Error detection/correction and fault detection/recovery – Data processing system error or fault handling – Reliability and availability
Reexamination Certificate
1998-04-08
2001-01-23
Le, Dieu-Minh T. (Department: 2785)
Error detection/correction and fault detection/recovery
Data processing system error or fault handling
Reliability and availability
C714S718000
Reexamination Certificate
active
06178526
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to electronic test systems, and more particularly to testers for memory modules including SIMMs and DIMMs.
BACKGROUND OF THE INVENTION
Most personal computers (PCs) use DRAM memory chips mounted on small, removable memory modules. Originally produced as single-inline memory modules (SIMMs) with memory organized into sizes such as 256K×9 and 1M×9, more recent memory modules use wider I/O. Thus 4M×32 modules are commonplace today. Additional I/O is facilitated by using dual-inline memory modules (DIMMs), such as 168-pin modules.
Huge demand for memory modules has resulted in an extremely crowded and competitive industry that is very cost sensitive. Testing costs are significant, especially for higher-density modules that have more memory locations that must be tested. Specialized, high-speed electronic test equipment is expensive, and the greater number of memory cells on high-speed memory modules increases the time spent on the tester, increasing costs.
Handlers for integrated circuits (ICs) have been used for many years in the semiconductor industry. These handlers accept a stack of IC chips that are fed, one at a time, to the tester. Once tested, the IC is sorted into a “bin” another stack of IC chips that have either passed or failed the test. ICs from good bins are packaged for sale, while ICs from bad bins are thrown out. Bins can be set up for different types of failures (open circuit, short circuit, functional failures, out-of-spec parameters, etc.) and statistics kept for analysis by engineers.
More recently, handlers have been made for memory modules. U.S. Pat. No. 5,704,489 by Smith, describes in detail a “SIMM/DIMM Board Handler” such as those in use today.
FIG. 1
shows a SIMM handler connected to a high-speed electronic tester. Handler
10
is of the type described by Smith. Memory modules
18
to be tested are loaded into the top of handler
18
in the input stack. Memory modules
18
as shown have DRAM chips surface-mounted to both sides of the substrate, as is well-known in the art. These modules
18
drop down, one-by-one, into testing area. Module-under test MUT
20
is next to be tested. Arm
26
pushes MUT
20
laterally until it makes contact with contactor pins
16
that clamp down on “leadless” connector pads formed on the substrate of MUT
20
.
Pins
16
thus make electrical contact with the
168
leadless contact pads of memory-module MUT
20
. Contactor pins
16
are also connected to test head
14
, which makes connection to tester
12
. Tester
12
executes parametric and functional test programs that determine when MUT
20
falls within specified A.C. and D.C. parameters, and whether all memory bit locations can have both a zero and a one written and read back. Shorts between adjacent memory bits cable detected by performing tests using various test patterns, such as walking-ones, walking zeros, and checkerboard.
Tester
12
can cost from ten-thousand to millions of dollars. Cost can be reduced if a less-expensive tester replaces tester
12
. Since most memory modules are intended for installation on PCs, some manufacturers test memory modules simply by plugging them into SIMM or DIMM sockets on PC motherboards. A test program is then executed on the PC, testing the inserted module. Since PCs cost only about a thousand dollars, tester
12
and handler
10
of
FIG. 1
are replaced by a low-cost PC. Equipment costs are thus reduced by a factor of a hundred.
FIG. 2
shows a PC motherboard being used to manually test memory modules. Substrate
30
is a glass-epoxy motherboard having multiple layers of patterned conductor traces sandwiched between insulating layers, as is well-known in the art. Components
42
,
44
are mounted on the top side of substrate
30
, such as by wave-soldering. Components
42
,
44
include ICs such as a microprocessor, logic chips, buffers, and peripheral controllers. Components
42
,
44
may be directly mounted onto the top surface, or may have pins that are fitted into holes in the substrate. These pins are then soldered to the backside of substrate
30
. Sockets for expansion cards
46
are also mounted onto the top or component side of substrate
30
, while their pins are placed through holes in substrate
30
and soldered to the back side of substrate
30
. Some of components
42
,
44
may also be mounted in sockets.
Memory modules
36
are SIMM or DIMM modules that fit into SIMM/DIMM sockets
38
. SIMM/DIMM sockets
38
(hereinafter SIMM sockets
38
) have metal pins that fit through holes in substrate
30
. These pins are soldered to solder-side
34
of substrate
30
to rigidly attach SIMM sockets to the PC motherboard. Both electrical connection and mechanical support are provided by SIMM sockets
38
.
While using PC motherboards for testing memory modules greatly reduces equipment costs, labor costs are increased. Memory modules must be inserted and removed manually. Manual insertion and removal of memory modules is slow and labor-intensive. It also wears the leadless contact pads on the modules, which can give the appearance that the modules is used rather than new.
While it is desirable to use a SIMM/DIMM handler to insert and remove memory modules for test, expansion cards
46
and cables
48
can block access to SIMM socket
38
. Thus the crowded area around SIMM socket
38
on the PC motherboard prevents putting a handler in close proximity to the SIMM socket. A person must reach in with his hands and manually insert SIMM
20
into SIMM socket
38
.
Connecting a handler to SIMM socket
38
using a long cable is possible, since the long cable allows the handler to be farther away from the crowded PC motherboard. However, the long cable is not desirable since it adds significant loading to the PC's memory bus. This loading slows the memory operation down, resulting in test failures for good memory modules. Interference can also be inserted into the memory bus by the long cable.
What is desired is a low-cost test apparatus for testing memory modules. It is desired to reduce testing costs by eliminating the expensive electronic tester. It is desired to use a PC motherboard or other target-system board to test the memory modules. It is further desired to use a SIMM/DIMM handler to automatically insert and remove memory modules that are tested by a PC motherboard. It is desired to connect the handler to a PC motherboard without a long cable so that the loading on the PC's memory bus is minimized, allowing full-speed testing.
SUMMARY OF THE INVENTION
An automated test apparatus tests high-speed memory modules using a memory-module handler. A target-system motherboard has components including a microprocessor, memory, and expansion-bus connectors mounted on a component-side of the target-system motherboard. The memory includes memory modules inserted into memory-module sockets mounted on the component-side.
A handler adaptor board has adaptor pins protruding out a first side and has connector sockets mounted on a second side opposite the first side. At least one of the memory-module sockets has been removed. The adaptor pins connect to the target-system motherboard on a solder-side of the target-system motherboard immediately opposite a location where the at least one memory-module sockets have been removed.
The connector sockets on the handler adaptor board connect to the memory-module handler. They connect signals from a memory module under test in the memory-module handler to a memory bus on the target-system motherboard. Thus the memory module under test in the memory-module handler is electrically connected to the target-system motherboard.
In further aspects of the invention a handler controller card is inserted into one of the expansion-bus connectors. The handler controller card communicates with the memory-module handler when the memory-module under test in the memory-module handler is tested by the target-system motherboard. Thus the memory-module handler is controlled by the target-system motherboard.
In still further aspects the
Chou Benjamin E.
Le Ngoc
Nguyen Thang
Auvinen Stuart T.
Kingston Technology Company
Le Dieu-Minh T.
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