At 07:56 PM 11/29/2000 +0800, michael wrote:
>Shirley:
>
>My $0.02:
>
>1. Surprised that you're using 7628 on a mobile phone.

<fwiw> Frequently the keypad in cellphones is on a separate simple 
doublesided or 4 layer with much lower density than the 
mainboard.  Depending on the mechanical design the keypad will need some 
stiffness (ergo thickness).

Of course, cost pressures are intense in cell phones when volume is 20K/day 
and higher so you'll see a push to use lot of  7628 to minimize material 
cost.  Save a nickel and you save several million $US per year.

I don't know what your nominal thickness is but we've had many cost 
sensitive 2 and 4 layer stackups that were 7628 in the center but with a 
1080 against the foil to give better/best surface smoothness.

Hope that helps clarify some...

regards,
Dwight

>  These are normally
>thinnish boards, so 7628 would not be our first choice of dielectric.
>2. Theory is: 7628 shouldn't be used next to outer layers, as the thick weave
>may cause uneven copper surface and ugly weave exposure-like phenomena. It
>shouldn't be used next to a lot of inner layers either, as its low resin 
>content
>doesn't fill copper-free areas very well. Did the customer approve use of 
>7628?
>3. 2116 would be better, or 2125. Is build not specified?
>4. I don't think there are any relevant specifications, but experience works
>quite well. Fact is, 7628 is a filler, and should be used sparingly, on 
>low-cost
>applications.

It's a mobile phone so by definition it is a low cost application.


>And who do you work for? You're hiding behind Yahoo!
>
>Good luck.
>
>Michael
>
>-----­ì©l¶l¥ó-----
>±H¥óªÌ: Shirley Xiao <[log in to unmask]>
>¦¬¥óªÌ: [log in to unmask] <[log in to unmask]>
>¤é´Á: Wednesday, November 29, 2000 19:44
>¥D¦®: [TN] Gold Plating Roughness of Mobile phone keypad
>
>
>|  My friend pass me another question. I hope someone
>|can give some inputs.
>|  The application is a mobile phone keypad (gold
>|plated), Motorola's engineer insists that it is not
>|acceptable if we can see the patten of glass fabric.
>|The microsection shows there is no weave exposure or
>|weave texture(use 0.014" H/H laminate,construction is
>|2 ply of 7628)
>|  1. Is it true that the circuit board surface is more
>|rough if we use 7628?
>|  2. What can do to improve the surface quality? Use
>|2116 instead of 7628 or modify the resin content of
>|7628 prepreg?
>|  3. Is there any related specification?
>|
>|  Thanks in advance!
>|  Shirley
>|
>|
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