第一部分 焊點失效機理與裂紋特征
第 1 章 焊點的可靠性 ............................................................................................ 3
1.1 焊點 ...........................................................................................................................................3
1.1.1 焊點的微觀組織結構及常見失效位置 ........................................................................4
1.1.2 焊點的失效標準 ............................................................................................................4
1.1.3 焊點的斷裂類型 ............................................................................................................5
1.2 導致焊點失效的載荷條件 .......................................................................................................7
1.3 焊點失效機理 ...........................................................................................................................7
1.3.1 溫度循環(huán)引發(fā)的焊點失效機理 ....................................................................................7
1.3.2 機械應力引發(fā)的焊點失效機理 ..................................................................................10
1.3.3 熱沖擊引發(fā)的焊點失效機理 ......................................................................................12
1.3.4 蠕變引發(fā)的焊點失效機理 ..........................................................................................13
1.4 焊點的可靠性評價 .................................................................................................................14
1.4.1 焊點的可靠性取決于 PCBA 的互連結構設計 ..........................................................14
1.4.2 焊點的可靠性工作 ......................................................................................................14
1.4.3 焊點失效原因分析流程 ..............................................................................................15
案例 1：某單板上的 BGA 使用兩年后失效 .............................................................15
第 2 章 溫度循環(huán)導致的焊點失效........................................................................... 17
2.1 疲勞失效的典型場景 .............................................................................................................17
2.1.1 整體熱膨脹失配 ..........................................................................................................17
2.1.2 局部熱膨脹失配 ..........................................................................................................18
2.1.3 內部熱膨脹失配 ..........................................................................................................18
2.2 疲勞失效的裂紋演進過程與特征 .........................................................................................18
2.2.1 片式元件焊點疲勞失效典型裂紋特征 ......................................................................19
2.2.2 翼形引腳焊點疲勞失效典型裂紋特征 ......................................................................19
2.2.3 BGA 焊點疲勞失效典型裂紋特征 .............................................................................20
SMT 單板互連可靠性與典型失效場景
2.2.4 QFN 焊點疲勞失效典型裂紋特征 .............................................................................21
2.2.5 CBGA 焊點疲勞失效典型裂紋特征 ..........................................................................22
2.2.6 CCGA 焊點疲勞失效典型裂紋特征 ..........................................................................23
2.2.7 通孔插裝焊點疲勞失效典型裂紋特征 ......................................................................24
2.2.8 焊接工藝對裂紋特征的影響 ......................................................................................24
2.3 小結 .........................................................................................................................................25
第 3 章 機械應力導致的焊點失效........................................................................... 27
3.1 機械應力失效的典型場景 .....................................................................................................27
3.1.1 沖擊 ..............................................................................................................................27
案例 2：BGA 脫落 ......................................................................................................27
3.1.2 瞬時彎曲 ......................................................................................................................29
案例 3：插件操作導致 BGA 焊點開裂 .....................................................................29
3.1.3 循環(huán)彎曲 ......................................................................................................................31
3.1.4 振動 ..............................................................................................................................31
3.2 機械應力失效的裂紋特征 .....................................................................................................31
3.3 脆性的界面 IMC ....................................................................................................................33
3.3.1 ENIG 鍍層形成的焊點具有脆性 ................................................................................34
案例 4：Ni 氧化導致焊點界面脆化 ...........................................................................37
3.3.2 不連續(xù)的塊狀 IMC ......................................................................................................40
3.4 典型應力敏感元件及應力失效 .............................................................................................41
3.4.1 應力敏感封裝 ..............................................................................................................41
3.4.2 片式電容 .....................................................................................................................41
3.4.3 球柵陣列封裝 ..............................................................................................................46
案例 5：ICT 測試導致 BGA 焊點開裂 ......................................................................46
案例 6：壓接導致 BGA 焊點開裂 .............................................................................48
第 4 章 焊點失效分析方法.................................................................................... 51
4.1 失效分析及方法 .....................................................................................................................51
4.1.1 失效分析 ......................................................................................................................51
4.1.2 失效分析思路 ..............................................................................................................51
4.1.3 失效分析基本流程與方法 ..........................................................................................51
