Method and apparatus for marking or erasing a marking on a semiconductor chip package

A method and apparatus for marking or erasing a marking on a semiconductor chip package having leads. The apparatus comprises a circular disk has many pockets on one surface near its circumference suitable for holding semiconductor chips. Each pocket has a pedestal rising from the bottom of the pocket and suitable for supporting the bottom portion of a semiconductor chip package. The edges of the pocket and the pedestal define between them space suitable for housing the leads of the package. The pedestal has a hole therein which can be evacuated so that the package is held to the pedestal by atmospheric pressure so that the top surface of the package may be marked or in marking thereon can be erased. Thus the package is held to the pedestal by sufficient force for the marking or erasing process. The leads of the package are therefore not bent or otherwise disturbed. Rotation of the disk allows the packages to be sequentially marked or erased.

BACKGROUND Of THE INVENTION 
This invention relates to a system for marking or erasing the marking of a 
semiconductor chip package with leads. 
Semiconductor chip packages are usually marked for a number of reasons. 
Thus the packages are frequently marked to identify the manufacturer; they 
are also marked to identify performance characteristics of the chip such 
as speed. When the packages are marked to identify a particular company, 
the package housing may be pre-marked before the housing is used to house 
the semiconductor chip. However, when the package is to be marked for 
speed or other performance characteristics, it is frequently desirable to 
perform the marking after the package is tested. Such testing is normally 
performed after the leads of the package have been trimmed and formed. The 
package is simply held manually for marking, as is sometimes performed 
conventionally. In such circumstances, it may be difficult to avoid 
bending or otherwise deforming the leads during the marking process. In 
quad-flat pack (QFP) packages, for example, it is crucial for the leads 
present on all four sides of the package to remain coplanar. Since the 
marking process causes a significant force to be applied to the package, 
it is difficult to avoid bending or otherwise disturbing the coplanarity 
of the leads during the marking process. 
Sometimes semiconductor chip packages may be mismarked so that it is 
necessary to erase a marking and then remark the package. The erasing and 
remarking processes are generally performed after the leads are trimmed 
and formed so that it is difficult to avoid bending or otherwise 
disturbing the leads during these processes. It is therefore desirable to 
provide a system for marking or erasing a marking from a semiconductor 
chip package having leads without bending or otherwise disturbing the 
leads. 
SUMMARY OF THE INVENTION 
The system of this invention includes a method and apparatus for marking or 
erasing a marking on a semiconductor chip package having leads. The 
apparatus comprises a support structure for supporting the package where 
the structure defines a conduit means therein, and means connected to the 
conduit means for evacuating it. The apparatus further comprises means for 
marking or erasing a marking on the package when the package is supported 
by said structure when the conduit means is evacuated by the evacuating 
means, so that the package is held to the support structure by sufficient 
force for the marking or erasing, and so that the leads of the package are 
not disturbed during the marking or erasing.

DETAILED DESCRIPTION OF THE INVENTION 
FIG. 1 is a cross-sectional view of a portion of an apparatus for 
supporting and holding a semiconductor chip package with leads with 
sufficient force and in a manner that would not disturb the leads when the 
package is being marked or when the marking is being erased from the 
package. As shown in FIG. 1, the portion 10 of an apparatus includes a 
support structure 12 and a vacuum device 14 for supporting and holding a 
semiconductor chip package 16. Package 16 has a top surface 16a suitable 
to be marked (or has a marking thereon that should be erased) and leads 
18. 
When surface 16a is marked or when a marking on surface 16a is to be 
erased, package 16 should be held with sufficient force in order for the 
marking or the erasing of a marking to be performed. On the other hand, 
when package 16 is held for such purpose, leads 18 are likely to be bent 
or otherwise disturbed, which is undesirable. It is therefore desirable to 
provide an apparatus which can hold package 16 with sufficient force for 
marking or for erasing a marking without bending or disturbing the leads 
18. Support structure 12 and vacuum device 14 together perform such 
function. 
Support structure 12 has a main surface 32 with a depression 34 therein 
defined by drop-off surfaces 34a and bottom surface 34b. A pedestal 36 
rises from the bottom surface 34b of the depression where the pedestal is 
suitable for supporting package 16 when the package is placed on top of 
the pedestal. Depression 34 is at an elevation below the main surface 32 
when the structure 12 is oriented in a position (as shown in FIG. 1) to 
support a package for marking or erasing. Pedestal 36 and drop-off 
surfaces 34a define between them a space surrounding the pedestal for 
housing leads 18 when the pedestal is supporting the package, so that the 
leads do not contact structure 12. 
Structure 12 defines therein a conduit 42 which may simply be a hole 
situated so that it is underneath package 16 when the package is supported 
by the pedestal. Vacuum tube 14 is connected to a vacuum pump (not shown) 
where the tube 14 is matched to hole 42 to evacuate the hole. Atmospheric 
pressure therefore applies a downward force on package 16 to hold package 
16 to the support structure 12 with sufficient force for marking or for 
erasing a marking from surface 16a. In such manner, package 16 is held to 
support structure 12 in a manner that does not bend or otherwise disturb 
leads 18 during the marking or erasing process. 
