Method and apparatus for unloading electronic circuit packages from zero insertion force sockets

Disclosed are methods and apparatus for rapidly and automatically unloading electronic circuit packages from zero insertion force sockets on a burn-in board or the like by inverting the burn-in board and placing sequential rows of the sockets in compressive rolling contact with a roller supported beneath the burn-in board. Means are provided to capture the electronic circuit packages as they fall from the sockets and to store the packages in carrier tubes.

FIELD OF THE INVENTION 
This invention relates generally to electronic circuit packages. More 
particularly, it relates to apparatus for rapidly unloading electronic 
circuit packages from zero insertion force sockets on burn-in boards or 
the like. 
BACKGROUND OF THE INVENTION 
In the semiconductor electronics industry, various semiconductor components 
are packaged in standard component packages. One such standard package is 
the dual-in-line package (known as a DIP) which essentially comprises an 
enclosed package containing the semiconductor component with parallel rows 
of leads extending from opposite edges of the package. Other known package 
designs include the flat pack and, more recently, the leadless chip 
carrier developed to contain large scale integration (LSI) type 
semiconductor components. Such LSI components are difficult to house 
efficiently in a standard DIP package because of the complexity of the 
interconnection between the package and the chip. In addition, a DIP 
package for an LSI component must be extended to a length which occupies 
an undesirably large surface area on a printed circuit board to 
accommodate the number of leads required to connect the device to the 
printed circuit board. The leadless chip carrier comprises a substantially 
flat rectangular ceramic or plastic base piece with a centrally located 
cavity on one face thereof. The chip is mounted on the floor of the cavity 
and the cavity enclosed and hermetically sealed with a ceramic or plastic 
cover. Terminal lands or contacts are arranged along the edges and/or the 
sides of the base piece providing a much more compact design than DIP 
packages. 
Because of the complexity of integrated circuits and other semiconductor 
components, particularly LSI components, it has become desirable to test 
each component. Standard testing procedures include mounting a plurality 
of semiconductor components on a test board, known as a burn-in board, and 
simultaneously subjecting the components to various environmental and 
electrical stresses while mounted on the burn-in board. The components are 
then removed from the burn-in board and tested. Those components failing 
the functional tests are discarded or classified according to test 
performance. Although the configuration of the burn-in board may vary for 
various reasons, all burn-in boards generally arrange the components in 
rows and columns of sockets mounted on the burn-in board with the number 
and spacing of the sockets varying according to the testing methods and 
the component to be tested. Various socket designs are also employed for 
similar reasons. 
Since it is desirable to burn-in or test the entire production output from 
an assembly line of semiconductor components, it is also desirable that 
the loading and unloading of the burn-in board be accomplished as rapidly 
and economically as possible. For this purpose, various configurations of 
burn-in boards are employed. However, semiconductor components, even when 
mounted in packages, must be handled carefully to avoid damage to 
themselves or to the package. For instance, the parallel leads on a DIP 
may be damaged or bent while being inserted on a socket on a burn-in board 
if not aligned correctly with the socket. Even if aligned correctly, the 
leads may become worn through repeated insertion and removal from a 
socket. Further, the force required to insert and remove electronic 
circuit packages of all types from a conventional socket imposes 
undesirable stresses on the component and the package. For this reason, 
zero insertion force sockets have been developed and, in particular, such 
sockets have been employed on burn-in boards. It is to this type of zero 
insertion force socket that the present invention is directed and in 
particular to the problem of unloading the electronic circuit package 
therefrom. 
Zero insertion force sockets for DIPs provide an opening for each lead on 
the DIP. The openings are of a much larger diameter than the lead and thus 
the component may be inserted or removed therefrom without appreciable 
resistance. When the component is inserted in the socket, a mechanism on 
the socket is engaged to grip the leads of the DIP and secure it in place. 
The mechanism must be disengaged to allow the component to be removed. It 
is known to resiliently bias the mechanism to an engaged position, 
requiring a compressive force to be applied to the socket in order to 
shift the mechanism to a disengaged position and enabling a DIP to be 
inserted or removed from the socket without substantial resistance. 
U.S. Pat. No. 4,491,397, issued Jan. 1, 1985, shows a zero insertion force 
socket for use with a leadless chip carrier. The socket includes a housing 
having a rectangular cavity for receiving the leadless chip carrier. A 
plurality of rigid contacts are vertically mounted in the housing about 
the cavity and are biased to engage the terminal lands on the leadless 
chip carrier when placed in the cavity. A spreader is mounted on the 
housing and is capable of reciprocal motion in a vertical direction 
although it is resiliently biased to an upper position. When the socket is 
compressed by forcing the spreader downwardly toward the housing, the 
spreader deflects the contacts outwards from the cavity, thus allowing the 
leadless chip carrier to enter the cavity without resistance. When the 
spreader is released, it automatically resumes the upper position, 
allowing the contacts to spring inwardly to engage the terminal lands on 
the leadless chip carrier and secure it in the socket. The leadless chip 
carrier may be released by compressing the socket a second time as 
outlined above and extracting the leadless chip carrier. 
