U.S. patent application number 09/821799 was filed with the patent office on 2001-10-11 for structure for connecting terminals on wiring board.
Invention is credited to Ota, Tsutomu.
Application Number | 20010029118 09/821799 |
Document ID | / |
Family ID | 18610564 |
Filed Date | 2001-10-11 |
United States Patent
Application |
20010029118 |
Kind Code |
A1 |
Ota, Tsutomu |
October 11, 2001 |
Structure for connecting terminals on wiring board
Abstract
In a structure for connecting terminals on wiring boards, lands
on a wiring board are respectively connected with lead terminals on
another wiring board through solder. Outline of each land has a
bump and a recess respectively on edges facing to terminal
arranging direction. Meanwhile the lead terminals are rectangular.
In plan view, the recess protrudes from an edge of respective lead
terminal while protrusions on ends of the recess protrude from
another edge of the respective lead terminal. Even when position of
the each land to the respective lead terminal deviates not so
excessively, the bump and the protrusion protrude from outline of
the lead terminal. Thus, on each of such protruding portions,
visible fillets of the solder are formed.
Inventors: |
Ota, Tsutomu; (Tokyo,
JP) |
Correspondence
Address: |
PILLSBURY WINTHROP LLP
1600 TYSONS BOULEVARD
MCLEAN
VA
22102
US
|
Family ID: |
18610564 |
Appl. No.: |
09/821799 |
Filed: |
March 30, 2001 |
Current U.S.
Class: |
439/65 |
Current CPC
Class: |
H05K 2201/09381
20130101; H05K 1/117 20130101; H05K 2201/09427 20130101; H05K 3/363
20130101 |
Class at
Publication: |
439/65 |
International
Class: |
H05K 001/00; H01R
012/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 30, 2000 |
JP |
2000-95696 |
Claims
What is claimed is:
1. A structure for connecting terminals on a wiring board
comprising: first terminals arranged on a first substrate;
rectangular second terminals arranged on a second substrate and
respectively superimposed on first terminals; conductive bonding
means electrically and mechanically connecting each of the first
terminals to respective one of the second terminals; fillets of the
conductive bonding means formed along fringe portions of the each
first terminal outwardly protruding from outline of the respective
second terminal; a recess being formed on outline of the each first
terminal and intersecting with first edge of the respective second
terminal; a bump formed on the outline of the each first terminal
and intersecting with second edge, opposed to said first edge, of
the respective second terminal.
2. A structure for connecting terminals on a wiring board according
to claim 1, wherein said conductive bonding means is a solder.
3. A structure for connecting terminals on a wiring board according
to claim 1, wherein, on each first terminal, shape and size of an
outline portion forming the recess are substantially identical with
those of another outline portion forming the bump.
4. A structure for connecting terminals on a wiring board according
to claim 1, wherein, with respect to one of the first terminals and
another one of the first terminals next to said one of first
terminals, first outline portion of said one of first terminal
faces second outline portion of said another one of first terminals
in such a manner that the first outline portion is substantially
congruent with the second outline portion if shifted in
parallel.
5. A structure for connecting terminals on a wiring board according
to claim 1, wherein the recess and the bump are substantially
trapezoid.
6. A structure for connecting terminals on a wiring board according
to claim 5, wherein base lines of trapezoid shape forming the
recess and the bump are arranged to be substantially parallel with
long edges of said second terminal.
7. A structure for connecting terminals on a wiring board according
to claim 5, wherein the recess and the bump are substantially
isosceles trapezoid.
8. A structure for connecting terminals on a wiring board according
to claim 5, wherein ends of the recess and ends of the bump are
connected with ends of linear outline portions that are
substantially parallel with long edges of said second terminal.
9. A structure for connecting terminals on a wiring board according
to claim 1, wherein said second terminals are lead terminals
arranged on a flexible wiring board.
10. A structure for connecting terminals on a wiring board
according to claim 1, wherein said first terminals are lead
terminals arranged on a flexible wiring board.
11. A structure for connecting terminals on a wiring board
according to claim 1, wherein said first terminals are lands
arranged on a print circuit board for driving a flat-panel display
device while said second terminals are input-side terminals
arranged on a tape carrier package for inputting drive signals to a
display panel.
12. A structure for connecting terminals on a wiring board
according to claim 1, wherein said second terminals are lands
arranged on a print circuit board for driving a flat-panel display
device while said first terminals are input-side terminals arranged
on a tape carrier package for inputting drive signals to a display
panel.
