35 Questions for SH-5300

Yes, that is true!  Let’s talk about leaded packages to keep things simple.  In general, for leaded packages, strip testing is done before the leads are formed.  This means that there is a large lead surface for contacting which obviously makes it easier to land the contactor’s pogo pins onto the lead in a good position.  Because of the large surface available to the contactor, it’s easy to make good contact and this results in a very high O/S yield.  One of the leading subcons reported at the Known Good Die Conference in October, 2009 that they had seen an average increase in first pass yields of 3.2% as compared to their test cells using singulated handlers.  In singulated testing, the leads are already formed and the part is inserted into a test socket.  This is where damage can occur and where O/S yields can suffer because of poor contacting.   Yield increases of 2% – 5% are common in strip test operations and that obviously translates into huge cost savings.

Fifteen (15) years ago, when strip test was just getting started, that was one of the primary worries.  It has now been proven in production that the trim and form operation is an insignificant source of part damage.  In fact, Amkor, in a paper presented at the Known Good Die Conference in October, 2009, reported that they had tested over 1 Billion parts without a single failure attributed to the trim and form operation.  In general, the quality level of a strip test operation will exceed that of a singulated test operation.

In fact, just the opposite is true.  More leads are damaged in singulated test due to the operation of inserting parts into a test socket. 

With strip test, the testing is done with leads un-formed and no side loading occurs since the strips are not mechanically précised into position.  The parts go thru the trim and form operation after test.  The result is that leads never get jammed into test sockets during test.  This eliminates the #1 cause of lead damage on leaded parts.  Some companies that have seen no lead damage when using strip test have eliminated 100% lead inspection altogether.

Lead inspection, if done at all, is almost always done on a sampling basis as opposed to 100% inspection that is generally required for singulated test operations.

No!  If we compare change kits for gravity, turret and strip test, there are two important facts to point out.  First, kits for gravity and turret handlers are almost always much more expensive than for a strip handler…anywhere from 2X to 4X more expensive in many cases.  Second, the time to change a kit on a gravity or turret handler can take many hours.  This is not so much due to the number of parts necessary to change as it is to the fact that there are so many subjective adjustments that must be made.  And those adjustments must be made by a highly skilled technician.

With the MCT strip handler, changing the handler from operating with an SOIC strip of a certain size to a TSSOP strip (of a different size), for example, is a simple matter.  In general, it would take about 15-20 minutes for a technician to convert the SH-5300 handler from one type of strip to another.   The reason is that the MCT kits have been designed for quick change.  This means there are three (3) things unique to the MCT change kits.   First, all parts are keyed or indexed so that they can only be put in one way…the right way.  It’s impossible to put a change kit part into the handler incorrectly.  Second, all fasteners are captive.  This means that bolts and screws do not fall out onto the floor and get lost when parts are being changed.  They stay captive with the part so they cannot be lost.  Third, and most importantly, there are absolutely no subjective adjustments with the MCT strip handlers.   You can literally change over from one strip size to another strip size in less than 20 minutes.  The MCT strip handler is the closest thing there is to a “universal” test handler when compared to gravity, turret or PnP handlers.

If the SOIC strip and the TSSOP strip (for example) have the same outside dimensions, then changeover is even easier.  Only a few parts would need to be change, resulting in less cost and faster changeover time.  Contact MCT for details about these so-called “mini change kits.”

Heat transfer, also known as heat flow, heat exchange or transfer of thermal energy is the movement of heat from one place to another.  When an object is at a different temperature from its surroundings, heat transfer occurs so that the body and the surroundings reach the same temperature (thermal equilibrium).  Strip handlers use either conduction or convection as the heat transfer mechanism.

Convection involves the transfer of heat between an object and its environment due to fluid (air) motion.  MCT’s competition uses convection heat transfer mechanisms in their handlers to thermally condition the strips under test.  In order to implement a convection-based approach, it is necessary to have a pre-soak chamber that holds multiple strips and then forces heated (or cooled) air around then to bring them to the correct temperature.

