IPC-A-600H-2010 中文版印制板的可接受性 (1).pdf - 第28页

This presentation was then given to the assembly standards groups for their consideration. The request was made that the requirements in the bare printed board and assembly documents be changed to track with each other. …

造成白斑/微裂纹状况的因素还有：树脂的成分、层压方法、

耦合剂，T

等。过去搜集到的报告显示，白斑和微裂纹范围超

过间距的50%以上时，也不会影响硬件的可靠性。既然所有

测试报告都显示白斑没有问题，而且没有使用失效的报告，

为什么我们还如此顾虑白斑和微裂纹现象呢？因为理论上看

来，如果导体之间布满白斑，同时伴有湿气或其他污染物，

那么在导体之间应该存在铜的迁移（即绝缘电阻失效）。

尽管上文分析了潜在的失效机理，但出现这样的失效（绝缘

电阻或迁移）几乎是不可能的。首先需要白斑填满导电图形

之间。其次，印制板/组件内需要有潮气，并伴有导电的或离

子的污染物，例如氯化物。

图23b图示了业界的一个典型实例，白斑位于两个镀通孔间的

中心处（见图23b），其宽度为0.4mm[0.0157in]。要想使铜迁

移成为可能，白斑必须占满两个镀覆孔之间的区域。这种情

况当然是不太可能发生的。另一个案例（见图23c）图示了两

个表面导体之间存在潜在失效机理的条件。它要求一根带正

（+）电的导体刚好落在纤维交织点上，同时还要求另一个带

负（-）电的导体也刚好落在纤维交织点上。要想这两个导体

通过基材产生电气短路，需存在以下这样一条导电通路：从

一个导电图形开始，经由尚存的介质材料（树脂和纤维）到分

离点（白斑），沿着分离处向另一个导电图形的方向，再经过

尚存的介质材料（树脂和纤维），最后到达另一个导电图形。

上述条件均符合的情况下，还需要这两个相邻导体之间有压

差。这是非常不可能的事情。这也是为什么业界至今尚无任

何由于白斑造成可靠性问题的原因。

确定电子组件验收准则时，要考虑上述所有可能发生的情

况。不应该把白斑看作不符合条件。应该将白斑看作为制程

警示，它告诉你制程正面临失控的可能。纠正问题，而不是

报废产品，分析上述种种可能，排查隐患。

Brief summary of the Third IPC Blue Ribbon Committee on

Measles

In 2004, the issue of printed board laminate degradation caused by

internal Conductive Anodic Filament (CAF) growth came to the

forefront of discussions among the IPC printed board assembly

standards groups (including the 7-31b IPC-A-610 and 5-22a

National Standard for Soldering task groups.) It was observed that

circuit density, operating speed, band pass and reduced operating

voltage had impacted the ability of circuits to operate under condi-

tions supporting dendrite or CAF development.

With the proliferation of finer line conductors and reduced spacing

in current designs, discussions within the assembly standards

groups questioned the role of measles within printed board lami-

nate materials as a potential catalyst for CAF growth.

For years, IPC standards for electronic production contained no

restrictions for the occurrence of measles in printed boards and/or

assemblies. Theoretically, measles could be continuous between

conductors and could exist throughout the printed board. It was

noted that this allowance was based on studies conducted nearly 30

years earlier based on circuit designs from that time period. It was

recognized that a need existed to reconsider the measles require-

ments for today's production designs and product environment.

In the interim, as a means to call attention to this potential problem,

IPC assembly documents were changed to include pass/fail (defect)

criteria for Class 3 assemblies that exhibited the visual appearance

of measles.

The new measles criteria created in the assembly documents

defined requirements that were stricter than those given in the

printed board documents unless the additional IPC-6012, Class 3A

(Military and Aerospace) requirements were considered. IPC-

6012, Class 3A does not allow measles in bare boards for these

industry segments, however Class 3 printed boards produced in

accordance with 6012, which exhibited measles, were no longer

acceptable for use in the assembly documents for Class 3 in gen-

eral. This requirement conflict was brought to the attention of the

IPC Technical Activities Executive Committee (TAEC) and that

body directed both groups to work together to come to some reso-

lution, based on test data that would bring the documents into

agreement on the acceptance criteria.