4.1.4 焊點失效分析的常用方法 ..........................................................................................52
4.2 X 射線檢測 .............................................................................................................................53
4.2.1 X 射線圖像的采集原理...............................................................................................54
4.2.2 X 射線圖像的分析.......................................................................................................56
4.3 超聲掃描顯微鏡 .....................................................................................................................58
4.3.1 超聲掃描顯微鏡概述 ..................................................................................................58
4.3.2 超聲掃描顯微鏡的工作原理 ......................................................................................58
4.3.3 分析步驟 ......................................................................................................................60
4.3.4 超聲掃描顯微鏡和 X 射線的對比..............................................................................61
4.4 切片 .........................................................................................................................................62
4.4.1 切片樣品的制備 ..........................................................................................................62
4.4.2 切片分析應用 ..............................................................................................................64
4.5 掃描電子顯微鏡 .....................................................................................................................65
4.5.1 掃描電子顯微鏡概述 ..................................................................................................65
4.5.2 掃描電子顯微鏡的工作原理 ......................................................................................66
4.5.3 SEM 的優(yōu)點 .................................................................................................................66
4.5.4 樣品的制備 ..................................................................................................................66
4.5.5 應用 ..............................................................................................................................67
4.6 染色滲透 .................................................................................................................................69
4.7 光學檢測 .................................................................................................................................70
4.8 傅里葉變換紅外光譜儀 .........................................................................................................71
案例 7：PCBA 白色污染物成分的分析 ....................................................................71
案例 8：材料一致性檢驗 ............................................................................................72
第 5 章 失效原因的基本判定................................................................................. 73
5.1 焊接問題與組裝問題的判定 .................................................................................................73
5.1.1 焊接合格的標準 ..........................................................................................................73
5.1.2 組裝應力引誘或導致的焊點失效 ..............................................................................75
5.2 焊點開裂裂紋特征圖譜 .........................................................................................................77
5.2.1 典型熱 / 機疲勞斷裂焊點切片圖 ...............................................................................77
5.2.2 典型機械應力導致的焊點斷裂切片圖 ......................................................................79
5.2.3 熔斷焊點切片圖 ..........................................................................................................80
5.2.4 枕頭效應焊點內窺鏡圖與切片圖 ..............................................................................82
5.2.5 無潤濕開焊（NWO）焊點內窺鏡圖與切片圖 .........................................................83
5.2.6 冷焊點切片圖 ..............................................................................................................83
5.2.7 Au 鍍層引起的焊點開裂 .............................................................................................84
5.2.8 小結 ..............................................................................................................................85
第二部分 高可靠性產(chǎn)品的焊點設計
第 6 章 高可靠性 PCBA 的互連結構設計 ...............................................................89
6.1 設計步驟 .................................................................................................................................89
6.2 影響焊點可靠性的設計因素 .................................................................................................91
6.2.1 主要設計參數(shù) ..............................................................................................................92
6.2.2 次要設計參數(shù) ..............................................................................................................93
6.3 提升熱膨脹匹配性的設計 ..................................................................................................... 94
6.3.1 PCB 的類型 .................................................................................................................. 94
6.3.2 有機 PCB ...................................................................................................................... 95
6.3.3 約束芯 PCB .................................................................................................................. 97
6.3.4 陶瓷 PCB ...................................................................................................................... 99
6.3.5 柔順性 PCB .................................................................................................................. 99
6.4 可靠性加固 ........................................................................................................................... 100
6.4.1 表面組裝元器件的可靠性加固 ................................................................................100
6.4.2 插件的點膠加固 ........................................................................................................106
6.4.3 關于可靠性加固的應用 ............................................................................................108
6.5 增強抗振動 / 沖擊能力的設計——應力槽 ........................................................................ 109
6.6 禁限設計 ............................................................................................................................... 110
第 7 章 高可靠制造的組裝熱設計.......................................................................... 117
