令人难以置信的收缩LED

　　令人难以置信的收缩LED

　　传统的硅芯片已经缩小晶圆制造增强功能，使更小的功能，热管理提高，和芯片的可靠性增加。日本电子制造商三菱1994首次推出芯片级封装（CSP）。现在CSPs（多以最小的附加功能的原始晶圆裂片）是家常便饭。这些设备的主要优点是巨大的节省空间，更便宜的组件成本，和由于如减少寄生效应因素的性能改进。

　　然而，直到最近，CSPs是不受欢迎的LED因为从这样小的设备中提取热量的困难；但增加耐受更高的温度和疗效（这是脆弱的LED前代的垮台）已经改变了这一状况。现在，LED制造商如Cree Lumileds公司和东芝宣布商业CSP LED。

　　本文着眼于最近的演变，在LED封装，并导致如何描述CSP LED从领先的制造商给设计师的自由想出了新的紧凑型的因素，是不切实际的与以前的一代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 aPCBto allow a component to both be held in place and make electrical connections––in favor of smallpads（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.