JP3362948B2 - Lead frame manufacturing method - Google Patents

Description

Detailed Description of the Invention

[0001]

The present invention relates to a method of manufacturing a lead frame.

[0002]

2. Description of the Related Art In a lead frame manufactured by a press punching process, after forming the leads into a predetermined pattern, the inner end of the inner lead is coined to correct the twist of the lead and the wire bonding portion is made flat. Give. FIG. 6 shows a conventional method for carrying out coining with the tips of the inner leads 10 connected by tie bars 12. In coining, a predetermined area of the tip of the inner lead is crushed by a coining punch. In the figure, the shaded portion is the coining portion 14 that has been crushed.

The coining process is performed by connecting the tips of the inner leads 10 with tie bars 12 as shown in FIG.
The connection with the tie bar 12 is performed in order to prevent the inner lead 10 from being deformed due to heating of the lead frame at the time when a plating process is performed in a later process. In recent years, the number of pins in a lead frame has further increased, and leads have been formed with extremely high density. This is because, in such a product, the leads are formed to have a narrow width and the lead interval is narrow, and therefore even a slight deformation of the leads has an important influence on the quality of the product.

[0004]

By the way, when the inner lead is subjected to coining, a cut line D for cutting the tip of the inner lead 10 is conventionally used as shown in FIG.
The coining portion 14 is provided in parallel with D ′ (broken line in the figure). In the figure, AA 'indicates the boundary line at the rear end position of the coining portion 14, BB' indicates the boundary line at the front end position of the coining portion 14, and CC 'indicates the edge line of the tie bar 12.
The cut line DD 'is not necessarily a straight line, and in many cases, the cut line DD' is designed to bend midway due to the positional relationship with the die pad or the like as shown in FIG.

FIG. 4 is an enlarged view of a coining portion provided on the inner lead 10. In the figure, the shaded portion is the coining portion, which is parallel to the cut line DD 'as described above, that is,
It shows a state in which the AA ′ line and the BB ′ line are coined so as to be parallel to the DD ′ line. By the way, the inner lead 10
Is arranged so as to surround the die pad, so that the inner lead 10 is slightly opened on the outer side. Therefore, the inner leads 10 are not completely parallel to each other, and the cut line D
When coining is performed in parallel with D ′, the areas of the coining portions 14 of the inner leads 10 are slightly different from each other. In the example shown in FIG. 4, the areas S ₁ , S ₂ , and S ₃ of the coining portion 14 have a relationship of S ₁ <S ₂ <S ₃ .

The coining process acts to slightly extend the leads, and the larger the area of the coining portion, the greater the amount of elongation. Therefore, when the area of the coining portion of each lead is different as described above, a difference occurs in the amount of extension (extends in the direction of the arrow in the figure) of each lead, and the lead position after coining is displaced from the regular lead position. Occurs. FIG. 5 shows how the lead is displaced from the regular position by coining. In the figure, the solid line is the lead position after coining, and the chain double-dashed line is the regular lead position. The amount of misalignment due to such coining is slight, but in the case of a multi-pin lead frame product in which the inner leads are formed with extremely high density, even a slight misalignment due to such coining will result in a good product. Have a significant impact on defects.

Further, when the lead frame is manufactured by press working, since the punching space is narrowed on the tip side of the inner lead, the tip side of the inner lead becomes thin due to the material being pulled by the punch during punching. FIG. 12 shows a conventional method of coining the inner lead 10 with the coining punch 16, and the broken line shows the inner lead 10 before coining. In the conventional coining process, since the crushing process is performed in parallel with the pedestal 18, the coining part 14 is shallow on the tip side and deep on the base side. As a result, the planar shape of the coining portion 14 becomes a shape in which the base side of the coining portion 14 is widened as shown in FIG. 7. In a multi-pin lead frame, the lead interval is extremely narrow, and thus, when the coining portion 14 is crushed to have a wide width, adjacent leads come into contact with each other and electrically short-circuit.

The present invention has been made in order to solve the problems caused by coining the tip portions of the inner leads in the case of manufacturing a lead frame by such press working. Is to provide a suitable manufacturing method of a lead frame capable of providing a highly accurate and highly reliable lead frame by preventing the positional deviation of the leads and the electrical short circuit between the leads caused by the coining process. is there.

