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电磁兼容(EMC)小小家学习园地 -> ◤技术讨论◢——静电放电(ESD)防护 -> ESD 测试问题

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ryangao

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ESD 测试问题

我们在做ESD 接触放电测试时,是打十下放一次电好还是打一下放一次电好啊?

[楼主] | Posted: 2007-05-21 11:55

ryangao

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标准上也没有提到这一点,不知道这样操作可行?

[1 楼] | Posted: 2007-05-21 12:32

shuangcong

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不过刚刚跟同事讨论一下，打一下放一次电是需要的，尤其是高电压的时候。所以我们美国同事做一台机器的静电测试要两个星期，每一个点都从最低达到最高，然后整个测试要在一个环境箱里面做。连欧洲的同事都说Crazy，尤其是很多莫名其妙的都要测更是受不了。不过从严谨性来讲这样才是最好的。

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[2 楼] | Posted: 2007-05-21 16:38

skyhua

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标准里面有讲打一次放一次电，看样子大家对标准还不是很熟悉，呵呵！
IEC61000-4-2 19页里面说得很清楚，在上面还有一个图。
非接地设备，必须要通过二个470K OHM的电阻接地，然后放电。

[3 楼] | Posted: 2007-05-21 17:05

銀翼之奇術師

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QUOTE:

引用第4楼skyhua于2007-05-21 17:05发表的“”:
标准里面有讲打一次放一次电，看样子大家对标准还不是很熟悉，呵呵！
IEC61000-4-2 19页里面说得很清楚，在上面还有一个图。
非接地设备，必须要通过二个470K OHM的电阻接地，然后放电。

19页没找着，可能是用的标准的版本不一样，能附张截图吗？

[4 楼] | Posted: 2007-05-28 08:24

ryangao

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我在标准里也没有看到关于接触放电打一次放一下电？
后来我请教我们公司的高人也说这样做会更加严格！

[5 楼] | Posted: 2007-05-28 08:56

stormkuku

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施打靜電時,是否放電問題,主要看客戶要求
(當然您如果就是賣到市場上,或是屬於驗證測試單位的,那就隨你高興)

測試上還會要看您的測試的系統是什麼? 例如cellura phone或是PC 之類

連打不放電是比較嚴苛的要求,因為一般IC會有記憶效應
當電荷in的速度,大於電荷out的速度,超過IC所能承受的狀況時,就會造成test fail (不一定燒毀,有的內部會設計自保電路),實例上大家應該都遇過第一槍測試時pass,但是到第7or8槍後掛掉的狀況,就是類似這種情形

在驗證上,通常不會做這類分級測試,但是在整改的過程中,會需要常常運用到這類測試來確認,下solution後,ESD耐受程度的差異,與失效的模式,以確認是否有效

我比較贊成打一次,放一次電的情形,這與靜電的一次釋放原則較像
但是實務上來說,打一次放一次電,很耗時間麻煩,一次20次打下去省事多了... ^^"

下的solution如果有效,不太會因為這種小小的測試上差異有很大的不同

當然如果遇到某些真的改不好的狀況,只能用這樣打一次,放一次電的測試方式去先測過再說...
唉一切都是為了生活啊~~~~

kuku

[6 楼] | Posted: 2007-05-28 22:36

robin

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Copy of the Standard

61000-4-2  IEC:1995+A1:1998 – 27 –
+A2:2000
7.1.3 Test method for ungrounded equipment
The test method described in this subclause is applicable to equipment or part(s) of equipment
whose installation specifications or design preclude connection to any grounding
system. Equipment, or parts thereof, includes portable, battery-operated and double-insulated
equipment (class II equipment).
Rationale: Ungrounded equipment, or ungrounded part(s) of equipment, cannot discharge
itself similarly to class I mains-supplied equipment. If the charge is not removed before the
next ESD pulse is applied, it is possible that the EUT or part(s) of the EUT be stressed up to
twice the intended test voltage. Therefore, double-insulated equipment could be charged at
an unrealistically high charge, by accumulating several ESD discharges on the capacitance of
the class II insulation, and then discharge at the breakdown voltage of the insulation with a
much higher energy.
The general test set-up shall be identical to the ones described in 7.1.1 and 7.1.2
respectively.
To simulate a single ESD event (either by air or by contact discharge), the charge on the EUT
shall be removed prior to each applied ESD pulse.
The charge on the metallic point or part to which the ESD pulse is to be applied, for example,
connector shells, battery charge pins, metallic antennae, shall be removed prior to each
applied ESD test pulse.
When one or several metallic accessible parts are subject to the ESD test, the charge shall be
removed from the point where the ESD pulse is to be applied, as no guarantee can be given
about the resistance between this and other accessible points on the product.
A cable with 470 kΩ bleeder resistors, similar to the one used with the horizontal and vertical
coupling planes, shall be used; see 7.1.
As the capacitance between EUT and HCP (table-top) and between EUT and GRP (floorstanding)
is determined by the size of the EUT, the cable with bleeder resistors may remain
installed during the ESD test when functionally allowed. In the discharge cable, one resistor
shall be connected as close as possible, preferably less than 20 mm from the EUT test point.
The second resistor shall be connected near the end of the cable attached to the HCP for
table-top equipment (see figure 8), or GRP for floor-standing equipment (see figure 9).
The presence of the cable with the bleeder resistors can influence the test results of some
equipment. In case of dispute, a test with the cable disconnected during the ESD pulse takes
precedence over the test with the cable installed during the test, provided that the charge has
sufficiently decayed between the successive discharges.
As an alternative, the following options can be used:
− the time interval between successive discharges shall be extended to the time necessary
to allow natural decay of the charge from the EUT;
− a carbon fibre brush with bleeder resistors (for example, 2 × 470 kΩ) in the grounding
cable;
− an air-ionizer to speed-up the "natural" discharging process of the EUT to its environment.

[7 楼] | Posted: 2007-05-30 06:57

dlc

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不理解这里所说的放电的概念,我没有放电棒,怎么放电啊?

[8 楼] | Posted: 2007-06-17 09:33

dlc

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我可是每次都把放电枪调到连续放电,设备会自动记数的

[9 楼] | Posted: 2007-06-17 09:37

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电磁兼容(EMC)小小家学习园地 -> ◤技术讨论◢——静电放电(ESD)防护

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