JP3463786B2 - Wiring board with lead - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a leaded wiring board having a wiring board on the center side and a lead frame having a large number of external lead terminals joined to the outside, which is called a flat package.

[0002]

2. Description of the Related Art A wiring board with leads is shown in FIG.
As shown in FIG. 5, a ceramic wiring board 80 having a substantially rectangular shape is provided on the center side, and a large number of terminal metallizations 82 are arranged along the outside thereof. To each terminal metallization 82, the inner ends of a large number of external lead terminals 88 extending in parallel to each other from the outer frame 86 of the lead frame 84 located around the wiring board 80 are brazed with silver solder or the like. . After that, by cutting off the outer frame 86, the circuit in the wiring board 80 is connected to an external mother board or the like (not shown) via the terminal metallization 82 and the external lead terminals 88.

[0003]

By the way, the outer frame 86 once expands due to the heating at the time of brazing, but then contracts by cooling. Then, since the tip of each external lead terminal 88 is fixed by the brazing material, there is a problem that the external lead terminal 88 is deformed in a bow shape in the vertical and horizontal directions. This deformation may cause a short circuit between the terminals 88, for example, because the overall shape of the large number of external lead terminals 88 and the intervals between the terminals 88 deviate from a predetermined range.

Therefore, as shown in FIG. 5B, an elongated slit 90 is formed in the outer frame 86 of the lead frame 84 along the outer lead terminals 88, and the outer lead terminals 88 are expanded and expanded. It may be possible to prevent deformation due to contraction. By forming the slit 90, the deformation of each external lead terminal 88 can be suppressed. However, as the outer frame 86 expands and contracts, the stress generated inside the outer frame 86 concentrates near both ends of the slit 90.

Therefore, as shown in FIG. 5 (C), both ends of the slit 90 are deformed inward, and at the same time, a narrow width of about 0.4 mm sandwiched between the slits 90 shown by the arrows in the figure in the vicinity thereof. There is a problem that the portion 87 is cracked. It is presumed that the cracks are caused by the breakage that occurs at grain boundaries in the metal structure of, for example, Kovar or the Fe-42% Ni alloy forming the lead frame 84. The presence of this crack may impair the performance and commercial value of the wiring board 80 with the lead frame 84. The present invention solves the problems described above, and even when each external lead terminal of the lead frame is brazed to each terminal metallization of the wiring board, the external lead terminal is not deformed, and the outer frame of the lead frame is not deformed. It is an object of the present invention to provide a wiring board with leads that is unlikely to cause local damage or deformation such as cracks.

[0006]

According to the present invention, in order to solve the above problems, a slit formed in an outer frame of a lead frame is formed so that stress due to heating / cooling is not concentrated at its end. It was made with the idea of.
That is, the wiring board with leads of the present invention (claim 1) includes a wiring board arranged on the center side and a plurality of external leads whose inner ends are joined to a plurality of terminals provided along the outside of the wiring board. A leaded wiring board including a lead frame having terminals inside, wherein an outer frame of a lead frame connecting outer ends of the plurality of outer lead terminals substantially orthogonally to each other, the outer lead terminals of the outer frame. A slit is formed at a position closer to the outer frame along the longitudinal direction of the outer frame, and both ends of the slit are biased toward the outer side and inside the both ends of the slit.
It is characterized in that a super-width portion or a wide-width portion is formed respectively .

According to this, deformation of each external lead terminal due to brazing can be eliminated or significantly suppressed. In addition, since both ends of the slit are biased toward the outside in advance, the outer frame in the vicinity of the slit has tapered portions or widths at both ends of the slit.
Widely become by the wide portion, for suppressing the thermal stress concentration, it is possible to prevent local destruction, such as the cracks. The length of the slit excluding the biased portions at both ends is longer than the distance between the external lead terminals at both ends on the same side of the outer frame, and the biased portions at both ends of the slit are at the corner portion of the outer frame. It is formed in the foreground. This makes it possible to maintain the strength of the entire lead frame as well as the above-described effects.

