially space-economically.
In
The lower surface of chip 2 in
In
The position of the bump row relative to direction x1 can also be shifted away from the center toward the second chip edge.
It is shown in
Corresponding, different-sized contact surfaces opposing the contact surfaces of the chip are provided for the different types of bumps on the carrier substrate (not shown here). The bumps are permanently joined to the contact surfaces of the chip and the carrier substrate.
The invention is not limited to the above-presented embodiments, specific materials or the number of illustrated elements.
Number | Date | Country | Kind |
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10 2004 037 817 | Aug 2004 | DE | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/EP2005/006165 | 6/8/2005 | WO | 00 | 6/12/2007 |
Publishing Document | Publishing Date | Country | Kind |
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WO2006/015642 | 2/16/2006 | WO | A |
Number | Name | Date | Kind |
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20020180307 | Taga | Dec 2002 | A1 |
20040094842 | Jimarez et al. | May 2004 | A1 |
Number | Date | Country |
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1 333 494 | Aug 2003 | EP |
WO0070671 | Nov 2000 | WO |
Number | Date | Country | |
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20080048317 A1 | Feb 2008 | US |