TA的首页翻译练习 1 Electrical Test Confidence
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我会将我的翻译放在上面,请大家指正. 所翻译的文章都是实际工作中常见问题.
Electrical Test Confidence
Every new test engineer eventually finds out that absolute certainty of test results can never be guaranteed, even if the most advanced automated test equipment (ATE) are involved. As such, there will always be instances wherein retest of units is necessitated, consuming valuable test capacity and increasing test cycle time without additional output.
Electrical test confidence, simply put, is a measure of how consistently an ATE system delivers the correct electrical test results. A test system with excellent test confidence makes retest unnecessary, saving precious test resources. Test confidence is therefore an indirect indicator of how efficient and productive a test process is.
If someone will collect all the test rejects after the first-pass screening of a lot and retest these, there is reasonable likelihood that some of these initially failing units will pass their second test. Since genuine failures can not be resurrected with retesting, the only explanation for their passing the second test is that they were never really electrically bad when they were first tested. Something, somehow, made them fail the first test.
An electrically good unit that fails electrical testing for whatever reason (and can therefore pass electrical retesting under more proper conditions) is often referred to as an 'invalid' reject or failure. One's test confidence in an ATE system may be measured in terms of the number of invalid failures encountered from the system.
Invalid failures occur due to a multitude of reasons, which include but are not limited to: 1) improper contact between DUT leads and the contactor; 2) poor design and fabrication of test hardware; 3) improper test equipment set-up; 4) oxidation and contamination of metal surfaces used for electrical connection in any part of the system; 5) condensation or excessive moisture build-up anywhere within the system; 6) tester/instrumentation repeatability and reproducibility. The performance variability of a marginally good device can also result in invalid failures.
Of the aforementioned causes of invalid rejections, improper electrical contact between the DUT and the contactor constitute a major slice of the pie for most companies. Improper contact between the DUT and the contactor can further be broken down into the following causes: 1) misalignment between the contactors and the DUT leads; 2) contactor wear-out or mechanical degradation; 3) oxidation/corrosion of any of the contactors or DUT leads; 4) moisture build-up or contamination on the contactors or DUT leads.
The fact that bulk of invalid failures are caused by contactor problems has led many companies to equate electrical test confidence to the confidence in making good electrical contact between the contactor and the DUT. After all, most of the other factors that contribute to invalid rejection can be corrected prior to the production release of the test process. Ways of achieving this include: 1) excellent test/software design and debugging; 2) proper test guardbanding; 3) use of good test equipment; 4) use of reliable boards and small hardware; 5) use of a well-designed test floor; and 6) a sound management system.
Based on the premise that electrical test confidence depends solely on the ability to achieve good electrical connection, 'test confidence' may then be defined as the probability that good connection will be achieved every time a DUT is tested. Thus, a test confidence of 90% means that for every 100 devices tested, 10 of these devices will encounter a contact problem that will prevent them from being tested properly.
If such a system tests 1000 devices, with 90% of them (or 900 units) being electrically good, only 810 units will pass the test. Ninety (90) of the 900 good units will experience contact issues during testing, becoming invalid failures. Subjecting these 90 invalid failures to retest will fail to recover all of them, since again, 10% of them (9 units) will become invalid failures.
Several retest cycles will eventually recover all the parts that have been invalidly rejected by the initial rounds of electrical testing, since all of them are good anyway. Such a process for recovering invalid rejects, however, is inefficient and not cost-effective. The value of recovering invalid failures through retesting is, therefore, determined by the system's test confidence as well.
The resulting first pass yield, Y1, is the product of the real or actual yield of the lot (denoted here as 'Y') multiplied by the test confidence of the ATE system (denoted here by 'C'), or Y1 = Y x C. Thus, if a test engineer knows the test confidence of a system, he can estimate the actual yield of the lot through the equation Y = Y1 / C.
If the engineer decides to recover the invalid failures, he'll have to retest all the fall-outs from the first test (denoted here by 'R2'). The retest quantity R2 is equal to the initial quantity (Q) multiplied by the first pass rejection rate, (1-Y1). Thus, R2 = Q (1-Y1).
The resulting yield of the retest (denoted here as 'Y2') is equal to the actual yield of the retest multiplied by C. The actual yield of the retest (denoted here as 'YY') equals the number of invalid failures Rinvalid divided by the retest quantity R2. Thus, YY = Rinvalid/R2 and Y2 = (Rinvalid/R2) x C.
