Example of Proposal
To: AAA - Project Manager, BBB
CC: CCC - Engineer, BBB
       Sid - Design Engineer, EEE
From: DDD �C IDAX Microelectronics
Subject: 15 mil Cap Proposal, GGG Card Assembly, FFF07.02.01
 1st  H/H/H  2nd
1st Report: Proposal & Analysis
  1. Object
2. Current way vs. Proposed way of Assembly
3. Glob Top Encapsulation vs. Metal cap Placement
4. Spec of Metal cap
5. Advantage of Metal cap
  1. Object:
  1.1 Solve the difficulty of assembly process
      on reaching "15 mil height above board surface" of JJJ card FFF07
1.2 Meet the product design requirement thru the proposed process
1.3 Save huge mfg cost & yield loss
2. Current vs. Proposed Way of Assembly
Procedures Statistic Height
Current Way
Proposed Way
Die attach epoxy
0.8~ 1.5 mil
0.8~ 1.5 mil
Die, e.g.
U1, microcontroller;
U5, finger print sensor
8.3 mil
7.0 mil
Wire-bond above die surface
2~ 5 mil
Glob top
See Para3
Epoxy dome
23~ 28 mil
Metal cap


See Para3
Flat cap
15 mil
3. Glob Top Encapsulation vs. Metal cap Placement
Glob Top Encapsulation w/epoxy Metal Cap Placement, non-conductive
Assembling work-Procedures Assembling work-Procedures
Build dam, epoxy-1 Yes Place the metal cap Snap placement Height is cap thickness,  or 15 mil
Dam height control manual Clamp the cap with Light force clip Snap
cure Yes Seal rim with epoxy manual
Trim or add the height of dam always cure Yes
Dispense the filling epoxy-2 manual --- ---
Epoxy-2 volume control hard Height 23~28 mil
Cure Yes
Material 2 kinds of epoxy 1 kind of epoxy
Metal caps, 4~5 ea/board
Equipment & Tools oven Oven
Light force clip, 4~5 ea/ board
4. Spec of Metal Cap
Material Alum 7075T7351
(originally developed for aircraft frames)
stronger than that of feeler gauge (or shim gage) stainless steel #304
high carbon steel 1045, 1065)
Material Source McMaster-Carr # 8885K11,
Ex. .032�� thk x 12�� x 12�� @$12.22
Manufacturing process Chemical etching Not machined thru machine shop
Manufacturing cost Not expensive Min. labor time to load and unload
Chemicals perform the machining job
Surface treatment Standard Anodizing become
non-conductive skin
Black colorized Block UV & absorb optical random light
Configuration To be designed
5 caps each board 4 kinds of size each board
Cap top thickness 2.2~2.5 mil
Cap rim width 12 ~20 mil
Cap shape .38~.5�� Dia. or Rectangular
15 mil th
5. Advantage of Metal Cap Placement
Advantage Metal Cap Placement Glob Top Encapsulation (comparative base, current way)
assembly process simple Complicate
High Cpk, or high process capability Low Cpk
Assembly time short Long
Skill level low High
Assembly labor cost Low High
Save million dollars from mfg cost
Quality Stable Un-stable in height and Varies a lot
No disturb on wire-bond like CDIP, LCC package Disturb wire-bond like PDIP, SOIC
Meet the original design requirement feels thin Can��t never meet the requirement
Looks and feels smart
Wire-bond rework Just remove cap and do it Not possible
Quick & easy
Save huge yield or (save million dollars from process flexibility)
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