The drop-off surfaces 34a are chamfered as shown in FIG. 1, so that when 
the package is placed into depression 34 and onto the pedestal 36, the 
package will be automatically centered onto the pedestal. Preferably, of 
course, the package 16 is placed carefully onto pedestal 36 so that leads 
18 will not touch the drop-off surfaces 34a to avoid bending or disturbing 
the leads. An apparatus for placing package 16 onto the pedestal which 
prevents the leads from touching surfaces 34a is described below. The top 
surface 36a of the pedestal is at such an elevation relative to the main 
surface 32 that when the package is in contact with surface 36a and 
supported by structure 12 as shown in FIG. 1, surface 16a of the package 
is above the main surface 32 so that the marking or erasing is 
conveniently performed. 
FIG. 2 is a schematic illustration of a system for marking or erasing a 
marking from a semiconductor chip package to illustrate the preferred 
embodiment of the invention. The system of FIG. 2 includes portion 10 of 
FIG. 1 as described below. Identical parts in the different figures of 
this application are identified by the same numerals. System 100 of FIG. 2 
includes a disk 102 with a number of depressions or pockets 34 of the type 
shown in FIG. 1. In other words, disk 102 includes the support structure 
12 of FIG. 1, except that disk 102 contains a plurality of such 
structures. As shown in FIG. 2, disk 102 contains a dozen or more pockets 
or depressions each for holding a semiconductor chip package for marking 
or erasing a marking there from sequentially. 
Disk 102 is rotated about its axis 120 past a marker 104 which is used to 
mark the package adjacent to it. Alternatively, the marker may be replaced 
by an erasing head for erasing a marking from the adjacent package. After 
the package is marked (or erased), rotation of disk 102 causes the marked 
package to enter a container 106 where the package is baked by means of 
ultraviolet light. Thus container 106 is equipped with an ultraviolet 
light source such as a lamp which illuminates all the packages when they 
are in box 106 for baking the package in order to cure the marking. 
System 100 also includes trays 112 for holding semiconductor chip packages 
before they are picked up and placed into disk 102 and trays 114 for 
holding the semiconductor chip packages after they have been marked or 
erased in a marking or erasing process. System 100 also includes tracks 
116 for one or more systems (not shown in FIG. 2) which pick up the 
packages from trays 112 and place them into depressions or pockets 34 in 
disk 102 and which pick up the marked or erased packages from disk 102 and 
place them in trays 114. 
FIG. 3 is a top view of a portion of system 100 which includes a vacuum 
pickup system for picking up and placing the semiconductor chip package to 
illustrate the preferred embodiment in more detail. The pick and place 
system is essentially a tube (not shown in FIG. 3) connected to a vacuum 
pump (not shown in FIG. 3) which picks up a semiconductor chip package by 
contacting a surface of the chip with the tip of the tube where the vacuum 
in the tube causes the surface of the chip to be pushed towards the tube 
by atmospheric pressure, so that the package may be picked up. After the 
tube picks up a package from tray 112 and places it in a pocket 34, the 
arm releases the package by operating a valve (not shown) to turn off the 
connection of the tube to the vacuum pump and to restore the inside of the 
tube to atmospheric pressure. Such pick and place mechanisms are 
well-known in the packaging art and will not be described in detail. In 
the system of FIG. 3, the tube of the pick and place system may pick up 
each package by contacting the top surface of the package. After the 
packages emerge from container 106, the markings have been cured so that 
contact between the top surfaces of the packages and the pick and place 
system will not cause the markings to smear. 
The tube under vacuum in the above description is connected to a vacuum 
pickup arm 122 which forms another part of the pick and place system; arm 
122 moves the tube to locations appropriate for picking up and depositing 
the package 16. As shown in FIG. 3, the vacuum pickup arm 122 is moved by 
two lead screws 124, 126 and two motors 128 so that arm 122 may be moved 
along the X and Y axis. Arm 122 is moved by a mechanism (not shown) 
operated by pneumatic pressure along the Z-axis (defined as a direction 
perpendicular to the X-Y plane of FIG. 3) in a conventional manner. Thus 
arm 122 may be moved to any location to pick up the package and to place 
it at a desired location. System 100 may include two such vacuum pickup 
systems, one for picking up packages from trays 112 and placing them in 
pockets 34 and the other for picking up the packages after marking or 
erasing from disk 102 and placing them in trays 114. 
FIGS. 4 and 5 are cross-sectional views of portions of system 100 to 
illustrate in more detail the preferred embodiment of the invention. As 
shown in FIG. 2, when disk 102 rotates a package to a location in the 
vicinity of marker 104, marker 104 (or erasing head) operates on the 
package to mark it or to erase a marking therefrom. As explained earlier, 
it is necessary to hold the package with sufficient force so that the 
marking and erasing process will be effective. This is performed by a 
vacuum assembly 150 which includes tube 14 of FIG. 1 as shown in FIG. 4. 