The electronic circuit packages, of whatever type, may be loaded and 
unloaded by hand from the zero insertion force sockets on a burn-in board. 
This method, however, is extremely time-consuming and therefore expensive. 
Another problem associated with electronic circuit packages is that they 
must frequently be inserted into carrier tubes in an end-to-end 
relationship after being unloaded from the socket. The carrier tubes are 
widely used to store and transport the electronic circuit packages in 
large numbers. It is undesirable to individually load the electronic 
circuit packages into the carrier tubes by hand. Finally, any apparatus in 
contact with the electronic circuit packages may damage the semiconductor 
component contained therein if electric current is present or if static 
electricity is allowed to accumulate. None of these difficulties are 
satisfactorily overcome by existing equipment or methods for unloading 
electronic circuit packages from burn-in boards or the like. 
SUMMARY OF THE INVENTION 
This invention provides a method and apparatus for rapidly and efficiently 
unloading electronic circuit packages from zero insertion sockets mounted 
in a rectangular array on a burn-in board or the like. The method, in one 
embodiment, includes the steps of supporting the array of sockets in an 
inverted position; providing a roller; and passing the inverted array of 
sockets over the roller in compressive rolling contact therewith so as to 
unload the electronic circuit packages. Alternatively, after the socket 
has been compressed the electronic circuit packages may be extracted from 
the socket by mechanical means or by suction without requiring that the 
burn-in board be inverted. 
The apparatus disclosed to accomplish this process includes a housing 
supporting a receptacle for supporting the burn-in board in an inverted 
position. Preferably, the apparatus is entirely pneumatically actuated and 
constructed of conductive materials which are grounded to avoid any 
possible electrical damage to the electronic circuit carriers. The 
receptacle is capable of reciprocal horizontal motion with respect to the 
housing between first and second positions. A roller is rotatively mounted 
in the housing beneath the receptacle. The roller is positioned so that it 
is placed in compressive rolling contact with the inverted sockets on the 
burn-in board as the receptacle and board are shifted to the second 
position. As each successive row of sockets on the burn-in board is 
compressed by the roller, the electronic circuit packages contained 
therein simultaneously fall from the sockets. 
Means are provided to capture the electronic circuit packages as they are 
unloaded from the sockets and transport them to carrier tubes. In the 
preferred embodiment of the invention the roller is provided with 
concentric slots, each aligned with one of the rows of sockets on the 
burn-in board. As a row of the electronic circuit packages fall from the 
sockets they are each received in one of the slots in the roller. The 
roller is induced to rotate when in rolling contact with the sockets of 
the burn-in board, thus the electronic circuit carriers are carried in the 
roller slots as the roller rotates. A wiper is positioned beneath the 
slotted roller and conveys the electronic circuit packages as they fall 
from the slots on the roller to a row of aligned carrier tubes. The 
electronic circuit packages from each column on the burn-in board are 
sequentially placed in the carrier tube aligned with that column in end to 
end relationship until the carrier tube is filled. The carrier tubes are 
then replaced with an empty carrier tube for receipt of further electronic 
circuit packages from the burn-in board. When the burn-in board reaches 
its second position all of the sockets will have been unloaded into the 
carrier tubes. 
In one embodiment of the invention, a second roller is rotatively mounted 
on the housing above the receptacle and opposite the slotted roller. A pad 
is interposed between the burn-in board and the second roller and 
comprises an upper rigid layer in rolling contact with the second roller 
and a lower cushioning layer in contact with the burn-in board. The second 
roller and pad apply pressure to support the burn-in board as the sockets 
are compressed and the electronic circuit packages are unloaded. 
DESCRIPTION OF THE DRAWINGS 
So that the manner in which the above recited features and advantages of 
the invention, as well as others which will become apparent to those 
skilled in the art, are obtained and can be understood in detail, a more 
particular description of the invention briefly summarized above may be 
had by reference to the embodiments thereof which are illustrated in the 
accompanying drawings, which drawings form a part of the specification and 
in which like numerals depict like parts in the several views. It is 
noted, however, that the appended drawings illustrate only a preferred 
embodiment of the invention and are therefore not to be considered 
limiting of its scope, for the invention may admit to other equally 
effective embodiments.

