1、Sources of VoidsSources of VoidsN2(g)Chamber2Pressure=P2P1P2LN2N2(g)Chamber1Pressure=P1Molten solder在錫球生產過程中,會使用兩個壓力不同的Chamber,上方镕解槽C的壓力大于下方冷卻槽,并借著壓力差使镕融的錫從Chamber 1被擠壓到Chamber 2滴落,并在Chamber 2冷卻成形在溶融的錫中,所有的氣泡都會因為浮力而懸浮在镕融的表面上,所以在溶融液中是沒有氣泡的镕融且未含氣泡的錫在冷卻階段隨著時間變成球形錫球生產的方式Sources of VoidsPackage sideFluxP

2、ackage sidePackage sidePackage sidePackage sideBoard sidePasteBoard sideBoard sidePackage sideBubblePackage side芯片植球的過程芯片Mount在主板上的過程有機會消散掉三明治結構讓氣泡無法散去Sources of Voids Shrinkage the interior of a solder joint is the last part of the joint to solidify so you expect it to have a void. Moisture and con

3、taminates supply gases that can be trapped. Flux in the paste degrades and becomes gaseous during ramp-up in the reflow oven. On a BGA the gases are tightly sandwiched between two surfaces and the voids that occur typically rise to the top of the solder joint. A high ramp rate can cause more voiding

4、 by not allowing time for void migration out of the joint (ramp rate example, 75 vs. 60C/minute) Paste flux to attach PBGAs tends to produce fewer voids than with solder paste. Too much flux added during the rework process can cause voids. Proper oven profile and clean parts can reduce solder voids錫

5、球內的氣泡通常導因于錫球陷縮,濕氣與錫膏揮發物-陷縮:通常,錫球的內部是在整個焊點的固化過程中最后冷卻凝固的部份,可以預期這樣的現象會導致陷縮孔產生-濕氣跟污染物在揮發時被錫球捕捉而形成錫球內氣孔-錫膏內的助焊劑在回焊爐升溫的過程中因為降解而呈現汽化的狀態.而在BGA中,揮發的氣體將被緊包在像三明治一樣的兩層PCB板間,而產生的氣泡也通常會上升到錫球的上方.通常一個比較快速的升溫曲線會使錫球內產生更多的氣泡,因為沒有足夠的時間讓氣泡可以移動到錫球表面消散掉-PBGA所使用的助焊膏比錫球用的助焊劑較不易產生氣泡-在維修過程中所加入的過多助焊劑會導致錫球產生氣泡-合適的爐溫及干凈的零件會降低錫球產

6、生氣泡Sources of Voids: Especially for ImAg BoardGalvanic Corrosion:電鍍銹蝕腐蝕當兩種不同的金屬直接接觸并曝露在水或含融鹽的水等電解質中，會產生電鍍銹蝕腐蝕。電流會在兩種金屬之間流動，類似電池的化學反應因而產生。兩種金屬之間的電位差越大，氧化的速度越快；反之，電位差越小，氧化的速度越慢。而銅與銀之間的電位差使得銅箔表面出現陷穴Sources of Voids: Especially for ImAg BoardImmersion AgCu caveFluxIMCIMCIMC銅箔中的陷穴,導致了氣泡的生成IPC-7095B對錫球的描述

7、Type A: Void(s) within the ball (package level) as received.Type B: Void(s) at the ball/package substrate interface as received.Type C: Void(s) within the ball after board level assembly process.Type D: Void(s) at the ball/package substrate interface after board level assembly process.Type E: Void(s

8、) at the ball/board substrate interface after board level assembly process.Voids classification in IPC-7095BMacrovoidsare the most widely occurring voids in solder joints. These are caused by volatile compounds that evolve during the soldering processes. These macrovoids generally do not affect the

9、solder joint reliability unless they are present at interfacial regions in the solder joints where cracks typically propagate.Macrovoids 是最常在錫球中廣泛出現的Void,導因是揮發性的成分在焊接過程中釋出的氣體.這類的Void并不會影響錫球的可靠度,除非是在出現在交界面上的Void,因為這類的Void通常會使裂痕增長Planar Microvoidsare a series of small voids, in relatively the same pla

