Tape structure and manufacturing method

Details Tape structure and manufacturing method Tape structure and manufacturing method

2002-06-21

2004-01-13

Lam, Cathy (Department: 1775)

Stock material or miscellaneous articles

All metal or with adjacent metals

Composite; i.e., plural, adjacent, spatially distinct metal...

C428S626000, C428S647000, C428S929000

Reexamination Certificate

active

06677055

ABSTRACT:

CROSS REFERENCE TO RELATED APPLICATIONS
This application claims the priority benefit of Taiwan application serial no. 91111435, filed May 29, 2002.
BACKGROUND OF INVENTION
1. Field of Invention
The present invention relates to a tape structure and its manufacturing method. More particularly, the present invention relates to a tape structure and manufacturing method capable of preventing the formation of whiskers and recess cavities on lead surfaces.
2. Description of Related Art
In this information saturated society, multimedia applications are expanding quickly. To prepare for multimedia expansion, integrated circuit packages are increasingly digitized, networked, locally interconnected and personalized. Correspondingly, the electronic devices must have a high processing speed and serve multiple functions. In general, electronic devices are highly integrated, compact and easily mass-produced. In the past, most integrated circuit packages were fabricated using wire-bonding techniques. However, with an increase in the number of devices packed within a given package, all the devices within the package can no longer be properly linked together due to intrinsic limitations of the wire-bonding technique. Consequently, the tape automated bonding (TAB) technique has been developed. Since packages formed by the tape automated bonding (TAB) technique occupy a small volume and are relatively light and flexible, subsequent assembling and packaging are very much facilitated.
FIG. 1
is a sectional view of a conventional tape structure. The tape is formed on a film
100
. The film
100
has a plurality of device holes
110
. A solder mask
108
is formed on the film
100
. A plurality of leads
102
is formed between the film
100
and the solder mask
108
. Each lead
102
extends from the film
100
into the interior of the device hole
110
. In general, the leads
102
are made from copper. The surface of each lead
102
has a metallic tin layer
106
. However, the leads
102
and the film
100
as well as the leads
102
and the solder mask
108
are in direct contact and hence the junction between has no intermediate metallic tin layer
106
. A tin-copper alloy layer
104
is formed between the metallic tin layer
106
and the leads
102
.
FIG. 2
is a flow chart showing the steps for producing the tape as shown in FIG.
1
. As shown in
FIG. 2
, the manufacturing process includes providing a film (
200
), forming the leads (
202
), coating a solder mask layer (
204
), tinning the leads (
206
) and baking (
208
).
To fabricate the tape structure, a film
100
is provided in step
200
. The film
100
with a tape profile has a plurality of device holes
110
therein. Leads
102
are formed in step
202
. To form the leads
102
, a copper film is pressed onto the film
100
and patterned by conducting photolithographic and etching processes. A solder mask
108
is formed in step
204
by coating a layer of solder material over the film
100
. The leads
102
are tinned in step
206
. In the tinning operation, the exposed lead surface is electroplated to form a metallic tin layer
106
. Finally, the assembly is baked in step
208
to form a tin-copper alloy layer
104
at the junction between the lead
102
and the metallic tin layer
106
.
After the aforementioned tinning operation, a recess cavity may emerge on the surface of the leads
102
(details explained below) and whiskers may appear on the upper surface of the metallic tin layer
106
.
FIG. 3
is a sectional view showing the emergence of a recess cavity in a conventional tape lead due to corrosion after a tinning operation. Since the edges of the solder mask
108
have a thickness smaller than the central region, the edges are more vulnerable to the corrosive attack by the tinning solution and hence are more likely to peel off from the leads
102
. The peel-off area between the solder mask
108
and the lead
102
is then subjected to an oxidation-reduction reaction. In the oxidation-reduction reaction, the copper atoms on the lead
102
are oxidized into copper ions and dissolved in the tinning solution. Ultimately, a recess cavity
110
will appear on the surface of the lead
102
. In the meantime, the electrons released from the copper atoms will reduce the tin ions in the tinning solution into metallic tin and adhere to the surface of the lead
102
.
FIG. 4
is a sectional view of another conventional tape structure. The tape is formed on a film
300
. The film
300
has a plurality of device holes
310
. A solder mask
308
is formed on the film
300
. A plurality of leads
302
is formed between the film
300
and the solder mask
308
. Each lead
302
extends from the film
300
into the interior of the device hole
310
. In general, the leads
302
are made from copper. The surface of each lead
302
has a metallic tin layer
306
. However, the leads
302
and the film
300
are in direct contact and hence the junction between has no intermediate metallic tin layer
306
. A tin-copper alloy layer
304
is formed between the metallic tin layer
306
and the leads
302
. In other words, there is a tin-copper alloy layer (
304
) and a metallic tin layer (
306
) between the solder mask layer
308
and the lead
302
.
FIG. 5
is a flow chart showing the steps for producing the tape as shown in FIG.
4
. As shown in
FIG. 4
, the manufacturing process includes providing a film (
400
), forming the leads (
402
), tinning the leads (
404
), baking (
406
) and coating a solder mask layer (
408
).
To fabricate the tape structure, a film
300
is provided in step
400
. The film
300
with a tape profile has a plurality of device holes
310
therein. Leads
302
are formed in step
402
. To form the leads
302
, a copper film is pressed onto the film
300
and patterned by conducting photolithographic and etching processes. The leads
302
are tinned in step
404
. In the tinning operation, the exposed lead surface is electroplated to form a metallic tin layer
306
so that the leads
302
have a metallic tin layer thereon aside from the junction between the leads
302
and the film
300
. The assembly is baked in step
406
to form a tin-copper alloy layer
304
at the junction between the lead
302
and the metallic tin layer
306
. Finally, a solder mask
308
is formed in step
408
by coating a layer of solder material over the film
300
.
Although the sequence of steps including lead tinning (
404
), baking (
406
) and solder mask coating is able to minimize the formation of recess cavities, whiskers still forms on the surface of the metallic tin layer
306
.
FIG. 6
is a sectional view of yet another conventional tape structure. The tape is formed on a film
500
. The film
500
has a plurality of device holes
510
. A solder mask
508
is formed on the film
500
. A plurality of leads
502
is formed between the film
500
and the solder mask
508
. Each lead
502
extends from the film
500
into the interior of the device hole
510
. In general, the leads
502
are made from copper. The surface of each lead
502
has a tin-copper alloy layer
504
. However, the leads
502
and the film
500
are in direct contact and hence the junction between has no intermediate. tin-copper alloy layer
504
. A metallic tin layer
506
is formed over the tin-copper alloy layer
504
, but the junction interface between the tin-copper alloy layer
504
and the film
500
as well as between the tin-copper alloy layer
504
and the solder mask layer
508
has no metallic tin layer
506
. In other words, there is a tin-copper alloy layer (
504
) between the lead
502
and the solder mask
508
but no metallic tin layer (
506
) therein.
FIG. 7
is a flow chart showing the steps for producing the tape as shown in FIG.
6
. As shown in
FIG. 6
, the manufacturing process includes providing a film (
600
), forming the leads (
602
), conducting a first tinning operation (
604
), baking (
606
), coating a solder mask layer (
608
) and conducting a second tinning operation (
610
).
To fabricate the tape structure, a film
500
is provided in step

Affiliated with

Also associated with

Rating

Tape structure and manufacturing method does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Tape structure and manufacturing method, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Tape structure and manufacturing method will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3200096