Having this extra pre-soak chamber adds additional cost.  In addition, since convection depends upon air as the transport mechanism for the heat, the time required to bring the strips to the correct temperature can be very long; sometimes as long as 120 seconds depending upon the package to be tested.  This is the reason that a pre-soak chamber is required.  If there were no pre-soak chamber, the strip handler would be severely soak limited since it would need to wait for long periods of time (to bring the strip(s) to temperature before testing could begin.

MCT solved the problems associated with convection heat transfer by implementing a system based on conduction.  Conduction involves the transfer of energy between objects that are in physical contact with each other.  As a result, conduction is much faster than convection.  In our laboratory tests, using conduction, it is possible to bring a strip from ambient to +125 Deg C in approximately 7-8 seconds!  Depending upon the thickness of the part to be tested, this could take up to 120 seconds in a typical convection system.

The SH-5300 has three (3) pre-soak stations (based on conduction) prior to the test chuck so that each strip can be soaked for at least 3X the amount of time that a strip is on the test chuck for testing.  This guarantees that sufficient soak time is always available and as a result, the SH-5300 is never soak limited.   And of course, no pre-soak chamber is needed or even offered as an option!

Yes and no.   The temperature spec for the standard SH-5300 Strip Test Handler is +/- 2 Deg C.  However, for applications requiring better temperature accuracy, MCT offers the HATS (High Accuracy Thermal System) option.  HATS consists of a special test chuck with multiple heater zones and real-time microprocessor control of each zone.  This enables HATS to hold the temperature of the test chuck very accurately; to better than +/- 0.1 Deg C in most cases.  However, that does not mean that the DUT’s can be tested at such an accurate temperature.  See Question #9 for more information on this topic.

Not exactly.  While HATS can control the temperature of the test chuck very accurately (as good as +/- 0.1 Deg C), it takes a bit more to control the temperature of the DUT more precisely.  MCT’s thermal management system for the SH-5300 consists of HATS plus TIM (Thermal Interface Manifold) plus TCCF (Thermal Contactor Conditioning Frame).   TIM provides heated air to the contactor and TCCF provides a heated frame for the contactor. 

These two optional sub-systems, TIM and TCCF, combine to make the temperature of the pogo pins in the contactor as close as possible to the set temperature for the test (and the same temperature as the test chuck).  

The whole idea is to make the thermal differential between the DUT’s and the contactor as small as possible so that heat flow between these two parts is an absolute minimum during contacting.  MCT has been selling the combination of HATS, TIM and TCCF for more than three (3) years and has extensive experience on how to achieve superior temperature accuracy and stability during strip testing.  It is certainly possible to achieve overall temperature accuracy, at the DUT, of +/- 1.0 Deg C and perhaps even better, depending upon the type of part being tested and the test temperature.  

Please contact MCT for more information on our thermal management system if you have packages that must be tested at very accurate temperature.

Yes it can.   Every SH-5300 is tri-temp ready, meaning that it can test parts from -55 Deg C to +160 Deg C.  The machine can run ambient and hot out of the box.  If you need to run cold as well, all you need to do is purchase MCT’s optional chiller.  No changes are required to the handler.  All you do is connect two (2) hoses from the chiller to the handler and it is ready to run Cold.

Yes, the SH-5300 can test leadless packages at ambient, hot and cold also.  However, the requirement for this is that the parts must be electrically isolated but still held in place in the lead frame.  Since most leadless packages now are block molded, there are only a couple of ways to achieve the electrical isolation of the parts;

1. Via the use of the so-called ½ saw process. In this process, the block-molded strip undergoes a sawing operation where only the lead frame (the metal portion) is cut.  Cutting the lead frame between adjacent parts electrically isolates them.   The strip is still held intact via the mold compound that has not been cut.  MCT has extensive experience with this process and the interested reader should contact MCT for additional information.
2. Isolation by design. In this case, the individual parts are electrically isolated by the very design of the strip.  This method is becoming increasingly more popular because of the ease of testing these types of strips with a strip handler.  Even though the process may cost more than a conventional lead frame assembly process, the savings in final test may more than make up for the added assembly cost.

