kicad-lib-committers team mailing list archive

[Jean-Paul Louis <louijp@xxxxxxxxx>]

As Lorenzo pointed out, glue was used in the 80’s, 90’s and early 2K’s when there was quite a few TH parts on an overall SMT board. The bottom side was SMT only, and NO fine pitch parts and NO large ICs.
So the bottom SMT parts were glued to the board as a first step process. Then the SMT top was processed, then TH parts added and soldered in a wave solder machine that soldered also the bottom SMT parts. To improve assembly yield, I designed special pads for SMT bottom (bullet shape).
I used that heavily (a few million boards) in the 90’s on fairly dense mixed tech boards for Telecom.
Now that TH parts are slowly disappearing (at least in % of total parts), the technology is almost obsolete.

Jean-Paul 
AC9GH


On Sep 15, 2014, at 7:57 AM, jp charras <jp.charras@xxxxxxxxxx> wrote:

> Le 15/09/2014 08:30, Lorenzo Marcantonio a écrit :
>> On Sun, Sep 14, 2014 at 07:09:32PM -0400, Carl Poirier wrote:
>>> The SMD resistors and capacitors have an adhesive dot in the middle. Should
>>> all SMD components have one? If so, is there a recommended size?
>> 
>> Adhesive is only used for some kind of manufacturing (SMD on wave
>> - mostly obsolete - and two side processing without differentiated
>> melting point). Size depends on the specifics of the adhesive and on the
>> weight of the component, so AFAIK there is no standard.
>> 
>> I'd leave it out of the standard library, it's a very specialized
>> feature. Never had to use glue in my life:P
>> 
> 
> I agree: a "glue" layer is not useful (mostly obsolete), and I also
> never had to use it.
> 
> Adhesive layers (note: they are not named glue layers) are certainly a
> very specialized feature.
> 
> On the other hand, they are paired layers.
> 
> Please see them like layers which can be used to draw some specific
> things closely related to a footprint, like its thermal radiator, a
> carbon paste layer ...
> 
> -- 
> Jean-Pierre CHARRAS
> 
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