Are Your Product Test Engineers Overwhelmed & Frustrated?
‘Overwhelmed’ and ‘frustrated’ are words often used by our prospective customers when relating their experiences of life before FloorVision and yieldHUB. A colleague recently mentioned that a prospective customer said they were “overwhelmed by the constant need to convert STDF to XML”, for example. Another described how they were “frustrated” by the limitations imposed by their previous desktop yield analysis solution, especially being required to start from scratch every time a new version of a report (e.g. Gage R&R) has to be generated.
Overwhelmed and frustrated are powerful words in both meaning and sound. The Collins Dictionary definition of overwhelm is ‘to overpower the thoughts, emotions and senses’ or ‘to weigh or rest upon overpoweringly’. Frustrate is defined as ‘to hinder or prevent (the efforts, plans or desires)’ or ‘to upset, agitate or tire’.
Consequences
Is it possible that engineers are overwhelmed and frustrated in the literal sense of these words? Are they correct in the use of these words to describe the consequences of daily use of inadequate systems to analyse their yield data? If so, what does this actually mean and what are the consequences for them and the organisations they work for?
I haven’t come across any survey results on the affects on engineers when their yield analysis tool is inadequate. It occurs to me as I write that engineers would be known more for their technical analytical ability more so than for their analysis of their behaviour and emotions. However, I suspect stress would eventually emerge, if not immediately, then certainly over time. The most commonly cited result of any workplace issues that are not dealt with would appear to be stress.
Stress can lead to problems for individuals, emotionally in terms of anxiety and irritability, for example, or in physical terms such as headaches and raised blood pressure. Stress can also affect a person’s intellectual performance, causing lack of concentration and difficulties with thought processes, for instance, and their behaviour. The outcome of these difficulties obviously have major consequences for organisations. High absenteeism and employee turnover, as well as poor performance, low morale and lack of motivation, to mention but a few. The bottom line is, of course, profits take a nose dive.
Freedom
Allow your engineers the freedom to do what they are trained to do. Free up their time to be innovative and creative and improve the processes already in place. Allow them the tools that will increase productivity and improve profits. Allow them to be overjoyed, not overwhelmed, calm and not frustrated!
- Colette O’Malley
STDF Datalog Analysis – Taking “Rescreen” into Account
In any good enterprise semiconductor Yield Management System, it is necessary to report the overall Yield of a lot based on consolidating the datalogs which were used to test the lot. The “Run Type”, parsed and recorded in yieldHUB for each datalog, is used in this calculation. This Yield figure is then the standard datalog-based Yield used throughout yieldHUB for that final test lotid. The process in yieldHUB is completely automated and the user has nothing to do once the consolidation flag is switched on within the yieldHUB database for a subcon.
For this all the work properly, it is necessary to mark each datalog so a system like yieldHUB can automatically determine the Run Type. This is good data management practice and is under the control of the test development engineer.
The parametric and bin information should also be consolidated in a similar manner. For example, the charts and statistics for a test should reflect one value per tested unit and this can be done through automated consolidation by yieldHUB.
The first chart here is before any consolidation is done for the test shown. The second chart is after consolidation is done and you can see that there are fewer fails for the test after consolidation:
The default automated method of consolidation within the yieldHUB processing engine is as follows:
- Ignore all QA and Correlation Run Types
- Treat any undefined Run Types as Raw (equivalent to “First Pass”)
- Apply the following algorithm to Raw and Re-screen Run Types:
- Ignore all rejects from Raw
- Ignore all rejects from any re-screen datalog up to the last re-screen datalog.
The result of the above is that the units that are left are good units from [all Raw datalogs + all re-screen datalogs] and rejects from [the last re-screen datalog]. The yield, bin and parametric results for the overall lot are then compatible with this algorithm.
Dice with and without X/Y Co-ordinates
In consolidating lots with datalogs that have X/Y coordinates, yieldHUB will use the latest datalog per unit based on the Start_Date of the datalog files. Since X/Y co-ordinates are assumed fixed, consolidating data using this method can be said to be accurate.
In cases where X/Y co-ordinates are not available, as is the case with most Final Test processes, yieldHUB assumes that all rejects from the raw test process are re-tested and datalogged in the re-screen datalogs. So during consolidation, all reject data from raw testing datalogs are removed and replaced with the re-screen data.
Sources of Inaccuracies
The above consolidation system is prone to inaccuracies if the re-screen process is not consistently followed in the final test floor. For example, assume that the raw testing of 1000 units had 70% yield and during re-screen, only 100 units were re-screened. The consolidated datalog file will therefore only have 700 good units + 100 units from re-screen.
Another case is that re-screening was repeatedly done by putting back the rejects into the handler but the datalog file was not closed. The effect is that it would appear that the lot size will grow. In the example above, if the re-screen was done on the 300 units with yield of 50% and the rejects put back again in the handler with yield of 20%, the effect is that there would appear to be 450 units retested with yield = (150 + 60)/(300+150) = 46.67%. Then the consolidated file yield becomes: (700 + 210)/(700+450) = 910/1150 = 70.13%.
For consolidation of datalog files without X/Y co-ordinates or any method of identifying each unit (like ChipID), the accuracy of the consolidation quantities is highly dependent on the operator compliance to the re-screen procedures.
Customisation
Mfg Vision can customize the smart re-screen algorithm to take into account any variation in how testing is done by your company, once consistent procedures are followed. For example, your company could be re-screening only certain bins. In that case we would encode an algorithm which includes all good units are un-re-screened fails from each qualifying datalog.
The good thing is that whatever algorithm matches your test operations, it can be automated within yieldHUB. Of course that is only useful for those lots where the procedures are followed.
There will always be non-idealities in production testing, but this feature will allow you to also identify non-idealities so that the algorithms you expect are operating in production are being adhered to.
read moreIs Geography History in Yield Analytics?
MFG Vision is headquartered in Co. Limerick, Ireland. All of our Irish based personnel do not work out of there all of the time. Many of our colleagues are based in the Philippines, some in Taiwan. We have agents working on our behalf in the States, Israel, the UK, and mainland Europe. We have customers in all of these places too, most of them having facilities worldwide.
Does geography really matter anymore? There was a time when working with colleagues or customers in other countries caused projects to take longer to be completed or deadlines to be missed, due to different time zones or different public holidays, for example. If you were in western Europe, for example, and required information from a colleague in Asia, you generally had to wait until the next day before you had access to their reply. But the problem wasn’t only caused by differing time zones. It was added to by being confined to desk top computers and land line telephones. Though revolutionary in their time, these confined people to receiving information only when in the office.
The idea now of being confined to receiving emails at your desk, in the office, simply seems archaic. If there is a deadline looming or if an emergency of some sort arises, the chances are high that the appropriate person can be contacted by mobile phone and an email very easily received, even out of normal working hours, if necessary.
What the laptop and its like and the latest mobile phone technology have done for transmitting emails, yieldHUB has done for semiconductor yield analysis. Put simply: It makes life easier. I don’t have to download any data, I don’t have to send data to a colleague in the other side of the world and wait for them to wake up, I don’t have to spend my weekend worrying about an issue that was flagged on Friday evening. All the information I require is available instantly, at my fingertips, to follow, save, share and comment on. No matter where I am or what I am doing I can get the information I require. I can be in control.
Geography is no longer a consideration. It has been confined to the history books.
Colette O’Malley
MFG Vision Ltd