[0009]

The present invention has the following constitution in order to achieve the above object. That is, after punching processing a lead frame material in a predetermined pattern, in the manufacturing method of the lead frame to produce is subjected to coining in the distal end side of the inner lead in the connected state the tip of the inner lead in the tie bar, the inner leads Use a coining punch that coins across the width,
One or both of the boundary lines that define the front end position or the rear end position of the coining portion formed by the coining punch are parallel to the cut line that cuts the tie bar from the tip of the inner lead over a plurality of inner leads. To set it at an angle to the position
Therefore, each of the inner leads
The feature is that coining is performed with the area of the inning portion kept constant . In addition, the lead frame material is patterned
After press punching into the
While connecting with a bar,
Manufacturing method of lead frame manufactured by applying inning process
In the method, using a coining punch for coining across the inner lead in the width direction, one or both of the boundary lines defining the front end position or the rear end position of the coining portion formed by the coining punch are set by a curve , Coin provided on each of the inner leads
It is characterized in that the coining process is performed while keeping the area of the ring portion constant . In addition, coining for performing the coining process
The inner surface of the punch is lower on the punch side of the inner lead.
The slope of the punch surface and coining the slope of the punch surface.
The plane that is relatively parallel to the processing cradle
Inner with thin tip end formed by punching
Coining processing by setting the gradient with the lead gradient added
Characterized in that it.

[0010]

The coining process applied to the inner leads is performed by crushing the inner leads with a coining punch. In the present invention, the coining portion provided on each lead at the time of the coining process has a front end position or a rear end position.
One or both of the boundary lines that define the position
Span the inner leads, and
Position that is parallel to the cutting line that cuts the tie bar from the end
Setting at an angle with respect to or coining
One of the boundary lines that defines the front end position or rear end position of the part
Alternatively, set both with a curve and set each inner
By the area of the coining portion provided on Rido constant, it is possible to eliminate the difference in the elongation of each inner lead, thereby preventing the inner lead is positioned deviated by coining process, to allow for high-precision processing can Ru.
Further, it is possible to obtain a lead frame having an effective bonding area by uniformly collapsing process the inner leads by providing a slope to the punch surface of the coining punch, and to prevent electrical shorting between the leads.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 shows an embodiment in which the inner lead 10 is subjected to coining in the method for manufacturing a lead frame according to the present invention. In the figure, 12 is a tie bar, 14 is a coining portion, the AA 'line indicates the rear end position of the coining portion 14, and the BB' line indicates the coining portion 1.
4 shows the front end position of No. 4.

The coining process of this embodiment is performed as shown in FIG.
The A ′ line is set parallel to the edge line CC ′ of the tie bar 12, that is, the cut line DD ′ of the inner lead 10, and the BB ′ line is inclined with respect to the edge line CC ′, so that each inner lead It is characterized in that the coining parts 14 provided in the parts 10 are processed to have the same area. In this embodiment, since the BB 'line is defined by a straight line over a certain range, the areas of the individual coining portions 14 do not completely match, but S ₁ and S ₂ , S ₂ and S ₃ ·
The angle of the BB ′ line can be set so that the difference in area between the coining portions 14 is minimized as in the case of.

FIG. 2 shows another method of making the areas of the coining portions 14 of the inner leads 10 equal, contrary to the above embodiment, by making the line BB 'parallel to the edge line CC'. Set the rear edge position (AA 'line) to the edge line CC'
I will show you how to coin by tilting.
In the illustrated example, the AA 'line is provided so as to be inclined from the midway position A ". Also in this embodiment, since the AA' line is a straight line, the areas of the coining portions 14 provided on the inner leads 10 are completely the same. Although not necessarily, the areas of the coining portions 14 can be made substantially equal by appropriately setting the inclination of the AA ′ line.

When the areas of the coining portions 14 provided on the inner leads 10 are made equal as shown in each of these embodiments, the inner leads 10 generated by the coining process are formed.
Since the elongation amounts of the inner leads 10 are substantially equal to each other, it is possible to prevent the inner leads 10 from being displaced from the regular position due to the different elongations of the inner leads 10 due to the coining process.

As described above, the lead frame manufacturing method according to the present invention is characterized in that, when the inner lead 10 is subjected to coining, the coining is performed so that the area of the coining portion 14 provided for each lead is constant. However, the method is not limited to the above example. For example, in the above embodiment, one of the AA 'line and the BB' line was inclined with respect to the cut line DD 'to make the area constant.
Both the A ′ line and the BB ′ line may be inclined with respect to the cut line DD ′ so that the area becomes constant.

