Surface Mount Glue / Adhiesive

Eric R

What is the adhiesive used under surface mount components and where can it be purchased? I assume this would make assembly go much easier for the home hobbiest.

Paul Baker

The majority of the time no adhesive is used at all. Solder flux becomes tacky after exposure to air and is enough to hold most chips in place (there is tacky solder paste which is even more adhesive, and considerably more expensive). With that said, if you choose to use adhesive be sure it's hydrophobic (does not absorb moisture) and does not expand or contract from temperature and finally is able to withstand high temperatures without affecting the bond.

The major reason adhesive is tyically not used is that if rework is nessesary, it greatly complicates the removal of both the chip and the residual adhesive.

Chris Savage

Eric,

·· We use Solder-Paste·on our surface mount devices, which are then put through an oven.

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Chris Savage
Parallax Tech Support
csavage@parallax.com

pjv

Hi Eric;

Adhesive is typically used on passive components on the underside of a PCB to hold the components in place while the top of the board is being populated. It also prevents the bottom side components from "floating away" while they go through (submersed) in the wave of a solder machine. Clearly, solder paste can not do this.

For small runs where it may be too costly to purchase a solder paste stencil, we will also use adhesive to populate the top of the board, and then after it sets, hand solder the components. This greatly increases the convenience of surface mount manufacturing, and is what I believe you are trying to accomplish.

I will get the brand we use and its source for you tomorrow.

Peter (pjv)

Eric R

Well, I guess solder paste was the answer. I thought I was looking for an adhesive to hold the parts while I soldered them. So, using this paste, you place the components and then stick it in the oven? How hot and how long? Is a solder mask required?

KenM

One technique that might help is to tack down two corners, then solder with the "brush" technique.

Eric R said...
Well, I guess solder paste was the answer. I thought I was looking for an adhesive to hold the parts while I soldered them.

Paul Baker

Here are some resources for surface mount soldering,
·
A tutorial on how to adapt a toaster oven.

A tutorial on how to use a hotplate.
·
A video on the drag soldering method. (2nd under xytronics videos)


Post Edited (Paul Baker) : 5/27/2005 3:46:42 AM GMT

Eric R

Thanks for the replies!



I am looking to make a smaller package using the SX20AC/SS in place of the current BS2. I guess with a little practice a guy could do it at home. Just wanted to make sure before I invested in the SX Tech Tool Kit Plus package.

pjv

Hi Eric;

The thermosetting SMT component adhesive we use is LOCTITE 348 chip bonder for about $25 per 10 mL tube.

One tiny dot is placed for each SMT component, and then the components are placed on with a pick-and-place machine. The assembly then goes into the oven for curing, and when set is removed and hand soldered.

For larger runs a stencil (too expensive for short runs) is used to apply solder paste, in which case the adhevive pass can be eliminated unless there are SMT components on both sides of the board, and then we typically slill glue the bottom side.

Cheers,

Peter (pjv)