According to another wiring board with leads of the present invention (claim 2) , the inner end is joined to the wiring board arranged on the center side and a plurality of terminals provided along the outside of the wiring board. And a lead frame having a plurality of external lead terminals inside, wherein an outer frame of the lead frame that connects the outer ends of the plurality of external lead terminals substantially orthogonally to each other. A plurality of slits are formed along the longitudinal direction of the outer frame at positions close to the external lead terminals on the same side of the frame, and at least the outermost ends of the slits located at both ends of the slit are biased toward the outer side. The taper part or the inner side of the outermost end of the slit.
Is characterized in that a wide portion is formed. According to this, the slit is divided into a plurality of parts to prevent the strength of the lead frame from being deteriorated, and the external lead terminals are deformed or the local portion near the outermost end of the slits located at both ends of the entire slit on the same side of the outer frame. Break the taper or
Allows to prevent by wide part .

The external lead terminals of the lead frame are brazed to four peripheral portions of the wiring board located at the center and also to only two opposing sides of the wiring board. Is also included. In addition, the deviation of the slit end portion includes the one in which a wide portion or a circular portion that is biased outward is communicated with the end portion of the slit. According to this, the thermal stress to the end of the slit can be dispersed and the crack can be prevented. Further, adjacent ends of the plurality of slits formed on the same side of the outer frame may be a plurality of staggered slits.
According to this, the slits are divided to prevent the strength of the lead frame from being reduced, the outer lead terminals are easily prevented from being deformed due to the narrow portions remaining between the slits of the outer frame, and the thermal stress is dispersed so that the middle of the outer frame is dispersed. It is possible to make it difficult for cracks and the like to occur. The wiring board includes a ceramic multilayer wiring board, a resin wiring board, or a wiring board having an electronic component such as an IC chip mounted on the upper surface.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION A preferred embodiment of the present invention will be described below with reference to the drawings. FIG. 1A is a plan view of a leaded wiring board 1 called a flat package. This leaded wiring board 1 is composed of a square ceramic wiring board 2 located at the center and a lead frame 10 arranged around the wiring board 2. The wiring board 2
Is obtained by screen-printing and firing a wiring pattern made of a refractory metal such as tungsten (W) or molybdenum (Mo) between alumina-based green sheets. An IC chip 4 is mounted on the upper surface of the wiring board 2,
It is electrically connected to the wiring pattern in the wiring board 2 through a wire group (not shown). Further, a terminal portion 6 in which a large number of terminal metallizations are arranged is formed along the periphery of the wiring board 2.

On the other hand, the lead frame 10 is, for example, Kovar (Fe-29% Ni-17% Co) or Fe-42% Ni.
A thin plate made of an alloy and having a thickness of about 0.1 mm is punched by a press. This lead frame 10
Is an outer frame 12 having a rectangular frame shape on the outer side thereof, and the terminal portion 6 of the wiring board 2 perpendicularly from the inside of each side of the outer frame 12.
And a large number of elongated external lead terminals 14 extending toward. Each lead terminal 14 has, for example, a length of about 16 mm and a width of about 0.14 mm, and elongated gaps of substantially the same size are formed between the lead terminals 14.
The widths of the lead terminals 14 and the gaps tend to become narrower in order to cope with higher density and smaller size of the wiring board.

A projecting piece 16 extending obliquely toward the center is formed at each inner corner of the outer frame 12, and a positioning hole 18 is formed at the tip end side thereof. This positioning hole 18
Is for positioning and fixing the lead frame 10 when the inner ends of the lead terminals 14 are brazed to the wiring board 2. In addition, the outer frame 1 of the lead frame 10
Each side of 2 has a narrow slit 20 with a width of about 0.2 mm at a position near each lead terminal 14 along the longitudinal direction of each side.
Are formed. At both ends of this slit 20, approximately 4
A bent portion 24 that is biased outward with an inclination of 5 ° is formed.
As shown in FIG. 1B, the linear portion 22 of the slit 20 is
Is the lead terminals 1 at both ends connected to the side of the outer frame 12.
It is formed to be longer than the space between the four, and the bent portions 24 communicate with both ends thereof. Moreover, each bent portion 24 is formed at a position in front of each corner portion of the outer frame 12 to maintain the rigidity of the outer frame 12.

Then, in order to obtain the leaded wiring board 1, a chip-shaped brazing material is placed in advance on each terminal metallization in the terminal portion 6 formed along the periphery of the ceramic wiring board 2. Lead frame 1 on it
The inner end portions of the external lead terminals 14 of 2 are overlapped with each other, for example, 70
Heat to 0 ° C and braze. Then, since the inner end side of each external lead terminal 14 is fixed by this brazing, expansion and contraction due to the heating is caused to occur in each external lead terminal 1.
4 appears on the outer frame 12 side on the outer end side. The outer frame 12 itself also expands and contracts with heating.