DETAILED DESCRIPTION OF THE INVENTION 
Referring now to FIG. 1, the reference numeral 10 generally indicates the 
apparatus of the present invention having a housing which includes a base 
plate 12 and defines longitudinal axis 14, front end 16, rear end 18, 
right side 20 and left side 22. Shroud 24 is mounted on the base plate and 
encloses the apparatus during operations. Shroud 24 is constructed of a 
rigid monolithic molded plastic piece. Preferably, the shroud and all the 
materials from which the components of the apparatus and the housing are 
constructed of materials that are electrically conductive to prevent the 
accumulation of static electricity which might damage the semiconductor 
components contained in the electronic circuit packages. Further, the 
apparatus is equipped with a ground wire (not shown) connected to the 
housing for attachment to an external ground circuit (not shown) to drain 
static charges away from the apparatus. The apparatus also includes index 
plate or receptacle 26 adapted to support burn-in board 28 fully loaded 
with a plurality of electronic circuit packages (not shown) which have 
been tested and now must be unloaded from the burn-in board. As shown in 
FIG. 1 the index plate is in a first position fully extended from the 
apparatus enabling the burn-in board to be placed thereon. FIG. 2 shows 
the apparatus with the shroud removed, revealing the apparatus housing as 
hereinafter described, and with the index plate shifted from its first 
position into the apparatus. Identical pairs of inner and outer shroud 
mounting rails 30 and 32 are mounted along the right and left edges of the 
base plate and define right and left grooves for receipt of the lower 
longitudinal edges of the shroud. The shroud may be bolted to the base 
plate or may be attached by any other appropriate means. 
FIG. 7 shows in detail a portion of burn-in board 28. Zero insertion force 
sockets 34 of the type previously discussed are arranged in a rectangular 
array of rows 36 and columns 38 and soldered to printed circuit burn-in 
board 28. Although not shown in FIG. 7, each of the sockets includes a 
plurality of rigid leads extending downwardly through openings in the 
printed circuit board. In the illustrated embodiment, the sockets are each 
adapted to receive leadless chip carrier 42, although it is recognized 
that the present invention may be adapted for use with zero insertion 
force sockets used with other types of electronic circuit packages such as 
DIPS. In any case, the sockets must be compressed in order to receive or 
release the electronic circuit packages and are biased to an engaged 
position. 
Returning to FIGS. 1 and 2, index plate 26 includes generally rectangular 
opening 44 having a length and width less than the length and width of the 
burn-in board. Front locater plate 46 and rear locator plate 48 are 
mounted on the index plate at the front and rear ends, respectively, of 
the index plate opening. The front and rear locator plates are generally 
C-shaped and extend along the end edges of the opening and partially along 
the longitudinal edges thereof. The index plate opening and the front and 
rear locator plates are constructed and positioned on the index plate to 
enable burn-in board 28 to be placed on the index plate in an inverted 
position with the array of sockets, each loaded with an electronic circuit 
packages, extending downwardly through the opening and prevented from 
horizontal movement by the front and rear locator plates. Handle 50 is 
formed on the front or exposed end of the index plate. A pair of parallel 
guide rails 52 are mounted on the bottom of the index plate along opposite 
longitudinal edges thereof by four rail mounting blocks 54. Stop block 56 
is transversely mounted on the upper surface of the index plate adjacent 
the rear end thereof. 
Referring now also to FIGS. 3-6, in which the index plate has been removed 
from the apparatus for clarity, the apparatus housing further includes 
right bearing plate 62 and left bearing plate 64 mounted on the base plate 
along opposite sides thereof. The bearing plates are secured on the base 
plate by screws or bolts or any other conventional means. Similarly, all 
other structural support members included in the apparatus housing 
described hereinafter are mounted on the base plate or to each other in 
the same or equivalent fashion. Front bearing rail 68 and rear bearing 
rail 66 are transversely mounted on the bearing plates above the base 
plate. Right upright 70 and left upright 72 are mounted on the base plate 
on the outside of right bearing plate 62 and left bearing plate 64. Air 
control mounting bracket 74 is mounted on the base plate at the rear end 
thereof. Right bridge upright 76 and left bridge upright 78 are mounted on 
the base plate adjacent opposite edges of the air control mounting plate. 
Bridge plate 80 is mounted transversely on the right and left bridge 
plates. Shroud mounting rail (not shown) is mounted on the front bearing 
rail transverse to the longitudinal axis of the housing and includes a 
groove extending along its length adapted to receive the front edge of the 
shroud. 
