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October 2010

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TechNet E-Mail Forum <[log in to unmask]>, "Hart, Dale L CTR USAF AFMC AFRL/RXSA" <[log in to unmask]>
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Mon, 4 Oct 2010 15:59:09 -0400
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Robert Kondner <[log in to unmask]>
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Dale,

 Bunch of issues here. That deflection, are you talking a constant sag? If
so then additional board supports might be needed. 

 The machines sense board height and have various Z direction acceleration
profiles to speed down towards the board yet touch down slowly and deliver
the component with a specific force. This force will cause some board
deflection. If a component is extra thick the fast Z down can smack the
board and cause vibration problems. 

 In general you want your board supported so they give you a "Stiff"
placement platform. 

 Many parts have their contact areas pushed down into the paste all the way
to the PCB copper, this is good. Other parts sit on top the paste which can
cause squish of paste for small parts. Minimum placement forces are often
very high for small parts.

 What you can adjust for a given tool or given part type is what makes a big
difference in PnP software.

Bob Kondner

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Hart, Dale L CTR USAF
AFMC AFRL/RXSA
Sent: Monday, October 04, 2010 2:26 PM
To: [log in to unmask]
Subject: [TN] pick and place /board deflection

 

I was on the shop floor and noticed deflection in the 8x8 inch panel that
was being populated.  Would the deflection in the middle of the panel cause
components to sit higher on the paste and thus have a slightly higher solder
joint height than components on boards along the rails?       Thanks in
advance

 

Dale L. Hart

Universal Technology Corporation (UTC)

Failure Analysis

1270 North Fairfield Road

Dayton, Ohio  45432-2600

(937) 656-9165

Fax (937) 656-4600

Email:  <mailto:[log in to unmask]> [log in to unmask]

 


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