No.  Other strip test handlers are soak limited and this is because they use a convection heat transfer mechanism to heat the strips.  Since convection uses heated (or cooled) air to heat (or cool) the strips, it can take a considerable amount of time to bring the strips to the correct temperature.

 In order to avoid being soak limited, handlers that use convection heat transfer generally offer some type of chamber to pre-heat or pre-cool the strips before they enter the handler’s test section. 

The heat transfer mechanism in the SH-5300 does not use convection.  It uses a patented conduction heat transfer mechanism where the strips are actually contacted by heated (or cooled) surfaces in order to bring the strips to the correct temperature.   The advantage of conduction heat transfer is that it allows the strips to come to the correct temperature about 8X to 20X faster than a convection system.  The SH-5300 uses three (3) soak stations that are internal to the handler.  This guarantees that each strip is subjected to hot or cold thermal conditioning for at least 3X longer than the total test time for one strip plus the index times.  The result is that the SH-5300 is never soak limited, even for the fastest test times. 

The conduction heat transfer system works so well that MCT does not even offer a traditional pre-soak chamber, thereby saving cost and floor space over systems using convection.

No. LN2 is not used in the SH-5300.  MCT achieves its superior thermal performance, and frost-free operation, with the use of a closed cycle chiller.   The SH-5300, with the optional chiller can operate from -55 Deg C to +160 Dec C. 

This is one of the trickiest things to resolve when comparing strip test handlers from different manufacturers.  The reason is because different manufacturers define index time in different ways. 

Generally speaking, the calculation of the true index time involves all of the following items;

1. Time to move a fully tested strip (strip #1) off of the test chuck plus the time to move the next un-tested strip (strip #2) onto the test chuck.
2. Time to do the alignment of the 2^nd strip once it reaches the test chuck. This involves using the uplook and downlook cameras to find the fiducials on the contactor and on the strip, then doing the required calculations and automatic adjustment of the stage to align the strip properly.
3. Time to read the 2DID code on the 2^nd strip so that the strip map can be constructed or read.

MCT includes all of the three (3) items above in the calculation of the total index time for the SH-5300.  Another way to describe this is that MCT’s total index time is the total time from the end of test on strip #1 to the start of test on strip #2. 

This definition leaves nothing out and is an accurate measure of the total index time.   Unfortunately, other manufacturers use a different definition and may report only the strip transport time as the index time, thereby failing to account for the alignment time and the time to read the 2DID code.  The SH-5300 total index time is 4.25 seconds.

The intra-strip index time refers to the time to move from one contactor location to the next contactor location on the strip.  Let’s say that the strip being tested has 200 total parts, but due to tester limitations, only 10 parts can be tested in one plunge.  That means that a total of 20 plunges (or touchdowns) are required to test all of the parts on the strip.  The time for each plunge is 350ms in the SH-5300.

True.  The reason is actually quite simple.  Strip test provides a much higher first pass yield which helps to eliminate the need for re-test.  In addition, since a strip handler handles only strips and not individual packages, a strip handler does not have anywhere near the jam rate of a gravity or turret handler.  Jams obviously take time to clear and that seriously reduces the amount of time the tester is available for testing.   The combination of superior first pass yields and tremendously better jam performance allows a strip handler to provide about 15% (on average) better tester utilization than a gravity or turret test cell.  This obviously translates into large cost savings.   As a broad guideline, a typical gravity handler may have an OEE (Operating Equipment Efficiency) of about 75%-80%.  A typical turret handler will be in the range of 65%-70%.   The MCT SH-5300 will have an OEE of 90%-95% due simply to the fact that it is much less prone to jams than the singulated handlers.