10、ne, located at the interface between the PCB Lands and the solder. These are caused by copper caves under ImAg- surface-finish coated lands. They do not affect initial product quality, but can affect long term solder joint reliability.Planar Microvoids是位在同一平面的一系列小氣泡,且通常座落在PCB面與Solder之間.這通常來自于化銀板表面處理

11、上的銅的孔洞.雖然不會影響初期的產品質量但是卻會對solder的壽命產生影響(化銀板容易有微氣泡)Shrinkage Voids are caused by the shrinkage during solidification, mostly for SAC and other lead-free solders. They do not generally appear near the solder-to-PCB land interface and do not impair the solder joint reliability.Shrinkage Voids導因于固化過程的收縮,

12、常出現于Sn-Ag-Cu等無鉛錫球上.這些Void不會出現在錫球跟PCB的接面上,且不會損害錫球的可靠度Voids classification in IPC-7095BMicrovia Voidsare caused by the presence of microvias designed in the PCB lands. Large Microvia Voids, if located in solder joints in high stress areas of a package, can impact solder joint reliability.Microvia Void

13、s是因為將微盲孔的設計應用在PCB板上所造成的.大型的微盲孔,如果位置是在芯片高應力區的錫球中,將會沖擊到錫球的可靠度IMC Microvoidsoccur within the Intermetallic Compound (IMC) formed between copper and high tin solders, including SAC and tin/lead solders. These IMC Microvoids do not form immediately after the soldering process, but after aging at high tem

14、peratures or during temperature cycling of the solder joints. The true root cause is still under investigation,but a Kirkendall voiding mechanism may play a part. These voids can affect solder joint reliability, particularly in instances when brittle fracture is initiated within the IMC during drop

15、or mechanical shock to the solderjoint.IMC Microvoids通常發生在含錫量高的錫球中的IMC層內錫球與銅之間,包括Sn-Ag-Cu跟錫/鉛類的錫球.這類IMC中的Microvoids不會在焊接過程中立刻出現,但是會因為高溫老化或是高溫循環而出現.真正的根源仍在調查中,但是Kirkendall微孔形成機制可能在其中扮演了一部分的角色.這些Void會影響錫球的可靠度,舉個特別的例子來說,這些Void會在IMC層中成為摔落或沖擊測試時粒子破裂的起始點.Pinhole Voidsare caused by pinholes in the copper l

16、ands of the PCB. With sufficient quantity, they can affect solder joint reliabilityPinhole Voids是因為PCB板銅面上的針狀凸點或凹陷造成.如果數量夠多的話,會影響到錫球的可靠度Voids classification in IPC-7095BWhen there is more than one void per solder ball, the dimensions of the voids will be added to calculate the total voiding in that

17、solder ball.如果錫球中的氣泡多于一個,則氣泡尺寸的計算必須根據所有氣泡的尺寸來加總In regard to voids and the percentage of voids within the ball, location of the voids is of greater concern. There is no evidence or empirical data that indicates that voids within the ball will cause failure. Voids at the interface between the ball-and

18、-package substrate as well as voids at the interface between the ball and the PCB will be more likely to contribute to solder joint cracking. This is because cracks (if they occur) will typically occur at the interface and the void or voids can provide (in time) a path to accelerate the cracking con

19、dition.相對于對Void本體及Void在錫球中的大小, Void的Location才是比較需要在意的.目前并沒有證據或是經驗值可以指出在錫球內的氣泡會導致失效發生.但是生成在芯片封裝底層跟錫球間與錫球跟PCB板之間的Voids比較可能使得錫球破裂.這是因為裂痕(如果有的話)通常會出現在接口層或是氣泡上,亦或是由氣泡提供了一個可以使破裂情況加速的途徑Intel JG Fab B Socket H X-sectionShrinkage VoidsIntel JG Fab B Socket H X-section + PCH D&PComponent sidePCB sidePlanar MicrovoidsComparison between Different Suppliers: Fab AEllingtonBTHC9350000EE & EBTTM9370003DBTCBTJG9410002W在Fab A,不同的Vendor所呈現的氣泡模式中,即可發現BTC與E&E不同,但也都出現在最具威脅性的IMC層上Comparison between Different Suppliers: Fab BE&EBTJG9460000TBTCBTJG9410005G在Fab B時, E&E的氣