Gold Emmersion

[Rod Ladwig]

Hi Tom

Have you go any comments on gold immersion verses HASL for BGA and fine pitch devices. Are there any technical references? Are there know problem areas like gold embrittlement and how to control this? Any high frequency problems with the NiAu barrier?
Has the IPC done any research in this area?

Thanks

Rod Ladwig
Unique Designs

[Tom]

Gold plated boards are much more robust in storage life and less handling critical, but are far more expensive based on gold’s market value. The gold may also have issues with solder joint integrity as the lands get smaller. Solder with excess gold in the joint causes solder embrittlement which affects long term reliability.

With the widespread use of ball grid arrays (BGAs) and finer pitch devices, the need for flatter board surfaces has become more critical.

In the nickel/gold finish, the lands of the board are over-plated with a layer of nickel and a thin coating of gold is then applied to protect the nickel's solderability. With nickel/palladium gold, first nickel is applied then a layer of palladium to enhance solderability of the nickel followed by gold for tarnish protection.

There are many other surfaces that also apply. All of these metallic finishes have their pros and cons, and it depends on the board manufacturer's capability to provide a solderable surface that work in conjunction with the solder mask requirements.

One of these is Hot Air Solder Leveling (HASL). This is the current predominant surface finish where the board is dipped into molten solder after the final copper plating process. In this process, the board is either dipped vertically or horizontally into the solder bath at approximately 260ºC and excess solder is blown away with hot air. The key problem with HASL processes is that solder thickness varies widely from 0.75um to 35um.

For more information, see this thread:

http://www.pcbstandards.com/forums/showthread.php?s=&threadid=935

[Ryan Marston]

Is there a list of Board Fabricators that do Immersion Gold somewhere. We are looking into alternate vendors and would like to find a list or other peoples opinions of vendors. Any help would be great!!

Thanks

[Tom]

Ryan,

I know exactly what you mean. For instance: Tyco in San Jose would rather give you a Gold Plate rather than a HASL Plate. Hallmark Circuits would rather give you a Silver Plate rather than a HASL Plate and there is no extra charge.

Tim Estes - "Between The Conductors" is doing market research for IPC on manufacturers capabilities www.cat-test.info. You can contact Tim at - tim.estes@cat-test.info.

Harvey Miller is the guy - hmiller560@aol.com or 650.327.2029
Harvey is in Palo Alto and is the creator of FabFile, which is updated quarterly. It is a very reliable source for U.S. and Canada companies. Unless a company is very new, it will be in Fabfile. Foreign companies are not tracked (i.e., Unitech). Unfortunately this is not a free service.

Also, Patricia J. Goldman knows every manufacturer in this country, but she gets her data from Harvey. Patricia is the sales representative for PPG Industries, Inc. They sell a Positive-Acting Eletrophotoretic Photoresist to the PCB manufacturing industry that will allow us to design 0.05mm trace/space technology.

Patty
Patricia J. Goldman
PPG Industries, Inc.
724-274-3417
goldman@ppg.com

There have been many changes in the manufacturing industry in the past year. Many fabricators have closed shop many have been acquisitioned and many more are on the chopping block. Dynamic Details got a stern warning from Wall Street that if they do not get their stock up to $1.00 per share for 6 consecutive weeks that NASDAQ will pull them off public trading. All of these activities are very difficult to keep up with.

[kungfucharlie]

Ther are some good references on Merix's website at http://www.merix.com/main_res.html. Attached is a pdf that covers most of your questions I downloaded from their site.