| Could someone give recommendation on the stencil opening for printing epoxy on HAL FR4 PCB for 0805 and 0603 size chips capacitors and resisitors. | My regular stencil manufacturer recommend the following: | Thickness: 8 mils | 0805 opening: Oblong 0.35 X 1.50mm (0.014" X 0.060") | 0603 opening: Oblong 0.28 X 1.10mm (0.011" X 0.043") | He does not sound very experience in this field that's why I am posting this msg. Thanks. | Thomas,
I'm guessing since your using mm's your inthe UK like myself so I'd be interested to find out which stencil sypplier your using for your glue printing maybe you can email me since we try and leave the name's outa here. I'm also guessing that your not too experienced with glue printing either, we had a small thread going last month so it may be worth searching the archives for it as well. As the sizes go they don't sound too far off the mark. Basically there are 2 schools of thought on printing adhesive's for SMD, dot's or slot's. Hereaus did a massive amount of work on their varidot technique and I have to say that it work's well, they will do the stencil design to match their glue so your getting the mix of appeture size / component / glue height and release based on their glues but then i your using something else you may need to tailor the set up. The dot technique basically uses different dim's of hole to produce higher dot's and is based on the 8thou' stencil. The slot's have certain advantages in that you can print wider than the body of the component which causes the glue to raise up the side of the component and give's it far greater streanth so the likely hood of it beeing 'knocked' off is greatly reduced and the chance of getting it onto the pad's is less as well. Typically I like the slot's, and I try to stick to using no more than about a 1/4 - 1/3 of the gap between the pad's for the appeture width but as I said print wider than the part. ( you still need to use dot's for the SO's normally but I recon with some work we could see them being slotted soon too). The thing you'll need to do is work on your set up of the Glue machine some folk's fall into the trap of putting in a print gap..don't do this for slot's, use on cntact get a good fast print speed to shear the glue and a stead snap off. If your not too confident in you stencil houses info contact the glue manufacturer and get them involved, it's a partnership after all and time is money so you don't want to waist it by printing bad boards and wiating for the 2nd try stencil to arrive.
hope it help's