SMT單板互連可靠性與典型失效場景

第一部分 焊點失效機(jī)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(jié)構(gòu)及常見失效位置 ........................................................................4
1.1.2 焊點的失效標(biāo)準(zhǔn) ............................................................................................................4
1.1.3 焊點的斷裂類型 ............................................................................................................5
1.2 導(dǎo)致焊點失效的載荷條件 .......................................................................................................7
1.3 焊點失效機(jī)理 ...........................................................................................................................7
1.3.1 溫度循環(huán)引發(fā)的焊點失效機(jī)理 ....................................................................................7
1.3.2 機(jī)械應(yīng)力引發(fā)的焊點失效機(jī)理 ..................................................................................10
1.3.3 熱沖擊引發(fā)的焊點失效機(jī)理 ......................................................................................12
1.3.4 蠕變引發(fā)的焊點失效機(jī)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(jié)構(gòu)設(shè)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(dǎo)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(nèi)部熱膨脹失配 ..........................................................................................................18
2.2 疲勞失效的裂紋演進(jìn)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(jié) .........................................................................................................................................25
第 3 章 機(jī)械應(yīng)力導(dǎo)致的焊點失效........................................................................... 27
3.1 機(jī)械應(yīng)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(dǎo)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(jī)械應(yīng)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(dǎo)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(yīng)力敏感元件及應(yīng)力失效 .............................................................................................41
3.4.1 應(yīng)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(dǎo)致 BGA 焊點開裂 ......................................................................46
案例 6：壓接導(dǎo)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 ...............................