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`(19) United States
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`(12) Patent Application Publication (10) Pub. No.: US 2006/0086532 A1
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` Ho et al. (43) Pub. Date: Apr. 27, 2006
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`US 20060086532A1
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`(54) PCB CAPABLE OF RELEASING THERMAL
`STRESS
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`(52) US. Cl.
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`............................................ 174/250; 174/255
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`(75)
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`Inventors: Shu Lin Ho, Su-Ao Township (TW);
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`Shih Chieh Wang, Hsinchu City (TW)
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`Correspondence Address:
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`HOFFMANN & BARON, LLP
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`6900 JERICHO TURNPIKE
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`SYOSSET’ NY 11791 (US)
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`(73) Assignee: Hannstar Display Corporation
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`(21) Appl. No.:
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`10/973,601
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`(22)
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`Filed:
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`Oct. 26, 2004
`Publication Classification
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`(51)
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`Int. Cl.
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`H05K 1/00
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`(2006.01)
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`(57)
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`ABSTRACT
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`A PCB comprises a slender substrate, a thermal compression
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`area and at least a slit. The thermal compression area, placed
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`on the slender substrate, has a plurality of bonding pads for
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`a plurality of TCPs to be mounted thereon and a plurality of
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`dummy pads placed between the TCPs. The slit transversely
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`crosses the thermal compression area and slices some of the
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`dummy pads. When the TCPs are connected to the bonding
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`pads of the PCB, the thermal compression area is heated to
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`around 150° C. to 2000 C. Therefore, the slit can block the
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`thermal expansion to be accumulated along the longitudinal
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`direction of the thermal compression area.
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`Page 1 of 7
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`Tianma Exhibit 1011
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`Tianma Exhibit 1011
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`Patent Application Publication Apr. 27, 2006 Sheet 1 of 4
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`US 2006/0086532 A1
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`FIG.1 (Background Art)
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`Page 2 of 7
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`Patent Application Publication Apr. 27, 2006 Sheet 2 of 4
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`US 2006/0086532 A1
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`FIG. 2(a) (Background Art)
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`15
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`14 13
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`FIG. 203) (Background Art)
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`Patent Application Publication Apr. 27, 2006 Sheet 3 of 4
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`US 2006/0086532 A1
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`Patent Application Publication Apr. 27, 2006 Sheet 4 0f 4
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`US 2006/0086532 A1
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`AV.on
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`ow
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`/; 1-39am;a"mag?"sasagas—"Ew3
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`Page 5 of 7
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`Page 5 of 7
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`

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`US 2006/0086532 A1
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`Apr. 27, 2006
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`PCB CAPABLE OF RELEASING THERMAL
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`STRESS
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`BACKGROUND OF THE INVENTION
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`1. Field of the Invention
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`[0001]
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`[0002] The present invention relates to a PCB (printed
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`circuit board) capable of releasing thermal stress, and more
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`particularly, to a PCB or a PWB (printed wiring board) with
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`slits for reducing thermal expansion.
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`[0003]
`2. Description of the Related Art
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`[0004] Recently, a liquid crystal display panel, a type of
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`flat display, has been widely used as a display for PDAs,
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`laptop computers, TVs, and so on.
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`[0005] As shown in FIG. 1, in a liquid crystal display
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`module adopting the aforesaid liquid crystal display panel,
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`tapes 13 with drive IC chips 14 thereon are used in con-
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`necting a liquid crystal display panel 11 and the IC chips 14.
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`Each of TCPs 15 (tape chip carriers), including an IC chip
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`14 and a tape 13, is connected to either a PWB (printed
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`wiring board) 121 or a PWB 122.
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`[0006] The structure of the PWB 121 gradually changed
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`into a 4-layer board from an early 6-layer board due to
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`reduction in cost. Similarly, the PWB 122 gradually changed
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`from a 4-layer board into a 2-layer board. Unfortunately, the
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`problem of thermal expansion for the PWB 121 or the PWB
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`122 in dimensions becomes worse than an early one, even
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`though the cost and weight are reduced. The thermal expan-
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`sion of the PWB 121 or the PWB 122 varies from supplier
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`to supplier no matter whether the circuit layouts are the
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`same, because the materials from various suppliers are
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`[0007] Referring to FIG. 2(a), in a thermal compression
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`process, the elongation AL of the PWB 121 is in direct
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`proportion to the length L of it, the coefficient of thermal
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`expansion or the temperature increment. The elongation AL
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`can be obtained by the following formula:
`AL=L0t(Tl—T2)
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`where (X is the coefficient of thermal expansion for the PWB
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`121, T1 is the temperature of thermal compression and T2 is
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`room temperature.