Description
BACKGROUND OF THE INVENTION
[0001] This invention relates to a structure for connecting
terminals, in which lands on a wiring board are connected with lead
terminals on other substrate through solder or the like.
[0002] Conventionally, as such structure for connecting terminals,
a structure of Prior Art 1 shown in FIG. 4 is known, for
example.
[0003] In the structure of Prior Art 1, near-square-form
rectangular lands 11 are arranged in a side-by-side manner on a
wiring board by pitch of 0.5 mm. Rectangular lead terminals 21 on
other substrate are superimposed on the lands 11. Long edges (long
sides) 23,24 of the lead terminals 21 are longer than respective
long edge 13,14 of the lands 11 by 0.1 mm, while short edges (short
sides) 22 of the lead terminals 21 are shorter than respective
short edges 12 of the lands by 0.1 mm.
[0004] As shown in the FIG. 4, the long edges 23,24 of the lead
terminals 21 outwardly distanced from the respective long edges
13,14 of the lands 11 by 0.05 mm when the lands 11 and the lead
terminals 21 are exactly in a designed position with each other. If
the lands 11 and the lead terminals 21 are bonded through solder or
similar conductive adhesives by automatic thermo-compression
bonding in use of heat tool, fillets 5 of the solder or the like
are formed on fringe portions on the lands 11 that outwardly
protrude from the long edges 23,24 of the lead terminals 21.
[0005] The structure shown in the FIG. 4 is disadvantageous because
even a 0.05 mm rightward or leftward deviation of the position of
the lands 11 with respect to the lead terminals 21 makes the fillet
5 on right-hand side or left-hand side invisible from upper side
through the other substrate, which has the lead terminals 21.
[0006] On the other hand, FIG. 5 shows another example of the
conventional structure for connecting terminals, as designated as
Prior Art 2.
[0007] In the structure of Prior Art 2, lands 11 as well as lead
terminals 21, each of which is superimposed to respective one of
the lands 11, are in a form of isosceles trapezoid, with longer
base edges 18 of the lands 11 being opposed to longer base edges 19
of the lead terminals 21. As shown in the FIG. 4, legs or oblique
edges of the each land 11 and respective lead terminal 21 are
intersected with each other, while shorter base edge 28 of the each
lead terminals 21 is placed within the respective land 11 when
exactly placed as designed. The fillets 5 are formed along
imposed-on-the-land portion of outline of the lead terminal 21. In
a designed position, the longer base edge 18 of the land 11 is
outwardly distanced from the shorter base edge 28 of the lead
terminal 21 by 0.05 mm, while the shorter base edge 19 of the land
11 is inwardly distanced by 0.05 mm from the shorter base edge 29
of the lead terminal 21.
[0008] The structure shown in the FIG. 5 is disadvantageous because
the fillet 5 becomes difficult to be recognized when position of
the lead terminal 21, which is superimposed on respective land 11,
is deviated in a length-wise or height-wise direction (Y direction)
of the land 11 and lead terminal 21. The Y direction is
perpendicular to a direction along which terminals are arranged.
When the shorter base edge 28 of the land 11 is placed outward from
the longer base edge 18 of the lead terminal 21, the
imposed-on-the-land portion of outline of the lead terminal 21
becomes short-sized. Thus, the fringe portion for the fillet 5
becomes short-sized, to make the fillet 5 be difficult to be
recognized.
[0009] When size of the lead terminal 21 is larger than that of the
lands 11, in particular, the lead terminal 21 would cover the land
11 almost entirely. In this way, the imposed-on-the-land portion of
outline of the lead terminal 21 would become only tiny bits along
legs or oblique edges of the lead terminal 21. Thus, the fillet 5
becomes difficult to be recognized. Moreover, no visible fillet is
found on shorter-base-edge-side of the land 11, on which outline of
the land 11 is totally covered by the lead terminal 21. Thus, it is
impossible to evaluate whether the bonding between the land 11 and
the lead terminal 21 on the shorter-base-edge-side of the land 11
is good or not.
[0010] FIG. 6 shows further example of the conventional structure
for connecting terminals, as designated as Prior Art 3.
