[sdiy] Why transistors arent square!

[karl dalen]

I still cant se your argument that the halfsphere are cheaper?
If you take a close look its not even halfspherish, its infact
made of twho very different millings for the tvo mold pieces.
The top is rectangular but has sort of slanting edges!

That mould design would be more expencier then a true half sphere
as you sugest, then i could have agreed to your sugestion!

Another argument are that SMT came first , however it may be
as you hint a tradition thing borrowed from the metal canned 
transistor era!?...... Yet its a drag! :)  

Reg
KD


--- Den mån 2009-02-16 skrev Tim Parkhurst <tim.parkhurst at gmail.com>:

> Från: Tim Parkhurst <tim.parkhurst at gmail.com>
> Ämne: Re: [sdiy] Why transistors arent square!
> Till: dalenkarl at yahoo.se
> Kopia: synth-diy at dropmix.xs4all.nl
> Datum: måndag 16 februari 2009 00.05
> On Sun, Feb 15, 2009 at 10:13 AM, karl dalen
> <dalenkarl at yahoo.se> wrote:
> 
> >
> > 2009-02-15  Tim Parkhurst
> <tim.parkhurst at gmail.com>:
> >
> > > My guess is that this is a very easy shape to
> make a mold
> > > for, and it's also
> > > a VERY easy finished product to get out of the
> mold.
> > > Basically it comes down
> > > to manufacturability. Molding technology has
> improved over
> > > the last few
> > > decades, but the half round is still a very
> simple thing to
> > > make. It might
> > > also have a slightly larger outside surface area
> (helps
> > > cooling).
> >
> > Nope, there are sot23 devices with worser spec
> who's more costly
> > then TO92's so the molde are no issue to the end
> cost of the product
> > at these levels. It's a managing problem,
> conservative managers destroys
> > products and markets just because they want to feel
> important and
> > want to flux their prestige!
> >
> > KD
> >
> >
> Yes, SOT23 packages are rectangular, but remember they:
> 
> 1 - were developed several decades later, when the molding
> technology has
> improved and decreased in cost a great amount.
> 
> 2 - are much smaller, and don't have the same style of
> leads.
> 
> 3 - are designed for placement with automated equipment.
> 
> In short, I think the half round package was probably the
> best choice at the
> time (1960s / 1970s), and this packaging style has
> continued until today out
> of tradition (although it may also be that the half round
> is still a very
> inexpensive package to manufacture). Modern SOT packages
> are rectangular
> because it's economically viable to make them this way
> and, most
> importantly, because SOTs are designed to be placed with
> automated
> equipment. I'll agree that there could well be egos and
> personal agendas in
> play when decsions are made, but I'd like to think that
> most engineers would
> chose a certain design because it works better and/or is
> significantly less
> expensive.
> 
> Tim (round peg / square hole) Servo
> -- 
> "A nation cannot prosper long, when it favours only
> the prosperous." -
> Barack Obama


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