Letter 1027

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My vendor is proposing a cost reduction of ~ $ 8.00 to the power supply Tray used in our unit. This will consist of changing the material from a post-plated material to a pre-plated material.

What difference that will make in term of material quality and performance?

Thanks.

Cliff B [last name deleted for privacy]

Normally, the cost advantages of preplating accrue from the fact that the raw material is plated as a continuous strip. The problem is that when you shear pieces out of this, there will be no plating on some or all of the edges.

Rarely will an unplated steel edge be a satisfactory finish unless you can roll it under to keep it unexposed. If you are zinc plating, maybe, since zinc is sacrificial to steel and can protect it to some extent even where the steel is not covered. But nickel or tin preplating? I don't think so.

 
Ted Mooney, P.E.
finishing.com Inc. - Brick, NJ

Hi Cliff,

Sorry to chime in late but it would be extremely helpful to us if you informed us of the materials of construction and the plated materials. In addition to sheared edges, if the material is to be worked at all in a forming operation the plating may crack and delaminate as well, unless the deposition process has been specifically tuned for a workable deposit. Electronics mfg runs into this as pre-plated IC leads must survive trim & form operations.

Rgds,

Dave Kinghorn
Chemical Engineer - Walnut, CA

We have been stamping pre-plated tin/on steel for the consumer electronics industries for years and have never had a problem with cracks or delaminations.

M. DAVID

I have spoken with mechanical engineers and designing for many electronics OEM's, and there is definitely a trend toward using preplated material.........PCs and other chassis are now frequently made from preplate.......the exposed steel on the sheared edges is not a problem to them. I am talking about companies like HP etc.

Regards,
Pat K

Pat Kelly

But it still depends on the environment and the plating material. Zinc is sacrificial, and protects steel despite the exposed edges; plus, most PCs are exposed to pretty benign environments.

Using a non-sacrificial plating with exposed edges in a less benign atmosphere is a big problem though. Most of the plating equipment suppliers have at one time or another put their electronic controllers out on the plant floor and seen what a damp, acid-laden, environment does to them. I have seen integrated circuits actually break off the board (not one leg, all 16 legs) in under 3 years in some of the older plating shops with poor ventilation and unsealed electronic cabinets.

 
Ted Mooney, P.E.
finishing.com - Brick, NJ

We make switch mode power supplies for telecommunications and have always used zinc plating with chromate conversion. Recently we have discussed going to pre-plated steel. Does anyone know exactly what kind of pre-plate the Personal Computer manufacturer's are using. From what we can tell it looks like it would do the job for us. Is it as good as zinc chromate for corrosion protection? Any responses would be appreciated.

Thanks,

Peter Stern
- Burnaby, BC, Canada

I represent the United States largest producer of preplated strip products. We supply a wide range of pre-plated nickel and zinc products into the automotive, electrical, computer, household, and office equipment markets. Not every application can be switched to preplated, but a great deal of them CAN and DO.

Mike Hartman
steel strip - Warren, Ohio

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