[0011] In the construction shown in the FIG. 6, near-square-form
rectangular lands 11 are arranged on a wiring board while
planar-dumbbell-shaped lead terminals 21 are respectively
superimposed on the lands 11. Each lead terminal 21 has larger
length-wise dimension and smaller width-wise dimension than those
of respective land 11, which are dimensions of long edges 13,14 and
short edges 12 of the rectangular land 11. Along
long-edge-corresponding portions 23,24 of the each lead terminal 21
both on right-hand side and on left-hand side, arc-shaped recesses
25 are formed. Thus, two short-edge-corresponding portions 22 of
the each lead terminal 21 are placed outward from short edges 12 of
the respective land 11. Meanwhile, the long-edge-corresponding
portions 23,24 of the each lead terminal 21 are inwardly placed
than the long edges 13,14 of the respective land 11. Therefore,
recesses 25 both on right-hand side and on left-hand side are
placed on the land 11.
[0012] Fillets 5, which are recognizable from upper side through a
wiring board arranged with the lead terminals 21, are formed on
long-edge-corresponding portions 23,24 including recesses 25.
[0013] The structure shown in the FIG. 6 is disadvantageous because
recognition of the fillets 5 would become difficult when position
of the lead terminals 21 is deviated in width-wise direction (X
direction) of the lands 11 and lead terminals 21. By such
deviation, on either of right-hand side or left-hand side of the
lead terminal 21, the fillet 5 is formed only along a recess 25.
The distance between a recess 25 and a long edge 13 becomes so
small by such deviation, that recognition of the fillets 5 becomes
difficult on either of right-hand side or left-hand side.
[0014] The long edges 13,14 of the each land 11 may be designed to
be sufficiently distanced outward from the long-edge-corresponding
portions 23,24. However, such design reduces the ratio of
superimposed area for the bonding between the land 11 and the lead
terminal 21 in terminals-arranging areas on wiring boards.
BRIEF SUMMARY OF THE INVENTION
[0015] In view of the above drawbacks, the present invention is
aimed to provide a structure for connecting terminals on a wiring
board, which structure enables easy evaluation by recognition of
the fillets whether bonding of terminals by solder or the like is
good or not, while keeping ratio of superimposed area between
terminals as sufficiently high among terminal arranging area on a
wiring board or other substrate.
[0016] According to present invention, a structure for connecting
terminals on a wiring board comprising: first terminals arranged on
a first substrate; rectangular second terminals arranged on a
second substrate and respectively superimposed on first terminals;
conductive bonding means electrically and mechanically connecting
each of the first terminals to respective one of the second
terminals; fillets of the conductive bonding means formed along
fringe portions of the each first terminal outwardly protruding
from outline of the respective second terminal; a recess being
formed on outline of the each first terminal and intersecting with
first edge of the respective second terminal; a bump formed on the
outline of the each first terminal and intersecting with second
edge, opposed to said first edge, of the respective second
terminal.
[0017] This feature assures a reliable recognition of fillets of
the conductive bonding means that connects the first and second
terminals.
[0018] The conductive bonding means is typically a solder formed of
metal alloy. Nevertheless, the conductive bonding means encompasses
electro conductive resin pastes, particularly electro conductive
adhesives formed of highly viscous resin. The solder encompasses
not only lead based ones but also silver based ones or the like and
ones having relatively high melting point.
[0019] In a preferred aspect, the recess and the bump are shaped
substantially as trapezoid.
[0020] In another aspect, on each first terminal, shape and size of
an outline portion forming the recess are substantially identical
with those of another outline portion forming the bump.
[0021] In a further aspect, with respect to one of the first
terminals and another one of the first terminals next to said one
of first terminals, first outline portion of said one of first
terminal faces second outline portion of said another one of first
terminals in such a manner that the first outline portion is
substantially congruent with the second outline portion if shifted
in parallel.
BRIEF DESCRIPTION OF THE DRAWING
[0022] FIG. 1 is a plan view showing outline shape of lands on a
wiring board of the Embodiment;
[0023] FIG. 2 is a plan view showing essence of a structure for
connecting terminals of wiring boards in the Embodiment;
[0024] FIG. 3 is a fragmentary perspective view showing an
essential part of a flat-panel display device of the
Embodiment;
[0025] FIG. 4 is a plan view showing essence of a structure for
connecting terminals of wiring boards in Prior art 1;
[0026] FIG. 5 is a plan view showing essence of a structure for
connecting terminals of wiring boards in Prior art 2;
[0027] FIG. 6 is a plan view showing essence of a structure for
connecting terminals of wiring boards in Prior art 3.
DETAILED DESCRIPTION OF THE INVENTION
[0028] An embodiment of the present invention is explained in
conjunction with the drawings.