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`[0008] As shown in FIG. 2(b), when ACFs (anisotropic
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`conductive film) are used to connect the input terminals of
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`TCPs 15 and the output terminals of the PWB 121 in a
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`thermal compression process, the connection areas of them
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`are heated to around 150° C. to 200° C. Moreover, the PWB
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`121, being still hot and expended, is attached to the TCPs 15
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`which have been already connected and fixed to the liquid
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`crystal display panel 11. Therefore, when the thermal com-
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`pression process is over and the PWB 121 is cooled down to
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`room temperature, the PWB 121 is bent in accordance with
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`contraction of itself. Consequently, the circuits on the tapes
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`13 are distorted by the bent PWB 121, and the tapes 13 on
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`the both sides of the PWB 121 are usually damaged due to
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`[0009] Now, a PCB or a PWB capable of releasing thermal
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`stress is in high demand because the length of it becomes
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`longer in response to the increment in the size of a liquid
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`crystal display.
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`Page 6 of 7
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`SUMMARY OF THE INVENTION
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`[0010] An objective of the present invention is to provide
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`a PCB capable of releasing thermal stress. During a thermal
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`compression process, the thermal expansion of a thermal
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`compression area on the PCB is isolated by a slit. That is, the
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`total elongation of the PCB does not completely relate to the
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`accumulation of thermal expansion along one of its dimen-
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`sion, and the thermal expansion is blocked by the slit.
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`[0011]
`To achieve the objective,
`the present
`invention
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`discloses a PCB capable of releasing thermal stress. The
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`PCB comprises a slender substrate, a thermal compression
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`area and at least a slit. The thermal compression area, placed
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`on the slender substrate, has a plurality of bonding pads for
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`a plurality of TCPs to be mounted thereon and a plurality of
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`dummy pads placed between the TCPs. The slit transversely
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`crosses the thermal compression area and slices some of the
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`dummy pads. When the TCPs are connected to the bonding
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`pads of the PCB, the thermal compression area is heated up
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`around from 1500 C. to 2000 C. Therefore, the slit can block
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`the thermal expansion to be accumulated along the longi-
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`tudinal direction of the thermal compression area.
`BRIEF DESCRIPTION OF THE DRAWINGS
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`[0012] The invention will be described according to the
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`appended drawings in which:
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`[0013] FIG. 1 is a pan view showing a liquid crystal
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`display module including a liquid crystal display panel
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`electrically connected to a conventional PWB through
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`TCPs;
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`[0014] FIG. 2(a) is an explanatory drawings showing the
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`elongation of a PWB during a thermal compression process;
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`[0015] FIG. 2(b) is a side view showing a bent PWB due
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`to the thermal contraction during a thermal compression
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`[0016] FIG. 3 (a) is a schematic diagram of a PWB with
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`a slit in accordance with the present invention;
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`[0017] FIG. 3 (b) is a partial enlarged view of FIG. 3 (a);
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`[0018] FIG. 4 is a schematic diagram of a PWB with a
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`plurality of slits in accordance with the present invention.
`PREFERRED EMBODIMENT OF THE PRESENT
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`INVENTION
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`[0019] FIG. 3 (a) is a schematic diagram of a PCB with
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`a slit in accordance with the present invention. A PCB 30
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`comprises a slender substrate 31, a thermal compression area
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`34 and a slit 35. The thermal compression area 34, placed on
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`the slender substrate 31, has a plurality of bonding pads 32
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`for the plurality of TCPs 13 to be mounted thereon and a
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`plurality of dummy pads 33 placed between the TCPs 13.