At this time, since the slits 20 are formed near the outer ends of the external lead terminals 14 at right angles to the outer ends of the outer lead terminals 14, even if the expansion or contraction is larger than that of the outer frame 12, the outer frame 1 is formed.
Inner piece 2 with a width of 0.4 mm sandwiched between two slits 20
6 is moved inward and outward. That is, each external lead terminal 1
The displacement of 4 is absorbed or mitigated by the slit 20. Specifically, the straight portion 22 of the slit 20 becomes narrow or wide. Therefore, as described above, each external lead terminal 14 is less likely to be deformed by bowing in the vertical and horizontal directions. Moreover , since the bent portions 24 are formed at both ends of the slit 20, the tapered portions 28, 28 are located inside the bent portions 24. This tapered portion 28, 28
Even if the inner piece 26 located between the two moves inward and outward as described above, the accompanying stress is not concentrated in the wide tapered portion 28 but is dispersed. Therefore, each tapered portion 28
No local damage such as cracks as in the prior art occurs inside the inside of the.

As described above, the leaded wiring board 1 in which the slits 20 having the bent portions 24 at both ends are formed on each side of the outer frame 12 maintains a predetermined distance from each other without deformation of the external lead terminals 14. Accurately brazed,
In addition, local damage such as cracks does not occur on each side of the outer frame 12 of the lead frame 10. Therefore, the leaded wiring board 1 can provide the ceramic wiring board 2 in which a large number of external lead terminals 14 are fixed with high density and high precision. The outer frame 12 of the lead frame 10 is punched out and removed later. As a result, the protruding outer end portion of each external lead terminal 14 is connected to a terminal such as a mother board by brazing.

FIG. 2A shows a plan view of a leaded wiring board 30 having a different form. The wiring board 30 includes a plate-shaped ceramic wiring board 32 having a substantially rectangular shape in a plan view, and a lead frame 34 disposed outside the ceramic wiring board 32. A large number of terminal metallizations (not shown) are formed along the long sides of the wiring board 32. On the other hand, the lead frame 34 is a rectangular frame-shaped outer frame 36 formed by punching a thin plate such as Kovar and a pair of upper and lower long sides 37 of the outer frame 36 extending at right angles toward the center side. It has a large number of external lead terminals 38. Further, each long side 37 has a width of about 0.
A 2 mm elongated slit 40 is provided. The vertical short side of the outer frame 36 in the figure is separated from the short side of the wiring board 32 with a narrow gap.

The slit 40 is composed of a straight portion 42 which is longer than the distance between the external lead terminals 38, 38 at both ends, and a bent portion 44 which is formed so as to communicate with both ends thereof. Figure 2
As shown in (B), this bent portion 44 is
To the outside via the curved portion 43, and extends downward with an inclination of 45 ° in the drawing. Then, in order to obtain the wiring board with lead 30, on each terminal metallization formed along the long side of the ceramic wiring board 32,
A chip-shaped brazing material is placed in advance, and the inner end portions of the external lead terminals 38 of the lead frame 34 are stacked on the brazing material, and heated and brazed in the same manner as described above.

Even if each external lead terminal 38 expands and contracts due to the heating of the brazing, since the linear portion 42 of the slit 40 absorbs the displacement in the inward and outward directions similarly to the above, each external lead terminal 38 becomes a bow. It is possible to maintain a predetermined shape and a mutual distance without being deformed. That is, the inner piece 46 having a width of about 0.5 mm sandwiched between the external lead terminal 38 and the linear portion 42 on each long side 37 moves inward and outward together with each external lead terminal 38 to narrow the linear portion 42 of the slit 40. Or to make it wider. Moreover , since the tapered portions 48, 48 located inside each bent portion 44 are present, the stress generated by the above-mentioned displacement is dispersed and absorbed at both ends of the slit 40, so that the occurrence of local fracture such as the crack is eliminated. It becomes possible.