The leadership of the printed board standards committees formed a

new Blue Ribbon Committee on Measles and designed and per-

formed testing to determine if measles contributed to CAF failures

in actual end product. This test protocol was completed in late 2006

and presented to the printed board standards committees at IPC

Printed Circuits Expo/APEX 2007. There was conclusive evidence

within the test that measles did not contribute to CAF growth; nor

did the presence of measles promote CAF failures in the end prod-

uct that exhibited CAF.

2.3 BASE MATERIAL SUBSURFACE（基材表⾯下）

Introduction (cont.)（引⾔（续））

19IPC-A-600H-2010 2010年4月

This presentation was then given to the assembly standards groups

for their consideration. The request was made that the requirements

in the bare printed board and assembly documents be changed to

track with each other.

The leadership of the assembly standards groups concurred that the

industry now had test data that addressed their original concerns

regarding the potential of measles to promote CAF failures. They

also agreed that the documents should be amended to eliminate the

conflicting measles requirements. The groups jointly drafted the

words, comments, and instructions for all documents regarding

measles and these were presented to the committee membership at

the 2007 IPC Midwest Conference. Copies of the test protocol sum-

mary are available through the IPC.

第三届IPC蓝带委员会关于⽩斑的概述

2004年，由于内部导电阳极丝（CAF）生长造成的印制板基

材质量退化问题在IPC印制板组装标准工作组（包括7-31b

IPC-A-610和5-22a国家焊接标准任务工作组）中成为了讨论

的焦点。据观察，电路密度、运行速度、通带、工作电压的

降低在有利于结晶或CAF生长的条件下均对电路的运行有影

响。

随着电流设计中细线条导体的增加和导体间距的减少，组装

标准工作组对印制板基材中白斑的作用提出了疑问，认为

其是CAF生长的潜在催化剂。

多年来，IPC电子生产的标准中均未涵盖对印制板和/或组装

板中白斑现象的限制。从理论上讲，白斑可能在导体之间连

续呈现，也可能存在于整块印制板。大家注意到了这种允许

规定是基于30年前在当时电路设计上的研究。大家认识到有

需要针对当今的生产设计和产品环境重新考虑白斑的要求.

在此期间，为了引起对这一潜在问题的关注，IPC对组装文件

作了变更，变更涵盖了对3级组装件中白斑外观的合格/不合

格（缺陷）的准则。

除了考虑采用IPC-6012中3A级（军用和航空）要求，否则在

组装文件中建立的关于白斑的新准则比印制板文件中规定的

要求更严格。IPC-6012中3A级不允许在这些行业领域的裸板

上出现白斑，但是，按照6012生产的3级印制板出现白斑时，

如用于组装3级产品，通常是不可接受的。这一要求的矛盾引

起了IPC技术活动执行委员会（TAEC）的关注，在该委员会

的指导下，两个工作组一起努力找到了解决方案，根据测试

数据，使文件中的验收准则达到一致。

在印制板标准委员会的领导下，成立了新的白斑蓝带委员

会。该委员会设计并进行了实验以确定白斑是否是实际整机产

品中CAF失效的原因。该实验程序于2006年后期完成，并于

IPC

2007

印制板展览会/APEX期间提交给印制板委员会。其

测试的总结性证据说明白斑不是CAF生长的起因，也不是出现

CAF的整机产品中CAF失效的促成原因。

该报告后期已提交给组装标准工作组，提请他们考虑更改组

装文件，以使裸印制板文件和组装文件的要求互相一致。

组装标准工作组的领导一致同意，提出现在行业中已有测试

数据解决了他们对潜在白斑引发CAF失效的最初顾虑。委员

会同时同意对文件进行修订从而排除对白斑要求的矛盾之

处。工作组联合起草了所有文件中关于白斑的文字、意见和

建议，并于2007年IPC中西部会议期间提交给委员会成员。该

测试程序总结可通过IPC获得。

图23b ⽩斑跨接了导电图形的案例

注：此图仅⽤作说明状况，并不要求做显微剖切评价。

0.35 mm

[0.0138 in]