The number of invalid failures Rinvalid is equal to the initial test quantity Q multiplied by the difference between the actual yield of the lot Y and first pass yield of the lot Y1, or Rinvalid = Q x (Y-Y1). But Y = Y1/C, so Rinvalid = Q x (Y1/C - Y1).
Thus, Y2 = {[Q(Y1/C-Y1)] / [Q (1-Y1)]} x C = [(Y1/C-Y1)/(1-Y1)] x C.
Simplifying, Y2 = (Y1(1-C))/(1-Y1), where Y2 is the expected yield of the retest based on the first pass yield Y1 and the test confidence C.
This equation can also be used by an engineer to compute for the test confidence exhibited by his test system, given first pass and retest yield data: 1-C = Y2(1-Y1)/Y1, or
C = 1 - [Y2(1-Y1) / Y1]
where C = confidence of your test system, Y1 is the first pass yield, and Y2 is the yield when the first pass rejects are retested.
According to Christopher Jones, author of the article "Analyze test Confidence to Enhance Throughput" upon which this article was based, their experience in testing millions of RF IC's every week has taught them the following:
1) never run a test if the test confidence is less than 85%;
2) retest of the rejects is not necessary if the test confidence exceeds 95%; and
3) retest of the rejects is recommended if the test confidence is between 85%-95%.
Of course, the above guidelines may not be applicable to every company, since different device groups and package types are subject to different economic factors, as well as exhibit different sensitivities to contactor degradation. It is the task, therefore, of a Test Manager to determine for his company how they can best apply the concept of test confidence management in improving their bottom lines.
Given the very competitive atmosphere of the IC testing industry today, every Test Manager must know when to do a retest, when it is not economical to do so, and when a test system should not be used at all. Being able to distinguish these situations from each other based on test confidence data and reacting to each of them appropriately is an important aspect of test engineering management.
我的翻译：
电测试可信度
每个年轻的测试工程师 最后都会发现 测试结果的绝对正确性并不能保证,即使
使用高短的自动化测试设备（ATE）.因为如此,Unit的反复测试成为必须,并总会出现。
反复测试不产生额外价值,不仅浪费测试能力,而且延长了测试时间。 电测试的可信度,简言之就是,如何保证ATE系统测试结果长期的正确性。优秀的
测试系统不需要反复测试,可以节省宝贵的测试资源。因此,测试可信度可以间接的反映
测试工艺的效率。 在一个Lot一次筛选后,someone会收集所有的不良品进行再次测试.第一次的不
良品通过第二次测试,看起来是有可能的.真正的不良品是不能通过重新测试的,但是有些
不良品可以通过第二次测试，唯一的解释就是在第一次测试时,不是真正的电性能的损坏
。这样或那样的原因,导致了第一次测试的失败。 无论何种原因测试失败的的良品通常看作是一次"无效的"失效.ATE系统的测试
可信度可以由系统的"无效测试Unit"数量来衡量. 导致"无效测试Unit"的原因有很多,包括:1)DUT leads与接触器的不良接触;2)测试硬件的设计/制造的不足;3)不恰当的测试设备的安装;4)系统中电气联结部分的金
属表面氧化和异物;5)系统组成中任何的液化和潮湿;6)测定者/仪器的重复性/再现性性能临界的产品的变化同样也导致"无效测试". 以上所涉及的"无效测试"的原因中,主要的是不恰当/不稳定的接触(DUT与连接
器)。以下原因会引起不恰当/不稳定的接触.1)连接器与DUT leads的定位不重合(不对准
,角误差,偏心率,误差方向);2)连接器的磨损或是机械退化;3)DUT 和 连接器的氧化/腐
蚀;4)DUT 和 连接器的潮湿与污染. 引起"无效测试"的主要原因是连接器的问题,使得大多数公司认为测试的可信度就是确保连接器和DUT的良好的电接触. 毕竟,引起"无效测试"的其它多数原因是可以纠
正的.纠正的方法:1)优秀的测试/软件设计和debug.2)恰当的测试保护频带;3)良好的测
试仪器;4)可靠的测试版及其它硬件; 5)设计优良的测试台 6)a sound management
system 基于以上前提,测试可信度仅决定于良好的电气连接,"测试可信度"可以定义为
每次DUT测试的良好联接的概率.因此,90%的测试可信度意味着100EA DUT测试中,10EA
DUT会因为联接的问题而不能进行正确的测试。 如果ATE测试1000EA DUT,90%(900EA DUT)为良品,仅仅810EA 会通过测试.900EA
中的90EA会在测试中因为接触问题,而成为"无效测试".90EA DUT再次测试同样会发生9EA
为"无效测试". 若干次重复测试后,所有因为最初的"无效测试"而被拒收的产品最终都会再生,
毕竟这些自身都是良品.这样的一个重复测试是没有效率和不产生价值的.因此,"无效测
试"的再生价值同样由测试系统的测试可信度决定. 首次的通过率Y1,等于该Lot的实际收率(Y)与ATE系统的测试可信度(C)的乘积.
