whinge Verb. To persistently complain, in an irritating manner. {Informal}.
Noun. To act in the manner of the verb. {Informal}.
whinger Noun. A person who whinges. {Informal}.
whingey Adj. In the manner of a whinger. {Informal}.
[http://www.peevish.co.uk/slang/w.htm]
----- Original Message -----
From: "<Peter George Duncan>" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Wednesday, January 09, 2002 5:34 PM
Subject: Re: [TN] Use of IPC-7095, -SM-782, and -7525
> George,
>
> To respond to your aside, my 2 cents worth is that the "mechanical" info
on
> component data sheets is very poor. Most of the content focusses on the
> electrical functionality of the device, but there's precious little help
> with mounting the b-----s. A few data sheets have land pattern
> recommendations if you're lucky (one diode spec I came across even had
> separate land pattern recommendations for both CR and Wave solder -
> exceptional! or may be there isn't enough to say about a diode otherwise
to
> fill a decent data sheet). BUT, there is little or nothing about
> "environment/habitat" requirements for where the component is going to
> live. How is it to be established in its new home, what sort of neighbours
> should it have/not have, how much space it needs from said neighbours,
etc.
> Particularly tiresome to find at times is lead finish information - it's
> available, often on a separate spec for the package, but there's no cross
> reference to where this info can be found, and you can be left guessing if
> it's not a "standard" package.
>
> Some more assistance to the poor board stuffer would be welcome instead of
> giving everything to our ethereal design engineers, who move on a higher
> plane. Many board designs, especially aerospace applications, use a great
> many components on a board, and to get all the needed information on each
> to integrate them all into a working design that can be manufactured is a
> herculean task. It could, I'm sure, be made a lot easier with the
> co-operation of the component manufacturers, though I guess there's a fair
> amount of butt protection involved - the more they say, the more they can
> be held liable for. Or am I getting too cynical now?
>
> I suggested a while ago on this forum that perhaps IPC could produce a
> guideline about component specs - their format, content, minimum info
> requirements for all those involved with using the component. It met with
> deafening silence - probably because there is an almost infinite number of
> design permutations and it would be impossible to cover all the bases with
> hard facts, but better information on how to determine our own solutions
> could be included, and not have the specs turn into Encyclopedia
> Britannica.
>
> End winge.
>
> Peter
>
>
>
>
> "Franck, George"
> <george_h_franck@RAY To: [log in to unmask]
> THEON.COM> cc: (bcc: DUNCAN
Peter/Asst Prin Engr/ST
> Sent by: TechNet Aero/ST Group)
> <[log in to unmask]> Subject: Re: [TN] Use
of IPC-7095, -SM-782,
> and -7525
>
> 01/09/02 10:12 PM
> Please respond to
> "TechNet E-Mail
> Forum."
>
>
>
>
>
>
> I have been playing around, blindly, with this topic for a little while.
> This is what I have learned, precious little that it is.
>
> The answer depends on the BGA construction. Many/most BGAs do not
actually
> have balls on them, they have 'bumps' of 63/37 solder. These bumps will
> completely melt during reflow, allowing the BGA to float on molten solder
> during the soldering process. For these components, you *generally* want
> the pad on the board to be the same size as the pad on the component.
With
> the pads being the same size, the resulting solder joint will be
> symmetrical, top to bottom. Since the writers of the Specs, (bless them
> all), can only guess at what pad size the manufacturers of future BGAs
will
> use, it becomes difficult to always have the right answer.
>
> Other BGAs have real 90% Pb balls on them. These do not melt, and the
> soldering process for these components create two solder joints. One from
> the Component to the 90% Pb ball, and a second from the ball to the board.
> In this case, the board pad size will depend on the ball size.
>
> There are other BGA configurations, such as solder columns, which, again,
> you have to look at individually.
>
> As an aside question (or complaint), Have people found that the
information
> the component manufacturers put in their component spec sheets (pad size
> and
> spacing, and what has to be done to route the pin out....) Have people
> found that these follow any kind of DFM process? In my experience, when
my
> Engineers choose the smallest, most dense component packages, we often end
> up with a very interesting Fab and Assembly designs.
>
> George Franck
>
> -----Original Message-----
> From: Lou Hart [mailto:[log in to unmask]]
> Sent: Tuesday, January 08, 2002 5:10 PM
> To: [log in to unmask]
> Subject: [TN] Use of IPC-7095, -SM-782, and -7525
>
>
> TechNetters, I have a question regarding consistency of 7095 (Design and
> Assembly Process Implementation for BGAs), SM-782 (the Surface Mount pad
> document), and 7525 (Stencil Design Guidelines), resulting from discussion
> with process engineers and techs earlier today.
>
> We were looking at a BGA, 20x20 package, with 1.27 mm pitch. The stencil
> design guidelines (7525, Table 1 on p. 4), call for an aperture of 0.75
mm.
> That table also refers to a 0.80 mm pad. SM-782 (section 14) says a
20x20
> BGA will have 0.75 mm balls that should go onto 0.60 mm pads. Do these
> documents contradict each other regarding pad size, and is 7525 wrong with
> regard to BGA stencils?
>
> Further, the bare board does have 0.60 mm pads for the BGA. 7095, in
> 6.2.1, p. 33, says "land diameter is usually smaller than the ball
> diameter..land size reduction of 20 to 25% has been determined to provide
> reliable attachment...".
>
> As always, thanks for any comments. Lou Hart
>
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