Four bearings 84 are mounted on the front and rear bearing rails in two 
spaced longitudinally aligned pairs, each pair aligned with the 
longitudinal axis of the housing. Preferably, the bearings are of the 
recirculating ball bearing type. The guide rails of the index plate are 
positioned and constructed of a size and shape so as to enable the guide 
rails to be inserted into and maintain a simultaneous sliding engagement 
with bearings 84 while supporting the index plate above the bearings. The 
shroud includes an opening (not shown in FIG. 1) in its front end enabling 
the index plate to be inserted within the shroud and into engagement with 
the bearings. When the guide rails are in engagement with the bearings, 
the index plate is capable of reciprocal horizontal movement parallel to 
longitudinal axis 14 of the apparatus. The travel of the index plate with 
respect to the apparatus is limited between a first fully extended 
position (as shown in FIG. 1) and a second fully inserted position (not 
shown) in which substantially the full length of the index plate is 
contained within the shroud. 
Means are included to provide a motive force to move the index plate 
between its first and second positions. As is shown also in FIGS. 8A and 
8B, motor upright 86 is mounted on the base plate between the right and 
left bearing plates and supports motor 88. A drive mechanism is provided 
to transmit the torque generated by the motor to other parts of the 
apparatus and to convert the rotary power into linear movement of the 
index plate. The drive mechanism includes drive gear 90 mounted on the 
shaft of the motor and extending through the motor upright toward the left 
bearing plate. Gear drive mounting plate 92 is mounted on the base plate 
adjacent the right bearing plate 62. Drive shaft 94 is rotatively mounted 
at one end on left bearing plate 64 and on the other end to the gear drive 
mounting plate. The drive shaft includes large transfer gear 96 mounted on 
the drive shaft adjacent the left bearing plate and positioned to engage 
the drive gear on the motor shaft. 
The other end of the drive shaft includes clutch transfer gear 98 adjacent 
the gear drive mounting plate. Clutch drive gear 100 is rotatively mounted 
on the drive gear mounting plate above the drive shaft and is positioned 
to engage the clutch transfer gear. Clutch 102, shown in FIG. 3 in a 
disengaged position, is connected to the clutch drive gear. Clutch piston 
104, shown in FIG. 3, is attached to the clutch and shifts the clutch 
between engaged and disengaged positions but is biased to a disengaged 
position. When the clutch is engaged by the clutch piston, the clutch 
drive gear is shifted toward the gear drive mounting plate to engage the 
clutch transfer gear. When the clutch is disengaged, the clutch drive gear 
is shifted away from the gear drive mounting plate, as shown in FIG. 3, 
and is pulled out of engagement with the clutch transfer gear. Index plate 
drive gear 106 is rotatively mounted on the drive gear mounting plate 
above the clutch drive gear and is positioned to engage the clutch drive 
gear when the clutch drive gear is engaged with the clutch transfer gear. 
Index plate rack gear 108 is mounted on the underside of the index plate 
along the right longitudinal edge thereof. When the guide rails of the 
index plate are engaged with the bearings, the index plate rack gear will 
be engaged with the index plate drive gear. In this manner, the rotational 
force of the motor is converted to a linear force inducing longitudinal 
movement of the index plate between its first and its second positions. 
The drive gear, drive shaft, transfer gear, clutch transfer gear, clutch 
drive gear index plate drive gear, and index plate rack gear all form part 
of the drive mechanism of this invention for transmission of power from 
the motor. 
Motor 88 may be an electric motor or powered by any other conventional 
means. However, in the preferred embodiment of the invention the motor is 
a pneumatic motor powered by a source of compressed air (not shown). The 
use of pneumatic pressure to power the motor avoids the possibility of 
damage to the semiconductor components inherent in the use of electrically 
powered equipment. For the purposes of clarity, the conduits forming the 
pneumatic system powering the motor have been omitted from FIGS. 1-6, 8A 
and 8B. However, FIG. 11 schematically shows the pneumatic control system 
including filter and moisture trap 110 (shown in FIG. 6) mounted on the 
air control mounting plate and connected by conduit 112 to the source of 
pressurized air. The filter and moisture trap acts to remove contaminants 
and moisture from the incoming air supply that might otherwise corrode the 
motor or other elements of the pneumatic control system. The output of the 
filter and moisture trap is connected to pressure regulator 114 which is 
mounted on the air control mounting plate for controlling the pressure of 
the air supplied to the motor to desired levels. Pressure gauge 116 is 
mounted on the pressure regulator and indicates the pressure of the air 
supplied to the pneumatic system of the apparatus downstream of the 
pressure regulator. The pressure regulator is connected by conduit 118 to 
inlet 120 of the pneumatic control valve 122 mounted on the opposite 
surface of the air control mounting plate and shown in FIGS. 3 and 4. 