7.1 熱風再流焊接熱特性 ........................................................................................................... 117
7.2 熱設計對焊接的影響及典型設計場景 ............................................................................... 117
7.2.1 與焊盤緊連接過孔的影響 ........................................................................................ 117
7.2.2 盤中孔 /POFV 孔的影響 ........................................................................................... 118
7.2.3 表層大銅皮的影響 .................................................................................................... 119
案例 9：BGA 四角焊點連接有長的導線，在特定工藝條件下會發(fā)生
縮錫斷裂 ...................................................................................................... 119
案例 10：QFN 與大銅皮緊連的焊點容易發(fā)生虛焊 ............................................... 120
案例 11：熱沉焊盤熱設計不當導致 QFN 傾斜和虛焊 .......................................... 120
7.2.4 屏蔽蓋的影響 ............................................................................................................122
7.2.5 高大封裝的密集布局 ................................................................................................122
7.3 熱設計總結 ........................................................................................................................... 123
第 8 章 高可靠 PCBA 的封裝選型........................................................................124
8.1 封裝對焊點可靠性的影響 ................................................................................................... 124
8.2 封裝特性 ............................................................................................................................... 124
8.2.1 封裝可靠性 ................................................................................................................124
8.2.2 封裝的固有疲勞壽命 ................................................................................................125
8.2.3 封裝的熱變形 ............................................................................................................126
8.3 封裝的選型 ........................................................................................................................... 129
8.3.1 封裝類別的選擇 ........................................................................................................129
8.3.2 工藝性的選擇 ............................................................................................................129
8.4 不推薦的封裝應用場景 ....................................................................................................... 129
第 9 章 陶瓷封裝應用要領................................................................................... 131
9.1 陶瓷封裝的結構與工藝特性 ............................................................................................... 131
9.2 LCCC 工藝要領...................................................................................................................131
9.3 CBGA 工藝要領 ..................................................................................................................134
案例 12：邊緣點膠（也稱為圍堰膠）對 CBGA 可靠性的影響研究① ..............136
9.4 CCGA 工藝要領 ..................................................................................................................137
案例 13：CBGA、CCGA 器件植球 / 植柱工藝可靠性研究① ............................138
9.5 CQFP 工藝要領 ...................................................................................................................139
案例 14：CQFP 器件板級溫度循環(huán)可靠性的設計與仿真① ................................140
案例 15：航天大尺寸 CQFP 器件引腳斷裂失效分析① .......................................142
第 10 章 焊點可靠性仿真分析與試驗評估..............................................................149
10.1 可靠性試驗 ........................................................................................................................149
10.1.1 可靠性試驗的分類 .................................................................................................149
10.1.2 可靠性加速試驗 .....................................................................................................150
10.2 焊點可靠性仿真技術 ........................................................................................................150
10.2.1 焊點可靠性仿真分析步驟 .....................................................................................151
10.2.2 焊點疲勞壽命模型 .................................................................................................151
10.3 溫度循環(huán)試驗 ....................................................................................................................155
10.3.1 溫度循環(huán)試驗簡介 .................................................................................................155
10.3.2 加速系數(shù)的計算 .....................................................................................................156
10.3.3 焊點可靠性評估試驗方案 .....................................................................................158
第三部分 環(huán)境腐蝕與三防處理
第 11 章 環(huán)境因素引起的失效..............................................................................163
11.1 環(huán)境引起的失效 ................................................................................................................163
11.1.1 電化學腐蝕 ..............................................................................................................163
11.1.2 化學腐蝕 ..................................................................................................................164
11.2 枝晶生長 ............................................................................................................................165
11.2.1 枝晶形貌 ..................................................................................................................165
11.2.2 枝晶生長的 3 個要素 ..............................................................................................165
11.2.3 枝晶生長的 3 個階段 ..............................................................................................166
11.2.4 影響枝晶生長的因素 ..............................................................................................167
11.2.5 枝晶生長測試 ..........................................................................................................168
案例 16：在高溫、高濕試驗環(huán)境下出現(xiàn)絕緣電阻下降 .......................................169
案例 17：常見的枝晶生長現(xiàn)象 ...............................................................................169
11.3 CAF ....................................................................................................................................170
