New Polymeric Materials for Electronics Packaging - American

Chapter 34

New Polymeric Materials for Electronics Packaging H. Hacker, K.-R. Hauschildt, J. Huber, H. Laupenmühlen, and D. Wilhelm

Downloaded by EMORY UNIV on April 17, 2016 | http://pubs.acs.org Publication Date: September 5, 1989 | doi: 10.1021/bk-1989-0407.ch034

Siemens AG, Research and Development Center, D-8520 Erlangen, Federal Republic of Germany

Low pressure moulding compounds for the encapsulation of electronic devices are usually polyepoxide/polyphenol based. We report on the base compounds of an accelerator-free system based on aromatic polyepoxide and a recently developed hardener, containing highly heat resistant structural units of the isocyanurate type. Due to this chemical structure, outstanding properties of the moulded material can be realized, such as glass transition temperatures > 200°C, low coefficient of linear thermal expansion, high impact strength, reduced combustibility without using bromine, long s h e l f - l i f e at room temperature and rapid curing at elevated temperatures. A survey w i l l be given on the synthesis of the hardener, the influence of the chemical structure on the reaction behavior of low pressure moulding compounds, different preparation methods of moulding compounds, and the thermomechanical performance of the moulded materials. S e m i c o n d u c t o r components f o r t h e e l e c t r o n i c s i n d u s t r y a r e s e n s i t i v e t o m e c h a n i c a l s t r e s s e s and c o r r o s i v e influences. In t h e e a r l y s e v e n t i e s , t h e f i r s t e p o x i d e r e s i n moulding m a t e r i a l s , developed e s p e c i a l l y f o r the encapsul a t i o n o f e l e c t r o n i c components, a p p e a r e d on t h e m a r k e t (1) . A p a c k a g i n g t e c h n o l o g y d e v e l o p e d p a r a l l e l t o a s e m i c o n d u c t o r t e c h n o l o g y , where e p o x i d e r e s i n m o u l d i n g mater i a l s o u t s t r i p p e d o t h e r s u b s t a n c e s by f a r . P a c k a g i n g t e c h n o l o g y b a s e d on t h e s e m a t e r i a l s c a n , on t h e one hand, meet h i g h demands and, on t h e o t h e r hand, k e e p c o s t s low.

0097-6156/89/0407-0414$06.00/0 o 1989 American Chemical Society

Lupinski and Moore; Polymeric Materials for Electronics Packaging and Interconnection ACS Symposium Series; American Chemical Society: Washington, DC, 1989.


34.

HACKER ET AL.

New Polymeric Materials for Electronics Packaging

W o r l d w i d e c o n s u m p t i o n was e s t i m a t e d a t a p p r o x . 40.00050.000 t o n s i n 1987. D e p e n d i n g on t h e d e v e l o p m e n t o f t h e e l e c t r o n i c m a r k e t , p r e d i c t i o n s o f t h e g r o w t h r a t e up t o 1991 v a r y between 3 % and 15 % ( 2 ) . Today the e p o x i d e - r e s i n base i s almost e x c l u s i v e l y e p o x i d i z e d c r e s o l - n o v o l a k , e s p e c i a l l y when p e r f o r m a n c e a t e l e v a t e d t e m p e r a t u r e s i s i m p o r t a n t . H a r d e n e d by an a r o m a t i c amine, t h e c u r e d m a t e r i a l has a h e a t d e s t o r t i o n t e m p e r a t u r e 50-60°C h i g h e r t h a n found f o r s i m i l a r c u r e d b i s p h e n o l A based systems. Flame r e s i s t a n t t h e r m o s e t s f r e q u e n t l y u s e b r o m i n a t e d b i s p h e n o l - A - b i s e p o x i d e s as co-component. Due t o t h e i n c r e a s i n g demands made on e l e c t r o n i c components, t h e p u r i t y of r e s i n s , e s p e c i a l l y with regard to the concent r a t i o n o f sodium and c h l o r i n e i o n s ( o r r a t h e r bonded c h l o r i n e ) , i s p a r t i c u l a r l y i m p o r t a n t . The p u r i t y q u e s t i o n a l s o a p p l i e s to curing agents. Criteria

f o r moulding

materials

are:

S t o r a g e s t a b i l i t y a t a m b i e n t t e m p e r a t u r e s > 6 months E a s y p r o c e s s i n g and r a p i d c u r i n g High mechanical s t r e n g t h High g l a s s t r a n s i s t i o n temperature Low c o e f f i c i e n t o f t h e r m a l e x p a n s i o n Low c o m b u s t i b i l i t y Moisture resistance C o m m e r c i a l l y a v a i l a b l e p a c k a g i n g m a t e r i a l s meet a l most a l l t h e s e demands, e x c e p t s t o r a g e s t a b i l i t y and h i g h g l a s s t r a n s i s t i o n t e m p e r a t u r e s . A t room t e m p e r a t u r e o r s l i g h t l y e l e v a t e d temperatures t h e i r storage l i f e r e t e n t i o n i s p o o r . The s t o r a g e t e m p e r a t u r e must be k e p t b e l o w 10°C o r t h e f l o w a b i l i t y c o n t i n u a l l y d e c r e a s e s . W i t h i n a p e r i o d o f a few weeks a t s t o r a g e t e m p e r a t u r e s between 20°C and 30°C a s i g n i f i c a n t f l o w v a r i a t i o n down t o 1/10 o f t h e i n i t i a l f l o w a b i l i t y can v e r y o f t e n be o b s e r v e d . The g l a s s t r a n s i t i o n t e m p e r a t u r e o f t h e m o u l d e d s u b s t a n c e s must be h i g h e r t h a n t h e e x p e c t e d o p e r a t i n g t e m p e r a t u r e s i n t h e e l e c t r o n i c component. T h i s a v o i d s exc e s s i v e s h e a r s t r e s s between e l e c t r o n i c component and m o u l d e d s u b s t a n c e s c a u s e d by change o f t h e CTE ( c o e f f i c i e n t o f t h e r m a l e x p a n s i o n ) i n t h e Tg r a n g e . The m o u l d - r e l e a s e r i g i d i t y i s a l s o i m p r o v e d i f a h i g h Tg i s o b t a i n e d i n t h e mould. Most o f t h e c o m m e r i c a l l y a v a i l a b l e h i g h - p e r f o r m a n c e m o u l d i n g m a t e r i a l s use e p o x i d i z e d c r e s o l - n o v o l a k / n o v o l a k ( e s p e c i a l l y p h e n o l i c n o v o l a k ) as a b a s e . S y s t e m s w i t h amine c u r i n g a g e n t s , f o r i n s t a n c e 4 , 4 ' - d i a m i n o d i p h e n y l s u l f o n e (2.) o r 4 , 4 ' - d i a m i n o d i p h e n y l m e t h a n e , do p r o v i d e h i g h - q u a l i t y moulding substances with a thermo-mechanical p e r f o r m a n c e c o m p a r a b l e t o o u r s y s t e m . T h e y a r e , however even l e s s s t a b l e under s t o r a g e .


415

416

POLYMERS FOR ELECTRONICS PACKAGING AND INTERCONNECTION

Curing

Component,


U s i n g s u i t a b l e b a s i c c a t a l y s t s l i k e sodium b e n z o a t e , a l k y l d i i s o c y a n a t e s ( I ) c a n be t r i m e r i z e d t o p o l y i s o c y a n a t o a r y l i s o c y a n u r a t e s w i t h > 95 % o f t h e t h e o r e t i c a l y i e l d o f 1,3,5-tris (3-isocyanato-4-alkylphenyl)-2,4,6-trioxohexah y d r o t r i a z i n e ( I I ) . The c o r r e s p o n d i n g p o l y a m i n e s ( I I I ) a r e o b t a i n e d i n a s i n g l e - s t e p p r o c e s s u s i n g an e x c e s s o f w a t e r i n t h e p r e s e n c e o f u n s o l u b l e , b a s i c magnesium s i l i c a t e - g e l as c a t a l y s t and w a t e r s o l u b l e s o l v e n t s l i k e d i oxane o r d i m e t h y l a c e t a m i d e a t e l e v a t e d t e m p e r a t u r e s - (See Figure 1.)

R =

CrC

4

F i g u r e 1.

III

alkyl

S y n t h e s i s of the c u r i n g component

T h e r e a r e two s t r u c t u r a l f e a t u r e s t h a t are of p a r t i c u l a r i n t e r e s t :

of

(schematic).

this

Polyamine

1.

The a r o m a t i c - h e t e r o c y c l i c m o i e t y has a h i g h C:H r a t i o . T h i s i m p r o v e s t h e c o m b u s t i o n r e s i s t a n c e (£) o f s y s t e m s compounded t h e r e f r o m , and

2.