First flow regulator 124 is mounted on the air control mounting plate and 
is connected by conduit 126 to outlet 128 of the air control valve. The 
flow regulator controls the rate of air flow downstream of the pneumatic 
control valve to the motor. Motor 88 is connected by conduit 130 to first 
flow regulator 124 so that the speed of the motor may be adjusted by 
altering the flow rate of the pressurized air from the first flow 
regulator. Lubricator 132 is interposed into conduit 130 to provide 
lubricating oil into the motor. Silencer or muffler 134 is also interposed 
into conduit 130 downstream of the lubricator to reduce the noise produced 
by the motor during operation. Conduit 136 connects second flow regulator 
138 to outlet 128 of the pneumatic control valve. Clutch piston 104 is 
connected to the second flow regulator by conduit 140 for shifting the 
clutch piston to an engaged position in the presence of compressed air and 
to enable the flow of compressed air supplied to the clutch piston to be 
controlled independently from the compressed air supplied to the motor. 
Manifold block 142 is mounted on the air control mounting plate adjacent 
the pneumatic control valve. Conduit 144 is connected at one end to inlet 
146 of the manifold block and at the other to conduit 118 upstream of the 
pneumatic control valve and therefore provides the manifold block with 
compressed air independent of the status of the pneumatic control valve. 
Conduit 148 is connected at one end to orifice 150 of the manifold block 
and at the other end to first pilot port 152 of the pneumatic control 
valve. Start switch 154 is inserted in-line in conduit 148 and is mounted 
on right upright 70 facing away from the housing. Conduit 156 is connected 
on one end to orifice 158 of the manifold block and commonly connected at 
the other end with conduit 148 to first pilot port 152 of the pneumatic 
control valve. Normally closed front limit switch 160 is inserted in-line 
in conduit 156 and is mounted by switch bracket 162 on the rear bearing 
plate facing toward the air control mounting plate. Conduit 164 is 
connected at one end to orifice 166 of the manifold block and at the other 
end to second pilot port 168 of pneumatic control valve 122. Emergency 
stop switch 170 is inserted in-line in conduit 164 and is mounted on right 
upright 70 above the start switch and facing outwardly of the drive 
mechanism. Conduit 172 is connected at one end to orifice 174 of the 
manifold block and commonly connected at the other end with conduit 164 to 
second pilot port 168 of the pneumatic control valve. Normally closed rear 
limit switch 176 is inserted in-line in conduit 172 and is mounted by 
switch bracket 178 on the left end of the rear bridge plate facing the 
bearing plates. The manifold block is constructed to carry compressed air 
to each of the start switch, emergency stop switch, front limit switch and 
the rear limit switch through the various conduits. 
The pneumatic control valve includes an internal piston (not shown) which 
is shiftable between two positions. In the first position, compressed air 
is enabled to flow through the pneumatic control valve from the inlet to 
the outlet and thereon to the motor and the clutch. In the second 
position, the piston blocks the flow of compressed air through the 
pneumatic control valve and disables the motor and the clutch. The 
position of the piston is determined by the differential pressure acting 
on the piston between the first pilot port and the second pilot port. In 
the absence of compressed air in either of the first and the second pilot 
ports, the piston of the pneumatic control valve is biased to the second, 
blocked position. 
If the start switch is manually shifted to an open position, compressed air 
will flow past the start switch through conduit 148 into the first pilot 
port of the pneumatic control valve. However, as previously discussed the 
piston of the pneumatic control valve is biased to the second position in 
which the pneumatic control valve is closed. In this position, the force 
exerted by the compressed air in the first pilot port from conduit 148 is 
insufficient to shift the piston to its first position. Only if the 
normally closed front limit switch is opened simultaneously with the 
manual opening of the start switch will compressed air flow through the 
front limit switch and sufficient pressure be placed on the piston from 
the first pilot port to shift it into its first position and enable the 
compressed air to flow through the pneumatic control valve and reach the 
motor and clutch. Once the front safety limit switch has been shifted to 
an open position and the start switch has been opened, the front safety 
limit switch is automatically maintained in an open position until conduit 
156 is depressurized. It then automatically returns to a closed state. 
Further, once the piston assumes its first position it is maintained in 
that position by the force exerted by the compressed air in the first 
pilot port until either the normally closed rear limit switch or the 
emergency stop switch are opened. In that case, pressurized air flows from 
the manifold block through either conduit 164 or conduit 172 into the 
second pilot port of the pneumatic control valve. The pneumatic control 
valve is constructed such that the presence of compressed air in the 
second pilot port from either of the conduits connected thereto will be 
sufficient to shift the piston to its second position against the force of 
the compressed air in the first pilot port and cut off the flow of 
compressed air to the motor and clutch downstream of the pneumatic control 
valve. 
