Status of JEITA Whisker Test Method project

Transcription

1 Status of JEITA Whisker Test Method project Ichi Sakamoto, OMRON Corp. 12,June 2003 at IPC and SOLDERTEC Global Conference in Brussels

2 JEITA Whisker Test Method Subcommittee members Chairman Ichizo Sakamoto,OMRON Co-chairman : Teruyoshi Kubokawa,ALPS ELECTRIC Katsuaki Suganuma, Osaka univ. Hidemi Nawafune, Konan univ. Norio Kaneko, Shinshu univ. Tutomu Tukui, Tokai Univ. Kazuyoshi Kagawa, ALPS ELECTRIC Tomio Kudo, ISHIHARA CHENICAL Fujio Asa, Uyemura Hiroshi Ishikawa, NEC-TOKIN Kazushige Minegishi, NTT Electronics Keiko Toi, ESPEC Shuichi Yoshikawa, OKUNO CHEMICAL INDUSTRIES Kinya Sugie, KYOWA ELECTRIC WIRE Koujirou kameyama, SANYO Yoshitaka Toyoda, SENJYU METAL INDUSTRY Hitoshi Ichikawa, Taiyo yuden Kiichi Nakamura, Ikuya Kawanishi, TOKO Hiroyuki Omura, Nihon Chemi-Con Kihichi Sasaki, Masao Ohsima, Fujitsu Kenji Kusakabe, Matsushita Electronic Components Akihiro Nakayama, Matsushita Electronic Components Seiichi Okada, MURATA Yasuhito Oike, MOTOROLA Japan Akiko Iura, ROHM Tomio Hayashi, KOBELCO

3 Flow Chart for Test Method Scope 1.Object Terminal of Electronics Devices 2.Material: Sn and Sn alloy plating 3.Stress: Consumer Electronics Hypothesis Relation for Relation Between Whisker and Stress Fundamental Study Various stresses are given to the deposit, confirming the relation between the whisker and stress. Accelerated Study Testing Method

4 Relation between Whisker and Stress We consider that several kinds of test methods can be proposed by the following viewpoints. Whisker Bending Stress Stress generated when using Mechanical Mechanical Compression Compression Stress Stress changing changing Component Design Oxidation Oxidation Humidity Humidity Cu3Sn Cu3Sn Cu6Sn5 Cu6Sn5 Deposit Design Recrystallization Recrystallization Internal stress Substrate Substrate and and Base Base materials materials From From 0 0 to to degc degc Sep/2002 Rev.2

5 Relation between Whisker and Stress There are three phase in Whisker Growth. Deposit design Component design Stress generated when using Know-How to control Whisker Select for testing method condition A whisker occurs by the recrystallization of tin, and grows up by the compression stress. The stress is generated by internal stress of plating deposit, diffusion, oxidization, and mechanical compression stress. They do not generate such stress simultaneously.

6 Matrix Table of JEITA Studies

7 1.Influence of Sn chemistry and Substrate Plating Whisker Mechanical Mechanical Compression Compression Stress Stress Oxidation Oxidation Cu3Sn Cu3Sn Cu6Sn5 Cu6Sn5 changing changing Humidity Humidity Bending Stress Internal stress Substrate Substrate and and Base Base materials materials From Recrystallization From 0 0 to to Recrystallization degc degc

8 620micron 1.Influence of Sn chemistry and Substrate Plating Appearance R Appearance Ratio Comarsion for SnA, SnB, SnC on copper at 1500 and 2000hrs. R.T. 3085% 5050% 5085% 6093% 8585% Testing method Comparison of Max. Whisker Length for SnA, SnB, SnC on copper at 1500 hrs. R.T. 3085% 5050% 5085% 6093% 8585% Testing method SnA-A SnB- SnC-I SnA-A SnB- SnC-I

9 1.Influence of Sn chemistry and Substrate Plating Why dose a whisker grows up most at room temperature? Since diffusion of Cu was considered to be the cause of a stress of growing whisker, the inter-metallic compound of Cu was analyzed by XRD. At Room Temperature, a Cu6Sn5 s existence ratio is high. At High Temperature, a Cu3Sn s existence ratio is high.