The a l k y l g r o u p s o r t h o t o t h e N H - g r o u p s e x e r t a s h i e l d i n g e f f e c t w h i c h e f f e c t i v e l y s l o w s down t h e - otherwise continued - r e a c t i o n with epoxide groups a t room t e m p e r a t u r e . 2

Packaging M a t e r i a l s , Production

and

Properties

R e s i n . P o l y g l y c i d y l compounds w i t h a t l e a s t two e p o x i d e g r o u p s p e r m o l e c u l e , s u c h as p o l y g l y c i d y l e t h e r on a b a s e o f n o v o l a k , b i s p h e n o l A, b i s p h e n o l F e t c . , a r e g e n e r a l l y s u i t a b l e as E P - r e s i n components. Our t e s t s were c a r r i e d o u t w i t h e p o x i d i z e d n o v o l a k s ( e p o x i d e number b e t w e e n 0.5 and 0.6) and t o t a l h a l o g e n c o n t e n t s < 0.1 % by w e i g h t .


34. HACKER ET AL.


C u r i n g A g e n t . The c u r i n g a g e n t u s e d was a p o l y a m i n o a r y l i s o c y a n u r a t e w i t h a p p r o x i m a t e l y 50 % c o n t e n t o f 1,3,5tris-(3-amino-4-methyl-phenyl)-2,4,6-trioxo-hexahydrot r i a z i n e w i t h an amine c o n t e n t o f 6.8 %. The i n i t i a l r a t i o between e p o x i d e f u n c t i o n a n d a m i n o - h y d r o g e n (NH) was 1:1. Q u a r t z powder ( S i l b o n d , Q u a r z w e r k e F r e c h e n ) s e r v e d as f i l l e r i n o u r experiments. R

P r o d u c t i o n of Moulding M a t e r i a l s .


were p r e p a r e d

b y two d i f f e r e n t

The m o u l d i n g m a t e r i a l s methods.

M e t h o d A (wet p r e p a r a t i o n ) By w e i g h t , 450 p a r t s o f an e p o x i d i z e d n o v o l a k w i t h an e p o x i d e number o f 0.57 were d i s s o l v e d i n 450 p a r t s b y w e i g h t o f a c e t o n e . To t h i s s o l u t i o n were a d d e d 300 p a r t s by w e i g h t p o l y a m i n o a r y l i s o c y a n u r a t e (amine c o n t e n t 6.8 % ) , d i s s o l v e d i n 300 p a r t s b y w e i g h t o f a c e t o n e . The s o l u t i o n o f 50 % r e s i n / c u r i n g a g e n t was t h e n compounded w i t h 1630 p a r t s b y w e i g h t q u a r t z powder a n d m i x e d i n t e n s i v e l y . S u b s e q u e n t l y , t h e m i x t u r e was d r i e d f o r 30 m i n u t e s a t 60°C/1 mbar. The m a t e r i a l o b t a i n e d p o s s e s s e s g r a n u l a r i t y and f l o w a b i l i t y . Method Β ( d r y p r e p a r a t i o n ) By w e i g h t , 6 00 p a r t s o f an e p o x i d i z e d n o v o l a k w i t h an e p o x i d e number o f 0.57 a n d 400 p a r t s b y w e i g h t p o l y a m i n o a r y l i s o c y a n u r a t e (amine c o n t e n t 6.8 % ) a s w e l l a s 2170 p a r t s b y w e i g h t q u a r t z powder were m i x e d t o g e t h e r i n a r o l l e r m i l l ( r o l l t e m p e r a t u r e 60°C) f o r a p e r i o d o f 30 m i n u t e s . The m a t e r i a l o b t a i n e d p o s s e s s e s g r a n u l a r i t y a n d flowability. T e s t P i e c e s . The m o u l d i n g m a t e r i a l s p r o d u c e d w i t h methods A a n d Β ( f i l l e r c o n t e n t 70 %) were p r o c e s s e d t o t e s t p i e c e s a c c o r d i n g t o t h e normal t r a n s f e r moulding t e c h n i q u e w i t h o u t p r o c e s s i n g a i d s , such as mould l u b r i c a n t s , c o u p l i n g a g e n t s , e t c . The m o u l d i n g t e m p e r a t u r e was 1 7 5 ° C , m o u l d i n g p r e s s u r e was 100 b a r a n d m o u l d i n g p e r i o d was 5 minutes.

