Article:
Circuit Board and Component Design Recommendations for Lead Free Wave Soldering

Customer View point

Contact Info

Subscription Info

Circuit Board and Component Design Recommendations for Lead Free Wave Soldering

In addition to machine changes, there is evidence that minor changes in the design of boards and components can have an affect on the number of defects observed in a lead free wave solder process. 

Production experience has proven that modifications to board design can reduce solder defects. One of the key areas of focus has been in reducing bridging defects on DIPs and connectors. Bridging defects on these parts are typically due to lack of pads immediately following the problem area on the board. By adding a scavenger pad immediately following the area in question, the solder has a place to contract to and reduces the chance of excess solder on the contacts, thus eliminating the chance of a bridged connection. The illustration below highlights the recommendations for eliminating bridging of connectors.

Design for Minimizing Bridges

No short because downstream joint onto which excess solder can jump during peel-back		Short because no downstream joint onto which excess solder can jump during peel-back

QFP orientation and use of corner solder scavenger pads also reduces bridging. Orienting the QFP at a 45° angle relative to board travel has been given the best results in lead free soldering.

Topside pad coverage is also improved by keeping the topside pad diameter less than 0.3mm.

Providing for Lower Spread

Components also can be modified to reduce defects in lead free wave soldering. The most common modification is in the lead length and experience has indicated that the shorter the lead is maintained the less chance of bridging and the greater through-hole penetration occurs. The shorter leads will heat quicker and allow the solder to wick up the through-holes giving better topside solder coverage. 

CUSTOMER INTERVIEW

KYUSHU MITSUMI CO., LTD.

Evaluation of Strength Test Results and Cost Factors

Iizuka-City, according to the Land Development Policy, has now transformed from land of coal mining into “The City of Information Industry”. Totally funded by Mitsumi Electric Co., Ltd, Kyushu Mitsumi Co., Ltd. was established in Iizuka-City in 1969. The company manufactures coils, switches, power supplies, and other customized products. However, it is the leader in the production of mobile phone adapters and the power supplies equipment of mobile electronic equipment, covering a total of about 60-70% of the domestic market share.

The company considered going lead-free in the beginning of 1999. Reliability tests and cost comparisons of all kinds of lead-free solder had been conducted continuously for a period of one year. Finally, the use of lead-free solder commenced in July 2000, and the Department of Power Supplies Equipment began the actual use of SN100C in October 2000. “In every kind of tensile strength tests, SN100C’s performance was not inferior to the tin-lead alloy. It is less costly when compared to the tin-copper-silver alloy, its wettability has improved and also dross generation is small. These are the reasons for choosing SN100C.”, expressed Mr. Isamu Kushida (Vice Counselor of the MPS project).

“Our power supplies printed circuit boards are all single sided, therefore there is no need to worry about lift-offs. And because the soldering method is for a wave soldering method, SN100C is just the right alloy for it. Furthermore, as SN100C is a patented product, we feel at ease in using it,” added Mr. Kushida.

The company is gradually shifting its production overseas with the power supplies equipment shifting to Tianjin Mitsumi Electric Co. Ltd. And Zhuhai Mitsumi Electric Co. Ltd. and the Philippines. Of the 14 soldering machines in Tianjin Mitsumi Electric Co. Ltd, 11 are lead-free and all use SN100C in their production. With plans to move forward in going lead-free, including international operations, Mr. Kushida requested, “We hope soldering materials manufacturer would put more effort in dealing internationally.”

SN100C has been patented by Nihon Superior and is offered worldwide through licensed manufacturers including FCT Solder for North America. We offer SN100C for wave solder and lead tinning, reflow solder paste applications, and SN100CL for lead free hot air solder leveling (HASL) of P.C. Boards.

We will be including in future newsletters, many of the advantages our current customers have discovered in switching to SN100C as their lead free alloy of choice and we welcome your comments and questions. We look forward to working with you to make your transition to lead free as successful as possible.

For more information about our products, please visit our web sites at www.finelinestencil.com for stencil products and www.fctassembly.com for solder products.

All files for stencils, templates and PCB carriers should be sent to sales@finelinestencil.com to assure immediate attention.

Think Green! Organizations and Companies that shift from paper-based flyers, postcards and direct mail pieces to web-based communications help reduce the number of trees that are cut down (as well as the quantity of junk mail that is instantly recycled or thrown away. More trees mean that the earth is able to convert CO2 (a product of greenhouse gasses) back into life-giving oxygen. And more trees mean more habitats for plants, animals and the creepy-crawly things of the world.

Subscription Info: If you do not wish to receive further notices from Fine Line Stencil or FCT Solder please go to this page on our web site to unsubscribe: click here

This newsletter is powered by BracewellWebWorks.com