[0029] FIG. 1 is a plan view showing outline shape of lands on a
first wiring board of the Embodiment; and FIG. 2 is a plan view
showing a state in which lead terminals on second wiring board are
superimposed on the lands.
[0030] FIG. 3 is a fragmentary perspective view showing an
essential part of a flat-panel display device of the Embodiment. In
the Embodiment, the first wiring board arranged with the lands 11
is a printed circuit board (PCB) 1 for driving a flat-panel display
device. Meanwhile, the second wiring board arranged with the lead
terminals is a flexible wiring board 2 which is a tape carrier
package (TCP) equipped to the flat-panel display device by outer
lead bonding.
[0031] As shown in FIG. 3, several flexible wiring boards 2 are
bonded onto peripheral connecting portions 31 of display panel
proper 3 through anisotropic conductive film (ACF) or the like. A
driver IC chip 4 is mounted on around center of the each flexible
wiring board 2.
[0032] A linear strap-shaped driver printed circuit board (PCB) 1
is arranged along the peripheral connecting portions 31 of display
panel proper 3. On the upper face of the PCB 1, several connecting
pads group 10 are arranged along a PCB(1)'s edge 1a facing the
peripheral connecting portions 31, each connecting pads group 10
being connected with respective input-side terminal group 20 on
lower face of the each flexible wiring board 2.
[0033] As shown in FIG. 1, the each connecting pads group 10 on the
PCB 1 is formed by arranging lands 11 in a side-by-side manner, in
a pitch of 0.5 mm, on a flexible insulator substrate 1b. Each land
11 is approximately rectangular with its width-wise direction being
a direction (X-direction) of arrangement of the lands 11. An
outline of the each land 11 is consisting of a pair of short edge
12 and a pair of long-edge-corresponding portions 13,14. One
long-edge-corresponding portion 13 among the pair is consisting of
linear portions 13a on both ends and bump 15 therebetween, which
bump 15 is shaped substantially as isosceles trapezoid. The bump 15
is consisting of a base line 13c in parallel with the linear
portions 13a as well as converging oblique lines 13b that extend in
a converging manner with each other from inner ends of the linear
portions 13a to ends of the base line 13c.
[0034] Meanwhile, another long-edge-corresponding portion 14 among
the pair is consisting of linear portions 14a on both ends and
recess 16 therebetween, which recess 16 is shaped substantially as
isosceles trapezoid. The recess 16 is consisting of a base line 14c
in parallel with the linear portions 14a as well as diverging
oblique lines 14b that extend in a diverging manner with each other
from ends of the base line 14c to inner ends of the linear portions
14a. The two long-edge-corresponding portion 13,14 are congruent
with each other when shifted in parallel.
[0035] As shown in FIG. 3, the input-side terminals group 20 is
consisting of lead terminals 21 arranged along an edge 2a of the
flexible wiring board 2. Each lead terminal 21 is rectangular with
its long edge being arranged perpendicular to the edge 2a.
[0036] As shown in FIG. 2, each rectangular lead terminal 21 on the
flexible wiring board 2 is superimposed and bonded electrically and
mechanically onto a respective land 11 on the PCB 1 through solder.
Long edges 23,24 of the lead terminal 21 are longer than
longitudinal length D of the land 11. In the illustrated
embodiment, short edges 22 of the lead terminal 21 are shorter than
short-edge-corresponding portion 12 of the land 11 by 0.05 mm;
length of the short-edge-corresponding portion 12 is tantamount to
interval between right and left long-edge-corresponding portions
13,14.
[0037] In a plan view as in FIG. 2, as the lead terminal 21 being
superimposed on the respective land 11, the bump 15 and the recess
16 of the land 11 on the PCB 1 intersect with respective long edge
23,24 of the lead terminal 21 on the flexible wiring board 2. That
is, the converging oblique lines 13b and the diverging oblique
lines 14b intersect with either of long edges 23,24 of the lead
terminal 21.
[0038] In a designed position of superimposition as shown in the
figure, the bump 15 of the land 11 protrude from a long edge 23 of
the lead terminal 21 by 0.1 mm, while linear portions 13a on both
ends of the bump 15 is inwardly distanced from the long edge 23 of
the lead terminal 21 by 0.05 mm. Base line 14c of the recess 16 is
inwardly distanced from another long edge 24 of the lead terminal
21 by 0.05 mm, while linear portions 14a on both ends of the recess
16 are outwardly distanced from the long edge 24 by 0.1 mm.
