PCB新聞 - PCB焊接中錫球產生的原因及解決方法研究

焊接過程中錫球產生的原因及解決方法研究 印刷電路板 soldering
In SMT process research and production, 合理的表面組裝工藝科技對控制和提高貼片生產質量起著至關重要的作用. We are on 這個 wave
The mechanism of tin beads produced in peak soldering and reflow soldering is analyzed, 並提出了相應的處理方法. The presence of solder balls in wave soldering and reflow soldering indicates the process
It is not completely correct, 電子產品中存在短路危險, 所以需要消除.
波峰焊中的錫球波峰焊中經常出現錫球. There are two main reasons:
a. 因為當焊接 印刷電路板板, the moisture near the through hole on the printed 板 is heated and turns into steam. 如果孔壁上的金屬鍍層很薄或有空隙, water vapor will pass through the hole wall
Rule out, 如果孔中有焊料, 當焊料凝固時, water vapor will create voids (pinholes) in the solder, 或擠壓焊料，在印製板正面產生焊球.
b. The solder balls produced on the reverse side of the printed board (that is, the side contacting the wave crest) are caused by improper setting of some process parameters in wave soldering. If the amount of flux applied
Increasing or setting the preheating temperature too low may affect the evaporation of the components in the flux. 印製板進入波峰時, the excess flux will evaporate at high temperature and remove the solder from

Splashes out of the tin bath, 在印刷電路板上產生不規則的焊球.
針對以上兩個原因, we take the following corresponding solutions:
a. 通孔中金屬鍍層的適當厚度非常重要. 孔壁上的最小鍍銅量應為25um, 不應該有空洞.
第二, 使用噴霧或泡沫塗抹助焊劑. 在發泡方法中, 調整焊劑的空氣含量時, 應產生盡可能小的氣泡. The foam and the
The 印刷電路板 接觸面相對减少.
第3, 波峰焊接機預熱區的溫度應設定為使電路板頂部表面的溫度至少達到100℃. 適當的預熱溫度不僅可以消除焊球, but also avoid
The circuit board is deformed by thermal shock.
回流焊中錫球形成的機理回流焊過程中產生的錫球通常隱藏在矩形晶片組件的側面之間或細間距引脚之間. Placed on the component
During the process, 焊膏放置在晶片組件的引脚和焊盤之間. 當印製板通過回流爐時, 焊膏熔化並變成液體.
如果潤濕性不好, 液態焊料會收縮，使焊縫填充不足, 所有的焊料顆粒不能聚集成一個焊點. 部分液體焊料將從焊縫中流出,
形成焊球. 因此, 焊盤和器件引脚的焊料潤濕性差是形成焊球的根本原因.
原因分析和控制方法焊料潤濕性差的原因有很多. The following mainly analyzes the reasons and solutions related to related processes:
a. 回流溫度曲線設置不當. 錫膏的回流是溫度和時間的函數. 如果未達到足够的溫度或時間, 焊膏不會回流. Preheating zone
The temperature rises too fast, 達到最高溫度的時間太短, 使焊膏中的水分和溶劑不會完全揮發, 當它們達到回流焊接溫度區時, it will cause
Moisture and solvent boil, 飛濺的焊球. 實踐證明，將預熱區的升溫速率控制在1 4°C是理想的/s.
b. 如果錫球總是出現在同一位置, 有必要檢查金屬板設計結構. 範本開口尺寸的腐蝕精度不符合要求, 而且墊子的尺寸有偏差.
大的, and the surface 材料 is soft (such as copper template), 導致焊膏缺失的輪廓不清晰, 相互橋接, this situation mostly occurs in the fine-pitch devices
When the pad is missing, 回流焊後，引脚之間不可避免地會產生大量的錫珠. 因此, 根據土地格局的不同形狀和中心距離, choose a suitable template
Material and template production process to ensure the quality of solder paste printing.
c. 如果從安裝到回流焊接的時間過長, 由於焊膏中焊料顆粒的氧化, 通量將惡化，其活性將降低, which will cause the solder paste to not reflow and the solder balls will
produce. Choosing a solder paste with a longer working life (we think at least 4 hours) will reduce this effect.
d. 此外, the PCBA with the wrong solder paste printing is not cleaned sufficiently, 將焊膏留在印製板表面和通孔上. 回流焊前, 放置的組件將重新對齊,
放置以使缺失的錫膏變形. 這些也是產生錫球的原因. 因此, 應加强操作人員和工藝人員在生產過程中的責任, 嚴格執行流程.
生產要求和操作程式, 加强過程品質控制.