Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Solder Balls at component side around Pin in Paste components

Views: 4138

#73059

Solder Balls at component side around Pin in Paste components | 13 November, 2014

Hello,

I'm fighting with problems of random solder balls that appears after reflow soldering around Pin in Paste component. I'm mounting this component with Pick and Place machine. I'm using solder paste type-3 and this is lead free product. This is one side board. Product it's not protected with any extra layer (i.e. coating) in further steps so it's not acceptable for customer. I'm doing a little over print during paste printing for this component to achieve proper volume of solder paste after reflow. Do You know any Expert/Master that it's not corelated with any solder paste, equipment manufacturer that could review my process and indicate area to improve?

reply »

#73060

Solder Balls at component side around Pin in Paste components | 13 November, 2014

Hola,

I've used the free e-book that I'm attaching when I implement the first Pin in Paste process, it was helpful.

http://www.smtnet.com/Forums/index.cfm?fuseaction=view_thread&CFApp=1&Thread_ID=17555&mc=10

One thing that was helpful was also the solder pre-forms, most of the solder paste suppliers can provide them, may be some samples to start with

Saludos!

reply »

#73085

Solder Balls at component side around Pin in Paste components | 14 November, 2014

Are you experiencing the solder balls on the opposite side of connector insertion or same side? If it's the same side as connector insertion how many strokes are you using at?

We've experienced a few issues with pin in paste, everything points back to your screen printing process.

reply »

#73087

Solder Balls at component side around Pin in Paste components | 15 November, 2014

Same side (component side) if You give me e-mail I can provide You more pictures. I'm making one stroke with same speed (I'm using closed proflow head and DEK printer). 5 mils thickness stencil. Products requirement - 3 IPC Class (75 % and more filling inside hole). I'm making overprint to achieve proper solder volume. How big impact on solder balls can have: - over printing - solder mask

Pin in paste component it's a big relay. A lot of small components (chips) around. Big Delta T between cold and hot spot during reflow.

reply »

#73097

Solder Balls at component side around Pin in Paste components | 17 November, 2014

Sounds like your snap off profile needs adjustment. More than likely there is paste under the stencil being transferred over to the board. Try adding a cleaning cycle after every board to determine if this is the issue. If the solder balls go away after cleaning after every cycle I'd look at the snap off speeds.

reply »

#73111

Solder Balls at component side around Pin in Paste components | 19 November, 2014

Probably not all the overpinted paste is flowing onto the joint. You may need a paste with great coalescence properties so it all flows together, and doesn't leave any on the resist. Does the paste drip out the through hole too ? If so it suggests it has poor hot slump, and that can make it poor for pin in paste...the printed paste can flow so far off the pad that it will never all reflow into the joint. Just forms solder balls on resist. Which paste are you using ?

reply »

#73154

Solder Balls at component side around Pin in Paste components | 25 November, 2014

Could be. I am making overprint to achieve proper amount of solder paste inside hole. Now I am trying to reduce maximum overprint and compensate it with step - up stencil. This could reduce effect that some particles of solder paste are not gathering together and occurs randomly on PCB. Are there any reccomendation regarding design rules for pin in hole components? I want to check how far I can go with modification. Regarding solder paste I'm currently using solder paste from Senju type -3. Is there any quick method to check coalescence of solder paste? Based on information from You I have three areas where I have to focus: a) paste printing - design of stencil, snap-off, understencil cleaning quality, solder paste coalescence parameter (I am not sure how could I check it). b) material impact - solder mask, I heard that roughness and surface tension could also have impact of amount of solder paste - I am looking for some simple method to check roughness and surface tension at each batch of PCB to make sure that this is not changing for each batch. I heard that surface tension could be reduced temporary with plasma treatment. I'm not sure if this is correct c) profile impact (I have to prepare trials with different profiles, linear, plateu profile, different setup of nitrogen levels)

reply »

SMT in-printer dispensing

PCB machines