Further, when the area is made constant, the AA 'line and the BB' line are not slanted lines in the entire range, but are made slanted lines only in a portion where a large difference in area appears so that the areas coincide with each other. You may Further, the inclinations of the AA ′ line and the BB ′ line can be changed in a certain range so that the difference in the area of the coining portion can be adjusted to be as small as possible. Further, although the AA 'line and the BB' line are straight lines in the above-mentioned embodiment, they can be designed by curved lines.

In coining, it is common to perform coining at once on the inner leads 10 surrounding the die pad. Therefore, the punching portion of the coining punch is manufactured in a predetermined shape in accordance with the arrangement of the inner leads 10 surrounding the die pad. When the coining processing is performed so that the coining portions 14 have the same area as described above, the punched portion is formed on the AA ′ line and the B portion.
By making the coins coincide with the line B ', the required coining can be performed by the same operation as the conventional coining method.

FIG. 3 shows another embodiment in which coining is performed so that the coining areas are equal. In the coining process of the above embodiment, the coining punch is applied so as to traverse a plurality of leads, so that the boundary line of the coining portion is oblique with respect to the longitudinal direction of the leads. Originally, the coining process is preferably performed by applying the punch portion in a direction orthogonal to the leads in order to suppress residual strain and perform accurate processing.

However, in the case of forming extremely fine leads such as a lead interval of 0.1 mm as in recent lead frame products, it is necessary to perform such coining processing for each lead in order to manufacture a coining punch. It is extremely difficult due to the above problems. However, as an ideal coining process, as shown in FIG. 3, the front end position (BB ′ line) and the rear end position (AA ′ line) of the coining portion 14 are set in the longitudinal direction of the inner lead 10 with respect to each inner lead 10. It is preferable to process the coining portions 14 so that the areas of the coining portions 14 are equal to each other.

When the coining process as shown in FIG. 3 is performed, the punch portion of the coining punch is used as the inner lead 1.
It is necessary to manufacture according to the individual arrangement of 0. Therefore, it is applied to a lead frame having a lead interval that can be manufactured due to the processing accuracy of the coining punch. According to this method, coining can be performed with high accuracy, and it can be effectively used depending on the design of the inner lead or the intended use of the product.

In the coining process of each of the above-described embodiments, when the coining process is performed on the inner leads 10, the coining process is performed so that the plane area of each inner lead 10 is constant. Regarding the direction, as shown in FIGS. 9 to 11, it is possible to perform a suitable coining process by forming a sloped surface with the tip end side lower than the surface parallel to the pedestal 18 of the coining punch 16. Is.

As described above, the inner lead 10 formed by pressing has a thinned front end side to form a sloped surface. The embodiment shown in FIG. 9 is an example in which the inner lead 10 is coined by setting the punching surface of the coining punch 16 to a slope angle substantially the same as the slope angle of the inner lead 10. The embodiment shown in FIG. 10 is an example in which the pedestal 18 is coined as an inclined surface in order to prevent the tips of the inner leads 10 from bouncing up by coining. In this case, the inclination angle of the pedestal 18 is θ, If the inclination angle of the lead 10 is α, the angle of the punch surface is θ
In this example, + α is used to coin the inner lead 10 at a uniform depth. The embodiment shown in FIG. 11 is an example of coining by changing the inclination angle of the pedestal 18 from θ to θ−α. Note that the actual angle of α is 0.4 to 0.5 ° below 1 °.
Θ is about 2 ° below a few degrees.

In the coining method of each of the embodiments shown in FIGS. 9 to 11, when the punch surface is viewed with reference to the pedestal 18 for coining, the punch surface is parallel to the pedestal 18. In contrast to the conventional method, the punch surface is set to an angle that is parallel to the pedestal and is further added to the inclination α on the tip side of the inner lead 10 for processing. FIG. 8 shows the inner lead 1 like this.
A plan view of the tip of the lead when coining is performed in consideration of the fact that the thickness of 0 becomes thin on the tip side.

