Hi Ken

Rainer did reply , kindly and discretely ;
yo're quite right none of the points apply apart from the precision.
The logic which Rainer pointed out is that in that precision assuring each
component
(on those dense boards must be a real chore)
does have it's set xyz (= not touching) :
the conformal coats do not suffer (crack) as the neighboring components go
to different CTE's .

Simple as that, cute care ;
now he instilled a guilty feelin' in me (of a 2 class commercial butcher).
Only luck is not having to concoat

O&O         paul

-----Original Message-----
From: Kenny Bloomquist [mailto:[log in to unmask]]
Sent: Friday, 7 January 2000 7:47
To: [log in to unmask]
Subject: Re: [TN] Component Stabilizing for Wave Solder


Paul,

You ask some very valid questions and that's why I started this thread.

In response to some of your questions:

>could you enlighten me please: why the spot-bond , and what is the
>detrimental effect occurring (?) with loose seat ?

Small PTH components can float and tip during wave solder.

>(upon loose cooling on crystalline formations ?)
>Always thought the joint is actually too robust (as those with cavities
>actually live longer),
>but if you say this kind of effort is worth it , than 'm missing something
.

I don't think this is the issue unless you have a jerky machine that can
knock components around, but then you have a lot bigger problem than
stabilizing some components.

>And how do you spot-bond actually (hand?)?

Some do it by hand but we use an Asymtek X-X-Z machine along with some hand
application.

>Would a delayed heat (quartz tube just behind wave) postpone the solidus
>just long enough to freeze in peace ?

Again I don't believe this is the concern.

>What would be the validated/qualified difference with and without (the
>spot-bond)?

Perfection of the product with no misaligned components.

Just some thoughts, I sure others will have more.


Ken Bloomquist
Sr. Principal Process Engineer
PRIMEX Aerospace Company
P.O. Box 97009
Redmond, WA 98073-9709
http://www.primextech.com

Ph:   425-885-5000
FAX: 425-882-5786
[log in to unmask]

Northcon/2000, Chairman of the Board
http://www.northcon.org

Electronics Manufacturers Association (EMA), President
http://www.ema-wa.org

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