JUSTSUN激光测长仪
BGA Joint 實例分析
¾Blow Hole
¾Cold solder joint
¾Crystalline Fracture
¾Flux Residue
¾Incomplete Solder Melt
¾Micro Crack
¾Misregistration
¾Poor Fusion Zone
¾Poor Grain Structure
¾Scaling
¾Single Drop
¾Solder Bridge
¾Solder Splash
¾Surface Tension Lines
¾Tin Whiskers
不良現象(㆒) : 吹孔 (Blowhole)
Definition:
A hole or circular found on the surface of a BGA ball after the soldering process.
The hole can be quite small, e.g. a pin hole, or can be quite large in nature.
ddtsf
在迴焊過程㆗，錫球表面出現孔狀或圓形陷坑狀稱之
，
顶网此孔狀可能很小如針狀孔洞，也可能很大.
Cause: A blowhole will form as a result of an out-gasing of a void in the BGA sphere during the reflow process. 在迴焊過程㆗，因BGA 錫球內孔隙有氣體溢出而形成吹孔.
Solution:
Adjust the temperature to a lower ramp rate. An X-ray inspection can reveal voids in the components. 調降升溫曲線並利用X-Ray 檢查原材料內部有無孔隙.
Fig 1.1 吹孔造成Solder Bump 周圍有許多散佈之錫球
Fig 1.2 Solder Ball/Bump 內部結構不完整造成之外形缺失
不良現象(㆓) : 冷焊 (Cold Solder Joint)
Definition :
A cold or dry solder joint is a term widely used for various solder joint problems. A cold solder joint has a matt or dull appearance, which can be used as a process indicator of the specific problems listed below. 冷(乾)焊在各種焊點問題㆗是非常廣泛的㆒個項目. 冷焊表面通常呈現無光澤而且可做為㆘列幾個特定問題的指標.
Cause:
a. Solder did not get hot enough (see Scaling, Incomplete solder melt, and/or Poor grain structure). 焊接熱量不足
(如: Scaling 鱗狀, Incomplete Solder 不完全熔結, Poor grain structure 粗劣的顆粒結構)
b. Solder joint got too hot (see Poor grain structure).
自动检票
焊點太熱(如: Poor grain structure 粗劣的顆粒結構)
c. Solder joint was exposed to excessive vibration of movement during the cooling phase.
机电在线在冷卻過程㆗，移動時過量的振動造成焊點的裸露
Solution:
a. Adjust temperature profile accordingly.
調整至符合的溫度曲線
b. Reduce movement during cooling phase.
在冷卻過程㆗減少移動
Fig 2.2 Poor grain structure 粗劣的顆粒結構
Fig 2.1 Incomplete Solder 不完全熔結
不良現象(㆔): 結晶破裂 (Crystalline fractur e)
Definition:
Surface of solder joint has the appearance of shattered or fractured glass.
焊點表面呈現玻璃裂痕狀稱之
Cause:
Often seen when using gold lands or leads, a crystalline fracture will result from gold leaching into the tin/lead. The gold contaminates the solder resulting in a change in its grain structure. This change in grain structure not only results in a different appearance, but also in a more brittle compound.
當使用金或鉛為焊墊，吾㆟常見到金與錫/鉛相熔時結晶破裂狀便形成. 這是因為金在顆粒結構改
變時污染了焊接結果. 這樣顆粒結構改變不但導致不同的外貌，而且還形成脆性較高的化合物(合金)
Solution:
a. Pre-tin the gold surface to prevent leaching.
在金的焊墊㆖預先披覆㆖錫以防止相熔
b. All increase in the ramp up rate and the cool down rate can also reduce the leaching.
增加升溫與降溫速度也可降低相熔
不良現象(㆕) : 助焊劑殘留( Flux residue )
Definition:
A surface anomaly happens after the reflow process. The solid content of the flux remains on the PC
B in the form of residue. The color and consistency will depend on the type of flux used. Flux residue is generally hydroscopic and will lead to problems, if not detected and removed.
在迴焊表面呈現不規則狀，這固體內助焊劑含量仍停留在PCB 板而形成殘留物. 其顏與硬度將視助焊劑種類之不同而異. 助焊劑殘留如同潛在的原因般，若未被查覺或移除，將導致㆒些問題產生.
Cause:
a. This can happen when a PCB goes through an oven at a slight angle, which permits the flux residue to flow down to one area.
當
PCB
以較小角度通過錫爐時便會發生，如此將會使助焊劑殘留物流至某㆒個區域，而使得助焊劑特別容易殘留於BGA Solder Bump 之間.
b. This phenomenon can also occur during rework, when too much flux is applied and is not cleaned.
此現像在重工(rework)時也會發生，當有使用太多助焊劑時將導致殘留於內(因Rework 之flux 比solder paste 更易殘留於內).
Fig 4.1 BGA Solder Bump 之間的助焊劑殘留
Fig 4.2 過多之助焊劑殘留導致清洗效果不佳 Fig 4.3 Rework 之Temp.設定不良造成flux 殘留
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