As an additional safety feature, first shunt 180 and second shunt 182 are 
each interposed in-line into conduit 144 extending from conduit 118 to the 
inlet of the manifold block and are normally closed. First shunt 180 is 
mounted on the top of the bridge plate and second shunt 182 is mounted on 
top of the rear bearing plate. Both shunts are normally closed and 
positioned so as to contact the shroud when the shroud is mounted on the 
base plate. When the shroud is properly mounted on the base plate, the 
shroud contacts both shunts and shifts them to an open position enabling 
the flow of the pressurized air to the manifold block. If the shroud is 
inadvertently or deliberately removed, the first and second shunts are 
automatically closed blocking the flow of compressed air to the manifold 
block and preventing the shifting of the pneumatic control valve piston to 
its first position and, consequently, transmission of pressurized air to 
the motor and clutch. 
In operation, burn-in board 28 is positioned on index plate 26 in an 
inverted position with the index plate in its first position as shown in 
FIG. 1. Front limit switch 160 is in contact with stop block 56 on the 
index plate, thereby shifting the front limit switch to an open position. 
The start switch is then manually opened, shifting the pneumatic control 
valve piston to its first position and supplying the pressurized air to 
the motor through conduit 130. The motor applies torque to the drive gear 
and, through the transfer gear of the drive shaft, begins to rotate the 
drive shaft. The clutch piston is actuated by the pressurized air supplied 
by the pneumatic control valve through conduit 136, shifting the clutch 
and the clutch drive gear toward the gear drive mounting plate and into 
engagement with the clutch transfer gear and the index plate drive gear. 
The clutch transfer gear on the drive shaft rotates the clutch drive gear 
and the index plate drive gear. Rotation of the index plate drive gear is 
converted by the index plate rack gear into horizontal motion in direction 
184 (as shown in FIGS. 8A and 8B) of the index plate toward its second 
position. If a predetermined amount of resistance is encountered by the 
index plate or the drive mechanism as the index plate is being shifted to 
its second position, the clutch slips and disengages the clutch drive gear 
from the clutch transfer gear on the drive shaft to stop the motion of the 
index plate. Alternatively, the motion of the index plate may be 
interrupted at any time by the manual actuation of the emergency stop 
switch. 
As the index plate achieves its second position, stop block 56 mounted on 
the index plate contacts the rear limit switch and opens it. Rear limit 
switch 176 then automatically interrupts the supply of pressurized air to 
the motor by shifting the piston of the pneumatic control valve into its 
second position and halts motion of the index plate. In addition, the 
supply of compressed air to the clutch piston is also interrupted so that 
the clutch and clutch drive gear are automatically disengaged. The index 
plate may then be manually returned to its first position without 
resistance by grasping the handle in the index plate and pulling the index 
plate outward from the apparatus in direction 186 (as shown in FIGS. 8A 
and 8B) to the first position of the index plate and the front safety 
limit switch is contacted. Once the front limit switch is opened, the 
motor may be activated again by manual opening of the start switch. In an 
alternate embodiment of the invention, the index plate is returned to its 
first position by reversing the motor rather than by manual force. 
Further, it is possible to substitute a pneumatic cylinder, mounted on one 
end to the base plate or to the air control mounting plate and connected 
at the other end to the index plate, for the motor. 
Referring now to FIGS. 8A, 8B, 9 and 10, roller 190 is rotatively supported 
at each end by right chute holder 192 and left chute holder 194 in a 
horizontal position transverse to the longitudinal axis of the apparatus. 
The roller is positioned at a desired predetermined point along the 
longitudinal axis of the housing. The right chute holder is mounted on the 
right upright and the left chute holder is mounted in an aligned position 
on the left upright so as to place the roller beneath the index plate. The 
diameter of roller 190 and the position of the roller with respect to the 
index plate will place the roller in compressive rolling contact with the 
inverted sockets on the burn-in board as the index plate shifts between 
its first and second positions. That is, the uppermost point on the roller 
is higher than the lowermost point of the sockets on the burn-in board 
when supported by the index plate. As each sequential row of sockets is 
passed over the roller at the predetermined point along the longitudinal 
axis of the apparatus, the sockets in a particular row will be 
simultaneously compressed by the roller and the electronic circuit 
packages released therefrom. After the electronic circuit packages are 
released from the sockets, they will fall from the sockets under the 
influence of gravity, thereby unloading the sockets. At the same time, the 
roller is rotated in clockwise direction 188 (as seen from the right side 
of the apparatus) due to the frictional contact with the sockets. 