Properties S p i r a l F l o w ( a c c o r d i n g t o t e s t method EMMI 1-66) - F o r method A a n d Β m a t e r i a l s , 60-80 cm were f o u n d . S t o r a g e S t a b i l i t y . The s t o r a g e s t a b i l i t y i s l o n g e r t h a n 1 y e a r . The m o u l d i n g m a t e r i a l s were s t o r e d i n p o l y e t h y l e n e bags u n d e r n o r m a l room c o n d i t i o n s . A f t e r one y e a r t h e y were p r o c e s s e d t o t e s t p i e c e s . N e i t h e r a d i f f e r e n c e i n t h e i r f l o w a b i l i t y nor i n the thermo-mechanical p e r f o r mance o f t h e moulded m a t e r i a l was f o u n d . T h i s i s an e x c e l l e n t r e s u l t , regarding the storage s t a b i l i t i e s of o t h e r m o u l d i n g compounds.


417

418

POLYMERS FOR ELECTRONICS PACKAGING AND INTERCONNECTION

G l a s s T r a n s i t i o n Temperature. The

g l a s s t r a n s i t i o n tem p e r a t u r e s a r e b a s e d on t o r s i o n modulus c u r v e s a c c o r d i n g t o DIN 53445. T a b l e I shows t h e d e p e n d e n c e of t h e g l a s s t r a n s i t i o n t e m p e r a t u r e on t h e p o s t - c u r i n g o f t h e m o u l d e d substances. No d i f f e r e n c e i n Tg was f o u n d between t e s t s a m p l e s p r e p a r e d f r o m method A and Β m a t e r i a l s a f t e r o p e n i n g t h e m o u l d . A d d i t i o n a l p o s t - c u r i n g , i . e . 2 h o u r s a t 190°C, p l u s 2 h o u r s a t 210°C, p l u s 2 h o u r s a t 220°C c a u s e s t h e Tg r i s e shown i n T a b l e I .


Table

I:

I n f l u e n c e of the P o s t - C u r i n g C o n d i t i o n s G l a s s T r a n s i t i o n T e m p e r a t u r e s Tg

T e s t Sample (60x10x1 mm)

Method A Method

Post-Curing Time (h) Temp.

(°C)

or 2 + 2 + 2

Β

190 210 220

Glass Tg

on

the

Transition (°C)

210 220 233 240

In c o n t r a s t t o Tg e v a l u a t i o n s , a s l i g h t d e c l i n e o f t h e f l e x u r a l s t r e n g t h a f t e r p o s t - c u r i n g of t e s t samples p r e p a r e d f r o m method Β m a t e r i a l s was o b s e r v e d . C o n s i d e r i n g t h e p e r m i s s i b l e v a r i a t i o n t h i s i s o f no s i g n i f i c a n c e (Table II) .

Table

I I : F l e x u r a l S t r e n g t h (DIN 53452) and Impact S t r e n g t h (DIN 53453) i n Dependence on C u r i n g Conditions

T e s t Sample (60x6x4 mm)

F l e x u r a l Strength (N/mm- ) 2

Impact S t r e n g t h (Nmm«mm- ) 2

Method A post-cureless post-cured *

169 162

+

±

20 18

6,0 6,1

+

Method Β post-cureless post-cured *

168 134

± ±

17 30

5,7 6,2

+

* up

to

+

+

1/5 1.1

1,4 1,0

220°C


34.

HACKER ET A L


C o e f f i c i e n t o f Thermal E x p a n s i o n . The l i n e a r t h e r m a l ex p a n s i o n c o e f f i c i e n t was d e t e r m i n e d by TMA measurement a c c o r d i n g t o VDE s t a n d a r d 0304, p a r t 1. I n t h e r a n g e f r o m room t e m p e r a t u r e up t o t e m p e r a t u r e s e x c e e d i n g 200°C a c o n s t a n t v a l u e o f 2 3 · 1 0 - Κ was found. 6