[0039] Bonding of each land 11 on the PCB 1 with respective lead
terminal 21 on the flexible wiring board 2 is made by an automation
bonding machine. After solder is mounted on each land 11 or each
lead terminal 21 by printing technique or the like, alignment is
made to near the designed position; then, automation bonding in use
of heat tool is made. In this way, each land 11 and respective lead
terminal 21 are bonded electrically and mechanically through
solder.
[0040] After such solder bonding, on the fringe portion of the land
11 outwardly protruding from the outline of the lead terminal 21,
fillets 5 of solder are formed, along long edges 23,24 of the lead
terminal 21, to be visible from upper side through the flexible
wiring board 2. In detail, fillets 5, which are visible through a
thin flexible insulator film 2a comprising the flexible wiring
board 2, are formed along a portion 52 of a long edge 23 that
intersects the bump 15 and along two portions 51 of another long
edge 24 that respectively intersect protrusions 17 offsetting the
recess 16; the protrusions 17 are ends part of the
long-edge-corresponding portion 14 of the land 11. These fillets 5
contribute to electrical and mechanical bonding between each land
11 and respective lead terminal 21. After completion of the bonding
with solder, operator can assess whether the bonding is sufficient
or not, by examining whether the fillets 5 are formed in good shape
or not.
[0041] By the hereto-described embodiment, in plan view, each of
the bump 15 and protrusions 17 on each land 11 surely protrudes
from rectangular outline of respective lead terminal 21. Such
protruding are assured even when position of each lead terminal 21
deviates in a direction (X direction) of arranging the lead
terminal 21 with respect to the lands 11, due to deviation of the
position of the heat tool for bonding. Either of such protruding is
lost only when the deviation in the X direction exceeds designed
protruding dimension of the bump 15 and the protrusions 17. In the
illustrated embodiment, the designed protruding dimension is 0.1
mm. By such enough and reliable protruding, formation of the
fillets 5 along both long edges 23,24 of each lead terminal 21 is
easily approvable by observation from upper side through the thin
flexible wiring board 2.
[0042] Moreover, the fillets 5 are formed over an entire area of
superimposition and bonding of each lead terminal 21 with
respective land 11, in respect of longitudinal direction (Y
direction). Thus, an operator is able to confirm sufficient bonding
with the solder in the entire bonding area in the Y direction by
approving formation of the fillets 5 in the entire bonding
area.
[0043] Further, An outward distance from outline of each land 11 to
long edges 23,24 of respective lead terminal 21 is set to be
smaller than designed protruding-wise dimensions of the bump 15 and
the protrusions 17. Thus, the area of superimposition and bonding
of each lead terminal 21 with respective land 11 is able to be set
sufficiently large. In particular, when the solder is applied on
the each lead terminal 21 by printing, formation of balls of the
solder or the like is sufficiently suppressed at portions where the
outline of each land 11 is placed inward from the long edges 23,24
of respective lead terminal 21.
[0044] In the illustrated embodiment, linear portions 13a on both
ends of a bump 15 of each land 11 are inwardly distanced from a
long edge 23 of respective lead terminal 21 by 0.05 mm. Meanwhile,
a base line 14c of a recess 16 is inwardly distanced from another
long edge 24 of respective lead terminal 21 by 0.05 mm. Distance of
these outline portions 13a, 14c of the land 11 from respective long
edges 23,24 are far smaller than the designed protruding dimensions
of a bump 15 and a recess 16 which are 0.1 mm.
[0045] On the other hand, as shown in FIGS. 1 and 3, bold
arch-shaped lands 11 each having a bump 15 and a recess 16 are
arranged in a manner that a bump 15 of one land 11 is facing with a
recess 16 of next land 11. Moreover, outline portion forming the
bump 15 is congruent with outline portion forming the recess 16.
Thus, distances in X direction between two neighboring lands 11 are
kept constant regardless of Y-direction-wise position in the lands
11. In the illustrated embodiment, the distances are kept at 0.lmm
for every two neighboring lands 11. Accordingly, short circuit
between the two neighboring lands 11 is sufficiently avoided.
[0046] Advantageous effect of the above embodiment is able to be
achieved even when outline shape of the lead terminals 21 is
exchanged with outline shape of the lands 11-each lead terminal 21
has the recess and the bump while each land 11 is simply
rectangular.
* * * * *