SEMICON Taiwan: Li-San Chan, Global Product Manager at Heraeus Electronics, explains which solder paste is the right choice for which application and how manufacturers can avoid production line delays and package defects.
Heraeus Solder Paste - System-in-Package
How does solder paste work?
Solder paste is a mixture of metallic alloy in powder form and flux. It can be applied via stencil printing, needle dispensing, direct dipping or jetting. After applying the solder paste, the entire substrate undergoes reflow process in an oven. Flux activates the solder powder to promote metal coalesces such that the parts are fused together for an electrical connection.
Which solder paste is the best for which use?
There are various types of solder paste for applications in communications and consumer electronics, like wireless and Bluetooth modules, but also medical technology or the automotive sector. For form factor sensitive devices, System in Package (SiP) substrates in varying sizes have more stringent requirements on solder pastes. The smaller the pad size on the substrates, the smaller the solder powder size is used for the solder paste application. For highly dense SiP applications, the spaces between components are less than 60um in width and the pad sizes are less than 100um. The corresponding powder size type must be used for effective and reliable connections. And at Heraeus, we have developed water soluble solder paste in Type 4, 6 and 7 to address customer’s needs.
But all those applications and especially those in miniaturization are very sensitive and highly prone to defects on wire bonding pads and under passive components and flip-chips.
Yes, that’s right. Manufacturers in semiconductor packaging and wafer bumping are often dealing with solder balling and solder beading. The SiP packages used in advanced packaging need fine pitch printing and better release of the solder paste. With our WS5112 paste you can print down to 70 micron pad size at a line spacing of 50um– without splashing/splattering during reflow process. These are clear benefits to defect reduction and yield improvements.
How can the solder paste achieve such a performance?
This is the result of two innovations. First of all, our Welco® solder powder has a very low oxide formation on the surface. This leads to lower voids. Secondly, the flux platform consists of carefully selected polymers that suppress splattering and splashing. Additionally, a long stencil life of up to 8 hours is achieved. Our objective is to reduce costly production line downs and eliminate package defects.
Li-San Chan is at her 21st year in the semiconductor and chip-making industry. Currently she is the Global Product Manager for Advanced Packaging solder materials at Heraeus Electronics. You can speak with her or attend her presentation at the Semicon Taiwan 2018 at booth K2968 (1st floor).
Water Soluble WS5112 Type 7 Solder Paste is the latest Advanced Packaging product offering from Heraeus Electronics, It uses the state of the art proprietary Welco® Type 7 powder (2-11um). The product is available for volume purchase and sample evaluation.
Heraeus Holding GmbH
Heraeusstr. 12 - 14
Phone: +49 (0) 6181/35-0
Fax: +49 (0) 6181/35-31 31
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