11.4 銀離子遷移 ........................................................................................................................171
11.5 Ag 的硫化腐蝕 ..................................................................................................................173
案例 18：片式電阻上硅膠覆蓋導致硫化腐蝕 .......................................................174
11.6 爬行腐蝕 ............................................................................................................................177
11.6.1 爬行腐蝕的概念 ......................................................................................................177
11.6.2 發(fā)生場景 ..................................................................................................................178
11.6.3 爬行腐蝕機理 ..........................................................................................................178
11.6.4 爬行腐蝕與枝晶、CAF 的對比 .............................................................................179
11.6.5 硫化亞銅的危害 ......................................................................................................179
11.6.6 防護措施 ..................................................................................................................179
11.6.7 關于爬行腐蝕的研究 ..............................................................................................180
11.7 實際環(huán)境下的腐蝕 ............................................................................................................180
案例 19：充電樁單板的“濕塵”腐蝕 ...................................................................180
案例 20：電源單板的“濕塵”腐蝕 .......................................................................181
案例 21：阻焊層（綠油）內 Cu 遷移 ....................................................................181
第 12 章 錫須...................................................................................................183
12.1 關于錫須 ............................................................................................................................183
12.2 錫須產(chǎn)生的原因 ................................................................................................................184
12.3 錫須產(chǎn)生的 5 種基本場景 ................................................................................................186
12.4 室溫下錫須的生長 ............................................................................................................186
12.5 溫度循環(huán)（熱沖擊）作用下錫須的生長 ........................................................................187
12.6 氧化腐蝕引起的錫須生長 ................................................................................................188
案例 22：某輕觸開關因錫須短路 ...........................................................................189
12.7 外界壓力作用下的錫須生長 ............................................................................................190
12.8 控制錫須生長的建議 ........................................................................................................191
第 13 章 清洗工藝 ............................................................................................193
13.1 清洗的作用 ........................................................................................................................193
13.2 清洗劑的選擇 ....................................................................................................................193
13.2.1 常見污物類型 .........................................................................................................193
13.2.2 清洗劑選擇的考慮因素 .........................................................................................194
13.2.3 清洗劑的種類及特點 .............................................................................................194
13.3 清洗設備的選擇 ................................................................................................................195
13.3.1 清洗方法與工藝 .....................................................................................................195
13.3.2 清洗設備的選擇要求 .............................................................................................196
13.4 超聲清洗工藝流程與參數(shù)設置 ........................................................................................196
13.5 助焊劑的選配 ....................................................................................................................197
13.6 清洗要求與常見不良 ........................................................................................................197
13.6.1 清洗要求 .................................................................................................................197
13.6.2 常見的清洗不良現(xiàn)象 .............................................................................................198
案例 23：清洗不干凈，有明顯可見的松香殘留物 ...............................................198
案例 24：清洗劑與鍍層不兼容或漂洗不干凈，引起鍍層變色腐蝕 ...................198
案例 25：元器件損壞 ...............................................................................................199
13.7 關于人工清洗 ....................................................................................................................199
第 14 章 敷形涂覆工藝 ......................................................................................201
14.1 敷形涂覆的目的 ................................................................................................................201
14.2 敷形涂覆材料的分類與特性 ............................................................................................202
14.2.1 敷形涂覆材料的分類 .............................................................................................202
14.2.2 常用敷形涂覆材料的物理性能 .............................................................................202
14.2.3 敷形涂覆材料的性能特性 .....................................................................................203
14.2.4 敷形涂覆材料的認證 .............................................................................................203
14.3 敷形涂覆材料的選擇 ........................................................................................................204
14.4 敷形涂覆工藝與方法 ........................................................................................................206
14.4.1 免洗工藝條件下涂覆前是否需要清洗 .................................................................206
14.4.2 涂覆工藝 .................................................................................................................208
14.4.3 常見的涂覆不良 .....................................................................................................211