The easy answer is almost every tester!  MCT has been doing strip test since 1999 and we now have over 35 tester interfaces in our tester interface library.  We have interfaced to every major tester brand and model.  In the event that we do not have an interface for your particular model of tester, it takes us about 2 weeks to develop an interface.  Most interfaces now use a GP-IB interface protocol.  MCT supplies new tester interfaces at no cost to the customer in most cases.

Great question and one that is often mis-understood by people not completely familiar with strip testing.  The maximum UPH for a strip test cell is really a function of the tester resources available and not a function of the handler per se. 

The handler’s only limitation is that it is designed to handle one strip at a time, so the theoretical maximum number of parts that can be tested in parallel is equal to the total number of parts on the strip, assuming that the tester resources are available.

The maximum UPH that can be achieved is therefore determined by the total number of parts on the strip; by the number of parts tested in parallel; and by the test time.  MCT provides a UPH calculator and can easily estimate the expected UPH as long as we know the degree of parallelism that the tester can support, the test time for the device and the strip layout (number of rows and columns in the strip).

Yes, that’s exactly what it means. The theoretical maximum UPH of the handler is limited by only three (3) things; the total number of parts on the strip, the test time, and lastly, the number of parts that can be tested in parallel. This last item is solely a function of the tester resources available.

The answer depends on a couple of factors, the most important being the type of part you are going to be testing and the tester resources available for testing them.

For example, with a digital device like a Serial EE or a standard logic part, MCT has tested as many as 384 parts in parallel. This was possible using our dual strip version of the SH-5000, which can accommodate two (2) strips on the test chuck at one time (the standard SH-5300 accommodates only one (1) strip at a time). With each strip of SO8’s holding 192 parts, this results in a 384 total parts.  It’s not uncommon for customers who run lots of digital parts to contact an entire strip in one touchdown.

For analog or mixed signal parts, the story is slightly different.  Here again, the determining factor in the degree of parallelism is the amount of tester resources available.  For most analog or mixed signal applications, tester resources will limit the degree of parallelism to something between 8-up and 32-up.

For Power Mosfets, parallelism of 4-up in a single insertion is now available with a special tester offered by one of MCT’s customers and in conjunction with an MCT Strip Handler or Film Frame Handler (depending upon the type of package).   Since most Mosfet testing today is done at 1-up, this represents a large increase in parallelism and hence capacity for a single test cell.

For RF parts, it’s yet another story.  Because of tester resources and the limitations of testing RF devices in close proximity to one another, high parallelism may be something between 2-up and possibly 8-up.

MCT has experience with RF and one of the advantages of a strip handler over a singlulated test handler is that the strip handler can accommodate a very large load board, making it much easier to route all of the signal “plumbing” necessary to accommodate multiple RF parts during test.

Ideally, you would like to select a degree of parallelism that optimizes the number of touchdowns required to test the entire strip.  For example, in the 13×50 case, a good choice for a contactor would be something that had multiples of 13 in one of the contactor axis.  If the tester resources were available, you might choose a contactor that was laid out as a 2×13, which would enable you to contact 26 parts at one time and make a total of 25 touchdowns to cover the entire strip.  Other good choices, depending upon the tester resources available would be 3×13, 4×13, etc., etc.

An important point to remember is that the SH-5300 has the ability to handle different degrees of parallelism than may be optimal for the strip being tested.  For example, in the example above, you might have the tester resources to allow 20 parts to be tested in one touchdown.  The software in the SH-5300 will accommodate this number of parts and adjust the touchdown pattern accordingly so that all parts are contacted using the minimum number of touchdowns.

Yes, it sure can, but we need a bit of explanation to understand the limitations.  The SH-5300 was designed primarily as a strip test handler, meaning that it was intended to handle leaded packages like SOIC, MSOP, TSSOP, QFP, TQFP, PDIP, etc, etc.  As you may know, the key requirement of being able to test packages in strip form is that the individual parts must be electrically isolated from one another but still held in place in their lead frame.  This is a straightforward and well known process for the traditional leaded packages mentioned above.   The process is done using a standard trim and form machine but with a special die set that does the lead isolation cut.  This process is often referred to as “punch isolation.”