Means are provided to receive the electronic circuit packages as they fall 
from the sockets. In the illustrated embodiment of the invention the 
receiving means takes the form of spaced concentric slots 196 formed in 
roller 190. A slot is formed for each column of the sockets in alignment 
therewith. Each of the slots is adapted to receive the electronic circuit 
packages at the uppermost point of the slot on the roller and are at least 
slightly wider and deeper than the width and thickness of the electronic 
circuit packages. In the preferred embodiment of the invention each of the 
slots includes spaced pairs of O-rings 198 positioned on the roller in 
alignment with the columns of sockets with one of the O-rings in each pair 
adjacent one of the edges of the slot. The tops of each pair of O-rings 
resiliently contacts and compresses the aligned sockets as the burn-in 
board moves past the slotted roller. The unloaded electronic circuit 
packages are received in the slots between the O-rings. Of course, it is 
possible to omit the O-rings and construct the roller so that it contacts 
the sockets directly. Rear stop plate 200 is mounted on spacer 202, which 
is mounted on front bearing rail 66. The rear stop plate includes a 
plurality of fingers 204, each interposed in one of the slots on the 
roller between the pairs of O-rings. The lower surfaces of the fingers 
adjacent the roller are preferably concave and concentric to the roller 
and closely positioned to the bottom of the slots by a distance less than 
the thickness of one of the electronic circuit packages. The fingers of 
the rear stop plate act to prevent any of the electronic circuit packages 
from falling off the roller in the wrong direction. 
In FIGS. 8A, 8B and 9, electronic circuit package 42A has just been 
unloaded from socket 34 on the burn-in board and has fallen into aligned 
slot 196 on the roller at the topmost point thereon. Although not shown, 
an identical electronic circuit package has been deposited in the same 
position in each of the other slots on the roller. As the roller rotates 
and additional electronic circuit packages are released from subsequent 
rows of sockets on the burn-in board, packages previously received by the 
slots will be continuously carried by the slots in clockwise direction 188 
away from the uppermost position on the slot as illustrated by the 
electronic circuit package labeled 42B. As the roller continues to rotate, 
the rows of electronic circuit packages carried in the slots are rotated 
on the roller to a point where they fall from the slots on the roller as 
illustrated by the electronic circuit package labeled 42C. 
Means are provided to capture and store the electronic circuit packages as 
they leave the slots on the roller. In the illustrated embodiment the 
means includes wiper 206 forming a concave surface, preferably concentric 
with but spaced apart from the outer surface of the roller, mounted on 
either edge to the right and left chute holders on the underside of 
bearing rail 68 beneath the roller. Also mounted on the either end to the 
left and right holders is chute 208 having an upper edge adjacent the 
lowermost edge of the wiper. The chute is inclined at an angle, which in 
the illustrated embodiment is 30.degree., toward the front of the 
apparatus. The chute includes a plurality of parallel longitudinal 
channels 210 (partially shown in FIGS. 2 and 4) each aligned with one of 
the slots on the roller and having a width slightly greater than that of 
the electronic circuit packages. Chute 208 includes a chute cover plate 
212 mounted on the chute and enclosing most of the length of the channels 
on the chute. The chute cover plate presents a concentric curved upper 
edge to the roller. 
A plurality of carrier tubes 214 may be used in conjunction with the 
apparatus of this invention, each adapted to receive and store the 
electronic circuit packages in end-to-end relation. Tube retaining bar 216 
is transversely mounted on the chute adjacent the lowermost edge thereof. 
The carrier tubes are each inserted into one of the channels of the chute 
beneath the tube retaining bar until the foremost ends of the carrier 
tubes contact shoulders 217 of the chute. The tube retaining bar includes 
means for securing the carrier tubes within the channels. In the 
illustrated embodiment, the securing means takes the form of a plurality 
of spring biased knobs (not shown) mounted in and projecting downwardly 
from the tube retaining bar over each of the channels. The knobs exert 
sufficient frictional force on the carrier tubes to retain the carrier 
tubes in the channels but permit the tubes to be removed when desired. 
Catch tray 218 is mounted on either end to the right and left chute 
holders beneath the chute separated from the underside of the chute by a 
pair of catch tray spacers 220 mounted along opposite edges thereof. The 
catch tray includes an arcuate section 218A extending generally 
concentrically about the slotted roller but having an upper edge higher 
than the top of the wiper and extending beyond the edges of the wiper from 
side to side. The catch tray also includes a lower section 218B extending 
downwardly parallel with the underside of the chute and terminating in an 
upwardly extending lip 222 along the full width thereof. 
In operation, the slotted roller compresses each sequential row of loaded 
sockets on the burn-in board as the index tray is shifted by the motor 
from its first position to its second position in one continuous motion. 
