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October 2003

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Subject:
From:
Afri Singh <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Thu, 23 Oct 2003 00:18:45 -0400
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Madhu

Please Inspect after UV 
and then again after the  150 c cure  to isolate the source

You may need to lower the temp to around 140 C

Try to cure them laying flat or support the board during the cure cycle

You  could be working with a low Tg material which will soften at these temp
and as the other respondant said an unbalanced cu board will cause warpage

You may need to balance the cu area 

 

-----Original Message-----
From: S.R. Madhuchandra [mailto:[log in to unmask]]
Sent: Wednesday, October 22, 2003 2:22 AM
To: [log in to unmask]
Subject: Re: [TN] Warpage after PLSM


Afri

In thermal curing, boards are baked at 150 deg C for 30 min with horizontal
stacking

We do UV curing to reduce cycle time for some selective jobs only
In UV curing, the boards are subjected to 3.1 joules at 160 deg C for
approx 1 min

Thanx in advance

Madhu




|---------+---------------------------->
|         |           "Afri Singh"     |
|         |           <[log in to unmask]>  |
|         |                            |
|         |           10/21/2003 03:25 |
|         |           AM               |
|         |                            |
|---------+---------------------------->
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  |                                                                                                                              |
  |       To:       "TechNet E-Mail Forum." <[log in to unmask]>, "S.R. Madhuchandra" <[log in to unmask]>                 |
  |       cc:                                                                                                                    |
  |       Subject:  RE: [TN] Warpage after PLSM                                                                                  |
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Madhu
What temp are you baking the boards at and how do you rack them ?

Also why do you do UV ?
Most shops only thermal cure peelables at 150 C for 5-15 minutes
You could try curing it at 140 C .

On the UV .How many joules and what does temp do these boards see

afri

-----Original Message-----
From: S.R. Madhuchandra [mailto:[log in to unmask]]
Sent: Monday, October 20, 2003 2:12 AM
To: [log in to unmask]
Subject: [TN] Warpage after PLSM


fellow technetters

In some of the part numbers, we are facing a strange phenomenon

The boards will be flat till the process of PLSM(peelable solder mask)
but after the PLSM, there will be severe warpage & wobbling

In PLSM, we are doing both UV & thermal curing

Can some one throw some light on this

Thanks in advance
Madhu


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