FIG. 3 relates to different configurations of both ends of the slit. FIG. 3A shows a wide portion 5 that is biased toward the outside at both ends of a slit 52 formed so as to be orthogonal to each external lead terminal 51 in the outer frame 50 of the lead frame.
4 is shown in communication. The wide portion 54 is composed of a straight portion 54a curved from the straight portion 53 of the slit 52 and extending obliquely outward and a curved portion 54b. Wide part 5
4 is wider than the straight line portion 53 by having the curved portion 54b.

Further, as shown in FIG. 3B, a wide portion 54 'having curved portions 54b on both sides may be formed. Even if stress is applied due to the displacement of each external lead terminal 51 at the time of brazing, by forming these wide portions 54, 54 'in communication with both ends of the slit 52, the opening area becomes large, and Since the inner tapered portion 50a exists, the stress can be easily dispersed. Therefore, it is possible to prevent local damage such as cracks near the tapered portion 50a.

Further, as shown in FIG. 3C, the circular portion 5 is formed at both ends of the slit 57 formed in the outer frame 55 of the lead frame so as to be orthogonal to each external lead terminal 56.
It is also possible to connect 9 so that they are biased toward the outside.
The circular portion 59 and the inner side of the straight portion 58 of the slit 57 are continuous at the tangent line of the circular portion 59. Therefore, even if stress is applied due to the displacement of each external lead terminal 56 during brazing, the circular portion 59 and the wide portion 55a inside thereof are formed.
By the presence of and, the stress generated at both ends of the slit 58 can be dispersed, so that local destruction near the wide portion 55a can be prevented.

FIG. 4 shows a form in which a plurality of slits are provided side by side on the same side of the outer frame of the lead frame. FIG. 4A shows a pair of slits 62 formed in the outer frame 60 of the lead frame so as to be orthogonal to each external lead terminal 61 and to be continuous with each other along the longitudinal direction on the same side of the outer frame 60. Show. Each slit 62, only the outermost end of the left or right in the illustrated of the line portion 63, have a bent portion 64 which is biasing inclined outward taper on its inner side
The part 64a is located . By using the pair of slits 62, it is possible to form the outer frame 60 having a long dimension without lowering its strength. In addition, the bent portion 64 at the outermost end of each slit 62 can prevent the occurrence of local damage such as cracks in the outer frame portion located inside the slit 62 during the brazing.

Further, FIG. 4B shows three sets of outer frames 65 of the lead frame which are formed in a straight line orthogonal to the external lead terminals 66 and along the longitudinal direction on the same side of the outer frame 65. The slits 67 and 67a are shown. In the figure, the left or right outermost end of each of the left and right slits 67 is formed with a bent portion 68 similar to the above, which is formed in communication with the inside thereof.
The pad portion 68a is located . Also, the central slit 67
“A” includes only a straight line portion, and the narrow portion 69 between the slits 67 on both sides is formed to have a narrow width. By forming these three sets of slits 67, 67a in the outer frame 65, it is possible to further absorb the displacement of each external lead terminal 66 during the brazing and prevent the deformation of each terminal 66. Further, it is possible to prevent the occurrence of cracks or the like in the outer frame portion located inside the bent portion 68 at the outermost ends of the left and right slits 67.

Further, FIG. 4C shows two sets of outer frames 70 of the lead frame which are orthogonal to the external lead terminals 72 and which are linearly formed along the longitudinal direction on the same side of the outer frame 70. The slits 74 and 75 are shown. Each slit 7
At the outermost end on the left or right of 4, 75, a bent portion 7 similar to the above is provided.
6 are formed to communicate with each other and taper inside them
The part 76a is located . In addition, a bent portion 76 and a small linear portion 77 are formed at the center side end of the right side slit 75 in the figure, and are formed so as to be staggered inward and outward with the left side slit 74. Two sets of slits 7
By forming 4, 75 on the outer frame 65, the bent portion 76 located at the left or right outermost end of each slit 74, 75 allows the outer portion located inside the bent portion 76 during brazing. It is possible to prevent local damage such as cracks from occurring in the frame portion. Further, even if there is a narrow portion 78 where the slits 74 and 75 are adjacent to each other, the slits 74 and 77 located on both the inner and outer sides thereof can absorb the displacement of the external lead terminal 72 located in the middle.