因此,测试工程师可以通过Y=Y1/C 估计出LOT的真实收率. 如果工程师决定再生所有的"无效测试"产品,就必须对首次测试全部"无效测试"
品进行再测试. 再次测试的产品的数量R2=Q.Q-LOT数量,Y1-首次的拒收率. 工程师计算ATE的测试可信度的公式 C = 1-/Y1]其中,Y2 - 首次的拒收品二次测试后的收率. Y1 - 首次的通过率 根据Christopher Jones的"测试可信度分析"的结论,每周测试的百万RF IC的经
验值: 1)如果测试可信度低于85%,不能进行测试; 2)如果测试可信度超过95%,不需要进行二次测试; 3)如果测试可信度在85%~95%之间,建议进行二次测试 当然,上述的指南并非适用于所有的公司,由于不同的设备和封装方式关联的经
济因素也不相同,还有不同的联接器的退化。因此,测试经理需要决定如何最佳的应用测
试可信度管理以提高 bottom lines. 在今天IC测试工业竞争激烈的今天,每位测试经理都需要知道什么情况进行重复
测试,什么情况进行是不经济的,还以什么情况测试系统不能再使用. 能够根据测试可信
度数据区分这些情况并且做出恰当的措施针对测试工程管理是重要的.
我会将我的翻译放在上面,请大家指正. 所翻译的文章都是实际工作中常见问题.
Electrical Test Confidence
Every new test engineer eventually finds out that absolute certainty of test results can never be guaranteed, even if the most advanced automated test equipment (ATE) are involved. As such, there will always be instances wherein retest of units is necessitated, consuming valuable test capacity and increasing test cycle time without additional output.
Electrical test confidence, simply put, is a measure of how consistently an ATE system delivers the correct electrical test results. A test system with excellent test confidence makes retest unnecessary, saving precious test resources. Test confidence is therefore an indirect indicator of how efficient and productive a test process is.
If someone will collect all the test rejects after the first-pass screening of a lot and retest these, there is reasonable likelihood that some of these initially failing units will pass their second test. Since genuine failures can not be resurrected with retesting, the only explanation for their passing the second test is that they were never really electrically bad when they were first tested. Something, somehow, made them fail the first test.
An electrically good unit that fails electrical testing for whatever reason (and can therefore pass electrical retesting under more proper conditions) is often referred to as an 'invalid' reject or failure. One's test confidence in an ATE system may be measured in terms of the number of invalid failures encountered from the system.
Invalid failures occur due to a multitude of reasons, which include but are not limited to: 1) improper contact between DUT leads and the contactor; 2) poor design and fabrication of test hardware; 3) improper test equipment set-up; 4) oxidation and contamination of metal surfaces used for electrical connection in any part of the system; 5) condensation or excessive moisture build-up anywhere within the system; 6) tester/instrumentation repeatability and reproducibility. The performance variability of a marginally good device can also result in invalid failures.
Of the aforementioned causes of invalid rejections, improper electrical contact between the DUT and the contactor constitute a major slice of the pie for most companies. Improper contact between the DUT and the contactor can further be broken down into the following causes: 1) misalignment between the contactors and the DUT leads; 2) contactor wear-out or mechanical degradation; 3) oxidation/corrosion of any of the contactors or DUT leads; 4) moisture build-up or contamination on the contactors or DUT leads.