1


Combustibi1Ity. The moulded m a t e r i a l shows s e l f - e x t i n g u i s h i n g p r o p e r t i e s w i t h o u t u s i n g h a l o g e n a t e d components due t o t h e p a r t i a l l y h e t e r o c y c l i c s t r u c t u r e o f t h e r e s i n component. The s t a g e o f c o m b u s t i b i l i t y c o n f o r m s w i t h UL 94 V - l , u s i n g t e s t s p e c i m e n s o f 3 mm t h i c k n e s s . W a t e r A b s o r p t i o n . The w a t e r a b s o r p t i o n was t e s t e d a c c o r d i n g t o ISO 62-1980, method 1 ( i m m e r s i o n i n w a t e r o f 23°C f o r 24 + 1 h o u r s ) , u s i n g a t e s t s p e c i m e n , o f 50 mm i n d i a m e t e r and a t h i c k n e s s o f 3 mm. The w a t e r u p t a k e was 0,05 %. C o m p a r a b l e n o v o l a k h a r d e n e d s y s t e m s have s l i g h t l y s m a l l e r w a t e r a b s o r p t i o n s i n t h e r a n g e o f 0,03 t o 0,04 %.

Evaluation The b a s i c s y s t e m u s i n g EP-novolak/polyamino-aryli s o c y a n u r a t e p r o v i d e s an i n t e r e s t i n g b a s e f o r e l e c t r o n i c p a c k a g i n g . The s y s t e m combines a w h o l e r a n g e o f d e s i r a b l e p r o p e r t i e s , such as: Processing

technology

- H i g h s t o r a g e s t a b i l i t y a t room t e m p e r a t u r e b e c a u s e o f the chemical s t r u c t u r e of the c u r i n g agent ( s h i e l d i n g e f f e c t of the - CH -groups). 3

- Cost e f f e c t i v e p r e p a r a t i o n of moulding m a t e r i a l s , s i n c e t h e t h e r m o m e c h a n i c a l and m e c h a n i c a l v a l u e s o f t h e m o u l d e d m a t e r i a l s o b t a i n e d by "wet p r e p a r a t i o n " do n o t d i f f e r s i g n i f i c a n t l y from the v a l u e s of moulded m a t e r i a l s o b t a i n e d by t h e l e s s c o s t l y " d r y p r e p a r a t i o n " , so t h a t t h e l a t t e r method c a n be a p p l i e d . - Good

flowability.

- Good a d h e s i o n t o m e t a l - Low

c o s t of

raw

products

surfaces. f o r the

hardener

synthesis.

- E a s y and c l e a n s y n t h e s i s i n t h e s e n s e o f p o l l u t i o n c o n t r o l , i . e . s o l v e n t l e s s s y n t h e s i s i n the f i r s t step and r e u s e o f s o l v e n t s o f t h e s e c o n d s t e p . Thermal/mechanical

Properties

- G l a s s t r a n s i t i o n t e m p e r a t u r e s > 200°C a r e a t t a i n a b l e i n the mould. T h i s l e a d s t o the advantages mentioned a t


419

420

POLYMERS FOR ELECTRONICS PACKAGING AND INTERCONNECTION the beginning s t r e s s o f the

w i t h r e s p e c t t o m o u l d r e l e a s e and e l e c t r o n i c component.

shear

- The b a s i c s y s t e m u s i n g n o r m a l s i l a n i z e d s i l i c a powder as a f i l l e r a l r e a d y shows a low l i n e a r t h e r m a l e x p a n s i o n c o e f f i c i e n t ( a i m = 23 · 1 0 K - ) , w h i c h i s c o n s t a n t up t o t e m p e r a t u r e s e x c e e d i n g 200°C. _ 6

; L

- Good m e c h a n i c a l p r o p e r t i e s , f l e x u r a l s t r e n g t h > 130 Nmm- , i m p a c t s t r e n g t h > 6 N m m « m m - . 2

2


- H i g h l y r e d u c e d c o m b u s t i b i l i t y due s t r u c t u r e o f the r e s i n matrix.

t o the

chemical

Literature Cited

1. S a l i n s k y , G.

I n s u l a t i o n / C i r c u i t s 1972,

5, 19-25.

2. Modern P l a s t i c s , 1986, 1 2 , 44-47. 3. H e i β l e r , H.; Scheer, W. German Patent 3 210

746,

1986.

4. Hacker, H.; H a u s c h i l d t , K.-R.; Huber, J . ; Laupenmühlen, H.; Wilhelm, D. European Patent 0 271 772, 1988. 5. Raβhofer, W. European Patent 0099537; US Patent 4 525 534, 1986. 6. V.Krevelen, D. Chem.-Ing. Techn.

1975, 47, 739 ff.

RECEIVED July 10,1989


New Polymeric Materials for Electronics Packaging - American

Recommend Documents