The present invention is not limited to each of the forms described above. For example, the ceramic wiring boards 2 and 32 shown in FIGS. 1 and 2 may be resin wiring boards using a resin such as polyimide as an insulating material, or the ceramic wiring board 2 may have a plurality of electronic components mounted on its upper surface. It can also be a multi-chip module. Further, instead of the bent portions 64, 68, 76 of the slits 62, 67, 74, 75 in FIG. 4, the wide portions 54, 5 in FIG. 3 are replaced.
The 4'and the circular portion 59 can be communicated with each other. Further, it is also possible to form an elliptical opening portion that is biased outward, or a flat triangular opening portion with rounded inner corners, at the ends (both ends or outermost ends) of the slits formed in the outer frame. Alternatively, the ends of the slits may be curved outward with a constant curvature. Also, if the straight line portion on the inner side of the slit is set longer than the distance between the external lead terminals at both ends connected to the outer frame in which the slit is formed, the outer side of the slit is It does not have to be a straight line except for a bent portion and the like. In addition to the above materials, Fe-18% Cr alloy, Fe-27% Cr alloy, Fe-52% Ni alloy, or the like can be applied to the material of the lead frame.

[0026]

According to the wiring board with leads of the present invention described above, when the external lead terminals of the lead frame are brazed to the central wiring board, the external lead terminals do not deform in a bow shape. The predetermined shape and the mutual interval can be maintained accurately. Moreover, even if the stress generated inside the outer frame by the brazing eliminates local damage such as cracks in the outer frame near both ends of the slit,
It can be significantly reduced. Therefore, it is possible to provide a leaded wiring board having a desired shape, spacing, and overall arrangement. According to the invention of claim 2,
The same effect as described above can be obtained while maintaining the strength of the lead frame by the plurality of slits.

[Brief description of drawings]

FIG. 1A is a plan view showing an embodiment of a wiring board with leads according to the present invention, and FIG. 1B is an enlarged view of a portion B surrounded by an alternate long and short dash line in FIG.

FIG. 2A is a plan view showing a wiring board with leads of a different form, and FIG. 2B is a portion B surrounded by a chain line in FIG.
Enlarged view of.

3A to 3C are partial plan views in the vicinity of an outer frame showing slits of different shapes.

4A to 4C are partial plan views in the vicinity of an outer frame showing slits of different configurations.

5A is a partial plan view showing a conventional wiring board with leads, FIG. 5B is a partial plan view showing a wiring board having a simple slit formed in the outer frame in FIG. 5A, and FIG. After attachment
FIG. 6B is a partial plan view showing the state of the wiring board having the slits of FIG.

[Explanation of symbols]

1,30 …………………………………… Lead wiring board 2.32 ……………………………… Ceramic wiring board
(Wiring board) 10,34 ……………………………… Lead frame 12,36,50,55,60,65,70 ………… Outer frame 14,38,51,56,61,66 External lead terminals 20,40,52,57,62,67,74,75 ...... Slits 24,44,64,68,76 ……………… Bends (both ends, outermost) End) 28, 48, 50a, 64a, 68a, 76a ……… Tapered part 54, 54 '………………………… Wide part (both ends, outermost end) 55a …………………… Wide part 59 …………………………………… Circular part (both ends, outermost end)

Claims (2)

(57) [Claims] 1. A lead including a wiring board arranged on the center side and a lead frame having inside a plurality of external lead terminals whose inner ends are joined to a plurality of terminals provided along the outside of the wiring board. A wiring board with a plurality of external lead terminals, the outer frame of the lead frame connecting the outer ends of the plurality of external lead terminals substantially orthogonally, in the longitudinal direction of the outer frame at a position near each external lead terminal of the outer frame. A slit is formed along it, and both ends of the slit are biased outward and
There are tapered or wide parts inside both ends of this slit.
Respectively are formed, leaded wiring board, characterized in that. 2. A lead including a wiring board arranged on the center side and a lead frame having inside a plurality of external lead terminals whose inner ends are joined to a plurality of terminals provided along the outside of the wiring board. A wiring board having a plurality of external lead terminals, the outer frame of the lead frame connecting the outer ends of the plurality of external lead terminals substantially orthogonally, the outer frame of the outer frame at a position close to each external lead terminal on the same side of the outer frame. A plurality of slits are formed along the longitudinal direction, and the outermost ends of the slits located at least at both ends of these slits are biased toward the outer side and inside the outermost ends of the slits.
A wiring board with leads, wherein a pad portion or a wide portion is formed.