As described above, disk 102 is rotated along its axis 120. Assembly 150 
remains unchanged in position in the X-Y plane and moves only in the 
vertical Z direction. Disk 102 is rotated in angular step motions so that 
when a hole 42 in the disk is directly above the assembly 150, the 
assembly moves upwards until the tip of tube 14 contacts the bottom 
surface of disk 102 immediately below hole 42. The other end of tube 14 is 
connected to a vacuum source (not shown) which evacuates hole 42. As 
described above, this causes a semiconductor package (not shown above 
assembly 150) to be held to pedestal 36 with sufficient force for the 
marking or erasing process. 
As described above, disk 102 should be rotated along its axis 120 by 
angular steps. Furthermore, in order to move tube 14 upwards at 
appropriate time to effectuate a vacuum in hole 42, it is desirable to 
sense the position of holes 42 in the disk so as to move the tube 14 
upwards at the appropriate time. Such functions are illustrated in 
reference to FIGS. 4 and 5. As shown in FIGS. 4 and 5, disk 102 defines 
reference or sensor holes 152 located at such positions in disk 102 that 
when a particular reference or sensor hole 152 is sensed by a sensor 154, 
a corresponding hole 42 will be directly above tube 14, so that a 
mechanism (not shown) can be actuated to move tube 14 upwards to contact 
disk 102. Disk 102 is rotated by means of a turntable 162. Turntable 162 
has a lower circular portion 164 of a smaller diameter which is rotated by 
means of a metal belt 166, spindle 168 and stepping motor 170. Motor 170, 
spindle 168 and belt 166 cause the turntable 162 to rotate in angular 
steps in order to position hole 142 of each pocket 34 above tube 14 
sequentially. 
Motor 170 and the mechanism for moving assembly 150 are both controlled by 
a controller (not shown) such as a microprocessor, which causes assembly 
150 to be moved upwards when sensor 154 senses a hole 152. After a 
predetermined time has elapsed after assembly 150 has been moved upwards 
to contact disk 102 to allow adequate time for the marking or erasing 
process, the controller causes assembly 150 to be moved downwards and 
motor 170 to rotate disk 102 by a preset angle which causes another hole 
42 to be immediately above tube 14 in order to mark or erase another 
package. Turntable 162 has protrusions 182 which fit snugly into 
indentations 184 in disk 102 so that the position of disk 102 may be 
accurately controlled by motor 170. This arrangement also permits 
different disks 102 to be used with the same drive mechanism (162, 164, 
166, 168, 170) which is advantageous for reasons explained below. 
Where the package to be marked or erased is rectangular in shape, the 
pedestal 36, depression 34 and the space surrounding the pedestal for 
housing the leads are also rectangular in shape. Obviously, the shapes of 
the pedestal, the depression and the space surrounding the pedestal may be 
altered to fit the particular type of package to be processed. Where the 
packages to be marked or to be erased are not rectangular in shape, a 
different disk with pockets shaped appropriately to hold such packages may 
be used to replace the disk with rectangular pockets. As shown in FIG. 2, 
the pockets or depressions 34 are preferably located on the circumference 
of an arc on surface 32 where the arc is centered at axis 120, so that 
rotation of disk 102 about axis 120 will cause the pockets to be 
sequentially immediately above tube 14. 
To summarize, the method for marking or erasing a marking on a 
semiconductor chip package is as follows. The package with leads is placed 
onto the pedestal in a particular pocket 34 in disk 102. In the preferred 
embodiment, a plurality of such packages are each placed onto the pedestal 
of a corresponding pocket in the disk. Each pedestal has a conduit which 
can be evacuated. The conduit of a particular pocket is then evacuated and 
the package sitting immediately above the conduit is then marked or 
erased, so that the package is held to the pedestal by sufficient force 
for the marking or erasing, and so that the leads of the package are not 
bent or otherwise disturbed during the marking or erasing. 
Where the process is to mark the package, the method further comprises 
heating the package after the marking to cure the ink. While in the 
preferred embodiment described above, a disk with many pockets and support 
structures is employed, it will be obvious that other configurations of 
support structures may be used and are within the scope of the invention. 
Whether or not a disk is used as described above, the plurality of 
packages supported by the support structure may be sequentially marked or 
erased by moving the structure relative to the marking or erasing head in 
order to sequentially mark or erase the packages. Where a disk is employed 
as in the preferred embodiment, such motion can be achieved by rotating 
the disk about its axis. Where the pockets 34 are located on the 
circumference of an arc centered at the axis of the disk, rotation of the 
disk will cause each pocket to be sequentially located immediately above 
tube 14 so that the packages can be sequentially marked or erased. 
While the invention above has been described by reference to a preferred 
embodiment, various modifications may be made without departing from the 
scope of the invention which is to be limited only by the appended claims.