The fact that bulk of invalid failures are caused by contactor problems has led many companies to equate electrical test confidence to the confidence in making good electrical contact between the contactor and the DUT. After all, most of the other factors that contribute to invalid rejection can be corrected prior to the production release of the test process. Ways of achieving this include: 1) excellent test/software design and debugging; 2) proper test guardbanding; 3) use of good test equipment; 4) use of reliable boards and small hardware; 5) use of a well-designed test floor; and 6) a sound management system.
Based on the premise that electrical test confidence depends solely on the ability to achieve good electrical connection, 'test confidence' may then be defined as the probability that good connection will be achieved every time a DUT is tested. Thus, a test confidence of 90% means that for every 100 devices tested, 10 of these devices will encounter a contact problem that will prevent them from being tested properly.
If such a system tests 1000 devices, with 90% of them (or 900 units) being electrically good, only 810 units will pass the test. Ninety (90) of the 900 good units will experience contact issues during testing, becoming invalid failures. Subjecting these 90 invalid failures to retest will fail to recover all of them, since again, 10% of them (9 units) will become invalid failures.
Several retest cycles will eventually recover all the parts that have been invalidly rejected by the initial rounds of electrical testing, since all of them are good anyway. Such a process for recovering invalid rejects, however, is inefficient and not cost-effective. The value of recovering invalid failures through retesting is, therefore, determined by the system's test confidence as well.
The resulting first pass yield, Y1, is the product of the real or actual yield of the lot (denoted here as 'Y') multiplied by the test confidence of the ATE system (denoted here by 'C'), or Y1 = Y x C. Thus, if a test engineer knows the test confidence of a system, he can estimate the actual yield of the lot through the equation Y = Y1 / C.
If the engineer decides to recover the invalid failures, he'll have to retest all the fall-outs from the first test (denoted here by 'R2'). The retest quantity R2 is equal to the initial quantity (Q) multiplied by the first pass rejection rate, (1-Y1). Thus, R2 = Q (1-Y1).
The resulting yield of the retest (denoted here as 'Y2') is equal to the actual yield of the retest multiplied by C. The actual yield of the retest (denoted here as 'YY') equals the number of invalid failures Rinvalid divided by the retest quantity R2. Thus, YY = Rinvalid/R2 and Y2 = (Rinvalid/R2) x C.
The number of invalid failures Rinvalid is equal to the initial test quantity Q multiplied by the difference between the actual yield of the lot Y and first pass yield of the lot Y1, or Rinvalid = Q x (Y-Y1). But Y = Y1/C, so Rinvalid = Q x (Y1/C - Y1).
Thus, Y2 = {[Q(Y1/C-Y1)] / [Q (1-Y1)]} x C = [(Y1/C-Y1)/(1-Y1)] x C.
Simplifying, Y2 = (Y1(1-C))/(1-Y1), where Y2 is the expected yield of the retest based on the first pass yield Y1 and the test confidence C.
This equation can also be used by an engineer to compute for the test confidence exhibited by his test system, given first pass and retest yield data: 1-C = Y2(1-Y1)/Y1, or
C = 1 - [Y2(1-Y1) / Y1]
where C = confidence of your test system, Y1 is the first pass yield, and Y2 is the yield when the first pass rejects are retested.
According to Christopher Jones, author of the article "Analyze test Confidence to Enhance Throughput" upon which this article was based, their experience in testing millions of RF IC's every week has taught them the following:
1) never run a test if the test confidence is less than 85%;
2) retest of the rejects is not necessary if the test confidence exceeds 95%; and
3) retest of the rejects is recommended if the test confidence is between 85%-95%.
Of course, the above guidelines may not be applicable to every company, since different device groups and package types are subject to different economic factors, as well as exhibit different sensitivities to contactor degradation. It is the task, therefore, of a Test Manager to determine for his company how they can best apply the concept of test confidence management in improving their bottom lines.
Given the very competitive atmosphere of the IC testing industry today, every Test Manager must know when to do a retest, when it is not economical to do so, and when a test system should not be used at all. Being able to distinguish these situations from each other based on test confidence data and reacting to each of them appropriately is an important aspect of test engineering management.
