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

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Barbara

#12573

Tombstoning | 18 February, 1999

What to look for that causes tombstoning and the corective action.

reply »

Justin Medernach

#12574

Re: Tombstoning | 19 February, 1999

| What to look for that causes tombstoning and the corective action.

| The three biggest causes that I can think of are placement machine component picking inaccuracy, placing inaccuracy, and design design design. If your placement platform is picking improperly, it will tend to catch the component on end and place in that fashion. this can happen if the pickup position is off in the x or z axis. Placing inaccuracy pretty much speaks for itself. If an end terminus isn't in the paste, it's not going to solder. Another problem is PCB layout. If one pad is SMD and the opposing pad is NSMD, you're in trouble. This will typically occur when one pad is on a plane and another is simply a routine pad. The pad gets hot before the plane in reflow and will cause the component to stand on end. This is typical of RF products. Hope this helps a little.

Regards, Justin Medernach

reply »

Steve Schrader

#12575

Re: Tombstoning | 23 February, 1999

| What to look for that causes tombstoning and the corective action. |

Check your land-patterns. If they do not meet IPC standards, change your CAD libraries to IPC (or some other industry accepted standards such as SMTPLUS). If you have "home-grown" land-patterns, changing them to IPC standards will fix a lot of your problems (tombstoning and otherwise).

If land-patterns are OK, check your placements. If they are OK, check your solderpaste printing and your reflow profile.

Most likely, your land-patterns are the culprit.

reply »

Randy Haller

#12576

Re: Tombstoning | 23 February, 1999

| What to look for that causes tombstoning and the corective action. | 1:check reflow profile 2:reduce pad size 3:reduce deposition of paste(stencil thickness/opening of aperatures) 4:Check components for solderability Good Luck

reply »

Manufacturing Software

ii-feed SMD Intelligent Feeder