Impact of Spread Performance of cored solder wire for LED Luminaire Assembly

Posted 11/1/2016 by Amit Patel, Project Manager - Engineer for the LED Technologies


Cored solder wire is widely used in the LED Lighting industry ranging from applications such as retrofit lamps, linear tube lights and down lights, with the main function being to connect different systems to create the luminaire / lamp. More specifically examples include assembling the connection of a power driver board to an LED engine array, assembly of an end / base cap for socket-based bulbs and board to board connections for linear lighting.

The performance of cored solder wire for the lighting industry can provide both unique areas of value associated specifically with the LED industry and values commonly seen in the traditional electronics industry. One particular value is the spreadability performance of cored solder wire which can directly impact areas such as throughput, reliability, material consumption and aesthetics.

A significant percentage of A19 retrofit lamps still utilize cored solder wire for assembling end cap sockets. In order to solder a diameter of 10mm around 0.5 to 0.7 grams of solder is used to create the electrical connection. Proper solder contact and surface uniformity are key metrics necessary for the solder point contact to reliably serve as the electrical gateway for the bulb which should last 10+ years. Furthermore, the volume required to create a reliable full contact solder joint can directly impact the system cost driven by material consumption.

Solder joint quality, contact reliability and volume are largely dependent on the degree of spread. It is important to understand that surface finish, level of surface contamination, flux % and flux chemistry are key drivers for revealing good vs. poor spreading performance. To quantify the effect of good vs poor spreading. ALPHA® Telecore HF-850 SnCu and Benchmark “A” SnCu were measured using the JIS protocol, both solder wires have the same flux % and diameter sizes. Repeating the JIS Test Method for 0.2 to 0.5 grams with 0.1 gram increments produces the following control chart.

Mass of Solder VS. Spreadability 

Figure 1 – Mass of Solder vs. Spreadability

The chart indicates that ALPHA® Telecore HF-850 produces a higher physical spread using less mass when compared to the Benchmark wire on the same process and surface conditions.

Applying the consumption control chart to the end cap/base socket soldering application we can calculate that 0.220grams of Alpha HF850 solder is needed to create a diameter of 10mm versus the 0.340grams needed for Benchmark Product “A”. This equates to an extra 0.120g (~55%) wire needed to make the same 10mm diameter using Benchmark Product “A”.

Deriving market based assumptions in unit volume production of A19 LED bulbs for a single customer produces the following savings in volume per year when compared to the Benchmark. ALPHA® Telecore HF-850 SnCu utilizes 35% less material in weight compared to the Benchmark over the course of 1 year.

A19 LED Bulbs Savings Per Year

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