我的翻译：
电测试可信度
每个年轻的测试工程师 最后都会发现 测试结果的绝对正确性并不能保证,即使
使用高短的自动化测试设备（ATE）.因为如此,Unit的反复测试成为必须,并总会出现。
反复测试不产生额外价值,不仅浪费测试能力,而且延长了测试时间。 电测试的可信度,简言之就是,如何保证ATE系统测试结果长期的正确性。优秀的
测试系统不需要反复测试,可以节省宝贵的测试资源。因此,测试可信度可以间接的反映
测试工艺的效率。 在一个Lot一次筛选后,someone会收集所有的不良品进行再次测试.第一次的不
良品通过第二次测试,看起来是有可能的.真正的不良品是不能通过重新测试的,但是有些
不良品可以通过第二次测试，唯一的解释就是在第一次测试时,不是真正的电性能的损坏
。这样或那样的原因,导致了第一次测试的失败。 无论何种原因测试失败的的良品通常看作是一次"无效的"失效.ATE系统的测试
可信度可以由系统的"无效测试Unit"数量来衡量. 导致"无效测试Unit"的原因有很多,包括:1)DUT leads与接触器的不良接触;2)测试硬件的设计/制造的不足;3)不恰当的测试设备的安装;4)系统中电气联结部分的金
属表面氧化和异物;5)系统组成中任何的液化和潮湿;6)测定者/仪器的重复性/再现性性能临界的产品的变化同样也导致"无效测试". 以上所涉及的"无效测试"的原因中,主要的是不恰当/不稳定的接触(DUT与连接
器)。以下原因会引起不恰当/不稳定的接触.1)连接器与DUT leads的定位不重合(不对准
,角误差,偏心率,误差方向);2)连接器的磨损或是机械退化;3)DUT 和 连接器的氧化/腐
蚀;4)DUT 和 连接器的潮湿与污染. 引起"无效测试"的主要原因是连接器的问题,使得大多数公司认为测试的可信度就是确保连接器和DUT的良好的电接触. 毕竟,引起"无效测试"的其它多数原因是可以纠
正的.纠正的方法:1)优秀的测试/软件设计和debug.2)恰当的测试保护频带;3)良好的测
试仪器;4)可靠的测试版及其它硬件; 5)设计优良的测试台 6)a sound management
system 基于以上前提,测试可信度仅决定于良好的电气连接,"测试可信度"可以定义为
每次DUT测试的良好联接的概率.因此,90%的测试可信度意味着100EA DUT测试中,10EA
DUT会因为联接的问题而不能进行正确的测试。 如果ATE测试1000EA DUT,90%(900EA DUT)为良品,仅仅810EA 会通过测试.900EA
中的90EA会在测试中因为接触问题,而成为"无效测试".90EA DUT再次测试同样会发生9EA
为"无效测试". 若干次重复测试后,所有因为最初的"无效测试"而被拒收的产品最终都会再生,
毕竟这些自身都是良品.这样的一个重复测试是没有效率和不产生价值的.因此,"无效测
试"的再生价值同样由测试系统的测试可信度决定. 首次的通过率Y1,等于该Lot的实际收率(Y)与ATE系统的测试可信度(C)的乘积.
因此,测试工程师可以通过Y=Y1/C 估计出LOT的真实收率. 如果工程师决定再生所有的"无效测试"产品,就必须对首次测试全部"无效测试"
品进行再测试. 再次测试的产品的数量R2=Q.Q-LOT数量,Y1-首次的拒收率. 工程师计算ATE的测试可信度的公式 C = 1-/Y1]其中,Y2 - 首次的拒收品二次测试后的收率. Y1 - 首次的通过率 根据Christopher Jones的"测试可信度分析"的结论,每周测试的百万RF IC的经
验值: 1)如果测试可信度低于85%,不能进行测试; 2)如果测试可信度超过95%,不需要进行二次测试; 3)如果测试可信度在85%~95%之间,建议进行二次测试 当然,上述的指南并非适用于所有的公司,由于不同的设备和封装方式关联的经
济因素也不相同,还有不同的联接器的退化。因此,测试经理需要决定如何最佳的应用测
试可信度管理以提高 bottom lines. 在今天IC测试工业竞争激烈的今天,每位测试经理都需要知道什么情况进行重复
测试,什么情况进行是不经济的,还以什么情况测试系统不能再使用. 能够根据测试可信
度数据区分这些情况并且做出恰当的措施针对测试工程管理是重要的.
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