14.5 PCBA 常見的環(huán)境失效模式.............................................................................................212
14.5.1 影響 PCBA 的環(huán)境因素 .........................................................................................212
14.5.2 典型的失效模式 .....................................................................................................214
第四部分 高可靠性產(chǎn)品的制造
第 15 章 潮敏元器件的應用 ................................................................................221
15.1 概述 ....................................................................................................................................221
15.2 潮濕敏感度等級 ................................................................................................................222
15.3 潮濕敏感度等級的評定 ....................................................................................................222
15.4 干燥包裝 ............................................................................................................................224
15.5 烘干 ....................................................................................................................................227
15.6 使用 ....................................................................................................................................228
15.7 吸潮失效案例 ....................................................................................................................231
案例 26：BGA 芯片與載板之間分層 ...............................................................................231
案例 27：塑封 BGA 載板分層現(xiàn)象 ..................................................................................232
案例 28：鉭電容過爐冒錫珠 ............................................................................................232
案例 29：SIP 內部空洞會導致過爐后冒錫珠 ..................................................................234
案例 30：光驅動器件的焊接 ............................................................................................235
| 目 錄 |
SMT 單板互連可靠性與典型失效場景
第 16 章 組裝工藝控制 ..................................................................................... 238
16.1 組裝工藝對可靠性的影響 ................................................................................................238
16.2 SMT 前工藝 .......................................................................................................................240
16.2.1 去金工藝 .................................................................................................................241
16.2.2 搪錫工藝 .................................................................................................................241
16.2.3 引線成形 .................................................................................................................242
16.3 SMT 工藝 ...........................................................................................................................246
16.3.1 表面組裝元器件的焊接 .........................................................................................246
案例 31：BGA 的球窩與開焊 .................................................................................246
16.3.2 焊膏印刷 .................................................................................................................247
16.3.3 鋼網(wǎng)設計 .................................................................................................................252
16.3.4 再流焊接 .................................................................................................................255
16.3.5 工藝關注點 .............................................................................................................259
16.4 SMT 后工藝 .......................................................................................................................262
16.4.1 印制電路板和模塊的分板 .....................................................................................262
16.4.2 檢測技術 .................................................................................................................262
16.4.3 篩選 .........................................................................................................................262
16.4.4 加速可靠性測試 .....................................................................................................263
第 17 章 缺陷焊點 ........................................................................................... 264
17.1 組裝缺陷焊點的分類 ........................................................................................................264
17.2 虛焊 ....................................................................................................................................264
17.2.1 冷焊 .........................................................................................................................264
17.2.2 無潤濕開焊 .............................................................................................................265
17.2.3 枕頭效應 .................................................................................................................266
17.2.4 焊點應力開裂 .........................................................................................................267
17.3 形態(tài)缺陷 ............................................................................................................................268
17.3.1 片式元件葡萄球焊點 .............................................................................................268
17.3.2 片式元件兩端焊點爬錫高度懸殊較大 .................................................................268
17.3.3 QFP 多錫 .................................................................................................................269
17.3.4 J 形引腳多錫 ...........................................................................................................269
17.3.5 插件包焊 .................................................................................................................270
17.4 熔斷焊點 ............................................................................................................................270
17.4.1 冷撕裂（縮錫開裂） .............................................................................................270
17.4.2 熱撕裂 .....................................................................................................................271
17.5 脆性界面焊點 ....................................................................................................................271
參考文獻 ......................................................................................................... 273