Each row of electronic circuit packages is caught in the slots on the 
roller and carried along as the roller rotates until the row of electronic 
circuit package fall off the roller. The wiper catches the row of 
electronic circuit packages as they fall from the slots on the roller and 
directs the electronic circuit packages to the chute. Each of the 
electronic circuit packages in the row slides into one of the aligned 
channels on the chute as illustrated by the electronic circuit package 
labeled 42D. After sliding down the channel, the package is received in 
the carrier tube that is inserted in each channel as illustrated by the 
electronic circuit package labeled 42E. Subsequent rows of the electronic 
circuit packages follow a similar path and are placed in the carrier tubes 
in sequential end-to-end relationship. The carrier tubes are easily 
replaced with empty carrier tubes when filled. If any of the electronic 
circuit packages do not fall on the wiper, the catch tray serves as a 
backup to capture the packages which slide down the catch tray and are 
deposited on lip 222 until manually retrieved by an operator. However, it 
is anticipated that the wiper will effectively capture substantially all 
the electronic circuit packages falling from the roller. In this manner 
the burn-in board is quickly and conveniently unloaded at rates up to 
10,000 electronic circuit packages hour. Once the index plate reaches its 
second position and contacts the rear limit switch it may be manually 
returned to its first position and the unloaded burn-in board removed and 
replaced by a new burn-in board requiring unloading. 
Due to the size, shape and thickness of the printed circuit boards used in 
most burn-in boards, the burn-in boards exhibit a large degree of 
flexibility. Therefore, the printed circuit board on which the sockets are 
mounted may give or bow when the sockets mounted thereon are placed in 
compressive rolling contact with the roller. If the bowing is sufficiently 
large, some or all of the sockets will not be compressed and consequently 
the electronic circuit packages contained therein will not be released. To 
counteract this undesirable feature and to support the burn-in board while 
the electronic circuit packages are being unloaded, pressure roller 224 is 
rotatively mounted on the right and left uprights 70 and 72 above the 
index plate and transversely to the longitudinal axis of the housing. The 
pressure roller extends horizontally and is positioned directly over the 
slotted roller. The center to center distance between the axis of rotation 
of the slotted roller and the pressure roller is adjusted so that the 
pressure roller is placed in rolling contact with the uppermost surface of 
the burn-in board (i.e. the surface without the sockets when inverted and 
mounted in the index plate). However, the pressure roller does not exert 
any independent force on the burn-in board but rotates in counterclockwise 
direction 226 (as seen from the right side of the apparatus) as the index 
plate and the burn-in board move to the second position. The pressure 
roller does exert a counter force to the compressive force exerted by the 
slotted roller on the sockets as the electronic circuit packages are being 
unloaded. The pressure roller may be constructed of a rigid material such 
as metal. Alternatively, the pressure roller or its outer layer may be 
constructed of a resilient or pliable material such as rubber. 
In the preferred embodiment of the invention the pressure roller is 
constructed of a conductive rigid material and pad 228 (also shown in FIG. 
1) is interposed between pressure roller 224 and the burn-in board. Pad 
228 includes cushion layer 230 which is constructed of resilient material 
such as rubber and placed face down in contact with the leads (not shown) 
of the sockets extending through the burn-in board. The pad also includes 
rigid layer 232, which may comprise a metal plate, bonded to the cushion 
layer and placed uppermost and in rolling contact with the pressure 
roller. The pad does not reduce the effectiveness of the pressure roller. 
However, it acts to protect the leads of the sockets or any other 
components which may be damaged while the electronic circuit packages are 
being unloaded. 
From the foregoing it will be seen that this invention is one well adapted 
to obtain all of the ends, features and advantages hereinabove set forth. 
together with other advantages that are obvious and that are inherent to 
the apparatus and method. It will also be understood that certain features 
and subcombinations are of utility and may be employed without reference 
to other features and subcombinations. This is contemplated by and is 
within the scope of the claims. Although the invention has been disclosed 
above with regard to particular and preferred embodiments, these are 
advanced for illustrative purposes only and are not intended to limit the 
scope of this invention. For instance, it is possible to adapt the 
channels of the chute to directly receive and store the electronic circuit 
packages from the burn-in board in end to end relation and to omit the 
carrier tubes. Further, it is possible to place the sockets of the burn-in 
board in compressive rolling contact with a roller while in an upright 
position. In such an embodiment it would be necessary to replace the force 
of gravity with a mechanism for extracting the electronic circuit package 
from the sockets as the sockets are compressed by the roller. For 
instance, a rod 301 having an internal vacuum may be inserted into the 
sockets to pick up the electronic circuit packages and lift them out of 
the sockets as illustrated in FIG. 12. Alternatively, a vacuum may be used 
to suck the electronic circuit package out of the sockets without 
contacting the packages directly. In yet another alternative, the sockets 
may be provided with an aperture beneath the electronic circuit packages 
and a mechanism provided to insert a plunger 300 upwardly through the 
aperture into contact with the underside of the electronic circuit package 
to push it upwardly out of the socket as illustrated in FIG. 13. A burst 
of compressed air could be substituted for the plunger to force the 
electronic circuit package out of the socket. These variations remain 
within the invention as claimed below. Although not shown, the apparatus 
of this invention may be adapted to unload an electronic circuit package 
from a single socket, whether mounted on a burn-in board or not, as well 
as a single row or column of sockets.