What is the smallest component my fellow TechNetters are capable of reliably
printing glue? I'm afraid the apertures for 0603 and below will be too
small to release the adhesive properly. I've always used 0805s as the
absolute smallest component I'll try to screen print glue. Am I mistaken?
The mix typically includes larger components which make me hesitant to use a
thinner stencil. I typically use 8-10mils for adhesive stencil thickness.
Your comments and advice are greatly aprreciated.
Mark
> -----Original Message-----
> From: Morse, Carrie [SMTP:[log in to unmask]]
> Sent: Wednesday, March 05, 2003 11:56 AM
> To: [log in to unmask]
> Subject: Re: [TN] Glue suppliers for chip-on-wave assembly
>
> Hi Doug.
> 1. We are using Loctite as our glue supplier and have no problems with
> their products.
> 2. We are using a stencil process to apply the glue. There are pros and
> cons to this as there are with any processes. One of the advantages is
> that if the board is fairly large, the time to print the glue is only
> seconds and you can use an existing paste printer to do so (no additional
> capital is needed). But, the disadvantage is that all glue heights are
> the same regardless of package. When using an X-Y dispenser, you can
> control the amount of glue with size of nozzle, time, and pressure. The
> disadvantage to the X-Y method is that if the nozzle clogs, it can be
> difficult to identify which dots are missing.
> 3. The biggest problem with a glue process is handling -- making sure the
> components do not get dislodged prior to wave. Other problems that pop up
> include bonding strength issues introduced when a components have mold
> release or other contaminants on them, or, problems with the cure profile.
>
> Also, waving some components can be a problem too especially if they are
> shadowed by others or run thru the wave in such a was as to cause them to
> shadow themselves. SOT-23's can be difficult in this aspect.
>
> -Carrie
>
> -----Original Message-----
> From: McCall,Doug [mailto:[log in to unmask]]
> Sent: Wednesday, March 05, 2003 10:17 AM
> To: [log in to unmask]
> Subject: [TN] Glue suppliers for chip-on-wave assembly
>
>
> Hi all,
>
> We have a couple of products that have come our way that are
> designed for glue-on-wave (i.e. 0805; SOT23 and some SOIC's)
> being glued at SMT and then flow-soldered in-amongst a whole
> lot of through-hole leads (500 leads on one of the assemblys).
>
> Clearances round the PTH leads make a pocketed flow-solder
> pallet not possible.
>
> 1) What manufacturers of glue do you guys recomend/use??
> 2) Does anyone use stencil printing of the glue onto the
> board before SMT or use x-y application??
> 3) What issues are there generally (boards are designed for
> this process);
>
> Generally any comments are welcome.
>
> Thanks for your inputs,
>
> Douglas I McCall,
>
>
>
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