注意事项：
1、请依照《SMT生产(X-Ray)工作指导书》操作X-Ray进行检测；
2、请在X-Ray 10倍放大下检视BGA偏移状况
创见资讯（上海）有限公司
标准：焊点饱满，球
径大小均匀，形状呈
圆形，颜色较深且，
无气泡等不良。
两个本来不连锡的锡球，过炉后连锡X-RAY照过某一球颜色较浅且球径较小1、锡球偏移≤25%为可接受2、锡球偏移＞25%为不可接受 图象模糊或偏白，或整体偏小，球的图象大小不一表现为BGA形状不规则1、气泡在X-Ray中观看呈现一个个圆形的白斑
2、越严重气泡图像越明亮气泡体积32.6%，拒收；25%为锡球体积的1/4DDR2颗粒 11×9单面正确之图片须空出4个PAD点锡球整体向第2列偏移一颗锡球。
JUSTSUNBGA Joint 實例分析¾Blow Hole¾Cold solder joint¾Crystalline Fracture¾Flux Residue¾Incomplete Solder Melt¾Micro Crack¾Misregistration¾Poor Fusion Zone¾Poor Grain Structure¾Scaling¾Single Drop¾Solder Bridge¾Solder Splash¾Surface Tension Lines¾Tin 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.在迴焊過程㆗,錫球表面出現孔狀或圓形陷坑狀稱之,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). 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. 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 PCB 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. 其顏色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Fig 4.4 Rework 之助焊劑殘留(塗佈不良)c. Additionally, fluxes will react differently depending on the PCB substrate material and temperature profile.此外, 在使用不同的PCB基板材料與溫度曲線之差異也會有不同的反應.Fig 4.5 Poor structure ㆗混有助焊劑殘留Solutions:a. Proper cleaning of the PCB after reflow or rework.在迴焊或重工後,適當的清洗PCB板,但由於BGA內部無法有效完全清除,如清洗劑與助焊劑在內部聚集殘留,反而易產生SIR不良問題.b. Changing the type of flux used can lead to a decrease in residue. Some fluxes will react differently on va.改變助焊劑種類可降殘留或適當調整預熱段溫度與時程將有助於降低Flux residue.不良現象(五) : 不完全熔結( Incomplete solder melt )Definition:Solder paste and/or solder ball (BGA) did not completely reach reflow temperature. An unmelted portion of the solder paste remains in the joint.錫膏與/BGA 錫球未完全達迴焊溫度,使得錫膏未熔化即加熱完成,而有部份仍停留在焊點㆖形成類似冷焊之不完全熔接; 另㆒情形為欠缺Solder Paste 及PCB ㆖缺Pad (Land).Cause:a. Peak temperature was not high enough or the dwell time at peak was not long enough to allow for complete reflow.尖峰溫度(Peak Temperature)不夠高或停滯時間(dwell time)不夠長來提供完全的迴焊，此外印刷時欠缺錫膏也會此情形。
