令人難以置信的收縮LED

　　傳統(tǒng)的硅芯片已經(jīng)縮小晶圓制造增強功能，使更小的功能，熱管理提高，和芯片的可靠性增加。日本電子制造商三菱1994首次推出芯片級封裝（CSP）?，F(xiàn)在CSPs（多以最小的附加功能的原始晶圓裂片）是家常便飯。這些設(shè)備的主要優(yōu)點是巨大的節(jié)省空間，更便宜的組件成本，和由于如減少寄生效應(yīng)因素的性能改進(jìn)。

　　然而，直到最近，CSPs是不受歡迎的LED因為從這樣小的設(shè)備中提取熱量的困難；但增加耐受更高的溫度和療效（這是脆弱的LED前代的垮臺）已經(jīng)改變了這一狀況?，F(xiàn)在，LED制造商如Cree Lumileds公司和東芝宣布商業(yè)CSP LED。

　　本文著眼于最近的演變，在LED封裝，并導(dǎo)致如何描述CSP LED從領(lǐng)先的制造商給設(shè)計師的自由想出了新的緊湊型的因素，是不切實際的與以前的一代LED。

　　Packaging evolution

　　Moore’s Law， which recently celebrated its 50th anniversary， states that the number of transistors on a chip of given dimensions doubles every 18 months as fabrication techniques improve. However， the law cuts both ways; every 18 months a chip with a consistent number of transistors shrinks to half its previous size. Such component shrinkage is a boon for designers faced with space constraints imposed when designing， for example， wearables.

　　But reductions in size due to technology improvements have proved insufficient to meet the demand for greater miniaturization. Chipmakers have responded by shrinking the volume of a component still further by systematically stripping away the packaging. The first major move in this direction was to develop surface-mount devices （SMDs）。 SMDs dispensed with the leads––which went through holes in a PCB to allow a component to both be held in place and make electrical connections––in favor of small pads （Figure 1）。 The SMD was then “placed” directly onto the surface of the PCB， with reflowed solder paste providing the mechanical and electrical connection， saving considerable space.