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`The slit 35 transversely crosses the thermal compression
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`area 35 and slices some of the dummy pads 32. When the
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`TCPs 13 are connected to the bonding pads 32 of the PCB
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`30, the thermal compression area 34 is heated to around 1500
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`C. to 2000 C. Therefore, the slit 35 can block the thermal
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`expansion to be accumulated along the longitudinal direc-
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`tion of the thermal compression area 34. In comparison with
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`the prior art in FIG. 1, the total elongation of the PCB 30 is
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`half the total elongation of the PWB 121.
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`Page 6 of 7
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`What is claimed is:
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`1. A PCB capable of releasing thermal stress, comprising:
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`a slender substrate;
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`a thermal compression area placed on the slender sub-
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`strate and including a plurality of groups of bonding
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`pads; and
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`at least one slit transversely crossing the thermal com-
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`pression area between two of the groups of the bonding
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`pads.
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`2. The PCB capable of releasing thermal stress of claim 1,
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`wherein the slit is at the middle of the thermal compression
`area.
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`3. The PCB capable of releasing thermal stress of claim 1,
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`wherein the thermal compression area includes a plurality of
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`groups of dummy pads between the groups of the bonding
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`pads.
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`4. The PCB capable of releasing thermal stress of claim 3,
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`wherein the slit slices at least one of the dummy pads.
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`5. The PCB capable of releasing thermal stress of claim 1,
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`wherein the slender substrate is a multilayer board.
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`6. The PCB capable of releasing thermal stress of claim 1,
`wherein the number of slits is less than the number of the
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`groups of the bonding pads by one.
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`7. The PCB capable of releasing thermal stress of claim 1,
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`wherein the slit can block the thermal expansion to be
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`accumulated along a longitudinal direction of the thermal
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`compression area.
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`8. The PCB capable of releasing thermal stress of claim 1,
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`wherein the slit has a slit length, the thermal compression
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`area has a width, and the slit length is larger than the width.
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`US 2006/0086532 A1
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`Apr. 27, 2006
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`alternative embodiments may be devised by persons skilled
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`in the art without departing from the scope of the following
`claims.
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`[0020] As shown in FIG. 3 (b), the slit 35 is from the edge
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`adjacent to the bonding pads across to the thermal compres-
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`sion area 35. It is preferred that the length H of the slit 35
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`is larger than the width h of the thermal compression area 35
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`so that the thermal contraction is independent between the
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`left and right portions of the thermal compression area 35.
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`Therefore, we can obtain the following:
`H>h+d
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`where d is the distance between the edge and the thermal
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`compression area 35. In some applications, d is zero, that is,
`H>h.
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`[0021] FIG. 4 is a schematic diagram of a PCB with a
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`plurality of the slits in accordance with the present inven-
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`tion. Similarly, a PCB 40 comprises a slender substrate 41
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`such as a multilayer board including a 4-layers board and
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`2-layers board, a thermal compression area 44 and a plural-
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`ity of slits 45. If the PCB 41 is for six TCPs 13 to mounted
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`thereon, it is preferred that the number of the slits is five.
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`That is, at least a slit is on a side of each group of the
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`bonding pads 42. The thermal compression area 44, placed
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`on the slender substrate 41, has the plurality of bonding pads
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`42 for the plurality of TCPs 13 to be mounted thereon and
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`a plurality of dummy pads 43 placed between the TCPs 13.
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`The slit 45 transversely crosses the thermal compression
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`area 45 and slices some of the dummy pads 42. When the
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`TCPs 13 are connected to the bonding pads 42 of the PCB
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`30, the thermal compression area 44 is heated to around 150°
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`C. to 200° C. Therefore, the slits 45 can block the thermal
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`expansion to be accumulated along the longitudinal direc-
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`tion of the thermal compression area 44. In comparison with
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`the prior art in FIG. 1, the total elongation of the PCB 40 is
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`one fifth of the total elongation of the PWB 121. Apparently,
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`if a PCB has N slits, the elongation of the PCB is one Nth
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`of the total elongation of the PWB 121 under the same
`environment condition.
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`[0022] The above-described embodiments of the present
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`invention are intended to be illustrative only. Numerous
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`Page 7 of 7
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`Page 7 of 7
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