10 1.Influence of Sn chemistry and Substrate Plating In high temperature, it turns out that Cu3Sn has occurred mostly. Moreover, it was thought that this Cu3Sn became to prevent growth of whisker under the influence of density. Whisker grows up by generating the compressive stress, when Cu6Sn5 that the density is small grows up. Sn =7.3 Cu6Sn5 =8.3 Cu =8.9 Sn =7.3 Cu =8.9 Sn Cu6Sn5 Cu3Sn =11.3 Cu The compressive stress decreases when Cu3Sn that the density is large grows up, and whisker does not grow up. RT 8585%

11 Sn layer Cu 6 Sn 5 layer Cu 3 Sn layer Cu layer 1 µm

12 1.Influence of Sn chemistry and Substrate Plating In the Cu substrate plating, A whisker grows up most at room temperature. In the Ni substrate plating, the difference is not seen in the any testing condition. Cu substrate RT RT Ni substrate RT

13 1-1.Sn-X alloy plating In Sn-Ag and Sn-Bi alloy plating, the whisker hardly grew. These can consider the diffusion prevention effect of Cu by Ag and Bi. Sn plating Max whisker length Sn-Pb alloy plating Sn-Cu alloy plating Aging time HC500 Sn-Ag alloy plating Sn-Bi alloy plating

14 Summary of 1 1. The plating chemistry has influence for whisker growth. However, even if the plating chemistry is differ, the tendency over temperature and humidity is the same. 2. From comparison of nickel and Copper substrate plating, it can be said that the influence of diffusion is high. 3. Cu6Sn5 under Cu diffusion does influence for whisker growth, diffusion of Cu3Sn become to prevent whisker growth.

15 2. Influence of Oxidation on Surface Whisker Mechanical Mechanical Compression Compression Stress Stress Oxidation Oxidation Cu3Sn Cu3Sn Cu6Sn5 Cu6Sn5 changing changing Humidity Humidity Bending Stress Internal stress Substrate Substrate and and Base Base materials materials From Recrystallization From 0 0 to to Recrystallization degc degc

16 2. Influence of Oxidation on Surface As for nickel substrate plating, a whisker was not observed in room temperature. However, the 14-micrometer crystal of Sn was observed under the condition of high humidity at high temperature in 4000 hours.

17 2. Influence of Oxidation on Surface For nickel substrate, surface oxidization is considered as a testing method... However... The depth of oxygen becomes unusually high value in high humidity. The whisker is not observed by room temperature studies as a fact. Depth of Oxygen at RT 4000hrs Depth of Oxygen at 6093%4000hrs

18 Summary of 2 1. The plating chemistry has influence for whisker growth. However, even if the plating chemistry is differ, the tendency over temperature and humidity is the same. 2. From comparison of nickel and Copper substrate plating, it can be said that the influence of diffusion is high. 3. Cu6Sn5 under Cu diffusion does influence for whisker growth, diffusion of Cu3Sn become to prevent whisker growth. 4. Although nickel substrate plating is not influenced by diffusion of Cu, a whisker grows in high humidity condition.

19 3.Influence of Changing Whisker Mechanical Mechanical Compression Compression Stress Stress Oxidation Oxidation Cu3Sn Cu3Sn Cu6Sn5 Cu6Sn5 changing changing Humidity Humidity Bending Stress Internal stress Substrate Substrate and and Base Base materials materials From Recrystallization From 0 0 to to Recrystallization degc degc

20 3. Influence of Changing A whisker grows with a heat changing in a ceramic chip. This has an influence of the heat expansion coefficient of the Base material. Ceramic chip 3085RH,after 4000hrs ,after 500cycle

21 Summary 1. The plating chemistry has influence for whisker growth. However, even if the plating chemistry is differ, the tendency over temperature and humidity is the same. 2. From comparison of nickel and Copper substrate plating, it can be said that the influence of diffusion is high. 3. Cu6Sn5 under Cu diffusion does influence for whisker growth, diffusion of Cu3Sn become to prevent whisker growth. 4. Although nickel substrate plating is not influenced by diffusion of Cu, a whisker grows in high humidity condition. 5. A whisker grows with a heat changing in a ceramic devices. It is thought that this has the large influence of the heat expansion coefficient of the base material.

22 Soldertec,NEMI and JEITA Agreement High temperature/humidity condition test 60degC, %RH Thermal cycling (TC) For the high temperature: 85degC For the low temperature: -40degC or -55degC For the dwell time, heating and cooling rates: to be determined Ambient conditions For the room temperature: 20 to 25 degc, or 15 to 35 degc, to be determined Other specific conditions, if necessary, shall be identified

23 Thank you very much for your kind attention.