It should be mentioned here that QFN and DFN packages that are pocket molded can also be easily strip tested using the SH-5300.  They are treated like other leaded packages in that they would go thru a lead isolation process via a punch process.

Leadless packages like QFN and DFN (that are block molded and in a lead frame format) can still be tested on the SH-5300 as long as there is a method for electrically isolating the leads.  This can be accomplished by one of several methods that are now available in the industry;

• A ½ saw process where the strip is put through a sawing process that cuts only lead frame but leaves the mold compound intact, therefore electrically isolating the leads.
• A chemical etch process which again etches away the metal in the lead frame but leaves the mold compound intact.
• A laser isolation process which cuts the metal in the lead frame but leaves the mold compound intact.

Of these three methods, MCT’s experience is that the ½ saw process is the most common and usually the least expensive.  

One word of caution….the half saw process is viable as long as the overall thickness of the lead frame is large enough such that the remaining mold compound (after the metal lead frame is cut) is strong enough to keep the strip held together such that it can withstand the handling process.   As a matter of practicality, the thinnest ½ sawn strips that MCT handles today are on the order of 0.50mm (500 microns) thick.  Since the lead frame is typically 0.2mm (200 microns) thick, this leaves 0.30mm (300 microns) of mold compound to hold the strip together.  Our experience is that this is enough for the handling process.  To run a thinner strip in the SH-5300 would probably require some handling tests to check the ability of the strip to be strong enough to be reliably handled.

MCT has extensive experience with the ½ saw process and can advise you on some of the practical steps that are necessary to insure the structural integrity of the strip after the ½ saw cut.  Understanding these steps is especially important when testing strips that are very thin.

If this is the case, the solution lies with MCT’s FH-1200 Film Frame Handler.  With the FH-1200, the strip is mounted onto sticky tape on a standard 200mm or 300mm wafer ring.  The strip (while mounted on the wafer ring) is then run thru a saw where the individual parts are completely isolated from one another via the saw process.  We refer to this as a full saw process since the saw must cut entirely thru both the lead frame metal as well as the mold compound.  After the saw process, the strip is cleaned and dried.  The individual parts are now completely singulated but held in their appropriate place by the sticky tape.   This entire process is referred to as testing on film frame.

The FH-1200 can accommodate both 200mm and 300mm wafer rings.  The handler can then present these rings to the test chuck so that the parts can be tested in parallel, much the same as with the SH-5300.  As of this date, film frame testing of QFN’s is only available for testing at ambient temperature.

The Electronic Strip Map (ESM) is a software record of every part on a specific strip that contains the results from the electrical tests.   It can also contain a record of any assembly rejects if that information is available and can be loaded onto the strip map from assembly operations. 

The strip map is typically contained in a central map server that is connected to the test handler via Ethernet.   It can also reside in the test handler’s on-board computer, as is the case with the SH-5300.

The Electronic Strip Map is used to keep a record for every part on the strip as to its tested bin code.  The information is used later in the process flow to enable the proper marking of the parts by a laser marker.

In strip testing, it is absolutely required to be able to identify each and every strip with its own unique identifier.  This information is needed to associate the physical strip with the electronic strip map that is generated after the electrical testing is completed.   Think of the 2DID code as a “unique license tag” for each strip. 

The 2DID code is actually a special type of bar code that has information contained in a 2-dimensional grid as opposed to a standard bar code, which is 1-dimensional.  The code is based on the Data Matrix Code and has the ability to house a large amount of information in a very small area.  Typical 2DID codes are usually about a ¼” square and may contain 25-30 characters of information.  A unique feature of the 2DID Data Matrix code is that it has an error-correction feature built into the algorithm.  It can also have up to 25% of the area damaged and still be readable.  One of the most important features is that if the code can be read, then the answer (i.e. the data) will be read correctly in spite of any damage to the code.  These features make it ideal to use in a manufacturing environment.