0.25 mm

[0.00984 in]

0.40 mm

[0.0157 in]

1.00 mm

[0.040 in]

图23c 两个表⾯导体之间潜在失效机理的案例

注：此图仅⽤作说明状况，并不要求做显微剖切评价。

0.80 mm

[0.031 in]

+-+

图23a 微裂纹案例

注：此图仅⽤作说明状况，并不要求做显微剖切评价。

2.3 BASE MATERIAL SUBSURFACE（基材表⾯下）

Introduction (cont.)（引⾔（续））

20 IPC-A-600H-20102010年4月

Measling: Measling manifests itself in the form of discrete white squares or ‘‘crosses’’ below the surface of the base material, and is usu-

ally related to thermally induced stress. Measles are subsurface phenomena that have been found in new laminated materials and in every

board type made from woven fiber reinforced laminates at one time or another. Since measles are strictly subsurface phenomena and occur

as a separation of fiber bundles at fiber bundle intersections, their apparent positions relative to surface conductors have no significance.

⽩斑：白斑表现为基材表面下不连续的白色方块或“十字”纹，其形成通常与热应力有关。白斑是一种基材表面下现象，在新层

压基材上和织物增强层压板制成的各种板上都时有发生。由于白斑绝对出现在表面下并且是在纤维束交叉处发生分离而出现，因

此，其出现的位置相对于表面导体毫无意义。

Target - Class 1,2,3（⽬标条件 - 1,2,3级）

• No evidence of measling.

• 无白斑迹象。

Acceptable - Class 1,2（可接受条件 - 1,2级）

• The criteria for measling is that the printed board is functional.

• 对白斑的准则是印制板仍具有功能。

Process Indicator - Class 3（制程警⽰ - 3级）

• Measled areas in laminate substrates exceed 50% of the physical spacing

between noncommon conductors.

• 层压基材中白斑面积超过非公共导体之间实际间距的50%。

Note: Measling is an internal condition which does not propagate as a

result of thermal testing that replicates future assembly processes and has not

been conclusively shown to be a catalyst for CAF growth. Delamination is an

internal condition which may propagate under thermal stress and may be a

catalyst for CAF growth. The IPC-9691 user's guide for CAF resistance test-

ing and IPC-TM-650, Method 2.6.25, provide additional information for

determining laminate performance regarding CAF growth. Users who wish to

incorporate additional criteria for measle conditions may consider incorporat-

ing the provisions of IPC-6012, Class 3A which does not allow measles.

注：白斑是层压板中的一种内部现象，不会由于模拟组装制程的热应力

测试而扩展，同时也无明确结论显示它是阳极导电丝（CAF）生长的诱

因。分层是一种在热应力作用下可能扩展的内部现象，同时也可能是

CAF生长的诱因。关于耐CAF测试，IPC-9691用户指南和IPC-TM-650测

试方法2.6.25均提供了确定层压板 CAF生长性能的其他信息。希望加

入白斑状况其他要求的用户可考虑纳入不允许白斑出现的3A级要求。

Note: Measles are observed from the surface. Cross-sections are for illustration purposes.

注：

白斑可从表面观察。剖面图仅用于图示。

图231b

注：此图仅⽤作说明状况，并不要求做显微剖切评价。

图231d

图231a

图231c

2.3 BASE MATERIAL SUBSURFACE（基材表⾯下）

2.3.1 Measling（⽩斑）

21IPC-A-600H-2010 2010年4月