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《舊文複習》有網友詢問關於電阻、電容這類SMD小零件(small chip)有空焊(solder empty)的問題。明明已經一再的檢查過所有回焊爐溫度(Reflow Profile)設定並確認無誤，可是還是經常發現這類電阻電容有空焊的情形發生，而且還出現在固定位置，觀察焊錫的狀況也未發現non-wetting或de-wetting的情形，百思不得其解？
回流焊溫度曲線(Reflow temperature profile)到底應該選擇設定成RSS型(馬鞍式)好？還是設定成RTS型(斜昇式)好呢？工作熊發現有許多的工程師都一直被這個問題給困擾著，因為有老闆要求走RTS，可是自己心理又怕怕的。
《How to use SMT Line to produce a printed circuit board? (5)》
When the small volume components such like capacitors, resistors and large volume such as BGA or connector has been placed on the circuit board by high-speed and general speed pick and place machine. The next critical step for the SMT( Surface Mount Technology) is reflowing to melt the solder paste. The temperature of the reflow will affect the final quality of the surface mount. Usually the melting point is about 217°C. and the maximum temperature should not exceed 250°C, otherwise the components will be melting and out of shape.
The temperature profile is the key to the reflow phase success. It has four different zones in temperature profile: pre-heat zone, soak zone, reflow zone, and cooling zone. Pre-heat zone usually increase the temperature slowly from normal to 150°C. And then the temperature increasing gradually to 190°C in soak zone. The reflow zone will be the highest temperature in entire zone. Ideally all the components should keep in same temperature and speed rate to ensure the reflow phase complete successfully. Finally that the product start to cooling. Generally, the maximum cooling rate is around 4 ° C / min. After that the whole PCB assembling process is done.
The reflow oven temperature profile is suited for characteristics of a particular circuit board assembly, the size and depth of the ground plane layer ... ... <看更多>
Reflow zone: The reflow zone, also referred to as the “time above liquidus” (TAL), is the part of the process where the highest temperature is reached. A common ... ... <看更多>
reflow profile 在 SMT回流焊的溫度曲線(Reflow Profile)解說與注意事項 - 工作狂人 的相關結果
電路板組裝的回流焊溫度曲線(reflow profile)共包括了預熱(pre-heat)、吸熱(Soak)、回焊(Reflow)和冷卻(Cooling)等四個大區塊，以下為個人的心得整理，如果有誤也請 ... ... <看更多>