According to this coining method, the tip of the inner lead 10 can be crushed at a substantially uniform depth, so that the tip of the inner lead 10 can be reliably crushed even if the coining depth is not so deep. . In this case, since it is not necessary to perform crushing more than necessary, it is possible to prevent the problem that the lead swells laterally at the base position of the coining portion 14 and an electrical short circuit occurs between the adjacent leads. Further, according to this method, as shown in FIG. 8, the coining portion 14 is formed with a substantially uniform width, and it becomes possible to secure an effective bonding area.

Thus, by making the punching surface of the coining punch 16 used for the coining process a sloped surface, effective coining can be performed. This method can be used in combination with the above-described method of coining with the area of the coining portion 14 applied to each inner lead 10 being constant. Therefore, when manufacturing the coining punch 16, use both methods to form the punch surface. Thus, it is possible to prevent the positional deviation of the inner leads 10 and prevent an electrical short circuit between the inner leads 10 to obtain a lead frame having an effective bonding area. In particular, the above method can be very effectively used for manufacturing a lead frame in which leads are formed with a large number of pins and at high density.

The lead frame coined by the above method is then subjected to required plating to be a lead frame product, and a product in which the inner leads 10 are further separated by separating the inner leads 10 from each other. May be The plating applied to the lead frame is plating for improving the bonding property, protective plating for protecting the inner leads, outer leads and the like.

[0027]

According to the manufacturing method of leadframe according to the present invention, as described above, it can be obtained to prevent positional deviation or the like of the inner lead with high precision lead frame during coining. Further, by coining with a coining punch having a gradient to the punch surface, to ensure volume bindings area, it is possible to obtain a lead frame capable of preventing electrical shorting between the leads. According to this method, a coining punch or the like can be easily manufactured, a conventional coining machine can be used, and a lead frame having a multi- pin fine lead pattern can be easily manufactured. It is very effective.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an embodiment showing a method for manufacturing a lead frame.

FIG. 2 is an explanatory view of another embodiment showing a method for manufacturing a lead frame.

FIG. 3 is an explanatory view of still another embodiment showing the method for manufacturing the lead frame.

FIG. 4 is an explanatory view showing a conventional example of a method for manufacturing a lead frame.

FIG. 5 is an explanatory diagram showing a positional deviation of inner leads that occurs during coining.

FIG. 6 is an explanatory view showing a portion where a coining process is performed on the lead frame.

FIG. 7 is a plan view of a coining portion when the inner lead is subjected to coining processing by a conventional method.

FIG. 8 is a plan view of a coining portion when the inner lead is subjected to coining by the method of the embodiment.

FIG. 9 is an explanatory diagram showing a method of an embodiment in which an inner lead is subjected to coining.

FIG. 10 is an explanatory view showing a method of another embodiment in which the inner lead is subjected to coining.

FIG. 11 is an explanatory view showing a method of yet another embodiment of subjecting inner leads to coining.

FIG. 12 is an explanatory view showing a conventional method of subjecting inner leads to coining.

[Explanation of symbols]

10 Inner lead 12 tie bar 14 Coining Department 16 coining punch 18 cradle

Claims (3)

(57) [Claims] 1. A method of manufacturing a lead frame, which comprises manufacturing a lead frame material by press punching into a predetermined pattern, and then coining the tip end side of the inner lead while the tip ends of the inner lead are connected by a tie bar. A carp for coining across the inner lead in the width direction
Using the training punch, before the coining portion formed by the coining punch
One of the boundary lines that defines the end position or the rear end position
Both of them are
Cut that cuts the tie bar from the tip of the inner lead
To set it by inclining to a position that is parallel to the line
More, the manufacturing method of lead frame, characterized in that the coining process in the constant area of the coining portion provided on the inner lead of each of said each. 2. A lead frame material is formed into a predetermined pattern.
After punching, tie bar the tip of the inner lead.
When the inner leads are connected, the coin
In the manufacturing method of the lead frame
And coining the inner leads across the width.
Using the training punch, before the coining portion formed by the coining punch
One of the boundary lines that defines the end position or the rear end position
Set both by a curve, and
Features and to Brighter over de production method of a frame to be coined with the area of the coining portion provided on de constant. 3. A coining punch for performing coining processing.
The slope of the punch surface of the inner lead is low.
Surface, and the slope of the punch surface is
Press punching on the surface that is relatively parallel to the pedestal
Inner leads with a thin tip formed by processing
Method for fabricating a lead frame according to claim 1 or 2, wherein by setting the gradient with a gradient fraction, characterized and this <br/> for coining the.