It is written with a laser marker during the assembly operation or just prior to test in the test operation. 

If there is assembly reject information that has been captured during assembly, then the 2DID marking would need to be done in assembly so that assembly information can be loaded into the electronic strip map.  As a side note, the 2DID code is typically written onto each strip in two (2) places for redundancy in case one of the locations gets damaged so badly that it cannot be read.

MCT builds a high-speed laser marker called the MH-3000, which is ideally suited for strip test applications.  It has the ability to write the 2DID codes plus the final package mark.

The SH-5300 supports two (2) types of basic process flows.  Each has its own advantages and dis-advantages.  The two flows have to do with whether or not the parts receive their final package mark before test (typically as part of the assembly operation) or after test. Questions #30 and #31 below explain each of these flows in more detail.

The “mark before test” flow refers to the fact that the strips to be tested are marked with the final package mark prior to being tested.  Typically, this is done as part of the assembly operation.  Marking the parts in assembly can minimize or even eliminate the need for a standalone laser marker in the final test operation.  The dis-advantage is that this flow requires that all parts be marked “good” before they are tested.  Obviously, this requires very good process controls to insure that “bad or reject” parts do not get passed as being good.

Until just recently, this flow required that the strips be sent to a standalone laser marker after being tested.  The laser marker would read the 2DID code marked on the strip and then retrieve the associated strip map from the map server.  The strip map contains the information from the testing and keeps a record of which parts failed the electrical tests.  The laser marker would then mark the reject or bad parts with a distinctive mark (like an “X”) so that the reject part could be easily sorted out by the downstream machine that moves the singulated parts to tape-and-reel or Jedec trays.

The SH-5300 can also be equipped with an optional built-in Reject Mark Laser (RML).  The RML option is used with the process flow just mentioned to mark rejects immediately after test.

The “mark after test” flow refers to the fact that the strips to be tested are completely un-marked prior to test and final package mark is applied only to tested good parts after test.  This flow is sometimes preferred because it avoids the issue of marking parts as being good before they are actually tested.  In this flow, the un-marked strips are tested in the SH-5300 and the test results stored in the electronic strip map (exactly in the same way as the “mark before test” flow).  After test, the strips are then sent to a standalone laser marker for marking of only the good parts with their appropriate final package mark.

Reject or bad parts are typically not marked at all, or are marked with a distinctive mark like an “X” that can be easily identified by an end-of-line sorting machine.

Having a built-in Reject Mark Laser (RML) is a very useful option when the overall process flow uses the so-called “mark before test” flow.  Having the RML built into the test handler eliminates the need for a separate standalone laser marker to mark reject parts after test. 

Immediately after the parts are tested, the test chuck in the SH-5300 is moved so that it is positioned under the RML.  The RML then uses the electronic strip map information that is still resident in the handler to mark only those parts that are rejects.

Yes, but only by a very small amount.  On typical strips, the test yield of good parts is usually very high, meaning that only a few parts on each strip are actually test rejects.  The time required by the RML to mark a reject part with an “X” is only about 30ms.  So even if 10 parts had to be marked as rejects, it would require only about 1/3 of a second to perform this operation.  That amount of time would have only a negligible effect on the overall handler throughput.

The easiest way is to use MCT’s proprietary SmartTrak™ system for Electronic Strip Map Management.  SmartTrak™ is a production proven system for managing the strip maps.  It includes a rule-based system to guarantee that strips are processed in the correct order and at the correct time.  SmartTrak™ also includes a full set of applications programs that allow the user to monitor the strip test cell from his own desk and do various levels of analysis on the data from the strip cell.

Yes, in many cases.  MCT has developed special test chucks to enable the testing of pressure sensors, relative humidity sensors, temperature sensors and light sensors.

We’d be happy to discuss your special needs to see if the SH-5300 might be a good solution.